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Sondrestrom Radar Observations of the Effect of the IMF by Component on Polar Convection,
SRI INTERNATIONAL MENLO PARK CA
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Average patterns of convection, derived from Sondrestrom radar observations, reveal that the interplanetary magnetic field dawn-dusk component IMF By strongly influences the nighttime polar convection. The convection for one orientation of By is not the mirror image of the other orientation. A positive By seems to organize the velocities such that, at all local times, they are predominantly westward within the radar latitude range. On a case-by-case basis, auroral oval boundaries can be determined by coincident DMSP particle data and by radar-measured E-region densities. On one occasion of positive By, sunward flow i.e., westward flow is observed in the polar cap between dusk and midnight. For large negative By, large southward velocities are observed about three hours before midnight. These are the only times when the predominant velocity component is clearly southward. When By is negative, in the midnight and dawn sectors, the plasma velocities appear random. However, the average drifts are mostly southward. The radar average patterns are compared with theoretical predictions.
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