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

Deciphering Deep-Origin of Active Regions From Analysis Of Magnetograms

Graphic image of active-regions' toroid patterns
Tuesday, February 23, 2021

Dikpati, et. al., derive magnetic toroids from surface magnetograms by employing a novel optimization method based on Trust Region Reflective algorithm. Toroids obtained are combinations of Fourier modes (amplitudes and phases) with low longitudinal wavenumbers.

Design of a Highly Efficient Polychromatic Full-Stokes Polarization Modulator for the CRISP Imaging Spectrometer

Graphic image depicting spectro-polarimetric data
Tuesday, February 2, 2021

In 2014 HAO built a polarimetric modulator for the CRISP instrument on the Swedish 1-m Solar Telescope in La Palma, using the principles of polychromatic modulation previously developed by HAO scientists. This paper discusses the processes by which the modulator was designed, built, and tested.

Detecting the Chromospheric Footpoints of the Solar Wind

Graphic image depicting SDO and IRIS full-disk observations
Tuesday, November 24, 2020

Coronal Holes present the source of the fast solar wind. However, the fast solar wind is not unimodal—there are discrete, but subtle, compositional, velocity, and density structures that differentiate different coronal holes as well as wind streams that originate within one coronal hole.

Simulations of prominence eruption preceded with large amplitude longitudinal oscillations and draining

Graphic depicting prominence-forming twisted coronal flux rope
Friday, November 6, 2020

We present magnetohydrodynamic (MHD) simulations of the evolution from quasi-equilibrium to eruption of a prominence-forming twisted coronal flux rope under a coronal streamer. The prominence condensations form at the dips of the twisted flux rope due to run-away radiative cooling.

Mapping the magnetic field in the solar corona through magnetoseismology

Graphic image of magnetoseismology observations
Friday, August 14, 2020

Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona.

Dynamics of Late-Stage Reconnection in the 2017 September 10 Solar Flare

Graphic depicting white light images
Tuesday, August 4, 2020

In this multi-instrument paper, we search for evidence of sustained magnetic reconnection far beyond the impulsive phase of the X8.2-class solar flare on 2017 September 10.

A distinct magnetic property of the inner penumbral boundary III. Analysis of simulated sunspots

Graphic image depicting radial profiles of continuum intensity
Friday, May 8, 2020

The analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary, the invariance of the vertical component of the magnetic field.

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.

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.