THEMIS observations of an earthward‐propagating dipolarization front

Runov, A.; Angelopoulos, V.; Sitnov, M. I.; Сергеев, В. А.; Bonnell, J. W.; McFadden, J. P.; Larson, D. E.; Glaßmeier, K.‐H.; Auster, U.

doi:10.1029/2009gl038980

Cited by 557 publications

(803 citation statements)

References 27 publications

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“…2. It is seen from the figure that the B Z pulses have the typical characteristics of DFs, such as the rapid increase of the B Z component preceded by the negative B Z variation, the decrease in density behind the front, and the decrease in plasma pressure, while magnetic pressure increases across the front (e.g., Shiokawa et al, 2005;Zhou et al, 2009;Runov et al, 2009). Grigorenko et al (2018) studied the magnetic gradients observed by closely located C3 and C4 in the vicinity of the strongest B Z pulse detected by C4 at ∼ 01:39:41 UT.…”

Section: Data Descriptionmentioning

confidence: 99%

“…Injections are observed not only at a geosynchronous orbit but also in the mid-tail region at X ∼ −9-−30 R E simultaneously with DFs (e.g., Runov et al, 2009Runov et al, , 2011. 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.…”

Section: Introductionmentioning

confidence: 99%

“…Case and statistical studies showed a good correlation between injections and transient bursts of fast flow as well as earthward-propagating dipolarizing flux bundles (DFBs) (e.g., Sergeev et al, 2005;Apatenkov et al, 2008;Runov et al, 2009Runov et al, , 2011Gabrielse et al, 2014). Injections are classified as "dispersionless" and "dispersed" (e.g., Sarris et al, 1976) based on the timing of the particle flux enhancements in different energy channels.…”

Section: Introductionmentioning

confidence: 99%

“…Spacecraft observations have shown that rapid enhancements in the B Z field represent spatial structures -dipolarization fronts (DFs) -which are typically observed at the leading edge of the earthwardmoving bursty bulk flows (BBFs) (e.g., Angelopoulos et al,742 A. Y. Malykhin et al: Contrasting dynamics of electrons and protons 1992; Nakamura et al, 2002;Runov et al, 2009). DFs are associated with electron and ion acceleration (e.g., Apatenkov et al, 2007;Asano et al, 2010;Zhou et al, 2010;Fu et al, 2011;Birn et al, 2011;Grigorenko et al, 2017) as well as with various wave activities, e.g., whistler emissions, lower hybrid and electron cyclotron waves (e.g., Le Contel et al, 2009;Zhou et al, 2009;Deng et al, 2010;Khotyaintsev et al, 2011;Hwang et al, 2011;Vilberg et al, 2014;Grigorenko et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…It was shown that dipolarizations occur at different timescales and can be roughly classified into two groups: (i) the propagating isolated DFs observed during a few minutes (e.g., Nakamura et al, 2002;Runov et al, 2009;Fu et al, 2011;Schmid et al, 2011) and (ii) the socalled "secondary" dipolarizations related to the flow braking and flux pile up in the near-Earth tail (e.g., ). The secondary dipolarizations are observed during much longer time periods (up to several hours) and usually are associated with the formation of the substorm current wedge (SCW) (McPherron et al, 1973;Sergeev et al, 2012;Yao et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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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: Data Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Dipolarization fronts as a consequence of transient reconnection: In situ evidence

Cao

Khotyaintsev

et al. 2013

Geophysical Research Letters

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[1] Dipolarization fronts (DFs) are frequently detected in the Earth's magnetotail from X GSM = À30 R E to X GSM = À7 R E . How these DFs are formed is still poorly understood. Three possible mechanisms have been suggested in previous simulations: (1) jet braking, (2) transient reconnection, and (3) spontaneous formation. Among these three mechanisms, the first has been verified by using spacecraft observation, while the second and third have not. In this study, we show Cluster observation of DFs inside reconnection diffusion region. This observation provides in situ evidence of the second mechanism: Transient reconnection can produce DFs. We suggest that the DFs detected in the near-Earth region (X GSM > À10 R E ) are primarily attributed to jet braking, while the DFs detected in the mid-or far-tail region (X GSM < À15 R E ) are primarily attributed to transient reconnection or spontaneous formation. In the jetbraking mechanism, the high-speed flow "pushes" the preexisting plasmas to produce the DF so that there is causality between high-speed flow and DF. In the transientreconnection mechanism, there is no causality between highspeed flow and DF, because the frozen-in condition is violated. Citation: Fu, H. S., et al. (2013), Dipolarization fronts as a consequence of transient reconnection: In situ evidence, Geophys. Res. Lett., 40,[6023][6024][6025][6026][6027]

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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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THEMIS observations of an earthward‐propagating dipolarization front

Cited by 557 publications

References 27 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

Dipolarization fronts as a consequence of transient reconnection: In situ evidence

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

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