Matthias Rempel https://www2.hao.ucar.edu/ en Refactoring the MPS/University of Chicago Radiative MHD (MURaM) Model for GPU/CPU Performance Portability Using OpenACC Directives https://www2.hao.ucar.edu/news/publication-highlight/refactoring-mpsuniversity-chicago-radiative-mhd-muram-model-gpucpu <span class="field field--name-title field--type-string field--label-hidden">Refactoring the MPS/University of Chicago Radiative MHD (MURaM) Model for GPU/CPU Performance Portability Using OpenACC Directives</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/6" typeof="schema:Person" property="schema:name" datatype="">whawkins</span></span> <span class="field field--name-created field--type-created field--label-hidden">Wed, 08/31/2022 - 11:20</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">whawkins</div> <div class="author_created__date text-gray-dark fs-6">Aug 31, 2022</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><p><em>PASC 2021:</em>  E. Wright, D. Przybylski, <strong>M. Rempel</strong>, C. Miller, S. Suresh, S. Su, R. Loft and S. Chandrasekaran</p> <p>The MURaM (Max Planck University of Chicago Radiative MHD) code is a solar atmosphere radiative MHD model that has been broadly applied to solar phenomena ranging from quiet to active sun, including eruptive events such as flares and coronal mass ejections. The treatment of physics is sufficiently realistic to allow for the synthesis of emission from visible light to extreme UV and X-rays, which is critical for a detailed comparison with available and future multi-wavelength observations. This component relies critically on the radiation transport solver (RTS) of MURaM; the most computationally intensive component of the code. The benefits of accelerating RTS are multiple fold: A faster RTS allows for the regular use of the more expensive multi-band radiation transport needed for comparison with observations, and this will pave the way for the acceleration of ongoing improvements in RTS that are critical for simulations of the solar chromosphere.<br /> We present challenges and strategies to accelerate a multi-physics, multi-band MURaM using a directive-based programming model, OpenACC in order to maintain a single source code across CPUs and GPUs. Results for a 288x288x288 test problem show that MURaM with the optimized RTS routine achieves 1.73x speedup using a single NVIDIA V100 GPU over a fully subscribed 40-core Intel Skylake CPU node and with respect to the number of simulation points (in millions) per second, a single NVIDIA V100 GPU is equivalent to 69 Skylake cores. We also measure parallel performance on up to 96 GPUs and present weak and strong scaling results.</p> <figure class="media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2022-08/Rempel_CPU-GPU.PNG?itok=zHy35v8i" width="926" height="641" alt="CPU-GPU strong scaling of a multi-band 288x288x288 dataset" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>CPU-GPU strong scaling of a multi-band 288x288x288 dataset. Shown is the code performance (measured in million gridcell updates per second) as function of the number of V100 GPUs or fully subscribed Skylake CPU nodes (40 cores). 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loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti"><span class="field field--name-title field--type-string field--label-hidden">Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI</span> </a> </h3> </div> </div> </div> </div> </div> </div> </div> </div> <div class="block block-layout-builder block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2022-08-31T12:00:00Z" class="datetime">Wed, 08/31/2022 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Wed, 31 Aug 2022 17:20:27 +0000 whawkins 687 at https://www2.hao.ucar.edu The Coronal Veil https://www2.hao.ucar.edu/news/publication-highlight/coronal-veil <span class="field field--name-title field--type-string field--label-hidden">The Coronal Veil</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Mon, 07/11/2022 - 14:15</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication: Astrophysical Journal; Authors: Malanushenko, A.; Cheung, M. C. M.; DeForest, C. E.; Klimchuk, J. A.; Rempel, M.</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Jul 11, 2022</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><figure class="align-left media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2022-07/AnnaM_simulatedCorona.png?itok=dLZZskbD" width="926" height="571" alt="3D view of the simulated corona; bottom panel: magnetogram; back panel: synthetic AIA 211A coronal image; middle vertical plane: volumetric emissivity. Field lines are included for reference." loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>3D view of the simulated corona; bottom panel: magnetogram; back panel: synthetic AIA 211A coronal image; middle vertical plane: volumetric emissivity. Field lines are included for reference.</p> </figcaption> </figure> <p>Coronal loops, seen in solar coronal images, are believed to represent emission from magnetic flux tubes with compact cross sections. We examine the 3D structure of plasma above an active region in a radiative magnetohydrodynamic simulation to locate volume counterparts for coronal loops. In many cases, a loop cannot be linked to an individual thin strand in the volume. While many thin loops are present in the synthetic images, the bright structures in the volume are fewer and of complex shape. We demonstrate that this complexity can form impressions of thin bright loops, even in the absence of thin bright plasma strands. We demonstrate the difficulty of discerning from observations whether a particular loop corresponds to a strand in the volume, or a projection artifact. We demonstrate how apparently isolated loops could deceive observers, even when observations from multiple viewing angles are available. While we base our analysis on a simulation, the main findings are independent from a particular simulation setup and illustrate the intrinsic complexity involved in interpreting observations resulting from line-of-sight integration in an optically thin plasma. We propose alternative interpretation for strands seen in Extreme Ultraviolet images of the corona. The "coronal veil" hypothesis is mathematically more generic, and naturally explains properties of loops that are difficult to address otherwise-such as their constant cross section and anomalously high density scale height. We challenge the paradigm of coronal loops as thin magnetic flux tubes, offering new understanding of solar corona, and by extension, of other magnetically confined bright hot plasmas.</p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-50bf44bc7dd9803f7c8a4f25775dc5261002ae9a5ed892305f0d4cf060930f1d"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/news-article/hawaiis-mauna-loa-erupts-after-38-years-mauna-loa-solar-observatory-temporarily" hreflang="en"><img 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block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2022-06-22T12:00:00Z" class="datetime">Wed, 06/22/2022 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/54" hreflang="en">Anna Malanushenko</a>, <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/3" hreflang="en">corona</a>, <a href="/taxonomy/term/57" hreflang="en">MHD</a>, <a href="/taxonomy/term/14" hreflang="en">solar magnetism</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Mon, 11 Jul 2022 20:15:00 +0000 kolinski 593 at https://www2.hao.ucar.edu Efficient numerical treatment of ambipolar and Hall drift as hyperbolic system https://www2.hao.ucar.edu/news/publication-highlight/efficient-numerical-treatment-ambipolar-and-hall-drift-hyperbolic-system <span class="field field--name-title field--type-string field--label-hidden">Efficient numerical treatment of ambipolar and Hall drift as hyperbolic system</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 03/03/2022 - 15:06</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication: Astrophysical Journal; Authors: M. Rempel and D. Przybylski</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Mar 3, 2022</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><figure class="align-right media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2022-03/Rempel_two-dimensionalTestSimulation%20copy.png?itok=pVrB8CDI" width="926" height="1156" alt="Snapshot from a two-dimensional test simulation setup with a 8x8Mm domain reaching from the upper convection zone into the transition region" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Snapshot from a two-dimensional test simulation setup with a 8x8Mm domain reaching from the upper convection zone into the transition region. Presented are a) temperature, b) density, c) magnetic field strength, d) ambipolar diffusivity, e) ambipolar drift velocity, and f) ambipolar heating. The latter two were computed using the hyperbolic treatment introduced in this publication.</p> </figcaption> </figure> <p>Partially ionized plasmas, such as the solar chromosphere, require a generalized Ohm's law including the effects of ambipolar and Hall drift. While both describe transport processes that arise from the multifluid equations and are therefore of hyperbolic nature, they are often incorporated in models as a diffusive, i.e. parabolic process. While the formulation as such is easy to include in standard MHD models, the resulting diffusive time-step constraints do require often a computationally more expensive implicit treatment or super-time-stepping approaches. In this paper we discuss an implementation that retains the hyperbolic nature and allows for an explicit integration with small computational overhead. In the case of ambipolar drift, this formulation arises naturally by simply retaining a time derivative of the drift velocity that is typically omitted. This alone leads to time-step constraints that are comparable to the native MHD time-step constraint for a solar setup including the region from photosphere to lower solar corona. We discuss an accelerated treatment that can further reduce time-step constraints if necessary. In the case of Hall drift we propose a hyperbolic formulation that is numerically similar to that for the ambipolar drift and we show that the combination of both can be applied to simulations of the solar chromosphere at minimal computational expense.</p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-123692b069bc57f2d3d8c1b8543bf2380d8a11fb4bf5f463ca86b9b2d18fa7a8"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a 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field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Maute_perturbationAmplitudes.jpg?itok=BRSLJoPb" width="480" height="326" alt="Seasonal variations of monthly-zonal-mean small-scale perturbation amplitudes" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti"><span class="field field--name-title field--type-string field--label-hidden">Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI</span> </a> </h3> </div> </div> </div> </div> </div> </div> </div> </div> <div class="block block-layout-builder block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2022-02-23T12:00:00Z" class="datetime">Wed, 02/23/2022 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/13" hreflang="en">modeling</a>, <a href="/taxonomy/term/14" hreflang="en">solar magnetism</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 03 Mar 2022 22:06:31 +0000 kolinski 417 at https://www2.hao.ucar.edu On the (In)stability of Sunspots https://www2.hao.ucar.edu/news/publication-highlight/instability-sunspots <span class="field field--name-title field--type-string field--label-hidden">On the (In)stability of Sunspots</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 03/03/2022 - 14:55</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication: Astronomy &amp; Astrophysics; Authors: H. Strecker, W. Schmidt, R. Schlichenmaier, M. Rempel</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Mar 3, 2022</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><p>The stability of sunspots is one of the long-standing unsolved puzzles in the field of solar magnetism and the solar cycle. The thermal and magnetic structure of the sunspot beneath the solar surface is not accessible through observations, thus processes in these regions that contribute to the decay of sunspots can only be studied through theoretical and numerical studies.</p> <p><em>Aims:</em> We study the effects that destabilise and stabilise the flux tube of a simulated sunspot in the upper convection zone. The depth-varying effects of fluting instability, buoyancy forces, and timescales on the flux tube are analysed.</p> <figure class="align-left media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2022-03/Rempel_magnetic%20field%20strength.jpg?itok=q3d2VaRN" width="926" height="1225" alt="Maps of the magnetic field strength at depth of z = −7.5 Mm beneath the solar photosphere at different times (indicated in red in each panel)" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Maps of the magnetic field strength at depth of z = −7.5 Mm beneath the solar photosphere at different times (indicated in red in each panel). The boundary of the sunspot (red line) is defined by the contour value Bc = 4781 G. At the beginning of the analysis, at t = 0 h, panel (a), the inner part of the flux tube is mainly undisturbed. Within 6 hours, regions of weaker field appear in the innermost part of the flux tube while the outer structure becomes more ragged, as is shown in panel (b). The increasing raggedness causes a degradation of the flux tube. This degradation process continues in time, as panels (c–e) show. At 29.75 h, the roundish structure of the flux tube has completely vanished. The degradation process takes place in all regions deeper than 1 Mm below the surface.</p> </figcaption> </figure> <p><em>Methods:</em> We analysed a numerical simulation of a sunspot calculated with the MURaM code. The simulation domain has a lateral extension of more than 98 Mm × 98 Mm and extends almost 18 Mm below the solar surface. The analysed data set of 30 hours shows a stable sunspot at the solar surface. We studied the evolution of the flux tube at defined horizontal layers (1) by means of the relative change in perimeter and area, that is, its compactness; and (2) with a linear stability analysis.</p> <p><em>Results:</em> The simulation shows a corrugation along the perimeter of the flux tube (sunspot) that proceeds fastest at a depth of about 8 Mm below the solar surface. Towards the surface and towards deeper layers, the decrease in compactness is damped. From the stability analysis, we find that above a depth of 2 Mm, the sunspot is stabilised by buoyancy forces. The spot is least stable at a depth of about 3 Mm because of the fluting instability. In deeper layers, the flux tube is marginally unstable. The stability of the sunspot at the surface affects the behaviour of the field lines in deeper layers by magnetic tension. Therefore the fluting instability is damped at depths of about 3 Mm, and the decrease in compactness is strongest at a depth of about 8 Mm. The more vertical orientation of the magnetic field and the longer convective timescale lead to slower evolution of the corrugation process in layers deeper than 10 Mm.</p> <p><em>Conclusions: </em>The formation of large intrusions of field-free plasma below the surface destabilises the flux tube of the sunspot. This process is not visible at the surface, where the sunspot is stabilised by buoyancy forces. The onset of sunspot decay occurs in deeper layers, while the sunspot still appears stable in the photosphere. The intrusions eventually lead to the disruption and decay of the sunspot.</p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-b8d66c2811279aa09463cff1aef3e9d6f3a222c1964714f802c8bd510df733e2"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/news-article/hawaiis-mauna-loa-erupts-after-38-years-mauna-loa-solar-observatory-temporarily" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/MLeruptionLava.png?itok=NHfdX7TB" width="480" height="320" alt="Mauna Loa November 2022 eruption" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 29, 2022</div> <h3 class="card-title"> <a href="/news/news-article/hawaiis-mauna-loa-erupts-after-38-years-mauna-loa-solar-observatory-temporarily"><span class="field field--name-title field--type-string field--label-hidden">Hawaii&#039;s Mauna Loa Erupts after 38 years; Mauna Loa Solar Observatory temporarily closed</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/thermospheric-neutral-density-variation-during-spacex-storm-implications" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/Lin_NeutralDensity_star.png?itok=oSivicLn" width="467" height="480" alt="Neutral density variations along the Starlink orbit" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 23, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/thermospheric-neutral-density-variation-during-spacex-storm-implications"><span class="field field--name-title field--type-string field--label-hidden">Thermospheric Neutral Density Variation during the &quot;SpaceX&quot; Storm: Implications from Physics-based Whole Geospace Modeling</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/synthetic-lyman-emissions-coronagraph-aboard-aso-s-mission-i-eruptive" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/Gibson_Lyman-alphaEmission2022.png?itok=7XE1F3AA" width="480" height="176" alt="Lyman-alpha emission" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 9, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/synthetic-lyman-emissions-coronagraph-aboard-aso-s-mission-i-eruptive"><span class="field field--name-title field--type-string field--label-hidden">Synthetic Lyman-α Emissions for the coronagraph aboard the ASO-S mission I: an Eruptive Prominence-cavity System</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-2"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/news-article/remembering-charlie-garcia" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/17.charlie_garcia_4.jpg?itok=4aE7GWqs" width="309" height="480" alt="Charlie outdoors at Mauna Loa with windswept hair" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 3, 2022</div> <h3 class="card-title"> <a href="/news/news-article/remembering-charlie-garcia"><span class="field field--name-title field--type-string field--label-hidden">Remembering Charlie Garcia</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/horizontal-wind-shears-lower-thermosphere-observed-icon" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Maute_maximumShear.jpg?itok=id9P5eHJ" width="480" height="241" alt="Example of maximum shear determination in zonal wind from 1 orbit of MIGHTI observations" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 14, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/horizontal-wind-shears-lower-thermosphere-observed-icon"><span class="field field--name-title field--type-string field--label-hidden">Horizontal wind shears in the lower thermosphere observed by ICON</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/investigation-post-sunset-extra-electron-density-peak-poleward" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Qian%2CLiying_Lat-longDistr.NmF2simula.png?itok=HZnaJDN2" width="480" height="250" alt="Latitude-longitude distribution and NmF2 simulation" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/investigation-post-sunset-extra-electron-density-peak-poleward"><span class="field field--name-title field--type-string field--label-hidden">Investigation of the Post-Sunset Extra Electron Density Peak Poleward of the Equatorial Ionization Anomaly Southern Crest</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-3"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/lagrangian-study-tidal-advection-mesospheric-water-vapor" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Pedatella_DW1advectedH2O.png?itok=QXmqdjt2" width="479" height="480" alt="DW1 advected H2O volume mixing ratio" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 19, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/lagrangian-study-tidal-advection-mesospheric-water-vapor"><span class="field field--name-title field--type-string field--label-hidden">A Lagrangian Study of Tidal Advection of Mesospheric Water Vapor</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/coronal-cavities-comp-observations" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Gibson_CavityWidths-SDO.AIA__0.png?itok=gN76eNR5" width="455" height="480" alt="Cavity widths observed by SDO/AIA" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 27, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/coronal-cavities-comp-observations"><span class="field field--name-title field--type-string field--label-hidden">Coronal Cavities in CoMP Observations</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/inter-hemispheric-asymmetries-high-latitude-electrodynamic-forcing-and" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Zhu_Temporal%20variations%20of%20the%20ion%20convection%20boundary.png?itok=xU0LXQHY" width="480" height="255" alt="Temporal variations of the ion convection boundary" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 14, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/inter-hemispheric-asymmetries-high-latitude-electrodynamic-forcing-and"><span class="field field--name-title field--type-string field--label-hidden">Inter-Hemispheric Asymmetries in the High-Latitude Electrodynamic Forcing and the Thermosphere During the October 8-9, 2012 Geomagnetic Storm: An Integrated Data-Model Investigation</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-4"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Maute_perturbationAmplitudes.jpg?itok=BRSLJoPb" width="480" height="326" alt="Seasonal variations of monthly-zonal-mean small-scale perturbation amplitudes" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti"><span class="field field--name-title field--type-string field--label-hidden">Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI</span> </a> </h3> </div> </div> </div> </div> </div> </div> </div> </div> <div class="block block-layout-builder block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2022-02-23T12:00:00Z" class="datetime">Wed, 02/23/2022 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/13" hreflang="en">modeling</a>, <a href="/taxonomy/term/14" hreflang="en">solar magnetism</a>, <a href="/taxonomy/term/46" hreflang="en">sunspots</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 03 Mar 2022 21:55:08 +0000 kolinski 416 at https://www2.hao.ucar.edu Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere https://www2.hao.ucar.edu/news/publication-highlight/acoustic-gravity-wave-propagation-characteristics-three-dimensional <span class="field field--name-title field--type-string field--label-hidden">Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 03/03/2022 - 14:49</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication: Philosophical Transactions of the Royal Society; Authors: B. Fleck; M. Carlsson; E. Khomenko; M. Rempel; O. Steiner; G. Vigeesh</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Mar 3, 2022</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><figure class="align-right media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2022-03/Rempel_v-phaseDiagrams.jpg?itok=fA28XhBt" width="926" height="512" alt="ν − z phase diagrams (cuts at constant horizontal wavenumber at approx. 2 and 4 Mm−1 through the stacks of the layer-by-layer two-dimensional k − ω phase difference diagrams) for various MURaM models" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>ν − z phase diagrams (cuts at constant horizontal wavenumber at approx. 2 and 4 Mm−1 through the stacks of the layer-by-layer two-dimensional k − ω phase difference diagrams) for various MURaM models. There is a dramatic difference between the subphotospheric layers (the convection zone) and the solar atmosphere above z = 0 km (τ5000 = 1) layer. In the atmosphere (z &gt; 0 km), we see in large parts the expected behaviour: green and red areas at the lowest frequencies in the gravity wave regime, followed by a transition into propagating acoustic waves with increasingly negative phase differences (purple and blue regions).</p> </figcaption> </figure> <p>There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades. Four of the most frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D and MURaM. Here we test and compare the wave propagation characteristics in model runs from these four codes by measuring the dispersion relation of acoustic-gravity waves at various heights. We find considerable differences between the various models. The height dependence of wave power, in particular of high-frequency waves, varies by up to two orders of magnitude between the models, and the phase difference spectra of several models show unexpected features, including ±180° phase jumps.</p> <p>This article is part of the Theo Murphy meeting issue 'High-resolution wave dynamics in the lower solar atmosphere'.</p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-e1af7fd10db76e13500ecaabee73df9db1103477180d5fc8cde235947a2b8fd1"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference 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block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2022-02-23T12:00:00Z" class="datetime">Wed, 02/23/2022 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/57" hreflang="en">MHD</a>, <a href="/taxonomy/term/13" hreflang="en">modeling</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 03 Mar 2022 21:49:36 +0000 kolinski 415 at https://www2.hao.ucar.edu The Dimmest State of the Sun https://www2.hao.ucar.edu/news/publication-highlight/dimmest-state-sun <span class="field field--name-title field--type-string field--label-hidden">The Dimmest State of the Sun</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 03/03/2022 - 13:10</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Authors: Kok Leng Yeo, Sami K. Solanki, Matthias Rempel, Anusha Bhasari, Natalie A. Krivova, Alexander I. Shapiro, Rinat V. Tagi</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Mar 3, 2022</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><figure class="align-right media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2022-03/Rempel_Measured-modelledTotalSolarIrradiance.png?itok=bpuHDWbS" width="926" height="573" alt="Measured and modelled total solar irradiance" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Measured and modelled total solar irradiance. (A) The model reconstruction of TSI (black) based on 3D MHD simulations and solar imagery from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, which operated from 2010, and the measurements from the Total Irradiance Monitor onboard the SOlar Radiation and Climate 5 Experiment (red), which monitored TSI over the same period except between August 2013 and February 2014. (B) A blowup of the boxed period, 1 March 2014 to 28 February 2015, which encompasses the maximum of solar cycle 24, which occurred in April 2014. The root-mean-square difference between the two time series is 0.068 Wm-2 and the Pearson’s correlation coefficient is 0.987, i.e., the model replicates about 97% of the apparent variability in the TIM 10 record.</p> </figcaption> </figure> <p>How the solar electromagnetic energy entering the Earth’s atmosphere varied since pre-industrial times is an important consideration in the climate change debate. Detrimental to this debate, estimates of the rise in total solar irradiance, TSI, between the Maunder minimum, an extended period of weak solar activity preceding the industrial revolution, and the last solar 15 cycle minimum in 2008 differ markedly, ranging from 0.4 to 6 Wm-2. As a consequence, the exact contribution by solar forcing to the rise in global temperatures over the past centuries remains inconclusive. Adopting a novel approach based on state-of-the-art solar imagery and numerical simulations, we establish that TSI could not have risen since the Maunder minimum by more than 2.1±0.7 Wm-2, restricting the role of solar forcing in global warming.</p> <p>Link to publication: <em><a href="https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020GL090243">Geophysical Research Letters</a></em></p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-68dcf1d004c34d5e6a75d075f130faf186baab8ef38de1a43d5afaf94b6ae0f5"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image 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field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/lagrangian-study-tidal-advection-mesospheric-water-vapor" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Pedatella_DW1advectedH2O.png?itok=QXmqdjt2" width="479" height="480" alt="DW1 advected H2O volume mixing ratio" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 19, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/lagrangian-study-tidal-advection-mesospheric-water-vapor"><span class="field field--name-title field--type-string field--label-hidden">A Lagrangian Study of Tidal Advection of Mesospheric Water Vapor</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden 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src="/sites/default/files/styles/large/public/2022-10/Zhu_Temporal%20variations%20of%20the%20ion%20convection%20boundary.png?itok=xU0LXQHY" width="480" height="255" alt="Temporal variations of the ion convection boundary" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 14, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/inter-hemispheric-asymmetries-high-latitude-electrodynamic-forcing-and"><span class="field field--name-title field--type-string field--label-hidden">Inter-Hemispheric Asymmetries in the High-Latitude Electrodynamic Forcing and the Thermosphere During the October 8-9, 2012 Geomagnetic Storm: An Integrated Data-Model Investigation</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-4"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Maute_perturbationAmplitudes.jpg?itok=BRSLJoPb" width="480" height="326" alt="Seasonal variations of monthly-zonal-mean small-scale perturbation amplitudes" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti"><span class="field field--name-title field--type-string field--label-hidden">Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI</span> </a> </h3> </div> </div> </div> </div> </div> </div> </div> </div> <div class="block block-layout-builder block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2022-03-01T12:00:00Z" class="datetime">Tue, 03/01/2022 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/13" hreflang="en">modeling</a>, <a href="/taxonomy/term/35" hreflang="en">Sun-Earth connection</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 03 Mar 2022 20:10:48 +0000 kolinski 413 at https://www2.hao.ucar.edu AAS Nova Features a Recent Publication by Philip Judge https://www2.hao.ucar.edu/news/news-article/aas-nova-features-recent-publication-philip-judge <span class="field field--name-title field--type-string field--label-hidden">AAS Nova Features a Recent Publication by Philip Judge</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 11/18/2021 - 12:36</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Nov 18, 2021</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><p>Understanding the magnitude and occurrence of solar storms is key to predicting events that can be harmful to thousands of Earth-orbiting satellites and the welfare of astronauts. A recent paper by Philip Judge et al was highlighted in AAS Nova in a their featured article entitled, "<em><a href="https://aasnova.org/2021/09/29/a-better-space-weather-forecasting-tool/">A Better Space Weather Forecasting Tool</a></em>."</p> <figure class="align-center media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2021-11/judge_2021_Figure2.png?itok=2Bpr8xPv" width="926" height="511" alt="Images to highlight the corrugated surfaces at which the centers of UV lines are formed (close to τ = 1) in MURaM calculations of the upper solar chromosphere" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Images to highlight the corrugated surfaces at which the centers of UV lines are formed (close to τ = 1) in MURaM calculations of the upper solar chromosphere. The calculations are from a numerical experiment where a magnetic flux system is emerging from beneath the solar atmosphere. The emergent fields carry with them plasma, which is revealed by the extended heights of the τ = 1 surfaces, which can exceed 10 Mm. Typically the Doppler line shifts in the lower transition region are smaller than the line widths (Athay &amp; Dere 1991). Therefore the τ = 1 surfaces were computed without taking into account Doppler shifts, at the centers of lines of Mg ii k, and several lines of Fe ii. The x–y images of height of formation are plotted in order of decreasing opacity from Mg ii to Fe ii 2769.75 Å. In the bottom right panel, slices of these τ = 1 surfaces are shown, taken along the black line in the five other panels. But the black lines in this final panel are magnetic lines of force in the y–z plane. Evidently, a combination of these and other lines of iron with a wide range of opacities spans the ranges of excursions of the surfaces away from a horizontal plane.</p> </figcaption> </figure> <p>Link to paper: <em><a href="https://iopscience.iop.org/article/10.3847/1538-4357/ac081f/meta">Measuring the Magnetic Origins of Solar Flares, Coronal Mass Ejections, and Space Weather</a></em></p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-8d019165ce0e826fcde3471851a37f2f167e2c022dab2de4ae6e73534a1e2c8f"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image 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field--label-hidden field__item"> <a href="/news/publication-highlight/thermospheric-neutral-density-variation-during-spacex-storm-implications" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/Lin_NeutralDensity_star.png?itok=oSivicLn" width="467" height="480" alt="Neutral density variations along the Starlink orbit" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 23, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/thermospheric-neutral-density-variation-during-spacex-storm-implications"><span class="field field--name-title field--type-string field--label-hidden">Thermospheric Neutral Density Variation during the &quot;SpaceX&quot; Storm: Implications from Physics-based Whole Geospace Modeling</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/synthetic-lyman-emissions-coronagraph-aboard-aso-s-mission-i-eruptive" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/Gibson_Lyman-alphaEmission2022.png?itok=7XE1F3AA" width="480" height="176" alt="Lyman-alpha emission" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 9, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/synthetic-lyman-emissions-coronagraph-aboard-aso-s-mission-i-eruptive"><span class="field field--name-title field--type-string field--label-hidden">Synthetic Lyman-α Emissions for the coronagraph aboard the ASO-S mission I: an Eruptive Prominence-cavity System</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-2"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/news-article/remembering-charlie-garcia" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-11/17.charlie_garcia_4.jpg?itok=4aE7GWqs" width="309" height="480" alt="Charlie outdoors at Mauna Loa with windswept hair" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Nov 3, 2022</div> <h3 class="card-title"> <a href="/news/news-article/remembering-charlie-garcia"><span class="field field--name-title field--type-string field--label-hidden">Remembering Charlie Garcia</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/horizontal-wind-shears-lower-thermosphere-observed-icon" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Maute_maximumShear.jpg?itok=id9P5eHJ" width="480" height="241" alt="Example of maximum shear determination in zonal wind from 1 orbit of MIGHTI observations" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 14, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/horizontal-wind-shears-lower-thermosphere-observed-icon"><span class="field field--name-title field--type-string field--label-hidden">Horizontal wind shears in the lower thermosphere observed by ICON</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/investigation-post-sunset-extra-electron-density-peak-poleward" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Qian%2CLiying_Lat-longDistr.NmF2simula.png?itok=HZnaJDN2" width="480" height="250" alt="Latitude-longitude distribution and NmF2 simulation" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/investigation-post-sunset-extra-electron-density-peak-poleward"><span class="field field--name-title field--type-string field--label-hidden">Investigation of the Post-Sunset Extra Electron Density Peak Poleward of the Equatorial Ionization Anomaly Southern Crest</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-3"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/lagrangian-study-tidal-advection-mesospheric-water-vapor" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Pedatella_DW1advectedH2O.png?itok=QXmqdjt2" width="479" height="480" alt="DW1 advected H2O volume mixing ratio" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 19, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/lagrangian-study-tidal-advection-mesospheric-water-vapor"><span class="field field--name-title field--type-string field--label-hidden">A Lagrangian Study of Tidal Advection of Mesospheric Water Vapor</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/coronal-cavities-comp-observations" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Gibson_CavityWidths-SDO.AIA__0.png?itok=gN76eNR5" width="455" height="480" alt="Cavity widths observed by SDO/AIA" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 27, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/coronal-cavities-comp-observations"><span class="field field--name-title field--type-string field--label-hidden">Coronal Cavities in CoMP Observations</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/inter-hemispheric-asymmetries-high-latitude-electrodynamic-forcing-and" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Zhu_Temporal%20variations%20of%20the%20ion%20convection%20boundary.png?itok=xU0LXQHY" width="480" height="255" alt="Temporal variations of the ion convection boundary" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 14, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/inter-hemispheric-asymmetries-high-latitude-electrodynamic-forcing-and"><span class="field field--name-title field--type-string field--label-hidden">Inter-Hemispheric Asymmetries in the High-Latitude Electrodynamic Forcing and the Thermosphere During the October 8-9, 2012 Geomagnetic Storm: An Integrated Data-Model Investigation</span> </a> </h3> </div> </div> </div> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-4"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti" hreflang="en"><img src="/sites/default/files/styles/large/public/2022-10/Maute_perturbationAmplitudes.jpg?itok=BRSLJoPb" width="480" height="326" alt="Seasonal variations of monthly-zonal-mean small-scale perturbation amplitudes" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 18, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/seasonal-variations-small-scale-waves-observed-icon-mighti"><span class="field field--name-title field--type-string field--label-hidden">Seasonal Variations of Small-Scale Waves observed by ICON-MIGHTI</span> </a> </h3> </div> </div> </div> </div> </div> </div> </div> </div> <div class="block block-layout-builder block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2021-10-01T12:00:00Z" class="datetime">Fri, 10/01/2021 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/65" hreflang="en">Joan Burkepile</a>, <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/44" hreflang="en">Paul Bryans</a>, <a href="/taxonomy/term/10" hreflang="en">Phil Judge</a>, <a href="/taxonomy/term/66" hreflang="en">Rebecca Centeno</a>, <a href="/taxonomy/term/36" hreflang="en">solar flare</a>, <a href="/taxonomy/term/62" hreflang="en">space weather</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 18 Nov 2021 19:36:28 +0000 kolinski 86 at https://www2.hao.ucar.edu Opposite Polarity Magnetic Fields and Convective Downflows in a Simulated Sunspot Penumbra https://www2.hao.ucar.edu/news/publication-highlight/opposite-polarity-magnetic-fields-and-convective-downflows-simulated <span class="field field--name-title field--type-string field--label-hidden">Opposite Polarity Magnetic Fields and Convective Downflows in a Simulated Sunspot Penumbra</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 11/18/2021 - 10:16</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication Name: ApJ; First HAO Author&#039;s Name: M. Rempel</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Nov 18, 2021</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><p>Recent numerical simulations and observations of sunspots show a significant amount of opposite polarity magnetic fields within the sunspot penumbra. Most of the opposite polarity fields are associated with convective downflows.</p> <figure class="align-left media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2021-11/Rempel_NormalizedContinuumIntensity-web.jpg?itok=-_59bXKp" width="926" height="1250" alt="Sunspot simulations" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Left panels: normalized continuum intensity at 630 nm. Middle panels: Stokes V far wing magnetogram. Right panels: bisector velocity at 80% for Fe i 6301.5 Å. First row: at simulation resolution. Second, third, and fourth rows: at Hinode (0.5 m), 1 m, and 1.5 m resolutions.</p> </figcaption> </figure> <p>We present an analysis of 3D MHD simulations through forward modeling of synthetic Stokes profiles of the Fe I 6301.5 Å and Fe I 6302.5 Å lines. The synthetic Stokes profiles are spatially and spectrally degraded considering typical instrument properties. Line bisector shifts of the Fe I 6301.5 Å line are used to determine line-of-sight velocities. Far wing magnetograms are constructed from the Stokes V profiles of the Fe I 6302.5 Å line. While we find an overall good agreement between observations and simulations, the fraction of opposite polarity magnetic fields, the downflow filling factor, and the opposite polarity-downflow association are strongly affected by spatial smearing and presence of strong gradients in the line-of-sight magnetic fields and velocity. A significant fraction of opposite polarity magnetic fields and downflows is hidden in the observations due to typical instrumental noise. 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block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2020-03-31T12:00:00Z" class="datetime">Tue, 03/31/2020 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/13" hreflang="en">modeling</a>, <a href="/taxonomy/term/14" hreflang="en">solar magnetism</a>, <a href="/taxonomy/term/46" hreflang="en">sunspots</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 18 Nov 2021 17:16:42 +0000 kolinski 71 at https://www2.hao.ucar.edu A distinct magnetic property of the inner penumbral boundary III. Analysis of simulated sunspots https://www2.hao.ucar.edu/news/publication-highlight/distinct-magnetic-property-inner-penumbral-boundary-iii-analysis <span class="field field--name-title field--type-string field--label-hidden">A distinct magnetic property of the inner penumbral boundary III. Analysis of simulated sunspots</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Thu, 11/18/2021 - 10:03</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication Name: A&amp;A; First HAO Author&#039;s Name: M. Rempel</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Nov 18, 2021</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><p>The analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary, the invariance of the vertical component of the magnetic field. We aim to analyse the magnetic properties of the umbra-penumbra boundary in simulated sunspots and thus assess their similarity to observed sunspots. Also, we aim to investigate the role of plasma $\beta$ and the ratio of kinetic to magnetic energy in simulated sunspots on the convective motions as these quantities cannot be reliably determined from observations. We use a set of non-grey simulation runs of sunspots with the MURaM code. The setups differ in terms of subsurface magnetic field structure as well as the magnetic field boundary imposed at the top of the simulation domain. These data are used to synthesise the Stokes profiles that are then degraded to the Hinode spectropolarimeter-like observations. Then, the data are treated like real Hinode observations of a sunspot and magnetic properties at the umbral boundaries are determined. Simulations with potential field extrapolation produce a realistic magnetic field configuration on their umbral boundaries.</p> <figure class="align-left media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2021-11/Rempel_RCE_sunspot_analysis.png?itok=p1UTs94e" width="926" height="557" alt="Radial profiles of continuum intensity (b), magnetic field inclination (c), total magnetic field strength (d), vertical magnetic field strength (e), and horizontal magnetic field strength (f)" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Radial profiles of continuum intensity (b), magnetic field inclination (c), total magnetic field strength (d), vertical magnetic field strength (e), and horizontal magnetic field strength (f). The continuum intensity map of the observed sunspot with contours marking relative radial positions from 0.1 to 1 is shown in panel (a). The solid vertical lines mark the umbra-penumbra boundaries, the dashed vertical lines mark the penumbra-quiet Sun boundary. The horizontal lines in (b) and (e) mark the 50% quiet Sun intensity and 1876 G contour, respectively. Only sunspot simulations with a potential field top boundary condition (type 1 and alpha=1) have a vertical magnetic field strength values at the umbra-penumbra boundary that are similar to those observed.</p> </figcaption> </figure> <p>Two simulations with potential field upper boundary, but different subsurface magnetic field structures, differ significantly in the extent of their penumbrae. Increasing the penumbra width by forcing more horizontal magnetic fields at the upper boundary results in magnetic properties that are not consistent with observations. This implies that the size of the penumbra is given by the subsurface structure of the magnetic field. Namely, the depth and inclination of the magnetopause shaped by the sunspot flux rope expansion with height. None of the sunspot simulations is consistent with observed properties of the magnetic field and direction of the Evershed flow at the same time. Strong outward directed Evershed flows are only found in setups with artificially enhanced horizontal component of the magnetic field at the top boundary that are not consistent with the observed magnetic field properties at the UP boundary. We want to stress out that the `photospheric' boundary of simulated sunspots is defined by a magnetic field strength of equipartition field value.</p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-8ef872208600f8db4e1a9fde1f4ba59685955256ae63357e2c03f73ebad0e5b5"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/news-article/hawaiis-mauna-loa-erupts-after-38-years-mauna-loa-solar-observatory-temporarily" hreflang="en"><img 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src="/sites/default/files/styles/large/public/2022-10/Gibson_CavityWidths-SDO.AIA__0.png?itok=gN76eNR5" width="455" height="480" alt="Cavity widths observed by SDO/AIA" loading="lazy" typeof="foaf:Image" class="image-style-large img-fluid" /> </a> </div> </figure> <div class="pb-1 text-gray-dark text-uppercase date--sm">Oct 27, 2022</div> <h3 class="card-title"> <a href="/news/publication-highlight/coronal-cavities-comp-observations"><span class="field field--name-title field--type-string field--label-hidden">Coronal Cavities in CoMP Observations</span> </a> </h3> </div> </div> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a href="/news/publication-highlight/inter-hemispheric-asymmetries-high-latitude-electrodynamic-forcing-and" hreflang="en"><img 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block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2020-05-08T12:00:00Z" class="datetime">Fri, 05/08/2020 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/13" hreflang="en">modeling</a>, <a href="/taxonomy/term/14" hreflang="en">solar magnetism</a>, <a href="/taxonomy/term/46" hreflang="en">sunspots</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Thu, 18 Nov 2021 17:03:20 +0000 kolinski 68 at https://www2.hao.ucar.edu On the contribution of quiet Sun magnetism to solar irradiance variations: Constraints on quiet Sun variability and grand minimum scenarios https://www2.hao.ucar.edu/news/publication-highlight/contribution-quiet-sun-magnetism-solar-irradiance-variations-constraints <span class="field field--name-title field--type-string field--label-hidden">On the contribution of quiet Sun magnetism to solar irradiance variations: Constraints on quiet Sun variability and grand minimum scenarios</span> <span class="field field--name-uid field--type-entity-reference field--label-hidden"><span lang="" about="/user/3" typeof="schema:Person" property="schema:name" datatype="">kolinski</span></span> <span class="field field--name-created field--type-created field--label-hidden">Wed, 11/17/2021 - 13:11</span> <div class="layout__region--twocol d-grid d-print-flex with-sidebar"> <div class="layout__region layout__region--main-top breadcrumb-wrapper mt-2"> <div class="block block-system block-system-breadcrumb-block"> <nav class="mb-2 d-print-none" role="navigation" aria-labelledby="system-breadcrumb"> <h2 id="system-breadcrumb" class="visually-hidden">Breadcrumb</h2> <ol class="breadcrumb"> <li class="breadcrumb-item"> <a href="/">Home</a> </li> <li class="breadcrumb-item"> <a href="/taxonomy/term/45">Matthias Rempel</a> </li> </ol> </nav> </div> </div> <main class="layout__region layout__region--main main-content-wrapper"> <div class="block block-layout-builder block-field-blocknodearticlefield-subtitle"> <p class="field field--name-field-subtitle field--type-string field--label-above mb-4 mt-n4">Publication Name: ApJ; First HAO Author&#039;s Name: M. Rempel</p> </div> <div class="block block-layout-builder block-extra-field-blocknodearticleauthor-and-created"> <div class="author_created row gx-0"> <div class="col"> <div class="fw-bold fs-6">Author:</div> <div class="author_created__name fs-6">kolinski</div> <div class="author_created__date text-gray-dark fs-6">Nov 17, 2021</div> </div> </div> </div> <div class="mt-3 mt-md-4 block block-layout-builder block-field-blocknodearticlefield-main-content"> <div class="field field--name-field-main-content field--type-entity-reference-revisions field--label-hidden field__items"> <div class="field__item"> <div class="paragraph paragraph--type--rich-text paragraph--view-mode--default"> <div class="clearfix text-formatted field field--name-field-body field--type-text-long field--label-hidden field__item"><p>While the quiet Sun magnetic field shows only little variation with the solar cycle, long-term variations cannot be completely ruled out from first principles. We investigate the potential effect of quiet Sun magnetism on spectral solar irradiance through a series of small-scale dynamo simulations with zero vertical flux imbalance (⟨Bz ⟩ = 0) and varying levels of small-scale magnetic field strength, and one weak network case with an additional flux imbalance corresponding to a flux density of ⟨Bz⟩ = 100 G.</p> <figure class="align-left media media--type-image media--view-mode-default figure mb-1 mb-md-4"> <p> <img src="/sites/default/files/styles/extra_large/public/2021-11/Rempel_Fig3.png?itok=jAjl-Vb8" width="926" height="370" alt="Plots of magnetic field and TSI with time" loading="lazy" typeof="foaf:Image" class="image-style-extra-large img-fluid" /></p> <figcaption class="figure-caption pb-1"> <p>Panel (a): Time evolution of the mean vertical magnetic field strength ⟨|Bz|⟩τ=1 for the setups SSD_WEAK (dark blue), SSD_QS (light blue), SSD_Strong (orange), and N100 (magenta). All cases were started at t = 0 hours from the same HD snapshot (with different magnetic initial states). Panel (b): Time evolution of the outgoing radiative energy flux for the setups (1) - (5). The HD case is shown in black. We consider 24 hour averages as indicated in the figure. In the right panel we apply a 2 hour running boxcar average for better readability, since short-term TSI fluctuations have amplitudes of 1 − 2%. These simulations provide a TSI sensitivity of 0.14% for each 10 G of average vertical magnetic field strength in the photosphere at an optical depth of 1.</p> </figcaption> </figure> <p>From these setups we compute the dependence of the outgoing radiative energy flux on the mean vertical magnetic field strength in the photosphere at continuum optical depth τ = 1 (⟨|Bz|⟩τ=1). We find that a quiet Sun setup with a mean vertical field strength of ⟨|Bz|⟩τ=1 = 69 G is about 0.6 % brighter than a non-magnetic reference case. We find a linear dependence of the outgoing radiative energy flux on the mean field strength ⟨|Bz|⟩τ=1 with a relative slope of 1.4 · 10^{−4} G^{−1}. With this sensitivity, only a moderate change of the quiet Sun field strength by 10% would lead to a total solar irradiance variation comparable to the observed solar cycle variation. While this does provide strong indirect constraints on possible quiet Sun variations during a regular solar cycle, it also emphasizes that potential variability over longer time scales could make a significant contribution to longer-term solar irradiance variations.</p> </div> </div> </div> </div> </div> <div class="views-element-container block block-views block-views-blockarticles-recent-news"> <h2 class="mb-md-2">Recent News</h2> <div><div class="view view-articles view-id-articles view-display-id-recent_news js-view-dom-id-367b1ce18daeb25ca3d34f8f153083202224b5a32997e062d1f1434f6fc2e3b4"> <div class="view-content"> <div class="views-view-grid horizontal cols-3 col-12 mb-2 mb-md-4"> <div class="row row-cols-1 row-cols-sm-2 row-cols-md-3 g-2 g-md-4 row-1"> <div class="col"><div class="pb-3 pb-md-0"> <figure> <div class="field field--name-field-primary-image field--type-entity-reference field--label-hidden field__item"> <a 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block-field-blocknodearticlefield-story-date"> <div class="field field--name-field-story-date field--type-datetime field--label-above"> <div class="field__label">Date</div> <div class="field__item"><time datetime="2020-05-08T12:00:00Z" class="datetime">Fri, 05/08/2020 - 12:00</time> </div> </div> </div> </main> <aside class="layout__region layout__region--sidebar resources-wrapper d-print-none"> <div class="block block-layout-builder block-field-blocknodearticlefield-article-tags"> <div class="resources-wrapper d-print-none"> <div class="resources related mb-4"> <h2 class="p-2 px-md-3">Tags</h2> <div class="p-2 px-md-3 py-md-3"> <a href="/taxonomy/term/45" hreflang="en">Matthias Rempel</a>, <a href="/taxonomy/term/14" hreflang="en">solar magnetism</a> </div> </div> </div> </div> </aside> </div> <div class="layout layout--onecol"> <div > </div> </div> Wed, 17 Nov 2021 20:11:54 +0000 kolinski 67 at https://www2.hao.ucar.edu