Accession Number : ADA188058

Title :   Upper-Thermospheric Observations and Neutral-Gas Dynamics at High Latitudes During Solar Maximum.

Descriptive Note : Doctoral thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s) : Tschan, Christopher R

PDF Url : ADA188058

Report Date : Jan 1987

Pagination or Media Count : 316

Abstract : The objective of this theses was to understand the neutral gas dynamics in the high latitude regions of the Earth's upper thermosphere. An understanding of the morphology of the neutral winds and the forces which drive or modify them. A unique 70 orbit December solstice dataset was established, which included satellite neutral winds and other supporting data from Dynamics Explorer 2 (DE-2), with coverage of both polar caps during the same orbit. Analysis of this data led to the characterization of four basic high latitude neutral-wind signature categories for each hemisphere under various interplanetary-magnetic-field (IMF) configurations. Furthermore, sunward neutral winds on the duskside of the polar cap, resulting from the mapping of the twin cell ion convection onto the neutral gas through ion-neutral collisions, were well established in all cases. However, the dawnside sunward neutral winds were not as well established. The existence of a small region of dawnside neutral winds was noted in the winter northern hemisphere, but was usually absent in the summer southern hemisphere. Analysis of the individual neutral gas forces for solar-maximum December-solstice from the NCAR thermospheric general circulation model (TGCM), led to the realization that the polar cap pressure gradient force in the winter northern hemisphere had a different orientation than in the summer southern hemisphere, resulting in the observed dawnside neutral-wind signatures. The variations in the orientation of the polar cap pressure gradient forces in opposite hemispheres were ascribed to temperature gradients, resulting from a superposition of solar EUV, Joule and cusp heating, as well as density variations.

Descriptors :   *GAS DYNAMICS, *THERMOSPHERE, ARTIFICIAL SATELLITES, CELLS, CONVECTION, GASES, HEATING, HIGH LATITUDES, IONS, NEUTRAL, NORTHERN HEMISPHERE, POLAR CAP, TEMPERATURE GRADIENTS, THESES, WIND, WINTER, PARTICLE COLLISIONS

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE