Testing the Physics of Solar and Stellar Flares with NASA's Solar Dynamics Observatory and Radiative MHD Simulations
Mark Cheung
Lockheed Martin Solar and Astrophysics Laboratory



Solar and stellar flares are the most intense emitters of X-rays and extreme ultraviolet radiation in planetary systems. On the Sun, strong flares are usually found in newly emerging sunspot regions. The emergence of these magnetic sunspot groups leads to the accumulation of magnetic energy in the corona. When the magnetic field undergoes abrupt relaxation, the energy released powers coronal mass ejections and heats plasma to temperatures beyond tens of millions of Kelvins. In part one of this talk, we show how extreme UV images of the solar corona taken by NASA's Solar Dynamics Observatory can be used to quantify the thermal structure and evolution of magnetically active regions on the Sun. The thermal structures inferred from extreme UV observations are consistent with their soft X-ray counterparts. Lessons learned from such studies guide the development of models of flares and eruptions. In the second part of this talk, we present radiative MHD simulations of flares and eruptions with sufficient realism for the synthesis of remote sensing measurements at visible, UV and X-ray wavelengths. These models allow us to explain a number of well-known observational features, including the time profile of the X-ray flux, chromospheric evaporation and condensation, the sweeping of flare ribbons in the lower atmosphere, global coronal waves, and the non-thermal spectral shape of coronal X-ray sources. Implications for how we interpret X-ray spectra from other astrophysical sources will be discussed.