Properties of an ultrarelativistic charged particle radiation in a constant homogeneous crossed electromagnetic field

TL;DR

This paper analyzes the radiation emitted by an ultrarelativistic charged particle in a constant crossed electromagnetic field, detailing its properties, different radiation components, and their spectral and angular characteristics.

Contribution

It provides a combined analytical and numerical study of radiation reaction effects, distinguishing between entrance and de-excited radiation components in such fields.

Findings

Entrance radiation resembles ultrarelativistic synchrotron radiation

De-excited radiation is soft, circularly polarized, and not confined to the motion plane

Maximum spectral distribution decreases with initial particle energy

Abstract

The properties of radiation created by a classical ultrarelativistic scalar charged particle in a constant homogeneous crossed electromagnetic field are described both analytically and numerically with radiation reaction taken into account in the form of the Landau-Lifshitz equation. The total radiation naturally falls into two parts: the radiation formed at the entrance point of a particle into the crossed field (the synchrotron entrance radiation), and the radiation coming from the late-time asymptotics of a particle motion (the de-excited radiation). The synchrotron entrance radiation resembles, although does not coincide with, the ultrarelativistic limit of the synchrotron radiation: its distribution over energies and angles possesses almost the same properties. The de-excited radiation is soft, not concentrated in the plane of motion of a charged particle, and almost completely circularly polarized. The photon energy delivering the maximum to its spectral angular distribution decreases with increasing the initial energy of a charged particle, while the maximum value of this distribution remains the same at the fixed observation angle. The ultraviolet and infrared asymptotics of the total radiation are also described.