Spatial scale of high‐speed flows in the plasma sheet observed by Cluster

Nakamura, R.; Baumjohann, W.; Mouikis, C.; Kistler, L. M.; Runov, A.; Volwerk, M.; Asano, Yasuhito; Vörös, Z.; Zhang, T. L.; Klecker, B.; Rème, H.; Balogh, A.

doi:10.1029/2004gl019558

Cited by 326 publications

(384 citation statements)

References 23 publications

(32 reference statements)

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“…[60] Comparing the ECR and BBF scale sizes, observational investigations have confirmed that BBFs are narrow and elongated structures, whose cross-tail scale size is of the order of 1 or a few R E [e.g., Sergeev et al, 1996a;Angelopoulos et al, 1997;Nakamura et al, 2004Nakamura et al, , 2005aWalsh et al, 2009]. Walsh et al [2009] estimated that the BBF size along the direction of the plasma flow is approximately ∼4R E .…”

Section: Ecr Scale Sizementioning

confidence: 99%

Energy conversion regions as observed by Cluster in the plasma sheet

et al. 2011

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[1] In this article we present a review of recent studies of observations of localized energy conversion regions (ECRs) observed by Cluster in the plasma sheet at altitudes of 15-20R E . By examining variations in the power density, E · J, where E is the electric field and J is the current density, we show that the plasma sheet exhibits a high level of fine structure. Approximately three times as many concentrated load regions (CLRs) (E · J > 0) as concentrated generator regions (CGRs) (E · J < 0) are identified, confirming the average load character of the plasma sheet. Some ECRs are found to relate to auroral activity. While ECRs are relevant for the energy conversion between the electromagnetic field and the particles, bursty bulk flows (BBFs) play a central role for the energy transfer in the plasma sheet. We show that ECRs and BBFs are likely to be related, although details of this relationship are yet to be explored. The plasma sheet energy conversion increases rather simultaneously with increasing geomagnetic activity in both CLRs and CGRs. Consistent with large-scale magnetotail simulations, most of the observed ECRs appear to be rather stationary in space but varying in time. We estimate that the ECR lifetime and scale size are a few minutes and a few R E , respectively. It is conceivable that ECRs rise and vanish locally in significant regions of the plasma sheet, possibly oscillating between load and generator character, while some energy is transmitted as Poynting flux to the ionosphere.

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Section: Ecr Scale Sizementioning

confidence: 99%

Energy conversion regions as observed by Cluster in the plasma sheet

et al. 2011

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“…Generally, this is observed during substorms or strong reconnection, as has been reported in the literature (e.g., Nosé et al, 2000a, b;Ono et al, 2009;Keika et al, 2013;Luo et al, 2014). Since the energization process has been observed to happen during substorms and localized dipolarization of the magnetic field, the acceleration process can be considered "local".…”

Section: Energy Gainmentioning

confidence: 86%

“…In the presence of substorms and local dipolarization of magnetic field, the most energized species is found to be oxygen, reaching energies larger than 200 keV (Nosé et al, 2000a, b;Ono et al, 2009;Luo et al, 2014). During those periods the magnetic fluctuations are generated by reconnection jets and produce a spatially localized acceleration of ions.…”

Section: Discussionmentioning

confidence: 99%

“…The parameter represents the decreasing scale of the vector potential, which we can imagine as the size of a magnetic cloud that interacts with the particle (see Perri et al, 2007). The positions r i are fixed randomly in the (x, y) plane and are oscillating with velocity V = 400 km s −1 (i.e., the typical value for the Alfvén speed in the magnetotail; Hoshino et al, 1994;Nakamura et al, 2004;Vörös et al, 2007) and with random phases. The electric field is obtained as E = − φ − ∂A(r, t)/∂t.…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…All the equations are normalized using the following normalization quantities: L = 10 5 km, B 0 = 2 nT and E 0 = 40 mV m −1 (see Perri et al (2011) for more details). Further, the fluctuating potential decrease scale is set to = 8000 km (e.g., Nakamura et al, 2004;Perri et al, 2011); the amplitude of electromagnetic fluctuations, A 0 / , is of the order of 10 nT, which is consistent with observations (Borovsky et al, 1997); the dawn dusk electric field is E 0y = 0.2 mV m −1 ; the normal component of magnetic field is B n = 3 nT; and the asymptotic value of the magnetic field in the lobes is B max = 20 nT = 10 B 0 (Sergeev et al, 2003). The magnetic field B x (z) reaches its maximum (minimum) value for z = L z (z = −L z ), but most of the variation happens on scale λ.…”

Section: Numerical Simulationsmentioning

confidence: 99%

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Proton and heavy ion acceleration by stochastic fluctuations in the Earth's magnetotail

et al. 2016

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Abstract. Spacecraft observations show that energetic ions are found in the Earth's magnetotail, with energies ranging from tens of keV to a few hundreds of keV. In this paper we carry out test particle simulations in which protons and other ion species are injected in the Vlasov magnetic field configurations obtained by Catapano et al. (2015). These configurations represent solutions of a generalized Harris model, which well describes the observed profiles in the magnetotail. In addition, three-dimensional time-dependent stochastic electromagnetic perturbations are included in the simulation box, so that the ion acceleration process is studied while varying the equilibrium magnetic field profile and the ion species. We find that proton energies of the order of 100 keV are reached with simulation parameters typical of the Earth's magnetotail. By changing the ion mass and charge, we can study the acceleration of heavy ions such as He ++ and O + , and it is found that energies of the order of 100-200 keV are reached in a few seconds for He ++ , and about 100 keV for O + .

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Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows

Cao

et al. 2013

JGR Space Physics

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[1] During the interval~07:45:36-07:54:24 UT on 24 August 2005, Cluster satellites (C1 and C3) observed an obvious loss of energetic electrons (~3.2-95 keV) associated with the growth of whistler mode waves inside some bursty bulk flows (BBFs) in the midtail plasma sheet (X GSM~À 17.25 R E ). However, the fluxes of the higher-energy electrons (≥128 keV) and energetic ions (10-160 keV) were relatively stable in the BBF-impacted regions. The energy-dependent electron loss inside the BBFs is mainly due to the energy-selective pitch angle scatterings by whistler mode waves within the time scales from several seconds to several minutes, and the electron scatterings in different pitch angle distributions are different in the wave growth regions. The plasma sheet energetic electrons have mainly a quasi-perpendicular pitch angle distribution (30°<α<150°) during the expansion-to-recovery development of a substorm (AE index decreases from 1677 nT to 1271 nT), and their loss can occur at almost all pitch angles in the wave growth regions inside the BBFs. Unlike the energetic electrons, the low-energy electrons (~0.073-2.1 keV) have initially a field-aligned pitch angle distribution (0°≤α ≤30°and 150°≤α ≤180°) in the absence of whistler mode waves, and their loss in field-aligned directions is accompanied by their increase in quasi-perpendicular directions in the wave growth regions, but the loss of the low-energy electrons inside the BBFs is not obvious in the presence of their large background fluxes. These observations indicate that the resonant electrons in an anisotropic pitch angle distribution mainly undergo the rapid pitch angle scattering loss during the wave-particle resonances.

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Spatial scale of high‐speed flows in the plasma sheet observed by Cluster

Cited by 326 publications

References 23 publications

Energy conversion regions as observed by Cluster in the plasma sheet

Energy conversion regions as observed by Cluster in the plasma sheet

Proton and heavy ion acceleration by stochastic fluctuations in the Earth's magnetotail

Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows

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