Energization pf polar-cusp electrons at the noon meridian

Observations gained with an electrostatic analyzer on board the low altitude, polar orbiting Aeriel 4 satellite demonstrate that the directional, differential spectra of polar-cusp electron intensities are regulated by the sign of the interplanetary magnetic field (IMF) elevation angle. In the energy range 200 is approximately less than E is approximately less than 700 eV, spectra of polar cusp electron intensities were not observed to respond to changes in the sign of the IMF elevation angle. At greater densities, spectra were found to be significantly harder when the IMF angle of elevation was greater than 0 deg, with a factor of approximately 10 typical for 2-keV electron intensities. These enhanced intensities appear to be localized within approximately a one hour sector of magnetic local time centered on the noon meridian