Evidence of strong energetic ion acceleration in the near-Earth magnetotail

Luo, Hao; Kronberg, Elena A.; Григоренко, Е. Е.; Fränz, M.; Daly, P. W.; Chen, G. X.; Du, Aimin; Kistler, L. M.; Wei, Yong

doi:10.1002/2014gl060252

Cited by 25 publications

(30 citation statements)

References 43 publications

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“…Authors showed that both trapping and quasi-trapping can produce rapid acceleration of protons by more than an order of magnitude of their initial energies. Statistical analysis of Cluster observations at X ≥ −15 R E performed by Luo et al (2014) confirmed that the increase in suprathermal ion population moving earthward is observed along with the high-speed bulk flows and DFs. Ono et al (2009) demonstrated the importance of the nonadiabatic acceleration of protons and heavy ions in the course of their resonant interaction with the low-frequency magnetic fluctuations in the region behind the dipolarization front.…”

Section: Introductionmentioning

confidence: 73%

“…Magnetic dipolarizations are also responsible for the appearance of energetic (≥ 50 keV) ion fluxes in the near-Earth tail (e.g., Ipavich et al, 1984;Nosé et al, 2000;Ono et al, 2009;Keika et al, 2010;Luo et al, 2014;Kronberg et al, 2014Kronberg et al, , 2015Grigorenko et al, 2017 and references therein). Among the proposed mechanisms, the nonadiabatic ion acceleration by the inductive electric field appearing in the course of the fast magnetic reconfiguration at a DF was considered in papers by Delcourt and Sauvaud (1994) and Delcourt (2002).…”

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: Introductionmentioning

confidence: 73%

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 energetic ion anisotropies in the near-Earth plasma sheet show no strong correlation with Auroral Electrojet (AE) index, indicating that its acceleration sources are localized (Luo et al, 2014). DFs can locally accelerate ions and electrons (Zhou et al, 2010;Fu et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Occurrence rate of dipolarization fronts in the plasma sheet: Cluster observations

et al. 2017

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Abstract. We investigate the occurrence rate of dipolarization fronts (DFs) in the plasma sheet by taking full advantage of all four Cluster satellites (C1-4) from years 2001 to 2009. In total, we select 466 joint-observation DF events, in which 318, 282, 254, and 236 DFs are observed by C1, C2, C3, and C4, respectively. Our findings are as follows: (1) the maximum occurrence rate is ∼ 15.3 events per day at X ∼ 15 R E in the XY plane, and the average occurrence rate is ∼ 5.4 events per day over the whole observation period; (2) the occurrence rate on the dusk side of the plasma sheet is larger and decreases with increasing B XY /B Lobe ; (3) the occurrence rate within |Y | < 6 R E increases gradually from X ≈ −19 to −15 R E and then decreases from X ≈ −15 to −10 R E ; (4) the occurrence rate when AE > 200 nT is much larger than that when AE < 200 nT, indicating that DFs preferentially occur during high geomagnetic activity. The magnetic pileup and earthward and duskward ion flows could contribute to the increases in the occurrence rate from X ≈ −19 to −15 R E . We suggest that both geomagnetic activity and multiple DFs contribute to the high occurrence rate of the DFs. In addition, the finite length of the DF in the dawn-dusk direction can affect the chance that a satellite observes the DF.

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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: 83%

“…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%

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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Evidence of strong energetic ion acceleration in the near-Earth magnetotail

Cited by 25 publications

References 43 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

Occurrence rate of dipolarization fronts in the plasma sheet: Cluster observations

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

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