A drastic change in the outer zone energetic electron distribution in the magnetosphere during Nov. 3-4, 1993 has been observed by SAMPEX. There was an overall flux drop after the strong activity associated with large negative Bz and strong solar wind pressure on later Nov. 3. In particular, the most energetic electrons ( > 3 MeV) appeared to be completely lost for L=3-8. This was a three order of magnitude decrease in the SAMPEX measurement down to the cosmic ray background of the detector. The decrease started at the beginning of Nov. 4 and continued for about 12 hours. There was no clear sign of enhanced electron precipitation which could lead to the total loss of the electrons. The outer zone electron fluxes increased back to higher level than before and moved to lower L-shell (L<3) over a time span of a day.
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