Dayside ion frictional heating: EISCAT observations and comparison with model results

Details Dayside ion frictional heating: EISCAT observations and comparison with model results Dayside ion frictional heating: EISCAT observations and comparison with model results

Jun 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995jatp...57..775d&link_type=abstract

Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169), vol. 57, no. 7, p. 775-793

Physics

13

Daytime, F Region, Ion Temperature, Ionospheric Electron Density, Ionospheric Heating, Kinetic Friction, Atmospheric Models, Comparison, Eiscat Radar System (Europe), Temperature Profiles, Velocity Distribution

Scientific paper

An extended period of intense dayside ion frictional heating was observed on 3 April 1992 with the UHF radar of the European Incoherent Scatter (EISCAT) facility during a run of the common program CP-I-J. The elevated F-region ion temperature resulted from an enhancement in the ion drift velocity, principally in the field-orthogonal zonal direction, which steadily increased, in a westward direction, to a value in excess of 2 km/s during a 4 h interval commencing at approximately 10 UT (12 MLT). The maximum enhancement in the field-parallel ion temperature measured at 300 km altitude exceeded 700 K. The electron concentration in the F-region was substantially depleted during the interval of ion frictional heating, which further resulted in an increase in the F-region electron temperature as, at the local time of the event, the plasma was solar illuminated. A zonal E logical and B velocity signature modeling that observed over EISCAT during the aforementioned interval was superimposed on the Sheffield University plasmasphere and ionosphere model (SUPIM), previously used to study the effects of sub-auroral ion drifts (SAID). The model yields densities, temperatures and field-aligned velocities for the six major ion species and for the electrons, and has recently been modified to account for O(+) temperature anisotropy. The plasma parameters modeled at F-region altitudes were compared with those measured by the EISCAT radar and, although they tended to exhibit the same general trends, the model results predicted substantially larger field-parallel ion temperature enhancements than were observed. However the inclusion of a time-dependent calculated neutral wind, caused by ion drag, reduced the modeled field-parallel ion temperature to the values measured by EISCAT without severely affecting the other parameters. During extended periods of high ion flow, particularly on the dayside, an enhanced neutral wind becomes highly significant in determining the extent of frictional heating of the ion population.

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