SPRG Seminars
October 15, 2013:
"Impact of partial ionization effects in the solar atmosphere using radiative-MHD simulations"
Juan Martinez-Sykora, Lockheed Martin
The chromosphere is the interface region between the solar surface and the corona. In fact, the chromosphere modulates the flow of mass and energy into the corona. IRIS was launched this year to study the chromosphere and is taking observations with high resolution, high throughput multi-channel UV imaging spectrograph at high cadence. The complexity of the chromosphere due to the several transitions that occur, e.g., from predominantly neutral to ionized Hydrogen, from collisional to collision-less behavior, from gas to magnetic dominated, etc, due to the complexity of the important physical processes, such as time dependent Hydrogen ionization, radiative transfer with scattered light, etc makes it challenging to interpret any chromospheric observations in general and from IRIS in particular. Therefore, it is crucial to combine IRIS observations with advanced radiative-MHD numerical modeling in order to interpret the observations. First of all, I will present briefly some recent observations taken from IRIS. Then, I will continue describing recent results from 2D radiative MHD simulations using the Bifrost code taking into account partial ionization effects which can be used to interpret the observations. These models presented here, in addition, include radiative transfer with scattering and thermal conduction along field lines. Partial ionization effects have been taken into account adding two new terms in the induction equation, so called Hall term and Pedersen resistivity (also referred as ambipolar diffusion). The Pedersen resistivity and Hall term have been calculated taken into account the thermal properties of the simulated atmosphere. We find that ambipolar (Pedersen) dissipation is important in the chromosphere in these radiative-MHD simulations. As a result, this effect impacts the chromosphere in terms of thermal properties, dynamics and magnetic evolution. Because of the coupling between the chromosphere and corona, I will show that these physical processes in the chromosphere also impact the corona.