Positron clouds within thunderstorms

TL;DR

This paper reports the detection of isolated positron clouds within a thunderstorm using airborne gamma-ray detectors, revealing new insights into high-energy particle phenomena in storm environments.

Contribution

First observation of positron clouds inside thunderstorms using airborne gamma-ray detection technology.

Findings

Detected two positron clouds within a thunderstorm

Positron clouds were more than a kilometer across

Gamma-ray spectra showed clear 511 keV annihilation line

Abstract

We report the observation of two isolated clouds of positrons inside an active thunderstorm. These observations were made by the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, which flew on a Gulfstream V jet aircraft through the top of an active thunderstorm in August 2009. ADELE recorded two 511 keV gamma-ray count rate enhancements, 35 seconds apart, each lasting approximately 0.2 seconds. The enhancements, which were about a factor of 12 above background, were both accompanied by electrical activity as measured by a flat-plate antenna on the underside of the aircraft. The energy spectra were consistent with a source mostly composed of positron annihilation gamma rays, with a prominent 511 keV line clearly visible in the data. Model fits to the data suggest that the aircraft was briefly immersed in clouds of positrons, more than a kilometer across. It is not clear how the positron clouds were created within the thunderstorm, but it is possible they were caused by the presence of the aircraft in the electrified environment.