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Topside Ionospheric Trough Morphology at Mid- and High-Latitudes.
Rept. for 1 Oct 77-31 Mar 78,
REGIS COLL RESEARCH CENTER WESTON MASS
Pagination or Media Count:
The main trough in the topside ionosphere has been studied using the thermal positive ion and electron densities measured over a three year period 1969-1972 by means of spherical electrostatic analyzers aboard the ISIS I and INJUN V satellites in the 560-3600 km altitude range. The trough is found to be a persistent feature at night with an occurrence frequency of approximately 95. The occurrence frequency decreases to approximately 60 near the dawn-dusk meridian and to approximately 48 near local noon. At altitudes below about 1500 km during quiet to moderate conditions Kp or 3 the trough equatorward boundary is found at L 3.5 or - 0.5 near midnight and L 12.5 or - 1.0 near local noon. The trough equatorward location on the nightside is in good agreement with published plasmapause locations. Near local noon the trough occurs at the equatorward edge of the magnetospheric cleft and is at significantly higher L values than those reported for the dayside plasmapause. The seasonal variation of the trough location at a given local time is negligible except near sunrise.
APPROVED FOR PUBLIC RELEASE