Rocket Observation of Suprathermal Electrons in the Energy Range 6.5-23 keV at Midlatitude

Electrons of energies between 6.5 and 23keV have been observed from a sounding rocket with a thin-window (37μg/cm2 polypropylene) proportional counter in the altitude range between 140km and 326km at the geomagnetic latitude of 20°N, the L-value at the apogee being 1.17.The directional dependence of the electron flux with respect to the magnetic line of force indicates that these electrons consist of two components, the one peaked perpendicular to the line of force and the other being isotropic in the upper hemisphere. The former is considered to be geomagnetically trapped and the latter to be precipitating along the line of force. The flux ratio of the trapped to the isotropic components is 0.77±0.12 and 1.7±0.2 at 200km and 300km, respectively. The isotropic component does not change between these altitudes, while the trapped component increases nearly twice as much. The observed intensities of the trapped and the isotropic electrons at 300km are (310±20) electrons·cm-2·sec-1·(4π sterad)-1 and (27±4) electrons·cm-2·sec-1·sterad-1, respectively.