Quasi-Analytic Models for Density Bubbles and Plasma Clouds in the Equatorial Ionosphere.

摘要

The equatorial ionosphere contains imbedded bubbles that rise though a horizontally stratified plasma. The motion of the bubbles are affect by gravity, neutral winds or external electric fields which produce electric fields in the F-Region density perturbations of the bubbles. Exact solutions for the electric potentials are derived assuming linear or circular symmetry to the density structures imbedded in the background plasma. A wide variety of analytic solutions for electric potentials are found for both density cavities and density enhancements. An analytic description of a rising bubble can be constructed by attaching a tail to the top half of a circular hole to from the electron density solution. The potential for this plume structure is a weighted sum of the analytic solutions for each separate piece. Using this electric potential, quasi-analytic solutions for the transport of the bubbles are derived using the continuity equation for the plasma with production and loss terms neglected. The analytic models of the electric fields provide incompressible motion that transports the locations of plasma cells but does not change the density of the plasma in each cell. This Lagrangean approach employs a time dependent coordinate mapping of the undisturbed layer grid. Using internal electric potentials of the bubbles and external polarizations of the F-layer as a whole, a transport model yields tilted plasma plumes that move through the F-Region. This time-dependent computer model provides useful plasma densities in a fraction of the time for fully numerical simulations.