Coupling of transient plasma structures observed in the plasma sheet boundary layer and in the auroral region Original Research Article

We present a statistical study of high velocity ion beams (beamlets) observed by Interball-1 (Tail Probe) and Interball-2 (Auroral Probe) satellites. In both data sets beamlets manifest themselves as bursty plasma events with duration ∼60s and ion energies about several keV accompanied by cold (200–300eV) electrons. We used an epoch superposition technique to define statistically the beamlet registration zones in the geomagnetic tail (X∼-25Re) as well as in the auroral region. We have found that in the Earth magnetotail beamlets are localized at about 0.6Re above the plasma sheet (PS) boundary. This distance corresponds to the invariant latitude interval of ∼0.5° from the high-latitude PS boundary. The same statistical analysis of Interball-Auroral data has shown that at the middle altitudes (∼3Re) bean-lets are registered also poleward from the high-latitude PS boundary inside a 0.8° latitudinal interval, that is in good agreement with Interball-Tail data. We made also a statistical analysis of beamlet energies versus latitude for both Interball-Auroral and Interball-Tail data. The analysis has shown the similar beamlet energy dependencies on latitude in the middle-altitude and in the mid-tail regions. When interplanetary magnetic field (IMF) was mostly southward beamlet energies increase with latitude while for northward IMF the inverse beamlet energy dependence is observed. Our statistical analysis proves that in both regions we encounter the similar phenomenon of transient plasma energization in distant parts of the Earthʹs magnetotail.