Evidence for injection of relativistic electrons into the Earth's outer radiation belt via intense substorm electric fields

Dai, Lei; Wygant, J. R.; Cattell, C. A.; Thaller, S. A.; Kersten, K.; Breneman, A. W.; Tang, Xiangwei; Friedel, R. H. W.; Claudepierre, S. G.; Tao, X.

doi:10.1002/2014gl059228

Cited by 45 publications

(56 citation statements)

References 44 publications

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“…This is consistent with simulation results showing that the convection electric field in the plasma sheet and substorm dipolarization electric field can cause MeV electron injections at the geosynchronous orbit [Ganushkina et al, 2013;Kress et al, 2014]. Dai et al [2014] presented observational evidence for injection of relativistic electrons into the electron radiation belt via the intense electric fields in the midtail. Based on the electron PSD at L~8, Lui et al [2012] suggested that the electrons in the near-Earth magnetotail during the magnetic field dipolarization (substorm dipolarization and magnetic pulse) can be a potential source of MeV electrons in the outer radiation belt.…”

Section: Introductionsupporting

confidence: 90%

“…Previous studies have shown that injected MeV electrons were detected at the geosynchronous orbit [Birn et al, 1998;Ganushkina et al, 2013;Kress et al, 2014;Dai et al, 2014]. Dai et al [2015] showed that the injected MeV electrons could be detected at L = 4.8.…”

Section: Prompt Enhancement Of the Outer Radiation Beltmentioning

confidence: 99%

“…Taylor et al [2004] have shown that the electrons in the midtail during some geomagnetic storm events are the source population of injected MeV electrons. Dai et al [2014] found that enhanced electrons of 100 keV in the midtail during substorm dipolarization (within the substorm time scale) were a source of injected MeV electrons at the geosynchronous orbit. Based on the electron PSD analysis, Lui et al [2012] suggested that the electrons at L~8 during the magnetic field dipolarization could be a potential source of MeV electrons in the outer radiation belt.…”

Section: The Source Population Of Injected Mev Electronsmentioning

confidence: 99%

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Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

et al. 2016

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We present multipoint simultaneous observations of the near‐Earth magnetotail and outer radiation belt during the substorm electron injection event on 16 August 2013. Time History of Events and Macroscale Interactions during Substorms A in the near‐Earth magnetotail observed flux‐enhanced electrons of 300 keV during the magnetic field dipolarization. Geosynchronous orbit satellites also observed the intensive electron injections. Located in the outer radiation belt, RBSP‐A observed enhancements of MeV electrons accompanied by substorm dipolarization. The phase space density (PSD) of MeV electrons at L*~5.4 increased by 1 order of magnitude in 1 h, resulting in a local PSD peak of MeV electrons, which was caused by the direct effect of substorm injections. Enhanced MeV electrons in the heart of the outer radiation belt were also detected within 2 h, which may be associated with intensive substorm electron injections and subsequent local acceleration by chorus waves. Multipoint observations have shown that substorm electron injections not only can be the external source of MeV electrons at the outer edge of the outer radiation belt (L*~5.4) but also can provide the intensive seed populations in the outer radiation belt. These initial higher‐energy electrons from injection can reach relativistic energy much faster. The observations also provide evidence that enhanced substorm electron injections can explain rapid enhancements of MeV electrons in the outer radiation belt.

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Section: Introductionsupporting

confidence: 90%

Section: Prompt Enhancement Of the Outer Radiation Beltmentioning

confidence: 99%

Section: The Source Population Of Injected Mev Electronsmentioning

confidence: 99%

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Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

et al. 2016

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“…Electrons likely also contribute significantly to the MHD pressure in injections, e.g., Dai et al . [] have shown that injection events can energize electrons to MeV energies.…”

Section: The 1 June 2013 Stormmentioning

confidence: 99%

Van Allen Probes investigation of the large‐scale duskward electric field and its role in ring current formation and plasmasphere erosion in the 1 June 2013 storm

et al. 2015

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Using the Van Allen Probes, we investigate the enhancement in the large-scale duskward convection electric field during the geomagnetic storm (Dst~À120 nT) on 1 June 2013 and its role in ring current ion transport and energization and plasmasphere erosion. During this storm, enhancements of 1-2 mV/m in the duskward electric field in the corotating frame are observed down to L shells as low as 2.3. A simple model consisting of a dipole magnetic field and constant, azimuthally westward, electric field is used to calculate the earthward and westward drift of 90°pitch angle ions. This model is applied to determine how far earthward ions can drift while remaining on Earth's nightside, given the strength and duration of the convection electric field. The calculation based on this simple model indicates that the enhanced duskward electric field is of sufficient intensity and duration to transport ions from a range of initial locations and initial energies characteristic of (though not observed by the Van Allen Probes) the earthward edge of the plasma sheet during active times (L~6-10 and~1-20 keV) to the observed location of the 58-267 keV ion population, chosen as representative of the ring current (L~3.5-5.8). According to the model calculation, this transportation should be concurrent with an energization to the range observed, 58-267 keV. Clear coincidence between the electric field enhancement and both plasmasphere erosion and ring current ion (58-267 keV) pressure enhancements are presented. We show for the first time nearly simultaneous enhancements in the duskward convection electric field, plasmasphere erosion, and increased pressure of 58-267 keV ring current ions. These 58-267 keV ions have energies that are consistent with what they are expected to pick up by gradient B drifting across the electric field. These observations strongly suggest that we are observing the electric field that energizes the ions and produces the erosion of the plasmasphere.

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“…Recently, the analyses of the 17 March 2013 event [ Baker et al , ; Boyd et al , ; Foster et al , ] have illustrated once again the importance of substorm injection of low‐energy seed electrons for the buildup of relativistic electron fluxes. The joint observations by several radially displaced satellites [ Dai et al , ] have shown the direct injection of relativistic electrons at the geostationary orbit during substorms. The studies on the 9 October 2012 event [ Reeves et al , ; Thorne et al , ] have demonstrated the rapid acceleration of relativistic electrons by chorus waves within 1 day.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Quantifying the relative contributions of substorm injections and chorus waves to the rapid outward extension of electron radiation belt

Zhu

Xiao

et al. 2014

JGR Space Physics

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We study the rapid outward extension of the electron radiation belt on a timescale of several hours during three events observed by Radiation Belt Storm Probes and Time History of Events and Macroscale Interactions during Substorms satellites and particularly quantify the contributions of substorm injections and chorus waves to the electron flux enhancement near the outer boundary of radiation belt. A comprehensive analysis including both observations and simulations is performed for the first event on 26 May 2013. The outer boundary of electron radiation belt moved from L = 5.5 to L > 6.07 over about 6 h, with up to 4 orders of magnitude enhancement in the 30 keV to 5 MeV electron fluxes at L = 6. The observations show that the substorm injection can cause 100% and 20% of the total subrelativistic (∼0.1 MeV) and relativistic (2–5 MeV) electron flux enhancements within a few minutes. The data‐driven simulation supports that the strong chorus waves can yield 60%–80% of the total energetic (0.2–5.0 MeV) electron flux enhancement within about 6 h. Some simple analyses are further given for the other two events on 2 and 29 June 2013, in which the contributions of substorm injections and chorus waves are shown to be qualitatively comparable to those for the first event. These results clearly illustrate the respective importance of substorm injections and chorus waves for the evolution of radiation belt electrons at different energies on a relatively short timescale.

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Evidence for injection of relativistic electrons into the Earth's outer radiation belt via intense substorm electric fields

Cited by 45 publications

References 44 publications

Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

Van Allen Probes investigation of the large‐scale duskward electric field and its role in ring current formation and plasmasphere erosion in the 1 June 2013 storm

Quantifying the relative contributions of substorm injections and chorus waves to the rapid outward extension of electron radiation belt

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