Nonlinear electron acceleration by oblique whistler waves: Landau resonance vs. cyclotron resonance

Artemyev, А. V.; Vasiliev, A. A.; Mourenas, D.; Agapitov, Oleksiy; Krasnoselskikh, V.

doi:10.1063/1.4836595

Cited by 57 publications

(89 citation statements)

References 79 publications

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“…The definition of resonance timescale is similar to that of resonance time introduced by Helliwell (1967), which was described as the time period when the electrons are fully bunched. For realistic magnetic field the "resonance timescale" is determined by the competition of wave field and magnetic field inhomogeneity (e.g., Shklayr and Matsumoto, 2009;Artemyev et al, 2013). Within the period of a resonance timescale, the variations of pitch angle and kinetic energy ( α 2 and E 2 ) due to localized resonance are stochastic, which is consistent with the results of Tao et al (2011).…”

Section: Discussionsupporting

confidence: 77%

Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

Chang

Bortnik

et al. 2014

Ann. Geophys.

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Abstract. Modulated high-frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low-frequency (ELF)/very low-frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with highenergy electrons in the plasmasphere. By ray tracing the magnetospheric propagation of ELF/VLF emissions artificially generated at low-invariant latitudes, we evaluate the relativistic electron resonant energies along the ray paths and show that propagating artificial ELF/VLF waves can resonate with electrons from ∼ 100 keV to ∼ 10 MeV. We further implement test particle simulations to investigate the effects of resonant scattering of energetic electrons due to triggered monotonic/single-frequency ELF/VLF waves. The results indicate that within the period of a resonance timescale, changes in electron pitch angle and kinetic energy are stochastic, and the overall effect is cumulative, that is, the changes averaged over all test electrons increase monotonically with time. The localized rates of wave-induced pitch-angle scattering and momentum diffusion in the plasmasphere are analyzed in detail for artificially generated ELF/VLF whistlers with an observable in situ amplitude of ∼ 10 pT. While the local momentum diffusion of relativistic electrons is small, with a rate of < 10 −7 s −1 , the local pitchangle scattering can be intense near the loss cone with a rate of ∼ 10 −4 s −1 . Our investigation further supports the feasibility of artificial triggering of ELF/VLF whistler waves for removal of high-energy electrons at lower L shells within the plasmasphere. Moreover, our test particle simulation results show quantitatively good agreement with quasi-linear diffusion coefficients, confirming the applicability of both methods to evaluate the resonant diffusion effect of artificial generated ELF/VLF whistlers.

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Section: Discussionsupporting

confidence: 77%

Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

Chang

Bortnik

et al. 2014

Ann. Geophys.

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“…Two main resonances contributing to such nonlinear interaction are Landau and first cyclotron resonances. The wave frequency variation with latitude seems to be not very important for Landau resonance since phase velocity of oblique waves propagating with Gendrin angle does not depend on the wave frequency (Artemyev et al, 2013b). In contrast, for the first cyclotron resonance, observed and model wave frequency variation with latitude can be very important.…”

Section: Discussionmentioning

confidence: 96%

Field-aligned chorus wave spectral power in Earth's outer radiation belt

Breuillard¹,

Agapitov

Artemyev

et al. 2015

Ann. Geophys.

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Abstract. Chorus-type whistler waves are one of the most intense electromagnetic waves generated naturally in the magnetosphere. These waves have a substantial impact on the radiation belt dynamics as they are thought to contribute to electron acceleration and losses into the ionosphere through resonant wave-particle interaction. Our study is devoted to the determination of chorus wave power distribution on frequency in a wide range of magnetic latitudes, from 0 to 40• . We use 10 years of magnetic and electric field wave power measured by STAFF-SA onboard Cluster spacecraft to model the initial (equatorial) chorus wave spectral power, as well as PEACE and RAPID measurements to model the properties of energetic electrons (∼ 0.1-100 keV) in the outer radiation belt. The dependence of this distribution upon latitude obtained from Cluster STAFF-SA is then consistently reproduced along a certain L-shell range (4 ≤ L ≤ 6.5), employing WHAMP-based ray tracing simulations in hot plasma within a realistic inner magnetospheric model. We show here that, as latitude increases, the chorus peak frequency is globally shifted towards lower frequencies. Making use of our simulations, the peak frequency variations can be explained mostly in terms of wave damping and amplification, but also cross-L propagation. These results are in good agreement with previous studies of chorus wave spectral extent using data from different spacecraft (Cluster, POLAR and THEMIS). The chorus peak frequency variations are then employed to calculate the pitch angle and energy diffusion rates, resulting in more effective pitch angle electron scattering (electron lifetime is halved) but less effective acceleration. These peak frequency parameters can thus be used to improve the accuracy of diffusion coefficient calculations.

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“…Equation (9) shows that φ variation is described by Hamiltonian (Artemyev et al 2013(Artemyev et al , 2014b):…”

Section: Analytical Estimatesmentioning

confidence: 99%

“…, where an escape position s * is defined by equation A(s * ) ≈ ε (see the equations in Artemyev et al (2013) for more accurate estimate of the escape positions). Collisions can decrease the final energy of trapped particles.…”

Section: Analytical Estimatesmentioning

confidence: 99%

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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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Nonlinear electron acceleration by oblique whistler waves: Landau resonance vs. cyclotron resonance

Cited by 57 publications

References 79 publications

Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

Resonant scattering of energetic electrons in the plasmasphere by monotonic whistler-mode waves artificially generated by ionospheric modification

Field-aligned chorus wave spectral power in Earth's outer radiation belt

Electron trapping and acceleration by kinetic Alfvén waves in solar flares

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