X‐ray enhancements detected during thunderstorm and lightning activities

Abstract

An X‐ray detector has been flown on‐board a NASA F‐106 jet into thunderstorms. We have concluded that significant quantities of 3 to >12 keV X‐rays are produced within thunderstorm clouds which support lightning discharge activity. It is inferred that the X‐rays are the bremsstrahlung radiation emitted from energetic electrons which have been accelerated through run‐away processes. It is suggested and supported that the structures responsible for the acceleration are strong double‐layers which are supported by the very high current densities attributed to lightning discharges.

High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena

“…12). In all the airplane data (Parks et al 1981;McCarthy and Parks 1985) and even the balloon data (Eack et al 1996a(Eack et al , 2000, it could always be either the motion of the detector's platform, or else a terminating flash, that limits the apparent duration of the event. It is quite possible that glows can be as long-lived as the high-field region in the storm producing them, but testing this requires longer data sets aloft and flight plans designed to sample the same cell repeatedly.…”

“…The modern era of observations of high-energy radiation in thunderstorms began with the airplane flights of Parks and collaborators from the University of Washington (Parks et al 1981;McCarthy and Parks 1985). A NASA F-106 jet carrying NaI scintillation detectors with thin entrance windows was flown directly into active thunderstorm cells.…”

Numerical simulations of local thundercloud field enhancements caused by runaway avalanches seeded by cosmic rays and their role in lightning initiation

“…The enhancements of penetrating radiation [Parks et al, 1981;McCarthy and Parks, 1985;Eack et al, 1996aEack et al, , 1996bEack et al, , 2000Torii et al, 2009;Tsuchiya et al, 2007Tsuchiya et al, , 2009 whose source was in thunderclouds [Babich et al, 2010], were recorded during thunderstorm activity. The enhancements observed by Parks et al [1981] and McCarthy and Parks [1985], preceded the lightning discharge and were "switched off" by the discharge itself. The bremsstrahlung of electrons multiplying and acquiring a high energy in the cloud electric field can be the only source of the enhancements.…”

“…The feedback also leads to very sharp, during a time on the order of milliseconds, rise in the number of high-energy REs and, consequently, of the flux of hard photons. However, airborne observations in thunderclouds have demonstrated only smooth growth of flux of hard X-rays with characteristic time in the second range [Parks et al, 1981;McCarthy and Parks, 1985] suggesting that relativistic feedback may not be important in the generation of lightning.…”

Balloon-Based High-Time Resolution Measurements of X-Ray Emissions From Lightning

“…In particular, most efforts lacked electric-field information that can be used to relate observed gamma-ray increases to either strong electric fields or large transients in the electric field. Only recent aircraft-based (Parks et al, 1981;McCarthy and Parks, 1985) and balloonbased (Eack et al, 1996a;Eack, 1997) measurements have provided strong evidence for gamma-ray production in thunderstorms, relying heavily on advances in electronics and thunderstorm ballooning techniques.…”