Mapping lightning in the sky with a mini array

TL;DR

This study demonstrates the first use of a mini array to detect and map distant lightning discharges in the sky by capturing very low frequency electromagnetic waves, revealing new potential for long-range lightning detection.

Contribution

The paper introduces a novel application of mini arrays for lightning detection and mapping, expanding their use beyond infrasonic and seismic studies.

Findings

Detected approximately 69 lightning pulses per second from distant thunderstorms.

Lightning pulses with clockwise phase progression are observed at higher elevation angles.

Long-range lightning detection networks could benefit from mini array wave propagation analysis.

Abstract

Mini arrays are commonly used for infrasonic and seismic studies. Here we report for the first time the detection and mapping of distant lightning discharges in the sky with a mini array. The array has a baseline to wavelength ratio $\sim$4.2 ${ \cdot}$ $10^{-2}$ to record very low frequency electromagnetic waves from 2 to 18 kHz. It is found that the mini array detects $\sim$69 lightning pulses per second from cloud-to-ground and in-cloud discharges, even though the parent thunderstorms are $\sim$900-1100 km away and a rigorous selection criterion based on the quality of the wavefront across the array is used. In particular, lightning pulses that exhibit a clockwise phase progression are found at larger elevation angles in the sky as the result of a birefringent subionospheric wave propagation attributed to ordinary and extraordinary waves. These results imply that long range lightning detection networks might benefit from an exploration of the wave propagation conditions with mini arrays.