Pitch Angle Distribution of > 40 keV Auroral Electrons Observed at Rocket Altitudes (a. Precipitating Particles and Auroras) (Proceedings of the Second Symposium on Coordinated Observations of the Ionosphere and Magnetosphere in the Polar Regions : Part I)

Abstract

Pitch angle distributions of auroral electrons with energies greater than 40 keV measured by three sounding rockets (S-210JA-20, -21 and S-310JA-2), which were launched from Syowa Station, Antarctica, during moderate disturbances of auroral activity, are presented. The observations were carried out in the altitude range up to 220 km near magnetic midnight. It is shown that pitch angle distributions above 110 km depend upon both energy and altitude. This is in contrast with pitch angle distributions measured at the quiet time or in the northern polar region, where the trapped type distribution with a peak at 90°pitch angle is observed regardless of energy and altitude. A possible influence of auroral X-rays on the observation results is discussed in connection with pitch angle.