On the possibility of radar echo detection of ultra-high energy cosmic ray- and neutrino-induced extensive air showers

TL;DR

This paper revisits a 60-year-old idea that radar detection of ionized air columns from ultra-high energy cosmic ray and neutrino showers is feasible, potentially offering a high-duty-cycle, complementary detection method.

Contribution

The paper extends and supports the possibility of radar detection of extensive air showers, highlighting its potential for detecting horizontal and distant showers, especially from ultra-high energy neutrinos.

Findings

Radar echoes can be produced by ionized air columns from high-energy air showers.

Radar detection could complement existing ground-based observatories.

Method is sensitive to horizontal and distant showers, including neutrino-induced ones.

Abstract

We revisit and extend the analysis supporting a 60 year-old suggestion that cosmic rays air showers resulting from primary particles with energies above 10^{18} eV should be straightforward to detect with radar ranging techniques, where the radar echoes are produced by scattering from the column of ionized air produced by the shower. The idea has remained curiously untested since it was proposed, but if our analysis is correct, such techniques could provide a significant alternative approach to air shower detection in a standalone array with high duty cycle, and might provide highly complementary measurements of air showers detected in existing and planned ground arrays such as the Fly's Eye or the Auger Project. The method should be particularly sensitive to showers that are transverse to and relatively distant from the detector, and is thus effective in characterizing penetrating horizontal showers such as those that might be induced by ultra-high energy neutrino primaries.