Radiation of de-excited electrons at large times in a strong electromagnetic plane wave

TL;DR

This paper analyzes the long-term radiation behavior of electrons in strong electromagnetic plane waves using the Lorentz-Dirac and Landau-Lifshitz equations, revealing universal asymptotic properties and spectral densities.

Contribution

It provides the first detailed asymptotic solutions for electron radiation in specific electromagnetic fields and establishes universal properties of radiation power at large times.

Findings

Total radiation power becomes independent of charge and field strength in certain regimes.

Spectral densities of radiation are derived for late-time asymptotics.

Radiation power approaches a universal value proportional to the particle's rest energy.

Abstract

The late time asymptotics of the physical solutions to the Lorentz-Dirac equation in the electromagnetic external fields of simple configurations -- the constant homogeneous field, the linearly polarized plane wave (in particular, the constant uniform crossed field), and the circularly polarized plane wave -- are found. The solutions to the Landau-Lifshitz equation for the external electromagnetic fields admitting a two-parametric symmetry group, which include as a particular case the above mentioned field configurations, are obtained. General properties of the total radiation power of a charged particle are established. In particular, for a circularly polarized wave and constant uniform crossed fields, the total radiation power in the asymptotic regime is independent of the charge and the external field strength, when expressed in terms of the proper-time, and equals a half of the rest energy of a charged particle divided by its proper-time. The spectral densities of the radiation power formed on the late time asymptotics are derived for a charged particle moving in the external electromagnetic fields of the simple configurations pointed above.