Upper-thermospheric observations and neutral-gas dynamics at high latitudes during solar maximum. Doctoral thesis

Technical Report · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5268818

Tschan, C R

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 that drive or modify them. A unique 70-orbit December solstice data set 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 these 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.

• Research Organization: Air Force Inst. of Tech., Wright-Patterson AFB, OH (USA)
• OSTI ID: 5268818
• Report Number(s): AD-A-188058/2/XAB; AFIT/CI/NR-87-135D
• Country of Publication: United States
• Language: English

Related Subjects

640104 -- Astrophysics & Cosmology-- Solar Phenomena
640200* -- Atmospheric Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGED PARTICLES
CONVECTION
EARTH ATMOSPHERE
EARTH PLANET
ENERGY TRANSFER
FLUIDS
GASES
GEOGRAPHICAL VARIATIONS
HEAT TRANSFER
HEATING
INTERACTIONS
IONS
LATITUDE EFFECT
MASS TRANSFER
NORTHERN HEMISPHERE
PLANETS
POLAR REGIONS
SOLAR ACTIVITY
SOLAR WIND
TEMPERATURE GRADIENTS
THERMOSPHERE
VARIATIONS