Engineering-Physics Space Plasma Seminar

Chengcai Shen, Harvard

Tuesday, November 19, 2019, 4:00–5:00pm

Wilder 202

"In-Line Non-Equilibrium Ionization Calculations in a Solar Eruption Simulation"

Non-equilibrium ionization (NEI) is important in many astrophysical environments where the thermodynamic time scale is shorter than the ionization time scale. In this work, we apply an NEI calculation module, which can be integrated into the well-developed MHD code to perform in-line NEI calculations. The ionization time advance can be performed while the MHD simulation is being performed. In this process, the time-dependent ionization equations are solved in a Eulerian frame using a high accuracy scheme, and the eigenvalue method is used to improve the computational stability and efficiency. This in-line calculation is robust in extreme environments, such as shocks. We then perform the combined MHD simulation using Athena code in a 2D solar eruption model and calculate ionization states for ten abundant chemical elements. In this simulation, the non-equilibrium ionic fractions are directly obtained throughout the whole simulation domain. We show here evolution and distribution features of charge states around the magnetic reconnecting current sheet in the flare.

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