Abstract
Abstract. In this paper, we consider the mechanism of ion acceleration by dipolarization fronts in the Earth's magnetotail. The statistics of dipolarization front observations by Interball-tail have been collected from 1995 to 1998 (51 events). We demonstrate that near dipolarization fronts bursts of energetic ions are often observed with an average energy of about 100–200 keV. We develop the analytical model of the ion resonance interaction with dipolarization fronts to describe the observed acceleration. We compare the model and the observations to estimate the width of fronts along the dawn-dusk direction, Ry. The mean value is ⟨ Ry ⟩ ~6 RE.
Highlights
IntroductionMultispacecraft missions (Cluster and THEMIS) reveal various mesoscale (a few RE ) transient structures in the Earth’s magnetotail (see review by Sharma et al, 2008)
During the last decade, multispacecraft missions (Cluster and THEMIS) reveal various mesoscale transient structures in the Earth’s magnetotail
One of the mesoscale structures actively studied during the last years are dipolarization fronts (DFs) (Nakamura et al, 2009; Runov et al, 2009, 2011; Schmid et al, 2011, and references therein) – a sharp increase of the Bz component of the magnetic field in the vicinity of the magnetotail neutral plane
Summary
Multispacecraft missions (Cluster and THEMIS) reveal various mesoscale (a few RE ) transient structures in the Earth’s magnetotail (see review by Sharma et al, 2008). One of the mesoscale structures actively studied during the last years are dipolarization fronts (DFs) (Nakamura et al., 2009; Runov et al, 2009, 2011; Schmid et al, 2011, and references therein) – a sharp increase of the Bz component of the magnetic field in the vicinity of the magnetotail neutral plane. In comparison with other mechanisms of particle acceleration by DF, the considered surfatron mechanism can produce a small population of ions with energy larger than keV under magnetotail conditions. If we consider the observed high energy particles as captured and accelerated population, we can estimate the “hidden” (not measured directly) parameters of DFs. We can derive the expression for the DF width along the dawn-dusk direction, Ry. one can determine the spatial scale Ry from the estimates of W and Ey∗ = −(vφ /c)B0z. Lutsenko et al, 2008)
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