Hybrid simulations of debris-ambient ion interactions in astrophysical explosions

Abstract

[1] Hybrid simulations (particle ions, massless fluid electrons) have been carried out to study the super-Alfvenic expansion of a dense, hot debris plasma against a relatively tenuous, relatively cool magnetized ambient plasma for the purpose of modeling the physics relevant to the early phase of explosions in astrophysical environments (supernovae, solar flares). We examine the stopping of the debris ions, the spatial distribution of the stopped ions, and their penetration across the compressed ambient magnetic field, using simulations run in a two-dimensional geometry. The simulations show that the expanding debris excludes the ambient magnetic field to form a diamagnetic cavity. The stopping distance of the debris is consistent with that determined from the debris ions overrunning an equivalent mass of ambient ions. The distribution of the stopped debris ions is strongly dependent on the debris gyroradius based on the initial directed velocity ρd, being highly peaked at the debris-magnetic field interface when ρd is large. The distance that debris ions penetrate into and mix with the excluded magnetic field is measured and shown to increase linearly with ρd. Copyright 2007 by the American Geophysical Union.