Particle acceleration in dipolarization events

Birn, J.; Hesse, Michael; Nakamura, R.; Zaharia, S.

doi:10.1002/jgra.50132

Cited by 169 publications

(223 citation statements)

References 71 publications

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“…In contrast to the high-shear case (Figure 2), the downward flow remains peaked near the center, although it splits up into several sites at later times. This is similar to the low-shear case, which has been studied more extensively in the context of the terrestrian magnetotail (e.g., Birn et al 2013Birn et al , 2014 and is therefore not shown here.…”

Section: Mhd Simulationssupporting

confidence: 67%

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Can Substorm Particle Acceleration Be Applied to Solar Flares?

Birn

Battaglia

Fletcher

et al. 2017

ApJ

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Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard two-ribbon flare picture in analogy to the standard magnetospheric substorm paradigm. In particular, we investigate the effects of the collapsing field ("collapsing magnetic trap") below a reconnection site, which has been demonstrated to be the major acceleration mechanism that causes energetic particle acceleration and injections observed in Earth's magnetotail associated with substorms and other impulsive events. We contrast an initially force-free, high-shear field (low beta) with low and moderate shear, finite-pressure (high-beta) arcade structures, where beta represents the ratio between gas (plasma) and magnetic pressure. We demonstrate that the energization affects large numbers of particles, but the acceleration is modest in the presence of a significant shear field. Without incorporating loss mechanisms, the effect on particles at different energies is similar, akin to adiabatic heating, and thus is not a likely mechanism to generate a power-law tail onto a (heated or not heated) Maxwellian velocity distribution.

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Section: Mhd Simulationssupporting

confidence: 67%

“…Thus, the betatron and Fermi acceleration of the electrons in the collapsing field are equivalent to the gradient B and curvature drift components, respectively, antiparallel to the electric field (see, Northrop 1963;Birn et al 2013). These terms dominate the acceleration.…”

Section: Typical Orbits and Accelerationmentioning

confidence: 99%

Can Substorm Particle Acceleration Be Applied to Solar Flares?

Birn

Battaglia

Fletcher

et al. 2017

ApJ

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“…The latter conclusion is supported strongly by test particle tracing in assumed or simulated propagating electromagnetic field pulses [Birn et al, 1997[Birn et al, , 1998[Birn et al, , 2004[Birn et al, , 2013[Birn et al, , 2014Li et al, 1998;Zaharia et al, 2000;Liu et al, 2009;Ashour-Abdalla et al, 2009Gabrielse et al, 2012;Pan et al, 2014aPan et al, , 2014b.…”

Section: Introductionmentioning

confidence: 84%

“…Using the three-dimensional time-dependent electric and magnetic field from magnetohydrodynamic (MHD) simulations of near-tail reconnection and flow bursts as basis for test particle studies, we have previously demonstrated major acceleration mechanisms and source regions and provided insights into spatial and temporal variations of electron and ion fluxes [Birn et al, 1997[Birn et al, , 2004[Birn et al, , 2013[Birn et al, , 2014. In addition to demonstrating that the major acceleration occurs in the v × B electric field associated with the dipolarization and flow…”

Section: Introductionmentioning

confidence: 99%

Energetic ions in dipolarization events

2015

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We investigate ion acceleration in dipolarization events in the magnetotail, using the electromagnetic fields of an MHD simulation of magnetotail reconnection and flow bursts as basis for test particle tracing. The simulation results are compared with “Time History of Events and Macroscale Interactions during Substorms” observations. We provide quantitative answers to the relative importance of source regions and source energies. Flux decreases at proton energies up to 10–20 keV are found to be due to sources of lobe or plasma sheet boundary layer particles that enter the near tail via reconnection. Flux increases result from both thermal and suprathermal ion sources. Comparable numbers of accelerated protons enter the acceleration region via cross‐tail drift from the dawn flanks of the near‐tail plasma sheet and via reconnection of field lines extending into the more distant tail. We also demonstrate the presence of earthward plasma flow and accelerated suprathermal ions ahead of a dipolarization front. The flow acceleration stems from a net Lorentz force, resulting from reduced pressure gradients within a pressure pile‐up region ahead of the front. Suprathermal precursor ions result from, typically multiple reflections at the front. Low‐energy ions also become accelerated due to inertial drift in the direction of the small precursor electric field.

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“…With regard to the geospace environment once more, ion acceleration at dipolarization fronts in the geomagnetic tail has been studied, among others, by Ashour-Abdalla et al (2011), Ukhorskiy et al (2013), Birn and Hesse (2014), Greco et al (2014) and Greco et al (2015). Perri et al (2009) and Greco et al (2010) considered the combined effect of a steady-state dawn-dusk electric field and of stochastic Fermi acceleration due to the presence of transient magnetic structures: by performing a two-dimensional (2-D) test particle simulation, they showed that proton energies of up to 80-100 keV can be reached, in agreement with the above observations.…”

Section: Introductionmentioning

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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Particle acceleration in dipolarization events

Cited by 169 publications

References 71 publications

Can Substorm Particle Acceleration Be Applied to Solar Flares?

Can Substorm Particle Acceleration Be Applied to Solar Flares?

Energetic ions in dipolarization events

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

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