Rocket measurements of energetic particles: 2. Electron results

Abstract

Fluxes, energy spectrums, and angular distributions of electrons with energies greater than 150 kev have been measured by five detectors on each of two rockets fired along a magnetic field line near L = 5.6. The flux above 150 kev increased with altitude along the field line to a value near 105 electrons/cm2 sec at an altitude of 400 km. The angular distributions were peaked at a pitch angle near 90° with a width less than the detector entrance aperture of 20°. The flux coming down the field line was about 1% of that mirroring and 3 times that coming up the field line. The energy spectrums were functions of altitude and pitch angle, the e-folding energy varying between about 55 and 280 kev. There were no significant intensity fluctuations on a time scale of several milliseconds to 1 second. Sinusoidal-like intensity fluctuations of a factor of 2 and a period near 19 seconds were observed. The qualitative features of the angular distributions and energy spectrums are explicable in terms of atmospheric diffusion of the electrons. Detailed properties of the 19-second periodicity require that an electron source be essentially on the field line of observation and that at least some of the electrons come directly from the source with insignificant atmospheric diffusion. The data are interpreted in terms of the nonconservation of the adiabatic invariants in the equatorial plane, resulting in the scattering from an equatorial reservoir of electrons observed at low altitudes. The data can also be explained in terms of low-altitude acceleration mechanisms or of the nonconservation of the adiabatic invariants along the entire length of the field line.