OSO-4 ELECTRON OBSERVATIONS IN THE EDGE OF THE INNER RADIATION ZONE.

Unidirectional electron flux intensities and differential energy spectra for 1. 25 sL si. 9 measured in March 1968 using a directional electron spectrometer on the OSO-4 spacecraft are reported.Unidirec tional differential intensities normal to the field line (j.) are given for E ^80. 5 keV and for eight energy ranges to 5. 33 MeV.Integral pitch-angle distributions are pre sented.Pitch-angle plots are also shown for November 1967 data.Favorable com parisons have been made with LLL's OGO-5 electron energy-spectra (March 1968), particularly at energies less than 1.0 MeV.The purpose of this paper is to exhibit portions of the OSO-4 electron data.These data have been organized in terms of con ventional space coordinates.Little effort has been made to analyze the data in terms of physical phenomena occurring in the earth's radiation belt.However, the data appear reasonable on the basis of expected fluxes and spectra resulting from our current knowledge of the inner zone.The orbiting spectrometer has pro vided useful measurements of energyanalyzed trapped electron fluxes and Although the instrument was also de signed to "ieasu re protons (1.73 to 65 MeV), the proton data was made invalid due to penetrating high-energy protons.Data were accumulated along the edge of the inner belt for 1.1 sL s2. 2 within a narrow band of X values that approach ed within a few degrees of the magnetic equa tor at the lower Lvalues and increased to about 45° at the higher L values.It appears that the more complete analysis of OSO-4 electron data can, in part, fill a gap in the time history of inner-zone electron events during the 1967-1968 time period.angular distributions on the outer edges of the inner Van Allen zone during late 1967 and early 1968.The spatial cov erage during this period was attained by means of a near-circular orbit that constrained measurements to a narrow range of X values on each L-shell.Nevertheless, this constraint is offset by the advantages offered by acquisition of many data samples over a compact region of space.Several investigators have followed the time decay of trapped electron fluxes since the Starfish nuclear detonation on