Observations and simulations of non-local acceleration of electrons in magnetotail magnetic reconnection events

Ashour‐Abdalla, M.; El‐Alaoui, M.; Goldstein, M. L.; Zhou, Meng; Schriver, D.; Richard, R. L.; Walker, Raymond J.; Kivelson, M. G.; Hwang, Kyotaek

doi:10.1038/nphys1903

Cited by 168 publications

(197 citation statements)

References 34 publications

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“…It was shown that the betatron and Fermi mechanisms can be responsible for the increases in the suprathermal electron flux at and behind a DF (e.g., Asano et al, 2010;Ashour-Abdalla et al, 2011;Fu et al, 2011Fu et al, , 2012a. Gabrielse et al (2016) demonstrated that a localized pulse of the inductive electric field associated with the earthward-propagating localized DFs or DFBs can accelerate electrons to suprathermal energies and, thus, be considered as an important source of short-lived (≤ 10 min) injections.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Abstract. The fortunate location of Cluster and the THEMIS P3 probe in the near-Earth plasma sheet (PS) (at X ∼ −7-−9 R E ) allowed for the multipoint analysis of properties and spectra of electron and proton injections. The injections were observed during dipolarization and substorm current wedge formation associated with braking of multiple bursty bulk flows (BBFs). In the course of dipolarization, a gradual growth of the B Z magnetic field lasted ∼ 13 min and it was comprised of several B Z pulses or dipolarization fronts (DFs) with duration ≤ 1 min. Multipoint observations have shown that the beginning of the increase in suprathermal (> 50 keV) electron fluxes -the injection boundary -was observed in the PS simultaneously with the dipolarization onset and it propagated dawnward along with the onset-related DF. The subsequent dynamics of the energetic electron flux was similar to the dynamics of the magnetic field during the dipolarization. Namely, a gradual linear growth of the electron flux occurred simultaneously with the gradual growth of the B Z field, and it was comprised of multiple short (∼ few minutes) electron injections associated with the B Z pulses. This behavior can be explained by the combined action of local betatron acceleration at the B Z pulses and subsequent gradient drifts of electrons in the flux pile up region through the numerous braking and diverting DFs. The nonadiabatic features occasionally observed in the electron spectra during the injections can be due to the electron interactions with high-frequency electromagnetic or electrostatic fluctuations transiently observed in the course of dipolarization.On the contrary, proton injections were detected only in the vicinity of the strongest B Z pulses. The front thickness of these pulses was less than a gyroradius of thermal protons that ensured the nonadiabatic acceleration of protons. Indeed, during the injections in the energy spectra of protons the pronounced bulge was clearly observed in a finite energy range ∼ 70-90 keV. This feature can be explained by the nonadiabatic resonant acceleration of protons by the bursts of the dawn-dusk electric field associated with the B Z pulses.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…The energization observed at DFs has been attributed to betatron and/or (first order) Fermi acceleration due to the local magnetic pile-up signature of DFs and the large-scale shortening of the magnetic field lines caused by radial convection of DFs (Birn et al 2004;Ashour-Abdalla et al 2011;Fu et al 2011) in association with conservation of the first and second adiabatic invariants, respectively. The energization occurring at DFs can also arise from non-adiabatic processes, including wave-particle interactions (Deng et al 2010b;Hwang et al 2011a;Hwang et al 2014a).…”

Section: Betatron and Stochastic Accelerationmentioning

confidence: 99%

“…Numerous DF observations at the near-Earth plasmasheet by Cluster (e.g., Nakamura et al (2002);Hwang et al (2011a);Fu et al (2011Fu et al ( , 2012; Schmid et al (2012);Hwang et al (2014a)) and THEMIS (e.g., Runov et al 2009;Sergeev et al 2009;Deng et al 2010b;Dubyagin et al 2010;Zhou et al 2010;Ashour-Abdalla et al 2011) have shown that DFs predominantly propagate earthward along the radial direction. Occasionally, however, as was the case for DF 6, a DF is observed to propagate tailward.…”

Section: Plasma Phenomena As Measured In Three Dimensionsmentioning

confidence: 99%

“…) Another possibility is that multiple DFs are related to the patchiness of near-Earth tail reconnection. Large-scale kinetic simulations (Ashour-Abdalla et al 2011) show that multiple reconnection sites appear over the entire near-Earth tail current sheet for this event.…”

Section: Plasma Phenomena As Measured In Three Dimensionsmentioning

confidence: 99%

“…DFs are thought to result from magnetic reconnection in which the exhaust jets and entrained magnetic fluxes from the reconnection region pile up, forming a front of increased current-sheet-normal magnetic field (Hoshino et al 2001;Hoshino 2005;Nakamura et al 2009;Sitnov et al 2009;Fu et al 2013). DFs have drawn wide attention because they significantly affect the acceleration and transport of plasmas (see e.g., Sergeev et al 2009;Zhou et al 2009;Deng et al 2010b;Ashour-Abdalla et al 2011;Fu et al 2011;Hwang et al 2011a;Birn et al 2013). DFs are also thought to play a significant role in populating the inner magnetosphere by transporting plasmas from the mid-tail (15-30 R E ) to the near-Earth (10-15 R E ) plasmasheet and, in some cases, into the inner magnetosphere (Delcourt et al 1990;Delcourt 2002;Jones et al 2006;Runov et al 2009;AshourAbdalla et al 2011).…”

Section: Plasma Phenomena As Measured In Three Dimensionsmentioning

confidence: 99%

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Multipoint observations of plasma phenomena made in space by Cluster

et al. 2015

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Plasmas are ubiquitous in nature, surround our local geospace environment, and permeate the universe. Plasma phenomena in space give rise to energetic particles, the aurora, solar flares and coronal mass ejections, as well as many energetic phenomena in interstellar space. Although plasmas can be studied in laboratory settings, it is often difficult, if not impossible, to replicate the conditions (density, temperature, magnetic and electric fields, etc.) of space. Single-point space missions too numerous to list have described many properties of near-Earth and heliospheric plasmas as measured both in situ and remotely (see http://www.nasa.gov/missions/#.U1mcVmeweRY for a list of NASA-related missions). However, a full description of our plasma environment requires three-dimensional spatial measurements. Cluster is the first, and until data begin flowing from the Magnetospheric Multiscale Mission (MMS), the only mission designed to describe the three-dimensional spatial structure of plasma phenomena in geospace. In this paper, we concentrate on some of the many plasma phenomena that have been studied using data from Cluster. To date, there have been more than 2000 refereed papers published using Cluster data but in this paper we will, of necessity, refer to only a small fraction of the published work. We have focused on a few basic plasma phenomena, but, for example, have not dealt with most of the vast body of work describing dynamical phenomena in Earth's magnetosphere, including the dynamics of current sheets in Earth's magnetotail and the morphology of the dayside high latitude cusp. Several review articles and special publications are available that describe aspects of that research in detail and interested readers are referred to them (see for example, Escoubet et al.

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Generation of Pi2 pulsations by intermittent earthward propagating dipolarization fronts: An MHD case study

et al. 2013

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[1] Using a global magnetohydrodynamic (MHD) simulation of the magnetosphere during a disturbed interval on 14 September 2004, we have investigated fluctuations in plasma properties of the magnetotail in the Pi2 range and their relationship to dipolarization fronts (DFs). Results from the MHD simulation indicate that this event is a very active interval with variable convection and disorder in the tail on a range of scales as small as 1 R E . DFs are observed in the simulation at the leading edge of fast earthward flows that originate from reconnection regions that form between -15 and -30 R E in the tail. Pi2 period fluctuations are identified in pressure, magnetic field, and velocity components inside -13 R E following each burst of DFs in the midnight sector. The fluctuations observed in the pressure appear to be generated by the successive DFs as they approach the interface between stretched tail field lines and dipolar field lines. Fluctuations in the velocity may be the result of interactions between successive DFs and are amplified directly following the passage of the DFs as they propagate earthward. Although the limited azimuthal extent of the pulsations near the plasma sheet, just inside of the braking region, makes it difficult to draw a direct comparison between the ground-based measurements and the pulsations at -6 R E , the temporal evolution of the simulated DFs and Pi2 pulsations approximately reproduces the timing of the variations observed by satellites and ground-based instruments. Therefore, we have been able to use the global simulation to track the bursty flows, dipolarization fronts, and associated Pi2 period fluctuations throughout the entire magnetosphere in order to understand the sources of the changes measured in the near-Earth region.

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Observations and simulations of non-local acceleration of electrons in magnetotail magnetic reconnection events

Cited by 168 publications

References 34 publications

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

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

Multipoint observations of plasma phenomena made in space by Cluster

Generation of Pi2 pulsations by intermittent earthward propagating dipolarization fronts: An MHD case study

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