STATISTICAL RELATIONSHIPS BETWEEN HIGH-LATITUDE IONOSPHERIC F-REGION TOPSIDE UPFLOWS AND THEIR DRIVERS - DE-2 OBSERVATIONS

A statistical analysis is conducted on the relationships among high-la titude topside (850 - 950 km altitude) ionospheric plasma parameters a nd precipitating soft (less than or equal to 1 keV) electron character istics based on DE 2 satellite measurements from seven auroral zone pa sses. The parameters examined statistically for these relationships ar e 1137 independent samples of the field-aligned ion flow velocities, f luxes, Mach numbers, densities, ion and electron temperatures, and sof t electron energy fluxes and average or characteristic energies. We fi nd that both ion upward velocities and upward fluxes are well correlat ed with electron and ion temperatures. Least squares fits to the data averaged in restricted bins show the following correlation coefficient s: Ion upward velocity with T-e, correlation coefficient r= 0.97; with T-i, r= 0.94; for ion upflux with T-e, r= 0.97; with T-i, r= 0.91. Th e somewhat higher correlations with T-e than T-i of both upflow veloci ties and upfluxes suggest the important role of enhanced ambipolar ele ctric fields associated with enhanced T-e, as heated by both direct co llisions with the precipitating electrons as well as downward magnetos pheric heat fluxes. The largest (greater than or equal to 10(10) ions cm(-2) s(-1)) ion upfluxes are associated with ''ultrasoft'' electron precipitation having average energies of less than or equal to 80 eV. Significant anticorrelations of electron (r= -0.90) and ion (r= -0.89) temperatures with the average energies of the precipitating soft elec trons suggest that for the same precipitation energy flux, the lowest- energy precipitating electrons are most effective in heating the topsi de thermal electrons. Finally, analysis of ion field-aligned flow Mach numbers shows that these Mach numbers were almost always less than 0. 4 and are typically less than 0.2. Such Mach number measurements sugge st that low-speed approximations in fluid transport models are usually valid for less than or equal to 1000 km altitude, even at high latitu des.