Radio Detection of Ultra-high Energy Cosmic Rays with Low Lunar Orbiting SmallSats

TL;DR

This paper proposes a novel method for detecting ultra-high energy cosmic rays by using low lunar orbiting SmallSats to observe Askaryan radio emissions in the Moon's regolith, aiming to identify their astrophysical sources.

Contribution

It introduces the Zettavolt Askaryan Polarimeter (ZAP), a new concept for radio detection of UHECRs from lunar orbit, enhancing source identification capabilities.

Findings

Conceptual design of ZAP for lunar orbit detection

Potential for improved source correlation of UHECRs

Advancement over previous Earth-based and atmospheric observatory methods

Abstract

Ultra-high energy cosmic rays (UHECRs) are the most energetic particles observed and serve as a probe of the extreme universe. A key question to understanding the violent processes responsible for their acceleration is identifying which classes of astrophysical objects (active galactic nuclei or starburst galaxies, for example) correlate to their arrival directions. While source clustering is limited by deflections in the Galactic magnetic field, at the highest energies the scattering angles are sufficiently low to retain correlation with source catalogues. While there have been several studies attempting to identify source catalogue correlations with data from the Pierre Auger Observatory and the Telescope Array, the significance above an isotropic background has not yet reached the threshold for discovery. It has been known for several decades that a full-sky UHECR observatory would provide a substantial increase in sensitivity to the anisotropic component of UHECRs. There have been several concepts developed in that time targeting the identification of UHECR sources such as OWL, JEM-EUSO, and POEMMA, using fluorescence detection in the Earth's atmosphere from orbit. In this white paper, we present a concept called the Zettavolt Askaryan Polarimeter (ZAP), designed to identify the source of UHECRs using radio detection of the Askaryan radio emissions produced by UHECRs interacting in the Moon's regolith from low lunar orbit.