Numerical Study of Coronal Mass Ejections, Shocks, and Turbulence: from Chromosphere to 1 AU.

Abstract

My dissertation focuses on one of the major source of destructive space weather: coronal mass ejections (CMEs). By helping develop and utilizing a new data-driven global MHD model: The Alfven Wave Solar Model (AWSoM) in the Space Weather Modeling Framework (SWMF), we achieve a more realistic CME event simulation from the chromosphere to 1 AU. A detailed investigation of the CME, CME-driven shock, and CME associated turbulence is conducted based on the numerical simulation results.

First, we perform a multi-spacecraft validation study for the new solar wind model in solar minimum conditions. We compare the observed plasma parameters and magnetic field of the heliosphere with that predicted by the model. Moreover, for the first time, we compare ionic charge states observed with ACE/SWICS with those predicted by our model. The validation results suggest that most of the model outputs can fit the observations very well, which will lead to a great improvement for CME and CME-driven shock modeling.

By employing the validated background solar wind model in both one-temperature (1T) and two-temperature (2T) modes, we present a numerical study of an event that occurred on 2011 March 7. We compare the propagation of fast CMEs and the thermodynamics of CME-driven shocks in both the 1T and 2T CME simulations. Our results demonstrate the importance of electron heat conduction in conjunction with proton shock heating in order to produce the physically correct CME structures and CME-driven shocks.

By separating electron and proton temperature, as well as implementing collisionless heat conduction, we simulate CME propagation from the chromosphere to 1 AU. A comprehensive validation study of the CME model is performed. By fitting the CME speeds near the Sun with observations, the CME-driven shock arrival time is within 1 hour of the observed arrival time and all the in situ parameters are correctly simulated. By applying a fully physical description of Alfven wave turbulence in the model, for the first time, we capture the CME turbulence interaction in the global MHD model.

These results illustrate the new capability of the model, which is a large step towards accurate space weather forecasting.