A selection of highlights culled from publications by HAO staff.
Sarah E. Gibson, et. al. discuss the Whole Heliosphere and Planetary Interactions (WHPI,) an international initiative to study the most recent solar minimum and its impact on the interconnected solar-heliospheric-planetary system by facilitating and encouraging interdisciplinary activities, placing it into the context of prior initiatives and describing the overall evolution of the system between 2018–2020.
Astrid Maute, Jeffrey Forbes, Chihoko Cullens, and Thomas Immel use the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) driven by observationally fitted tides via the Hough Mode Extension (HME) method to isolate the effect of the changing upward propagating tides on the dynamics, composition, and plasma distribution .
Sarah E. Gibson et. al. emphasize the need of understanding and predicting the major phenomena taking place in the solar corona, such as flares and Coronal Mass Ejections (CMEs), the heating and evolution of the solar atmosphere, and the acceleration of the solar wind, are fundamental challenges to predict our own star. These challenges are related to the solar magnetism and to the physical properties of solar plasma.
H.-L. Liu, W. Wang, J. D. Huba, P. H. Lauritzen, and F. Vitt analyze the Hunga Tonga-Hunga Ha'apai Volcano waves that have been recorded by ground and satellite instrumentation. This event provides a rare opportunity to study the strong and direct connection of the whole atmosphere system. The high-resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM-X) can simulate the global propagation of the waves, and the model results compare favorably with observations from the surface to the thermosphere and ionosphere.
JGR-Space: Liying Qian, Wandi Yu, Nicholas Pedatella, Jia Yue, Wenbin Wang examine hemispheric asymmetry of the annual and semiannual variation of the ratio of O and N2 concentrations (O/N2) using observations by the GUVI instrument onboard the TIMED satellite and compare them with WACCM-X model simulations. They observe and compare the equatorial region (“equinox peaks”) in varying months and hemispheres.
The contribution of plasma sheet bubbles to stormtime ring current buildup and evolution of the energy composition
Kevin Pham et al. utilize numerical modeling to investigate ring current buildup for a specific solar storm, and find that flows that are medium scale relative to the system size and referred to as plasma “bubbles”, are responsible for at least half of the total buildup of ring current plasma. Our analysis also shows that the bubbles displace some of the background plasma on their way Earthward, which is important when calculating their net contribution to the ring current.
Limitations and biases in the retrieval of the polar magnetic field I: the role of the magnetic filling factor in Milne-Eddington inversions of simulated Hinode/SP data
Rebecca Centeno, Ivan Milic, Matthias Rempel, Nariaki Nitta, Xudong Sun study the extent to which Milne-Eddington inversions are able to retrieve and characterize the magnetic landscape of the solar poles from observations by the spectropolarimeter onboard Hinode. In particular, they evaluate whether a variable magnetic filling factor is an adequate modeling technique for retrieving the intrinsic magnetic properties from every pixel in the polar field of view.
Breno Raphaldini, Mausumi Dikpati, and Carlos F. M. Raupp introduce the Hamiltonian formulation for a model that reasonably describes the dynamics of large-scale flows in stars and planets. They find two kinds of invariants of the system, the Casimirs, and the zonal momentum.
Authors L. Lomidze, D. J. Knudsen, M. Shepherd, J. D. Huba, and A. Maute observe that the terrestrial ionosphere displays significant equinoctial asymmetry despite the upper atmosphere receiving similar levels of solar ionization energy at a given location and local time in spring and fall during similar solar activity conditions. Satellite analysis data and model simulations provide better insights into the atmosphere-ionosphere coupling processes.