Limits on radio emission from meteors using the MWA

TL;DR

This study used the MWA to search for meteor radio emissions in the 72-103 MHz range but found no detections, setting limits on the spectral index and demonstrating the array's capability to detect space debris.

Contribution

First survey to set upper limits on meteor radio emission spectral index at these frequencies using the MWA.

Findings

No meteor transient detections in 322 hours of data.

Established an upper limit of -3.7 on the spectral index.

Successfully detected and tracked space debris signals.

Abstract

Recently, low frequency, broadband radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broadband spectra between 20 and 60 MHz were captured for several events, while the spectral index (dependence of flux density on frequency, with $S_\nu \propto \nu^\alpha$) was estimated to be $-4\pm1$ during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Widefield Array (MWA) at 72-103 MHz. In our 322-hour survey, down to a $5\sigma$ detection threshold of 3.5 Jy/beam, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of -3.7 (95% confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, like reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.