Lightning Initiation and Propagation

It has been recently discovered that x-rays are emitted by lightning. Spacecraft, aircraft and ground-based measurements at the International Center for Lightning Research and Testing (ICLRT) are being used to investigate these emissions. In particular, rocket-triggered lightning is measured using the Thunderstorm Energetic Radiation Array (TERA). This research is also aimed at understating how lightning is initiated and how it propagates.

The Thunderstorm Energetic Radiation Array (TERA) is an experiment designed to measure energetic radiation (x-rays and gamma rays) from thunderclouds and lightning. The TERA array is also part of an experiment called the MSE (Multiple Station Experiment), which is used to study the electric and magnetic fields from rocket-triggered lightning and nearby natural lightning. Besides the x-ray detectors, the MSE/TERA stations are also equipped with instrumentation to measure electric fields and their derivatives as well as magnetic fields using flat plate antennas and loop antennas. The flat plate antennas are used to measure the vertical component of the electric field and its derivative for nearby storms. Due to some charge movement during the leader formation process, a process which is still not yet fully understood, electromagnetic pulses are produced; these pulses are picked up by the sensitive antennas. After accounting for the propagation delay through the fiber optic and the electronics, the radiation source of these pulses is located using TOA techniques that are based on the arrival times of the dE/dt pulses. The 24 TERA instruments are distributed at different stations across the ~1 km2 ICLRT site, centered on the rocket-triggered lightning launch tower. Monte Carlo simulations are compared with data from TERA to infer properties of the x-ray emissions from lightning as well as properties of the lightning leaders.

This project investigates not only how rocket-triggered lightning works, but how lightning is initiated inside the thunderclouds, and how terrestrial gamma-ray flashes are made.