Gamma Rays From Thunderclouds

KentuckyFC sends us a report of gamma rays detected at a Japanese nuclear plant, whose origin was thunderclouds high overhead (abstract, article PDF). The theory is that showers of electrons caused by cosmic rays, when they encounter the high electric fields present in thunderstorm clouds, can be accelerated to energies above 10 MeV and result in bremsstrahlung photons detectable on the ground.

Comments

Or Lightning Fusing Hydrogen?

[DumbSwede]

Or possibly the fusion of deuterium/hydrogen in rain water by lightning?

I actually posted an article about this back in 2005. Lightning Fusion And Other Hot News

Not so simple

[DumbSwede]

And neutrons will crash into other nuclei and there will be secondary fissions and fusions. Neither fission nor fusion is an entirely straight forward reaction with only one set of byproducts. Muon catalyzed fusion produces gamma rays directly.

Our own star the Sun produces gamma rays from the PP-I fusion chain 4 1H 1 4He + 2 positrons + 2 neutrinos + 2 gamma rays The by-products provide the source of luminosity: * Positrons: anti-electrons (e+) - collide with electrons (e-) * Neutrinos: rapidly escape from the star * Gamma rays (photons): travel outwards through star interacting many times with atomic gas. Energy is also provided by the PP-II and PP-III chains

Depends on who you're talking to.

[Wilson_6500]

It's really one of those jargon-related things that happen so often in physics. Your average physicist uses "intensity" in ways that make optical scientists rip their hair out, since in optics intensity has a very specific definition. In the same vein, radiation scientists reserve "gamma" to describe photons originating from nuclear processes. Physicists in other specializations generally just go by energy because gammas tend to be higher in energy than X-rays. It's not necessarily the case though.

Re:They are X-rays, not gamma rays

[ceoyoyo]

Yup. The cosmic ray usually isn't a photon, it's a particle of some type that slams into the atmosphere and turns into a bunch of other particles, which slam into the atmosphere some more and eventually turn into some sort of photon. That is opposed to the gamma ray which IS a photon.

Suspected relation

[RogerWilco]

There is a suspected but yet unproven relation between cosmic rays and lightning. The theory is that when a cosmic particle strikes the atmophere, it ionises a path though the atmophere. This then provides a conduit for lightning.
This is currently a hot research topic in particle physics and meteorology.

A professor in Nijmegen and a collegue of mine are studying this phenomena (Heino Falcke and Lars Bähren)
http://www.physorg.com/news4162.html
http://www.lofar.org/workshop/23Apr07_Monday02/LOF ARWorkshop_Apr07_HeinoFalcke.pdf