Magnetic field depression within electron holes

Vasko, I. Y.; Agapitov, Oleksiy; Mozer, F. S.; Artemyev, А. V.; Jovanović, D.

doi:10.1002/2015gl063370

Cited by 37 publications

(33 citation statements)

References 28 publications

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“…Impulsive spikes in the magnetic field associated with phase space holes have been reported in a number of studies using observational data (Andersson et al, ; Malaspina et al, ; Tao et al, ; Vasko, Agapitov, Mozer, Artemyev, & Jovanovic, ; Vasko, Agapitov, Mozer, Artemyev, Drake, & Kuzichev, ) as well as theoretical studies (Haynes et al, ; Treumann & Baumjohann, ; Wu et al, ). Both positive B ∥ (Malaspina et al, ; Tao et al, ; Treumann & Baumjohann, ; Wu et al, ) and negative B ∥ (Haynes et al, ; Vasko, Agapitov, Mozer, Artemyev, & Jovanovic, ; Vasko, Agapitov, Mozer, Artemyev, Drake, & Kuzichev, ) have been reported.…”

Section: Discussionmentioning

confidence: 92%

A Census of Plasma Waves and Structures Associated With an Injection Front in the Inner Magnetosphere

et al. 2018

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Now that observations have conclusively established that the inner magnetosphere is abundantly populated with kinetic electric field structures and nonlinear waves, attention has turned to quantifying the ability of these structures and waves to scatter and accelerate inner magnetospheric plasma populations. A necessary step in that quantification is determining the distribution of observed structure and wave properties (e.g., occurrence rates, amplitudes, and spatial scales). Kinetic structures and nonlinear waves have broadband signatures in frequency space, and consequently, high‐resolution time domain electric and magnetic field data are required to uniquely identify such structures and waves as well as determine their properties. However, most high‐resolution fields data are collected with a strong bias toward high‐amplitude signals in a preselected frequency range, strongly biasing observations of structure and wave properties. In this study, an ∼45 min unbroken interval of 16,384 samples/s field burst data, encompassing an electron injection event, is examined. This data set enables an unbiased census of the kinetic structures and nonlinear waves driven by this electron injection, as well as determination of their “typical” properties. It is found that the properties determined using this unbiased burst data are considerably different than those inferred from amplitude‐biased burst data, with significant implications for wave‐particle interactions due to kinetic structures and nonlinear waves in the inner magnetosphere.

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Section: Discussionmentioning

confidence: 92%

A Census of Plasma Waves and Structures Associated With an Injection Front in the Inner Magnetosphere

et al. 2018

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“…Some of TDS exhibit parallel magnetic field depressions seen in Figure a as short‐duration negative spikes superimposed on magnetic field fluctuations of lower frequency. The parallel magnetic field depression of about few tens of picotesla is a typical property of TDS in the outer radiation belt [ Vasko et al , ]. Figures c and d provide an expanded view of the electric and magnetic fields of one particular TDS.…”

Section: Observationsmentioning

confidence: 99%

“…The perpendicular temperature of the trapped population can be estimated based on the analysis of EH magnetic field signatures [ Vasko et al , ]. It has been found in simulations [ Umeda et al , ; Wu et al , ] that the parallel magnetic field should be amplified within EHs due to E ⊥ × B drift of trapped and untrapped electrons [see also Treumann and Baumjohann , ].…”

Section: Perpendicular Temperature Of Trapped Electron Populationmentioning

confidence: 99%

“…Vasko et al [] have suggested that E ⊥ × B drift can be overwhelmed by diamagnetic drifts due to sufficiently hot trapped population (the electron pressure gradient is then significant). The drifts and corresponding magnetic field perturbation δ B can be described by making use of the hydrodynamic pressure balance across an EH

\nabla_{⊥} ((), ϖ_{normaltr}^{⊥} + ϖ_{normalut}^{⊥}) = e n_{0} \nabla_{⊥} Φ + rot δ boldB \times {boldB}_{0} / 4 π

where

ϖ_{normaltr}^{⊥}

and

ϖ_{normalut}^{⊥}

are perpendicular pressures of trapped and untrapped electrons.…”

Section: Perpendicular Temperature Of Trapped Electron Populationmentioning

confidence: 99%

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Electron holes in the outer radiation belt: Characteristics and their role in electron energization

et al. 2017

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Van Allen Probes have detected electron holes (EHs) around injection fronts in the outer radiation belt. Presumably generated near equator, EHs propagate to higher latitudes potentially resulting in energization of electrons trapped within EHs. This process has been recently shown to provide electrons with energies up to several tens of keV and requires EH propagation up to rather high latitudes. We have analyzed more than 100 EHs observed around a particular injection to determine their kinetic structure and potential energy sources supporting the energization of trapped electrons. EHs propagate with velocities from 1000 to 20,000 km/s (a few times larger than the thermal velocity of the coldest background electron population). The parallel scale of observed EHs is from 0.3 to 3 km that is of the order of hundred Debye lengths. The perpendicular to parallel scale ratio is larger than one in a qualitative agreement with the theoretical scaling relation. The amplitudes of EH electrostatic potentials are generally below 100 V. We determine the properties of the electron population trapped within EHs by making use of the Bernstein‐Green‐Kruskal analysis and via analysis of EH magnetic field signatures. The density of the trapped electron population is on average 20% of the background electron density. The perpendicular temperature of the trapped population is on average 300 eV and is larger for faster EHs. We show that energy losses of untrapped electrons scattered by EHs in the inhomogeneous background magnetic field may balance the energization of trapped electrons.

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“…Thus, the scenario of electron acceleration by waves seems promising for the description of electron acceleration in the region with higher electron density. Landau wave damping and particle reflection from waves can be responsible for moderate electron acceleration (electrons can gain velocity of about two local Alfvén speeds (Fletcher & Hudson 2008;Vasko et al 2015). However, the inhomgeneous magnetic field of solar loops and the parallel electric field, which is induced by waves, can run the non-linear mechanism of electron acceleration, including particle trapping (e.g.…”

Section: Introductionmentioning

confidence: 99%

Electron trapping and acceleration by kinetic Alfvén waves in solar flares

Artemyev

Zimovets

Rankin

2016

A&A

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Context. Theoretical models and spacecraft observations of solar flares highlight the role of wave-particle interaction for non-local electron acceleration. In one scenario, the acceleration of a large electron population up to high energies is due to the transport of electromagnetic energy from the loop-top region down to the footpoints, which is then followed by the energy being released in dense plasma in the lower atmosphere. Aims. We consider one particular mechanism of non-linear electron acceleration by kinetic Alfvén waves. Here, waves are generated by plasma flows in the energy release region near the loop top. We estimate the efficiency of this mechanism and the energies of accelerated electrons. Methods. We use analytical estimates and test-particle modelling to investigate the effects of electron trapping and acceleration by kinetic Alfvén waves in the inhomogeneous plasma of the solar corona. Results. We demonstrate that, for realistic wave amplitudes, electrons can be accelerated up to 10−1000 keV during their propagation along magnetic field lines. Here the electric field that is parallel to the direction of the background magnetic field is about 10 to 10 3 times the amplitude of the Dreicer electric field. The acceleration mechanism strongly depends on electron scattering which is due to collisions that only take place near the loop footpoints. Conclusions. The non-linear wave-particle interaction can play an important role in the generation of relativistic electrons within flare loops. Electron trapping and coherent acceleration by kinetic Alfvén waves represent the energy cascade from large-scale plasma flows that originate at the loop-top region down to the electron scale. The non-diffusive character of the non-linear electron acceleration may be responsible for the fast generation of high-energy particles.

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Magnetic field depression within electron holes

Cited by 37 publications

References 28 publications

A Census of Plasma Waves and Structures Associated With an Injection Front in the Inner Magnetosphere

A Census of Plasma Waves and Structures Associated With an Injection Front in the Inner Magnetosphere

Electron holes in the outer radiation belt: Characteristics and their role in electron energization

Electron trapping and acceleration by kinetic Alfvén waves in solar flares

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