Solar Transients and Space Weather

Overview and Research Goal

Observations of the Solar Transients and Space Weather provide the physical boundary conditions for the outer solar atmosphere and heliosphere. Historically, the STSW is comprised of the photospheric and chromospheric "layers". The photosphere is the first visible layer of the Sun's atmosphere where the ubiquitous magnetic field is routinely measured. Those magnetic structures interact with the turbulent convective processes of the solar interior throughout the STSW to drive the solar plasma dynamics. This lies at the heart of the outer atmosphere's mass and energy transport producing the solar wind, ultra-violet radiation, and Space Weather.

The research activities of HAO's STSW section are concerned with determining how the Sun's magnetic field both structures and drives the dynamics of the outer solar atmosphere. The present emphasis of its research activities focuses on observing and modeling the emergence, organization, and evolution of solar surface magnetic flux concentrations, from the visible solar surface into the tenuous corona.

The research goals of the STSW section are to develop models, analysis techniques, and instrumentation to undertake and facilitate investigation into the magnetism and dynamics of the outer solar atmosphere and their impact on short-term solar variability and space weather events.

Research Highlights

Constraining nonlinear dynamo models using quasi-biennial oscillations from sunspot area data

Graphic depicting continuous wavelet spectra of the sunspot area (SSA)
Thursday, July 25, 2019

Solar magnetic activity exhibits variations with periods between 1.5–4 years, the so-called quasi-biennial oscillations (QBOs), in addition to the well-known 11-year Schwabe cycles. The solar dynamo is thought to be the responsible mechanism for the generation of the QBOs.

What the Sudden Death of Solar Cycles Can Tell us About the Nature of the Solar Interior

140 year record of solar filaments
Monday, July 1, 2019

We observe the abrupt end of solar activity cycles at the Sun’s Equator by combining almost 140 years of observations from ground and space.

Space Weather: Big and Small—A Continuous Risk

Artistic rendering of the Sun and its atmosphere consist
Friday, May 10, 2019

"Space Weather" is the term used to describe the relentless barrage of particles that bathe the Earth and other planetary bodies of the solar system that originate in the steady evolution, and catastrophic breakdown, of magnetic structures on the Sun.

Three-dimensional modeling of chromospheric spectral lines in a simulated active region

Simulated images of Ca II 8542 Å, Ca II K, Mg II k, and H
Friday, May 3, 2019

Recently, the radiative magnetohydrodynamic (R-MHD) code MURaM was extended to include the corona. The code was used to simulate a bipolar active region with additional parasitic flux emergence near one of the sunspots that produced a flare.

Solar eclipse observations from the ground and air from 0.31 to 5.5 microns

Plot showing Spectra of the limb photosphere during the 21st August 2017 eclipse
Friday, March 29, 2019

We present spectra and broad-band polarized light data from a suite of instruments deployed during the 21st August 2017 total solar eclipse. Our goals were to survey solar spectra at thermal infrared wavelengths during eclipse, and to test new technology for measuring polarized coronal light.

Removal of Spectro-Polarimetric Fringes by 2D PCA

Graph depicting the transformation of the PCA basis through a series of carefully chosen rotations
Monday, February 25, 2019

We investigate the application of 2-dimensional Principal Component Analysis (2D PCA) to the problem of removal of polarization fringes from spectro-polarimetric data sets.

Triggering the Birth of New Cycle's Sunspots by Solar Tsunami

Image depicting global tachocline fluid top surface deformations
Monday, February 18, 2019

We demonstrate a novel physical mechanism, namely, that a “solar tsunami” occurring in the Sun’s interior shear-fluid layer can trigger new cycle’s magnetic flux emergence at high latitudes, a few weeks after the cessation of old cycle’s flux emergence near the equator.

The Extended Solar Cycle: Muddying the Waters of Solar/Stellar Dynamo Modeling Or Providing Crucial Observational

Graph depicting extended solar cycles
Monday, December 3, 2018

In 1844 Schwabe discovered that the number of sunspots increased and decreased over a period of about 11 years, that variation became known as the sunspot cycle.

The Effect of Small-Scale Magnetic Structures on Inferred Solar Continuum Brightness

Average intensity of magnetic structures
Monday, December 3, 2018

Solar irradiance models indicate that irradiance variations are dominated by changes in disk-coverage of magnetic structures, whose brightness is thought to be determined by their size and average magnetic flux density.

MHD simulation of prominence eruption

A 3D MHD simulation of the eruption of a prominence-carrying coronal flux rope
Monday, August 6, 2018

Yuhong Fan and others carry out magnetohydrodynamic (MHD) simulations of the quasi-static evolution and eruption of a twisted coronal flux rope under a coronal streamer built up by an imposed flux emergence at the lower boundary.