Simulation of radio emission from cosmic ray air shower with SELFAS2

TL;DR

This paper introduces SELFAS2, a new autonomous simulation code for radio emissions from cosmic ray air showers, based on a microscopic approach tracking individual particles without relying on external air shower generators.

Contribution

SELFAS2 is a novel autonomous simulation tool that computes radio emissions from air showers microscopically, based on air shower universality, without external generators like AIRES or CORSIKA.

Findings

Radio emission mainly due to the time derivative of the transverse current.

Transverse current effects dominate over charge excess in most cases.

Validation confirms earlier results about emission mechanisms.

Abstract

We present a microscopic computation of the radio emission from air showers initiated by ultra-high energy cosmic rays in the atmosphere. The strategy adopted is to compute each secondary particle contribution of the electromagnetic component and to construct the total signal at any location. SELFAS2 is a code which doesn't rely on air shower generators like AIRES or CORSIKA and it is based on the concept of air shower universality which makes it completely autonomous. Each positron and electron of the air shower is generated randomly following relevant distributions and tracking them along their travel in the atmosphere. We confirm in this paper earlier results that the radio emission is mainly due to the time derivative of the transverse current and the time derivative of the charge excess. The time derivative of the transverse current created by systematic deviations of charges in the geomagnetic field is usually dominant compared to the charge excess contribution except for the case of an air shower parallel to the geomagnetic field.