We report here the results of modeling work aimed at understanding the development of ionospheric O+ field-aligned upflows that develop in response to high-latitude E¿B drift induced frictional heating. The model used is a collisional semikinetic model which includes ion-neutral resonant charge exchange and polarization collisions as well as Coulomb self-collisions. It also includes the process of chemical removal of O+ as well as all of the macroscopic forces: ambipolar electric, gravity, magnetic mirror, and centripetal. Model results show the development of several types of non-Maxwellian velocity distributions including toroids at low altitude, distributions with large heat flow in the perpendicular component at intermediate altitudes, and distributions with a separate upflowing population or upward superthermal tail at high altitudes.

Whenever the convection electric field increases from a small value (<25 mV/m) to a large value (100--200 mV/m) in 6 min or less large upflows develop with parallel drift speeds which peak (below 1000 km) at values between 500 m/s and 2 km/s, parallel fluxes which peak between 6.0¿108 and 3.2¿109 cm-2 s-1, and parallel per particle heat flows which peak between 8.0¿10-9 and 8.0¿10-8 ergs cm/s. The higher values in these ranges occur for a cooler neutral atmosphere, with a larger convection electric field that is turned on quickly. The model produces field-aligned O+ flow speeds that are larger than those produced by a 20-moment generalized transport model but smaller then those produced by an isotropic hydrodynamic model for comparable values of the convection electric field and convection turn on times. The model results compare favorably with some topside satellite and radar data. ¿ American Geophysical Union 1994