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

We examine the relationship of energetic equatorial electron flux enhanceme nts occurring near L = 4.2 and 6.6 associated with 26 well-defined high-spe ed solar wind streams (HSSWS) detected by Wind between December 1994 and Se ptember 1996. Events were selected for having high-energy (>2 MeV) geosynch ronous electron daily average fluxes surpassing 10(3) cm(-2) s(-1) sr(-1) f or at least a day as measured by GOES 7 or GOES 9. Los Alamos differential- energy electron data fi-om SOFA (0.2 - 2.0 MeV) at L = 6.6 and the GPS BDD- II dosimeters (0.2 - 3.2 MeV) at L = 4.2 illustrate that flux dropouts are typically observed in all energy channels at both equatorial altitudes with in the fil st day of each event. While SOFA consistently records postdropou t flux enhancements, GPS dosimeters detect equatorial postdropout enhanceme nts in 1.6-3.2 MeV electron fluxes in only 15 of 26 events and all are eith er concurrent (1 event) with or follow (14 events) the geosynchronous incre ases of electrons with similar values of the first adiabatic invariant, mu similar to 2.1 x 10(3) MeV G(-1). In addition, 10 of 15 GPS growth periods produced electron enhancements above predropout levels. For all 26 events t he phase space density for electrons of similar mu is consistently greater at geosynchronous altitude than at GPS equatorial altitude. The critical fa ctor leading to GPS L = 4.2 electron flux enhancements is elevated geomagne tic activity levels Of Kp similar to 3.0 - 3.5 and above Tor extended perio ds. A combination of enhanced solar wind ram pressure, electric field (with B-south), and velocity also appears to be necessary. If outward phase spac e density gradients are combined with the large electric fields generally a ccompanying elevated Kp, then sufficient conditions may exist to promote th e inward radial diffusive transport of equatorial electrons that ultimately lead to electron flux enhancements at GPS altitudes. Comparison of observe d and theoretically estimated electron growth rates is consistent with this picture of inward radial transport for these equatorially mirroring partic les with mu similar to 2.1 x 10(3) MeV G(-1) at L = 4.2.