Intense whistler-mode waves at foreshock transients: characteristics and regimes of wave-particle resonant interaction

Abstract

Thermalization and heating of plasma flows at shocks result in unstable charged-particle distributions which generate a wide range of electromagnetic waves. These waves, in turn, can further accelerate and scatter energetic particles. Thus, the properties of the waves and their implication for wave-particle interactions are critically important for modeling energetic particle dynamics in shock environments. Whistler-mode waves, excited by the electron heat flux or a temperature anisotropy, arise naturally near shocks and foreshock transients. As a result, they can often interact with supra-thermal electrons. The low background magnetic field typical at the core of such transients and the large wave amplitudes may cause such interactions to enter the nonlinear regime. In this study, we present a statistical characterization of whistler-mode waves at foreshock transients around Earth bow shock, as they are observed under a wide range of upstream conditions. We find that a significant portion of them are sufficiently intense and coherent to warrant nonlinear treatment. Copious observations of background magnetic field gradients and intense whistler wave amplitudes suggest that phase trapping, a very effective mechanism for electron acceleration in inhomogeneous plasmas, may be the cause. We discuss the implications of our findings for electron acceleration in planetary and astrophysical shock environments.

Submitted to APJ

References in corpus (7)

• Statistical Study of Whistler Waves in the Solar Wind at 1 AU
• Relativistic electrons produced by foreshock disturbances
• Observational Evidence for Stochastic Shock Drift Acceleration of Electrons at the Earth's Bow Shock
• Whistler wave generation by halo electrons in the solar wind
• Statistical study of particle acceleration in the core of foreshock transients
• Fermi acceleration of electrons inside foreshock transient cores
• On quasi-parallel whistler waves in the solar wind

Cited by in corpus (2)

• Revealing an unexpectedly low electron injection threshold via reinforced shock acceleration
• Electron Heating in 2D Particle-in-Cell Simulations of Quasi-Perpendicular Low-Beta Shocks