Rocket Measurements of Auroral-Zone Energetic Electrons at Syowa Station, Antarctica I. Characteristics of Electrons under no Geomagnetic Disturbance

摘要

A sounding rocket measurement was made, using a plastic scintillation counter and two proportional counters, of the high energy electrons greater than 40 keV at Syowa Station (L=6.1), Antarctica, in order to search fundamental properties of the energetic electrons under the geomagnetic quiet condition unaccompanied with auroral phenomena. Energy spectra and pitch angle distributions of the electrons were determined as functions of altitude, on the basis of spin-modulated data obtained in the altitude range 70km-120km. Peak fluxes were found of the order of (10)^3/(cm)^2・ster・sec・keV. The pitch angle distribution over the angle range of 0°-135°peaked at a pitch angle somewhat smaller than 90°, and total integrated fluxes of electrons having pitch angles smaller than 90°were beyond those having pitch angles greater than 90°. Such asymmetry of distribution was established for different energies and altitudes. The exponent of the power law fitting the energy spectrum decreased steadily from 5.7 to 4.0 with increasing pitch angle from 10°to 90°. Fractional contribution of upward and downward electrons is discussed.