Electrostatic emissions studied in high resolution

Abstract

Specific examples are presented for two types of electrostatic emission which have been studied on GEOS 1 and GEOS 2 with high spectral and fast temporal resolution. 1. (A) In the mid-morning hours (6 – 9 LT) the strongest electrostatic emissions are often observed as bursts lasting from less than a second to several hours. Simultaneously rapid changes are observed in the warm electron distribution and at ELF (15 – 450 Hz) only on the large electric antenna. High spectral resolution ( Δf ∼ 11 Hz) shows that these emissions near the plasma frequency (∼ 30 KHz) sometimes display spectral features whose separation in frequency is equal to the frequency of the electrostatic ELF emission in the region of the lower hybrid frequency. 2. (B)Around local midnight following a substrom rapid step like changes occur in the intensity of electromagnetic ELF emission. Simultaneously the normal structured electrostatic ( n + 1 2 f ce emission features are replaced by an intense broad spectrum. Relations between these variations and auroral pulsations Observed at the foot of the field line are presented.