Study of the Uncertainties of the Galactic Radio Background as a Calibration Source for Radio Arrays

TL;DR

This paper evaluates the uncertainties in using Galactic radio emission as a calibration source for radio arrays detecting cosmic rays, comparing models and considering solar influence to improve calibration accuracy.

Contribution

It compares different Galactic emission models and assesses their uncertainties for calibrating radio arrays, including the impact of the quiet Sun.

Findings

Systematic uncertainties in Galactic emission models are quantified.

Comparison shows model differences impact calibration accuracy.

The quiet Sun influences the Galactic background measurements.

Abstract

The indirect detection of cosmic rays via the radio signal of extensive air showers is gaining a lot of ground. Many new arrays of radio antennas are under construction or in the phase of development. Calibrating these arrays is important for the reconstruction of observed events and for the comparability between observatories. Using reference antennas in calibration campaigns is not ideal because of uncertainties on their signal output strength that are large or difficult to assess. In a different approach the arrays can be calibrated against the Galactic radio emission as the dominant source of background. This so-called Galactic Calibration relies on predictions of the diffuse Galactic radio emission, for which models are publicly available. We present a comparison of these models in the frequency range from 10 to 408 MHz in order to estimate the systematic uncertainties on the strength of the Galactic background. We do this comparison on a global level as well as adapted for selected radio arrays and discuss implications for applying the Galactic calibration method. Furthermore we study the influence of the quiet Sun as an additional source of radio emission in the sky.