Note on the electron energy spectrum in the inner Van Allen Belt

The energy spectrum of trapped electrons predicted by the neutron-albedo theory was tested experimentally with a magnetic electron spectrometer for the energy range 40≤E≤110 kev. This detector was flown on the State University of Iowa radiation research satellite Injun I at an altitude of about 1000 km in the inner radiation zone over South America. Another detector on the same satellite measured the directional intensity of electrons with E≥40 kev. The data are consistent with a peak directional intensity of electrons in this region of N(E)∼104 exp ( −E/160) particles (cm2 sec ster kev)−1, or with a power-law spectrum with a differential exponent of −(1.0±0.2) for 40≤E≤110 kev. This result is significantly in disagreement with the predictions of the neutron-albedo theory.