Contrasting dynamics of electrons and protons in the near-Earth plasma sheet during dipolarization

Malykhin, A. Yu.; Григоренко, Е. Е.; Kronberg, Elena A.; Koleva, R.; Ganushkina, N. Y.; Kozak, L.V.; Daly, P. W.

doi:10.5194/angeo-36-741-2018

Cited by 25 publications

(40 citation statements)

References 86 publications

(124 reference statements)

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“…At R < 12 R E , the occurrence peak shifts slightly to earlier MLTs for ions and to the later MLTs for electrons. Malykhin et al () have found the difference between proton behavior and electron behavior near 9 R E in the postmidnight region. It is possible that the diversion between ions and electrons can occur well beyond geosynchronous orbit.…”

Section: Summary and Discussionmentioning

confidence: 99%

Proton and Electron Injection Path at Geosynchronous Altitude

et al. 2019

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Using tens to hundreds of keV proton and electron flux measurements and simultaneous magnetic field measurements from three Geostationary Operational Environmental Satellites [GOES-13 (75°W), GOES-14 (105°W), and GOES-15 (135°W)], we investigate proton and electron injections and their relationship to the substorm current wedge at geosynchronous altitude. Proton and electron injection processes occur only in the initial formation of the substorm current wedge, the width of which is less than 2 hr in local time in the premidnight region, for moderate substorms. Proton injections are closely related to the formation of a substorm current wedge at geosynchronous altitude, and thus the onset of a substorm, even before local dipolarization in the magnetic field. Proton injections take place only under the western upward field-aligned currents of the current wedge. Electron injections in the energy range of <100 keV are tightly coupled with local dipolarization in the magnetic field, and these take place mostly in the central region of the current wedge, extending in the region under the western upward field-aligned currents. Variations in the magnetic field during substorms have also been studied at geosynchronous altitude (e.g.,

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Section: Summary and Discussionmentioning

confidence: 99%

Proton and Electron Injection Path at Geosynchronous Altitude

et al. 2019

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“…Thus, it is appropriate to ask the question, to what extent individual localized dipolarizations integrate into a large-scale dipolarization of the inner magnetosphere characteristic of the substorms expansion (Kepko et al, 2015)? A closely associated question, whether the so-called substorm current wedge (SCW) is composed of individual wedgelets, has received significant attention recently (Birn et al, 2011;Birn & Hesse, 2014b;Forsyth et al, 2014;Liu et al, 2015Liu et al, , 2018Malykhin et al, 2018;Palin et al, 2016;Sergeev et al, 2000). Panov et al (2016) used a fortuitous alignment of magnetospheric spacecraft and ground-based magnetometers and imagers to infer that during a weak substorm (the AE index was about 100 nT) the substorm dipolarization could have been produced by a single BBF.…”

Section: Introductionmentioning

confidence: 99%

Contribution of Bursty Bulk Flows to the Global Dipolarization of the Magnetotail During an Isolated Substorm

et al. 2019

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This paper addresses the question of the contribution of azimuthally localized flow channels and magnetic field dipolarizations embedded in them in the global dipolarization of the inner magnetosphere during substorms. We employ the high-resolution Lyon-Fedder-Mobarry global magnetosphere magnetohydrodynamic model and simulate an isolated substorm event, which was observed by the geostationary satellites and by the Magnetospheric Multiscale spacecraft. The results of our simulations reveal that plasma sheet flow channels (bursty bulk flows, BBFs) and elementary dipolarizations (dipolarization fronts, DFs) occur in the growth phase of the substorm but are rare and do not penetrate to the geosynchronous orbit. The substorm onset is characterized by an abrupt increase in the occurrence and intensity of BBFs/DFs, which penetrate well earthward of the geosynchronous orbit during the expansion phase. These azimuthally localized structures are solely responsible for the global (in terms of the magnetic local time) dipolarization of the inner magnetosphere toward the end of the substorm expansion. Comparison with the geostationary satellites and Magnetospheric Multiscale data shows that the properties of the BBFs/DFs in the simulation are similar to those observed, which gives credence to the above results. Additionally, the simulation reveals many previously observed signatures of BBFs and DFs, including overshoots and oscillations around their equilibrium position, strong rebounds and vortical tailward flows, and the corresponding plasma sheet expansion and thinning.

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“…During the prolonged "secondary" dipolarizations the increases in fluxes of suprathermal electrons, protons and heavy ions are often observed (Nosé et al, 2000;Apatenkov et al, 2007;Asano et al, 2010;Grigorenko et al, 2017;Malykhin et al, 2018a, b). Malykhin et al (2018b) studied the dynamics of fluxes and energy spectra of suprathermal electrons during the prolonged dipolarizations and showed that electrons can be accelerated by a betatron mechanism up to ∼ 90 keV. On the contrary, the behavior of ion energy spectra indicates the nonadiabatic character of ion acceleration in the course of dipolarizations (e.g., Nosé et al, 2000;Grigorenko et al, 2017;Malykhin et al, 2018a).…”

Section: Introductionmentioning

confidence: 99%

Acceleration of protons and heavy ions to suprathermal energies during dipolarizations in the near-Earth magnetotail

et al. 2019

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Abstract. In this work we present an analysis of the dynamics of suprathermal ions of different masses (H+, He+, O+) during prolonged dipolarizations in the near-Earth magnetotail (X>-17RE) according to Cluster/RAPID observations in 2001–2005. All dipolarizations from our database were associated with fast flow braking and consisted of multiple dipolarization fronts (DFs). We found statistically that fluxes of suprathermal ions started to increase ∼1 min before the dipolarization onset and continued to grow for ∼1 min after the onset. The start of flux growth coincided with the beginning of a decrease in the spectral index γ. The decrease in γ was observed for protons for ∼1 min after the dipolarization onset, and for He+ and O+ ions for ∼3 and ∼5 min after the onset respectively. The negative variations of γ for O+ ions were ∼2.5 times larger than for light ions. This demonstrates more efficient acceleration for heavy ions. The strong negative variations of γ were observed in finite energy ranges for all ion components. This indicates the possibility of nonadiabatic resonant acceleration of ions in the course of their interaction with multiple DFs during dipolarizations. Our analysis showed that some fraction of light ions can be accelerated up to energies ≥600 keV and some fraction of oxygen ions can be accelerated up to ∼1.2 MeV. Such strong energy gains cannot be explained by acceleration at a single propagating DF and suggest the possibility of multistage ion acceleration in the course of their interaction with multiple DFs during the prolonged dipolarizations.

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Contrasting dynamics of electrons and protons in the near-Earth plasma sheet during dipolarization

Cited by 25 publications

References 86 publications

Proton and Electron Injection Path at Geosynchronous Altitude

Proton and Electron Injection Path at Geosynchronous Altitude

Contribution of Bursty Bulk Flows to the Global Dipolarization of the Magnetotail During an Isolated Substorm

Acceleration of protons and heavy ions to suprathermal energies during dipolarizations in the near-Earth magnetotail

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