Thresholdless stochastic particle heating by a single wave

TL;DR

This paper demonstrates through simulations that even minimal spatial inhomogeneity in electromagnetic waves can eliminate the amplitude threshold for stochastic particle heating, broadening its potential applications.

Contribution

It introduces a thresholdless stochastic heating mechanism enabled by weak spatial inhomogeneity, supported by numerical simulations and Hamiltonian analysis.

Findings

Thresholdless stochastic heating occurs with weak inhomogeneity.

Interaction duration replaces wave amplitude as a key parameter.

Applicable to various inhomogeneous systems.

Abstract

Stochastic heating is a well-known mechanism through which magnetized particles may be energized by low-frequency electromagnetic waves. In its simplest version, under spatially homogeneous conditions, it is known to be operative only above a threshold in the normalized wave amplitude, which may be a demanding requisite in actual scenarios, severely restricting its range of applicability. In this work we show, by numerical simulations supported by inspection of the particle Hamiltonian, that allowing for even a very weak spatial inhomogeneity completely removes the threshold, trading the requirement upon the wave amplitude with a requisite upon the duration of the interaction between wave and particle. The thresholdless chaotic mechanism considered here is likely to be applicable to other inhomogeneous systems.