3D Multi-fluid MHD Simulation of the Early Time Behavior of an
Artificial Plasma Cloud in the Bottom Side Ionosphere
Abstract
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 10s 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.