====== Terrestrial gamma-ray flashes ======

//Terrestrial gamma-ray flashes// (TGFs) were first reported using data from the Burst and Transient Source Experiment (BATSE) onboard NASA's [[https://en.wikipedia.org/wiki/Compton_Gamma_Ray_Observatory|Compton Gamma-Ray Observatory]] (CGRO) in 1994.

The short duration (0.2 to 3.5 milliseconds) atmospheric bursts of gamma rays (i.e. very high energy photons) were initially thought to be caused by relativistic runaway electron avalanches acting on natural background radiation, or extensive cosmic-ray air showers - these theories are now largely discounted.

Current research is concentrating on the possibility of relativistic feedback or runaway electron production caused by super-accelerated electrons in the very strong electric fields inside thunder clouds.

See :__ BROKEN-LINK:[[http://onlinelibrary.wiley.com/doi/10.1029/2007JD009248/full|Journal of Physical Research]]LINK-BROKEN__ 2008

Two 2023 research projects which analysed thunder-cloud data collected by very high altitude aircraft (rather than orbiting satellites) found that the flashes are far more common than previously thought. The sensors also picked up longer flashers - lasting a few tens of milliseconds - as well as gamma ray 'glows' persisting for tens of seconds. ([[https://www.nature.com/articles/s41586-024-07893-0.epdf?sharing_token=qojgq--m2OBvwhVajwukGdRgN0jAjWel9jnR3ZoTv0NHsBj4R9dnTW4fYplV6anv1-11A1uKV6_5ePnCGhCe5BZJ8FiUWSRetpbTHkRoDSjZOVA6mbBBReH7QibN31c-NDxpGUHLVJk2hDLUU-e2ikgP9bUE8dBIoT4v45m0FWvLd8G0COPV4t6-fYeGm5apKjibz40NW_YZXacPEwZEXaf5_Wnjth5A8M02GB54u8w%3D|ref. 1]]{{:oa_padlock_grn.png?16}} and [[https://www.nature.com/articles/s41586-024-07936-6.epdf?sharing_token=mvvNk4BzpnU804dNJfIB29RgN0jAjWel9jnR3ZoTv0NOFB9py7vLM5bLfqfpobIKJt39BGqiQfmukidMg6mjd-RBHouVHuswiKtRreIC7NfGMGnRIsEBUtXTXWb_mtjGe2mLVYdaR5aiklSqo6dGMfi3nhTnNsqGIxFi3FS2NGFfCMUFeVOPB8WuJ3wTqiNWT1ucPJYMQcbRwZqaCQ8jJMk6V92yiO2VBujXu1y3Po4%3D|ref, 2]]{{:oa_padlock_grn.png?16}})

However. the exact mechanisms for the generation of the gamma rays are still unclear.

//Notes ://

[1] It's now known that the gamma ray emissions are strongly linked with (and synchronized to) [[content:earth_sciences:lightning|lightning stikes]]

[2] Gamma ray flashes have also been observed around volcanic eruptions ([[http://wwlln.net/publications/briggs_tonga_grl2022.pdf|ref.]]{{:oa_padlock_grn.png?16}})