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

Thermal Properties of Coronal Cavities

Graph depicting temperature of cavities and surrounding streamers
Tuesday, March 31, 2020

We have analyzed 33 cavities observed between 2012 and 2018, from solar activity maximum to minimum. For each cavity we applied a differential emission measure method to obtain both a temperature distribution and a value of the average temperature.

Space Weather Challenge & Forecasting Implications Of Rossby Waves

Graph depicting solar magnetic weather
Tuesday, March 31, 2020

Rossby waves arise in thin layers within fluid regions of stars and planets. These global wave-like patterns occur due to the variation in Coriolis forces with latitude. In the past several years observational evidence has indicated that there are also Rossby waves in the Sun.

Opposite Polarity Magnetic Fields and Convective Downflows in a Simulated Sunspot Penumbra

Graphic image of opposite polarity magnetic fields
Tuesday, March 31, 2020

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.

Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare

Graphic of intensity and polarization data
Wednesday, February 12, 2020

We examine spectropolarimetric data from the CoMP instrument, acquired during the evolution of the September 10th 2017 X8.2 solar flare on the western solar limb. CoMP captured linearly polarized light from two emission lines of Fe XIII at 1074.7 and 1079.8 nm, from 1.03 to 1.5 solar radii.

Sun-Like Stars Shed Light on Solar Climate Forcing

Seasonally averaged data for the CaII“S-index” and for the average magnitudes of the Strömgrenbplusy filters
Tuesday, January 7, 2020

Recently published, precise stellar photometry of 72 Sun-like stars obtained at the Fairborn Observatory between 1993 and 2017 is used to set limits on the solar forcing of Earth’s atmosphere of ±4.5 W m−2 since 1750.

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.