Parametric instabilities and particles heating of circularly polarized Alfv\'en waves with an incoherent spectrum: two-dimensional hybrid simulations

TL;DR

This study uses 2D hybrid simulations to explore how parametric instabilities of incoherent Alfvén waves contribute to ion heating in plasma, revealing that small propagation angles optimize alpha particle heating in space physics contexts.

Contribution

It demonstrates the role of wave-wave coupling and wave-particle interactions in plasma ion heating, highlighting the impact of wave spectrum angles on heating efficiency, a novel insight in space plasma physics.

Findings

Small propagation angles enhance alpha particle heating.

Wave-wave coupling is crucial for ion heating.

Incoherent Alfvén spectra are effective in plasma heating.

Abstract

Plasma ions heating (especially minor heavy ions preferential heating) in fast solar wind and solar corona is an open question in space physics. However, Alfv\'en waves have been always considered as a candidate of energy source for corona heating. In this paper, by using a two-dimensional (2-D) hybrid simulation model in a low beta electron-proton-alpha plasma system, we have investigated the relationships between plasma ions heating and power spectra evolution of density and magnetic field fluctuations excited from the parametric instabilities of initial pump Alfv\'en waves with an incoherent spectrum at different propagation angles theta_k0B0 (an oblique angle between the initial pump wave vector k0 and the background magnetic field B0). It is found that, the wave-wave coupling as well as wave-particle interaction play key roles in ions heating, and an Alfv\'en spectrum with small propagation angle (e.g. theta_k0B0=15degree) can most effectively heat alpha particles in perpendicular direction as well as in parallel direction for both proton and alpha particle than the case of a monochromatic Alfv\'en wave or an Alfv\'en spectrum with larger propagation angle.