Subjects:Atmospheric and Oceanic Physics (physics.ao-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)
In this paper, we present the first observation of optical emission of a
downward-directed terrestrial gamma ray flash (TGF). The optical emission was
observed by a high-speed video camera Phantom v2012 in conjunction with the
Telescope Array (TA) surface detector, lightning mapping array,
interferrometer, fast antenna, and the national lightning detection network.
The suite of gamma and lightning instruments, timing resolution, and source
proximity offers us an unprecedented look at the TGF phenomena. On September 11
of 2021 we observed a storm above the TA detector. The storm resulted in six
extremely energetic TGF events that were produced by flashes with return stroke
peak currents up to 223 kA. The observed TGFs were found to correlate directly
to the initial burst pulse signal of the lightning flash while producing an
intense optical signature. Results from this study allow us to furthers the
understanding regarding the initiation mechanism of TGFs.
