2017 Winner: The Existence of Terrestrial Gamma-Ray Flashes that Paralyze RHESSI

Project Information
The Existence of Terrestrial Gamma-Ray Flashes that Paralyze RHESSI
Physical and Biological Sciences
We present a new subclass of Terrestrial Gamma Ray Flashes (TGFs), which are bursts of gamma-rays that are developed in thunderclouds. These bursts were first discovered in 1994 by the Burst And Transient Source Experiment (BATSE) on the Compton Gamma-ray Observatory, an experiment originally focused on cosmic gamma-rays. Surprisingly, BATSE found that high energy radiation was also coming from lightning storms on earth. Since the publication of this foundational result, physicists and meteorologists alike have used other low earth orbit satellites, including the Reuven-Ramaty High Energy Solar Spectroscopic Imager (RHESSI), to interrogate the structure of TGFs. We add to this body of work: we show that there exist TGFs that are brighter than what was hitherto presented in the RHESSI literature. We do this by implementing a search algorithm which looks for count-rate outliers in the data, and then arguing that these outliers are TGFs by explaining their structure and showing that they have a statistically significant correlation with lightning location data. For more details, I attach my scientific abstract, which avoids overly technical language in the interest of clarity anyways.

We argue for the existence of Terrestrial Gamma-ray Flashes (TGFs) that paralyze the Reuven-Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We present a catalog of candidate RHESSI-paralyzing TGFs (RPTs), and show that the candidates originate from thunderclouds as opposed to cosmic sources. We do this by (1) indicating properties in the RPTs' time series that are associated to TGF characteristics and (2) demonstrating a correlation between the candidate RPTs with World Wide Lightning Location Network (WWLLN) radio sferics and the Grefenstette catalog of standard TGFs (Grefenstette et al. 2009). For (1), we show that the hitherto accepted TGF production mechanism known as the Relativistic Runaway Electron Avalanche (RREA) and the Compton scattering of gamma-rays in the atmosphere both produce observable characteristics in the candidates' time series. For (2), we produce empirical distributions for three quality factors using 1000 randomly generated catalogs. The quality factors are (1) WWLLN storm match rate, (2) WWLLN flash match rate, and (3) geographical/seasonal correlation with the Grefenstette catalog of TGFs. We show that the candidate RPTs are not a random set of dates with greater than 98\% confidence in all cases, where we assume that the errors in our sample distributions are negligible.
PDF icon 888.pdf
  • Alexander Gerd-Dara Infanger (Kresge)