Electrons in the Van Allen Zone measured with a scintillator on Explorer 14

The energy spectrum of electrons in the energy range from 5 to 160 kev is investigated near the equator, at L shells between 2 and 10, by using scintillator measurements on Explorer 14. We find: (1) peak values of 8×108 electrons/cm2/sec with an average energy of ∼50 kev at L∼5; (2) peak values of 1.6×109 electrons/cm2/sec with an average energy of ∼10 kev at L≳8; (3) time variations of intensity by factors of 10 or less above L∼4 during the 15 days of data under study; and (4) a discontinuity of the energy spectrum at L∼7, with a general tendency for the spectrum to become softer at higher L. The 10-kev electrons measured at L∼8 are trapped in the earth's magnetic field and appear not to be a tail of the outer belt electrons. These electrons are unable, without an accompanying replenishing mechanism, to supply the auroral regions.