Accession Number:

ADA232372

Title:

Thermal Ion Upwelling in the High-Altitude Ionosphere

Descriptive Note:

Doctoral thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1990-01-01

Pagination or Media Count:

242.0

Abstract:

High latitude observations of thermal ion outflows, traditionally known as the polar wind, and heavy ion upwellings, consisting chiefly of heated O, suggest that the terrestrial ionosphere acts as an important,and at times, dominant source of ions for the magnetosphere. The topside ionospheric processes responsible for modulating both types of polar ion flows were examined to quantify the magnitudes and compositional variability of steady-state polar wind flows and to identify the role of low-altitude frictional heating in transient heavy 0 upwellings. Theoretical and experimental approaches were used to elucidate the high-latitude processes that influence ionospheric source strength and transient behavior. A time-dependent hydrodynamic model was used to examine solar cycle and seasonal dependencies under steady-state assumptions. Seasonal influences were found with large wintertime flux variations for both ions caused by ionization source strengths. A marked shift towards 0 enriched upwellings occurred at solar maximum and for wintertime, at certain noontime locations. The role of low-altitude ion frictional heating was examined by coupling the National Center for Atmospheric Research - ThermosphereIonosphere General Circulation Model NCAR-TIGCM to the polar wind model to specify time-dependent frictional heating during a period of observed high-altitude O outflow. Preferential 0 heating resulted in a factor of four increase in modeled 0 fluxes, which coincides in both space and time with the observed heavy ion outflows. Finally, the role of frictional heating and global heating morphology was related to observations of high-altitude ion outflows using Dynamics Explorer-2 satellite data and incoherent scatter radar observations.

Subject Categories:

  • Atmospheric Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE