General description of electromagnetic radiation processes based on instantaneous charge acceleration in `endpoints'

TL;DR

This paper introduces an 'endpoint formulation' for calculating electromagnetic radiation from accelerated charged particles, providing a general, versatile method that unifies classical radiation processes and clarifies the dominant emission mechanisms in high-energy particle cascades.

Contribution

The paper presents a novel, comprehensive endpoint-based methodology that unifies various radiation processes and applies to complex particle interactions, including particle creation and destruction.

Findings

The endpoint formulation reproduces classical radiation processes like synchrotron and Cherenkov radiation.

It reveals that coherent bremsstrahlung dominates the Askaryan effect in dense media.

The method enables analysis of radio emissions from ultra-high-energy particle interactions.

Abstract

We present a new methodology for calculating the electromagnetic radiation from accelerated charged particles. Our formulation --- the `endpoint formulation' --- combines numerous results developed in the literature in relation to radiation arising from particle acceleration using a complete, and completely general, treatment. We do this by describing particle motion via a series of discrete, instantaneous acceleration events, or `endpoints', with each such event being treated as a source of emission. This method implicitly allows for particle creation/destruction, and is suited to direct numerical implementation in either the time- or frequency-domains. In this paper, we demonstrate the complete generality of our method for calculating the radiated field from charged particle acceleration, and show how it reduces to the classical named radiation processes such as synchrotron, Tamm's description of Vavilov-Cherenkov, and transition radiation under appropriate limits. Using this formulation, we are immediately able to answer outstanding questions regarding the phenomenology of radio emission from ultra-high-energy particle interactions in both the Earth's atmosphere and the Moon. In particular, our formulation makes it apparent that the dominant emission component of the Askaryan Effect (coherent radio-wave radiation from high-energy particle cascades in dense media) comes from coherent `bremsstrahlung' from particle acceleration, rather than coherent Vavilov-Cherenkov radiation.