3D Multi-fluid MHD Simulation of the Early Time Behavior of an Artificial Plasma Cloud in the Bottom Side Ionosphere

摘要

A multi-fluid magnetohydrodynamic model has been developed to investigate artificial clouds in the lower ionosphere. The model is based on the five-moment approximation of the fluid equations with separate continuity and momentum equations for each species. The model can have multiple neutral and ion species, background and cloud designation of species, and multiple chemical reactions between species. The model is used to simulate a barium cloud initiated in the bottom side ionosphere. The neutral barium cloud is observed to expand radially with a spherical density distribution. The barium ion cloud, produced by ionization of the neutral barium cloud, expands mostly along the magnetic field lines. Both the barium and oxygen ions are observed to rotate about the magnetic field. A diamagnetic cavity develops quickly and then collapses within the 10-s model period. Initially, there is an oxygen ion density enhancement in the center of the cloud that later evolves into a depletion with enhancements on opposite field-aligned sides of the depletion. The direction of the ion rotation about the magnetic field alternates with time. The associated magnetic field twist propagates away from the cloud along the field line as a shear Alfvén wave. This last result, previously unreported, results from the additional physics included in the multi-fluid formulation of the fluid equations.