Nonlinear local parallel acceleration of electrons through Landau trapping by oblique whistler mode waves in the outer radiation belt

Agapitov, Oleksiy; Artemyev, А. V.; Mourenas, D.; Mozer, F. S.; Krasnoselskikh, V.

doi:10.1002/2015gl066887

Cited by 88 publications

(137 citation statements)

References 61 publications

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“…The energization of electrons trapped into the Landau resonance requires some energy source supporting TDS propagation to sufficiently high latitudes. A similar question about energy sources has been previously raised for large‐amplitude whistler waves observed in the outer radiation belt [ Cattell et al , ; Cully et al , ; Kellogg et al , ; Wilson et al , ] and capable of providing fast energization of electrons trapped into the Landau or cyclotron resonances [ Trakhtengerts et al , ; Agapitov et al , , ; Osmane et al , ]. Shklyar [] has shown that whistler wave energy is insufficient to provide transport of resonant trapped electrons to 30°–40° latitude, where whistlers are still observed [ Cattell et al , ; Kellogg et al , ; Agapitov et al , ].…”

Section: Introductionmentioning

confidence: 80%

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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Section: Introductionmentioning

confidence: 80%

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

et al. 2017

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“…Electron acceleration through Landau resonance by the parallel electric field of highly coherent oblique whistler mode waves was first considered by Artemyev et al [], who showed that it could lead to tens of keV acceleration in 100 ms for electrons with 50–100 keV initial energy. Recent Van Allen Probes observations provide evidence for the occurrence of such fast, nonlinear acceleration of radiation belt electrons with energies of 20–100 keV [ Agapitov et al , ]. To account for this additional source of electron energization, we obtain both the instantaneous frequency from the zero crossings of the E ∥ wave and the instantaneous wave amplitude E ∥ from the maximum E ∥ between zero crossings.…”

Section: Nonlinear Electron Acceleration In Vlf Riser Subpacketsmentioning

confidence: 99%

“…We then separately apply subpacket analysis to E ∥ to calculate the Landau resonance acceleration efficiency for nonlinear trapping in the parallel electric field of the chorus wave, using the expression

Δ E_{Landau} (eV) = \sum ([], 0.5 J_{0} (β) (||, bold E_{∥}) V_{p} V_{g} δt {((), \frac{V_{g} - V_{p}}{1 - (V_{g} V_{p}) / c^{2}})}^{- 1}) .

Similar to the perpendicular wave calculations, the total and maximum single‐subpacket energy gain for electrons in Landau resonance with the parallel component of the wave electric field are shown in Figure b. The energy range <200 keV for efficient acceleration by Landau resonance is consistent with previous studies [ Agapitov et al , ; Artemyev et al , ].…”

Section: Nonlinear Electron Acceleration In Vlf Riser Subpacketsmentioning

confidence: 99%

Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear interactions with VLF chorus

et al. 2017

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Prompt recovery of MeV (millions of electron Volts) electron populations in the poststorm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly nonlinear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant nonadiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of nonlinear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy of hundreds of keV to 3 MeV can be accelerated by 50 keV–200 keV in resonant interactions with a single VLF rising tone on a time scale of 10–100 ms.

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“…In Nunn and Omura (), resonant particle distribution functions, resonant currents, and nonlinear growth rates of oblique wave‐particle interactions are discussed, and the gyroaveraging method for electron motions interacting with oblique whistler mode waves is derived. Local nonlinear acceleration of electrons through the parallel electric field from 1–10 keV to 100–300 keV are analyzed from observations (Agapitov et al, , ). Artemyev et al () reviewed observations of oblique whistler mode waves, showing the occurrences, distributions, propagation, and damping processes, and discussed wave‐particle interactions with electrons less than 1 MeV under both quasi‐linear diffusion and nonlinear trapping models.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Evolution of Radiation Belt Electron Fluxes Interacting With Oblique Whistler Mode Chorus Emissions

2020

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Nonlinear whistler mode wave‐particle interaction is one of the processes to generate relativistic electrons in the Earth's outer radiation belt. Applying test particle simulations with a pair of whistler mode chorus emissions, we traced a large number of electrons in various initial conditions along an L=4.5 magnetic field line to build a set of Green's functions for analyzing evolution of the electron distribution under the chorus emissions. Employing convolution integral for the Green's functions, we tracked the formation of relativistic electron fluxes from an injected energetic electron through interaction with consecutive chorus emissions. We compared the simulation results among a purely parallel wave model and two oblique wave models with wave normal angles gradually increased from 0° to 20° and 60°. Multiple resonances result in a higher probability of nonlinear trapping. Hence, the trapped electrons for the oblique cases are scattered to a wider range of pitch angles than those for the parallel case. Oblique chorus can accelerate 10–30 keV electrons to MeV level rapidly in several wave emission cycles (about 10 s), which is much faster than that of the parallel wave model. The study shows comprehensive evolutions of electron fluxes interacting with oblique chorus emissions through cyclotron and Landau resonances in the outer radiation belt.

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Nonlinear local parallel acceleration of electrons through Landau trapping by oblique whistler mode waves in the outer radiation belt

Cited by 88 publications

References 61 publications

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

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

Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear interactions with VLF chorus

Nonlinear Evolution of Radiation Belt Electron Fluxes Interacting With Oblique Whistler Mode Chorus Emissions

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