Upward high-energy field-aligned electron beams above the polar edge of auroral oval: observations from the SKA-3 instruments onboard the Auroral Probe (Interball-2)

I I Cherkashin,B A Ilyin,L S Gorn,A K Kuzmin,F K Shuiskaya,B I Khazanov,A A Klimashov,M V Iovlev,A Y Safronov,V A Stepanov,Y I Galperin

doi:10.1007/s005850050675

Abstract

A new phenomenon was found at the polar edge of the auroral oval in the postmidnight-morning sectors: field-aligned (FA) high-energy upward electron beams in the energy range 20â40 keV at altitudes about 3RE, accompanied by bidirectional electron FA beams of keV energy. The beam intensity often reaches more than 0.5Â·103 electrons/sÂ·srÂ·keVÂ·cm2, and the beams are observed for a relatively long time (~3Â·102â103s), when the satellite at the apogee moves slowly in the ILAT-MLT frame. A qualitative scenario of the acceleration mechanism is proposed, according to which the satellite is within a region of bidirectional acceleration where a stochastic FA acceleration is accomplished by waves with fluctuating FA electric field components in both directions.Key words. Ionosphere (particle acceleration; wave-particle interactions) Â· Magnetospheric physics (magnetosphere-ionosphere interactions)

Highlights

The Interball Auroral Probe carries the SKA-3 experiment whose goal was to investigate high energy particle intensities at high latitudes
We present a case study of upward electron beams in the energy range 20±40 keV only, i.e., at energies which are substantially higher than typical auroral electron energies
Some results of observations made by the time-of- ̄ight instruments EM-1-1 and EM-1-2 are presented here

Summary

Introduction

The Interball Auroral Probe carries the SKA-3 experiment whose goal was to investigate high energy particle intensities at high latitudes (i.e. above the auroral oval and inside the northern polar cap). In several cases at the polar edge of the oval in the postmidnight ± morning sectors in the energy range 20±40 keV the SKA-3 instruments detected ®eld-aligned high-energy upward electron beams (see Galperin, 1997; Stepanov et al, 1997). These beams were observed as ®eld-aligned (FA) monodirectional (upward), while simultaneous measurements made by the ION spectrometer Interesting features of the low-energy ions observed simultaneously with the upward high-energy electron beams are beyond the scope of this study

Results

Discussion

Conclusion