Enhancement of equatorial energetic electron fluxes near L = 4.2 as a result of high speed solar wind streams

We examine the relationship of energetic equatorial electron flux enhancements occurring near L = 4.2 and 6.6 associated with 26 well-defined high-speed solar wind streams (HSSWS) detected by Wind between December 1994 and September 1996. Los Alamos differential-energy electron data from SOPA at L =...

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Bibliographic Details
Published in:Journal of Geophysical Research 2000-10, Vol.105 (A10), p.23
Main Authors: Hilmer, R V, Ginet, G P, Cayton, T E
Format: Article
Language:English
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Summary:We examine the relationship of energetic equatorial electron flux enhancements occurring near L = 4.2 and 6.6 associated with 26 well-defined high-speed solar wind streams (HSSWS) detected by Wind between December 1994 and September 1996. Los Alamos differential-energy electron data from SOPA at L = 6.6 and the GPS BDD-II dosimeters at L = 4.2 illustrate that flux dropouts are typically observed in all energy channels at both equatorial altitudes within the first day of each event. While SOPA consistently records postdropout flux enhancements, GPS dosimeters detect equatorial postdropout enhancements in 1.6-3.2 MeV electron fluxes in only 15 of 26 events. In addition, 10 of 15 GPS growth periods produced electron enhancements above predropout levels. The critical factor leading to GPS L = 4.2 electron flux enhancements is elevated geomagnetic activity levels of Kp in the 3.0-3.5 range and above for extended periods. A combination of enhanced solar wind ram pressure, electric field (with B-south), and velocity also appears to be necessary. If outward phase space density gradients are combined with the large electric fields generally accompanying elevated Kp, then sufficient conditions may exist to promote the inward radial diffusive transport of equatorial electrons that ultimately lead to electron flux enhancements at GPS altitudes. (Author)
ISSN:0148-0227