Accession Number : ADA116848

Title :   Electron Velocity Shear Instability in the Auroral Ionosphere.

Descriptive Note : Memorandum rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s) : Keskinen,M J ; Huba,J D

PDF Url : ADA116848

Report Date : 25 Jun 1982

Pagination or Media Count : 38

Abstract : A linear electrostatic kinetic theory of velocity sheared electron streams flowing parallel to the geomagnetic field is presented. Our development, which includes the effects of density gradients, background ions and electron collisions, is valid for arbitrary T sub e/T sub i, where T sub e and T sub i are the electron and ion temperatures, respectively. For applications to the auroral ionosphere, we find that the interface between downward flowing hot electrons and upward flowing return current cold electrons, commonly seen near auroral arcs, is unstable to a high frequency electron velocity shear driven instability. The mode is characterized by gamma less than or = .001 omega pe and r sub Li k to the -1 power r sub Le, where gamma is the growth rate, omega pe is the electron plasma frequency, k is the wavenumber, and r sub L alpha is the mean Larmor radius of species alpha. In the nonlinear regime, it is anticipated that this instability can evolve into a vortex configuration and as a result, can act as a block near the edges of the electron flow. (Author)

Descriptors :   *Geomagnetism, Electron emission, Electron density, Aurorae, Ionosphere, Kinetic theory, Interfaces

Subject Categories : Astrophysics
      Geomagnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE