The lepton spectra in the kinetic energy ranges 0.2 to 40 GeV for e(-) and
0.2 to 3 GeV for e(+) were measured by the Alpha Magnetic Spectrometer (AMS
) during space shuttle flight STS-91 at altitudes near 380 km. From the ori
gin of the leptons two distinct spectra were observed: a higher energy spec
trum and a substantial second spectrum with positrons much more abundant th
an electrons. Tracing leptons from the second spectra shows that most of th
ese leptons travel for an extended period of time in the geomagnetic field
and that the e(+) and e(-) originate from two complementary geographic regi
ons. (C) 2000 Elsevier Science B.V. All rights reserved.