The Role of Overlying Magnetic Field and Poloidal Flux Injection in Modeling Coronal Mass Ejections
Abstract
Recent models and observations have revealed that the magnetic fields overlying active regions play an important role in the eruption or confinement of flux ropes due to the torus instability. Flux ropes are now generally accepted to be the magnetic configuration of coronal mass ejections (CMEs) but their initiation is still not clear. In this study the external magnetic field profile of the well-developed flux rope model (see J.Chen 1989, 1996) is examined. We model the process of poloidal flux injection that adds energy into the system and affects the kinematical evolution of the resulting CME before it becomes unstable to the torus instability. We also propose and test the idea that poloidal flux injection is a proxy for flux conversion between external overlying and internal poloidal field and is dependent on the external magnetic field profile. The external magnetic field of the model represents overlying coronal loops, and it is assumed that the only magnetic field component that affects the flux rope evolution is the one that is perpendicular to the flux ropes major axis. The gradient index for the prescribed magnetic field profile is studied and it is found that above a critical value the flux rope is eruptive and below this value it is confined, in agreement with observations and simulations. Implications of our results are that the torus instability is the most likely candidate in driving the eruption of flux rope CMEs. We also suggest that the bulk poloidal flux injection is created through the magnetic reconnection in the corona.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2009
- Pub Date:
- August 2009
- Bibcode:
- 2009shin.confE.170O