Stability of the polar wind

Journal Article · Wed Apr 01 00:00:00 EST 1987 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA092iA04p03409· OSTI ID:6836206

Barakat, A R; Schunk, R W

The classical polar wind is an ambipolar outflow of thermal plasma from the terrestrial ionosphere at high latitudes. At altitudes above about 3000 km, the H/sup +/ flow becomes supersonic and collisionless, and the H/sup +/ velocity distribution becomes non-Maxwellian. The non-Maxwellian features include a temperature anisotropy, with the parallel H/sup +/ temperature greater than the perpendicular temperature (T/sub i//sup parallel/ > T/sub i//sup perpendicular/), and an asymmetry, with an elongated tail in the upward direction. These distortions from a Maxwellian increase as the H/sup +/ gas escapes in the diverging geomagnetic field, and at 10 earth radii the parallel-to-perpendicular temperature ratio is about 50 and the elongated tail is sufficiently long to move the drift velocity point off the peak of the distribution function. The stability of these highly non-Maxwellian H/sup +/ velocity distributions was studied with regard to the excitation of electrostatic waves and the plasma was found to be remarkably stable for a wide range of electron temperatures (0.1less than or equal to T/sub e//T/sub i//sup parallel/10). This indicates that the various macroscopic formulations of the classical polar wind are valid. The stability of a perpendicularly heated polar wind was also studied, assuming bulk perpendicular heating of H/sup +/ in the cusp, followed by the subsequent convection of the heated plasma into the polar cap. Two regions of instability were found.

• Research Organization: Center for Atmospheric and Space Sciences, Utah State University, Logan
• OSTI ID: 6836206
• Journal Information: J. Geophys. Res.; (United States), Vol. 92:A4
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
IONOSPHERE
PLASMA DRIFT
CONVECTION
ELECTRON TEMPERATURE
ELECTROSTATICS
EXCITATION
HYDROGEN IONS
ION TEMPERATURE
PLASMA HEATING
POLAR REGIONS
STABILITY
SUPERSONIC FLOW
VELOCITY
WIND
CHARGED PARTICLES
EARTH ATMOSPHERE
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
FLUID FLOW
HEAT TRANSFER
HEATING
IONS
MASS TRANSFER
PLANETARY IONOSPHERES
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena