A time-dependent gyro-kinetic model of thermal ion upflows in the high-latitude F region
- NASA Marshall Space Flight Center, Huntsville, AL (United States)
- Univ. of Western Ontario, London (Canada)
Ample evidence supports the significance of the high-latitude ionospheric contribution to magnetospheric plasma. Assuming flux conservation along a flux tube, the upward field-aligned ion flows observed in the magnetosphere require high-latitude ionospheric field-aligned ion upflows of the order of 10{sup 8} to 10{sup 9} cm{sup {minus}2} s{sup {minus}1}. Since radar and satellite observations of high-latitude F region flows at times exceed this flux requirement by an order of magnitude, the thermal ionospheric upflows are not simply the ionospheric response to a magnetospheric flux requirement. Several ionospheric ion upflow mechanisms have been proposed, but simulations based on fluid theory do not reproduce all the observed features of ionospheric ion upflows. The concept of a discontinuous neutral exobase and the assumption of a constant and uniform polarization electric field reduce the ion guiding center motion in the frame of a convecting flux tube to simple one-dimensional ballistic trajectories. The authors thus are able to analytically calculate a time and height-dependent ion velocity, parallel and perpendicular temperature, and parallel flux. Using their model, they simulated the response of a convecting flux tube between 500 km and 2500 km to various frictional heating inputs; the results were both qualitatively and quantitatively different from fluid model results, which may indicate an inadequacy of the fluid theory approach. The gyro-kinetic frictional heating model responses to the various simulations were qualitatively similar: (1) initial perturbations of all the modeled parameters propagated rapidly up the flux tube, (2) transient values of the ion parallel velocity, temperature, and flux exceeded 3 km/s, 2x10{sup 4}K, and 10{sup 9} cm{sup {minus}2} s{sup {minus}1}, respectively. 50 refs., 11 figs.
- OSTI ID:
- 166269
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A9 Vol. 99; ISSN JGREA2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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