Signatures of two distinct driving mechanisms in the evolution of coronal mass ejections in the lower corona

Abstract

We present a comparison between two simulations of coronal mass ejections (CMEs), in the lower corona, driven by different flux rope mechanisms presented in the literature. Both mechanisms represent different magnetic field configurations regarding the amount of twist of the magnetic field lines and different initial energies. They are used as a "proof of concept" to explore how different initialization mechanisms can be distinguished from each other in the lower corona. The simulations are performed using the Space Weather Modeling Framework (SWMF) during solar minimum conditions with a steady state solar wind obtained through an empirical approach to mimic the physical processes driving the solar wind. Although the two CMEs possess different initial energies (differing by an order of magnitude) and magnetic configurations, the main observables such as acceleration, shock speed, Mach number, and θBn (the angle between the shock normal and the upstream magnetic field) present very similar behavior between 2 and 6 R ⊙. We believe that through the analysis of other quantities, such as sheath width and postshock compression (pileup and shock indentation compressions), the effect of different magnetic configurations and initializations can be distinguished. We discuss that coronal models that employ a reduced value of polytropic index (γ) may significantly change the energetics of the CME and that the background solar wind plays an important role in the CMEs' shock and sheath evolution. Copyright 2011 by the American Geophysical Union.