HAWC response to atmospheric electricity activity

TL;DR

This study utilizes the HAWC observatory's data to investigate how electric fields inside storm clouds accelerate electrons, revealing 20 rate enhancements linked to storm activity and providing insights into atmospheric particle acceleration.

Contribution

The paper demonstrates the use of HAWC's scaler data to detect and analyze electron acceleration events inside storm clouds, a novel application of gamma-ray observatory data.

Findings

Identified 20 rate enhancements during storm periods without cloud-earth discharges.

Electrons with tens of MeV energy are accelerated by electric fields of tens of kV/m.

Preliminary analysis suggests a link between electric fields and particle acceleration inside clouds.

Abstract

The HAWC Gamma Ray observatory consists of 300 water Cherenkov detectors (WCD) instrumented with four photo multipliers tubes (PMT) per WCD. HAWC is located between two of the highest mountains in Mexico. The high altitude (4100 m asl), the relatively short distance to the Gulf of Mexico (~100 km), the large detecting area (22 000 m$^2$) and its high sensitivity, make HAWC a good instrument to explore the acceleration of particles due to the electric fields existing inside storm clouds. In particular, the scaler system of HAWC records the output of each one of the 1200 PMTs as well as the 2, 3, and 4-fold multiplicities (logic AND in a time window of 30 ns) of each WCD with a sampling rate of 40 Hz. Using the scaler data, we have identified 20 enhancements of the observed rate during periods when storm clouds were over HAWC but without cloud-earth discharges. These enhancements can be produced by electrons with energy of tens of MeV, accelerated by the electric fields of tens of kV/m measured at the site during the storm periods. In this work, we present the recorded data, the method of analysis and our preliminary conclusions on the electron acceleration by the electric fields inside the clouds.