THEMIS observations of the near‐Earth plasma sheet during a substorm

Tang, C. L.; Li, Z. Y.; Angelopoulos, V.; Mende, S. B.; Glassmeier, K.; Donovan, E.; Russell, C. T.; Li, Lü

doi:10.1029/2008ja013729

Cited by 18 publications

(21 citation statements)

References 41 publications

(56 reference statements)

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“…Mauk, 1986;Zhou et al, 2010), and both the ion density and β could increase several times after the dipolarization process (e.g. Zhang et al, 2007;Tang et al, 2009), which indicate that the R value of plasma should increase. There are also many observations that show that the dipolarization process, coupled with electron acceleration and wave particle interactions, can account for electron heating (see, for example, Ashour-Abdalla et al, 2009;Fu et al, 2011).…”

Section: Discussion and Summarymentioning

confidence: 99%

Cluster and TC-1 observation of magnetic holes in the plasma sheet

Sun

Shi

et al. 2012

Ann. Geophys.

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Abstract. Magnetic holes with relatively small scale sizes, detected by Cluster and TC-1 in the magnetotail plasma sheet, are studied in this paper. It is found that these magnetic holes are spatial structures and they are not magnetic depressions generated by the flapping movement of the magnetotail current sheet. Most of the magnetic holes (93 %) were observed during intervals with B z larger than B x , i.e. they are more likely to occur in a dipolarized magnetic field topology. Our results also suggest that the occurrence of these magnetic holes might have a close relationship with the dipolarization process. The magnetic holes typically have a scale size comparable to the local proton Larmor radius and are accompanied by an electron energy flux enhancement at a 90 • pitch angle, which is quite different from the previously observed isotropic electron distributions inside magnetic holes in the plasma sheet. It is also shown that most of the magnetic holes occur in marginally mirror-stable environments. Whether the plasma sheet magnetic holes are generated by the mirror instability related to ions or not, however, is unknown. Comparison of ratios, scale sizes and propagation direction of magnetic holes detected by Cluster and TC-1, suggests that magnetic holes observed in the vicinity of the TC-1 orbit (∼7-12 R E ) are likely to be further developed than those observed by Cluster (∼7-18 R E ).

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Section: Discussion and Summarymentioning

confidence: 99%

Cluster and TC-1 observation of magnetic holes in the plasma sheet

Sun

Shi

et al. 2012

Ann. Geophys.

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“…After the substorm injections, the electron fluxes had very significant increases (Figures 3b and 3c). The rest of electron energy spectra (marked by the gray bar in Figures 4a and 4b) indicated that RBSP-A was located in the near-Earth plasma sheet [e.g., Lui, 1996;Tang et al, 2009]. For 1.8 MeV electrons, the substorm injections yielded P r = j 3 /j 2 = 3.4 and P e = j 3 /j 1 = 2.1 (P r and P e are the recovery and enhancement coefficients of 1.8 MeV electron fluxes, respectively).…”

Section: Themis-a and Geosynchronous Orbit Satellite Observationsmentioning

confidence: 99%

“…Usually, the intensive electric fields can propagate inward and produce dipolarization and dispersionless injections in the outer radiation belt [e.g., Li et al, 1998;Sarris et al, 2002]. After~03:12 UT (as indicated by the second vertical dashed line), the intensive electron fluxes were also observed (Figure 2d), which indicated that THEMIS-A was in an expanding plasma sheet [e.g., Lui, 1996;Tang et al, 2009]. After~03:12 UT (as indicated by the second vertical dashed line), the intensive electron fluxes were also observed (Figure 2d), which indicated that THEMIS-A was in an expanding plasma sheet [e.g., Lui, 1996;Tang et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

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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“…During the tailward‐moving dipolarization interval, the plasma temperature T i and pressures ( P t and P p ) at P4 and P5 increased. These changes are the typical signatures in the near‐Earth tail during the dipolarization interval [ Tang et al ., ]. Meanwhile, the magnetic field configuration in the near‐Earth tail became more dipolar (see Figures b and b).…”

Section: Observationsmentioning

confidence: 99%

“…Understanding the intrinsic nature of the dipolarization phenomenon is crucial for clarifying the substorm onset question. One possible explanation for the dipolarization is that the ballooning [ Roux et al ., ] or cross‐field current instabilities [ Lui et al ., ; Tang et al ., ] produce the disruption of cross‐tail current in the near‐Earth tail. Another explanation is that dipolarizations are caused by the pileup of the magnetic flux at the inner edge of the plasma sheet where the earthward flows encounter a high‐pressure region and are braked [ Shiokawa et al ., ; Baumjohann , ; Tang et al ., ].…”

Section: Introductionmentioning

confidence: 99%

THEMIS observations of electron acceleration associated with the evolution of substorm dipolarization in the near‐Earth tail

Tang

Zhou

et al. 2013

JGR Space Physics

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[1] We present the evolution of dipolarizations in the near-Earth tail during a substorm on 15 March 2009, based on the two-point measurements in the nightside plasma sheet at X~À8.0 R E. The earthward-moving dipolarization, the magnetic flux pileup, and the tailward-moving dipolarization were observed. For the 30-200 keV electrons, betatron acceleration was the dominant process, which was caused by the much larger gradient of the magnetic field there during the earthward-moving dipolarization or by a local compression of the magnetic field during the magnetic flux pileup and tailward-moving dipolarization. These near-perpendicular distributions for the 30-200 keV electrons are interpreted as produced by a two-step acceleration: Electrons were first accelerated in the dipolarization fronts in the midtail or the near-Earth tail and then were further accelerated near the tail current disruption region. For the more than 200 keV electrons, Fermi acceleration was the dominant process, which was caused by the shrinking length of magnetic field line during the tailward-moving dipolarization. The source region of the more than 200 keV electrons may be near the tail current disruption region, but these electrons were accelerated locally. These field-aligned electrons can precipitate into the ionosphere and form the discrete auroral arcs. Two parallel arcs were clearly observed around the substorm onset: one propagated equatorward, another propagated poleward. We suggest that the earthward-moving dipolarization, the magnetic flux pileup, and the tailward-moving dipolarization near the tail current disruption region can well explain the auroral evolution around the substorm onset.Citation: Tang, C. L., L. Lu, M. Zhou, and Z. H. Yao (2013), THEMIS observations of electron acceleration associated with the evolution of substorm dipolarization in the near-Earth tail,

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THEMIS observations of the near‐Earth plasma sheet during a substorm

Cited by 18 publications

References 41 publications

Cluster and TC-1 observation of magnetic holes in the plasma sheet

Cluster and TC-1 observation of magnetic holes in the plasma sheet

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

THEMIS observations of electron acceleration associated with the evolution of substorm dipolarization in the near‐Earth tail

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