Ionospheric disturbances. Evidence for the contraction of the plasmaphere during severe geomagnetic storms
BS>Continuous measurements of the ionospheric total electron content (TEC) provide a parameter well suited for the study of F-region disturbance effects. In this investigation, five cases of large and rapid drops in TEC observed near the sunset peniod are interpreted as being due to the contraction of the plasmasphere to L values less than 3. A model calculation is performed for the specific case of November 1, 1968 using simultaneous Alouette I data to define the position and magnitude of the ionospheric trough. The results indicate that the motion of a deep trough across the ray path from a geostationary satellite to an observing station can cause drastic changes in the measured amounts of Faraday rotation and therefore in the derived values of TEC. All of the TEC data sources available for the five events are then examined in an attempt to describe more completely the latitude dependence of the effects. It is suggested that during severe geomagnetic storms, the large and rapid decays in TEC during the 18 to 21 LT period to values significantly below normal can be used as a criterion to determine the approximate latitudinal extent of the contracted plasmasphere. (auth)
- Research Organization:
- Air Force Cambridge Research Labs., Bedford, MA
- NSA Number:
- NSA-29-022159
- OSTI ID:
- 4346808
- Journal Information:
- Planet. Space Sci., v. 22, no. 2, pp. 223-236, Other Information: Orig. Receipt Date: 30-JUN-74; Bib. Info. Source: UK (United Kingdom (sent to DOE from))
- Country of Publication:
- United Kingdom
- Language:
- English
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