One of the major drivers of radiation belt dynamics, electron resonant interaction with whistler-mode chorus waves, is traditionally described using the quasi-linear diffusion approximation. Such a description satisfactorily explains many observed phenomena, but its applicability can be justified only for sufficiently low intensity, long duration waves. Recent spacecraft observations of a large number of very intense lower-band chorus waves (with magnetic field amplitudes sometimes reaching ∼ 1% of the background) therefore challenge this traditional description and call for an alternative approach when addressing the global, long-term effects of the nonlinear interaction of these waves with radiation belt electrons. In this paper, we first use observations from the Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms spacecraft to show that the majority of intense parallel chorus waves consist of relatively short wave packets. Then, we construct a kinetic equation describing the nonlinear resonant interaction of radiation belt electrons with such short and intense wave packets. We demonstrate that this peculiar type of nonlinear interaction produces similar effects as quasi-linear diffusion, that is, a flattening of the electron velocity distribution function within a certain energy/pitch angle range. The main difference is the much faster evolution of the electron distribution when nonlinear interaction prevails. Key Points:• The theory of electron nonlinear interaction with short intense chorus packets is presented • A generalized kinetic equation including nonlinear interactions with short chorus packets is derived • Nonlinear interactions with short wave packets produce essentially similar effects as quasi-linear diffusion but on a much faster timescale Citation:Mourenas, D., Zhang, X.-J., Artemyev, A. V., Angelopoulos, V., Thorne, R. M., Bortnik, J., et al. (2018). Electron nonlinear resonant interaction with short and intense parallel chorus wave packets.

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A 3D volume-preserving system is considered. The system differs by a small perturbation from an integrable one. In the phase space of the unperturbed system there are regions filled with closed phase trajectories, where the system has two independent first integrals. These regions are separated by a 2D separatrix passing through nondegenerate singular points. Far from the separatrix, the perturbed system has an adiabatic invariant. When a perturbed phase trajectory crosses the two-dimensional separatrix of the unperturbed system, this adiabatic invariant undergoes a quasi-random jump. The formula for this jump is obtained. If the geometry of the system allows for multiple separatrix crossings, the destruction of adiabatic invariance is possible, leading to chaotic behavior in the system. An example of such a system is given.

International audienceThis paper is devoted to the study of the nonlinear interaction of relativistic electrons and highamplitude strongly oblique whistler waves in the Earth’s radiation belts. We consider electrontrapping into Landau and fundamental cyclotron resonances in a simplified model of dipolarmagnetic field. Trapping into the Landau resonance corresponds to a decrease of electronequatorial pitch-angles, while trapping into the first cyclotron resonance increases electronequatorial pitch-angles. For 100 keV electrons, the energy gained due to trapping is similar forboth resonances. For electrons with smaller energy, acceleration is more effective whenconsidering the Landau resonance. Moreover, trapping into the Landau resonance is accessible fora wider range of initial pitch-angles and initial energies in comparison with the fundamentalresonance. Thus, we can conclude that for intense and strongly oblique waves propagating in thequasi-electrostatic mode, the Landau resonance is generally more important than the fundamentalone

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