EFFECTS OF FRICTIONAL ION HEATING AND SOFT-ELECTRON PRECIPITATION ON HIGH-LATITUDE F-REGION UPFLOWS

Observed ionospheric F-region upflows associated with convection-drive n frictional ion heating and soft electron precipitation at high latit udes arl modeled with a dynamic ionospheric fluid code. Precipitating soft (less than or equal to 1 keV) auroral electrons are effective in rapidly enhancing the F-region ionization and electron temperature, wh ich leads to a strong upward plasma expansion. It is shown, for exampl e, that an electron flux of 1 erg cm(-2) s(-1) with a characteristic e nergy df 150 eV can produce a 10(9) cm(-2) s(-1) Of outflow at altitud es of 700-800 km. The more widely-recognized Convection ion heating is indicated to be significant but somewhat smaller effects on the upflo ws. We have performed comparisons with published HILAT and DE-2 observ ations. Using a latitudinal distribution of ionospheric flux tubes wit h ''inputs'' of the observed average precipitating electron energies, energy fluxes and convection drift velocities, we find satisfactory ag reement with latitudinal profiles of ion upflow velocities, densities, fluxes, and ion and electron temperatures. Therefore, we suggest that the combined effects of soft electron precipitation and frictional io n heating may be identified as the principal drivers of these upflows.