Note on the Electron Energy Spectrum in the Inner Van Allen Belt

Department of Physics and Astronomy ~ / ’, , State University of Iowa, Iowa city jQ s CJ 17 , w=,. > Abstract. The energy spectrum of trapped electrons predicted by the neutron-albedo theory waa tested experimentally with a magnetic electroh spectrometer for the energy range 40 5 E 5 110 kev. This detector waa 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 2 40 kev. The data are consistent with a peak directional intensity of electrons in this region of N ( E ) lo4 exp ( -E/160) particles (cml sec ster kev)-l, or with a power-law spectrum with a differential exponent of -(1.0 f 0.2) for 40 5 E 5 110 kev. This result is significantly in disagreement with the predictions of the neutron-albedo theory.