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The phenomenon of ‘earthquake lights’ has long sat at the fringes of science, though the anecdotal evidence for their occurrence is fairly strong (see this previous story on earthquake lights in Italy for example). But what could be the cause of these mysterious lights in the sky? A new and fascinating paper on Arxiv.org may provide an answer: a connection between ground and atmosphere that sees the ionosphere becoming massively charged with electrons with the onset of an earthquake.

Technology Review has a good wrap-up of the research:

Geologists have long puzzled over anecdotal reports of strange atmospheric phenomena in the days before big earthquakes. But good data to back up these stories has been hard to come by.

In recent years, however, various teams have set up atmospheric monitoring stations in earthquake zones and a number of satellites are capable of sending back data about the state of the upper atmosphere and the ionosphere during an earthquake.

…Today, Dimitar Ouzounov at the NASA Goddard Space Flight Centre in Maryland and a few buddies present the data from the Great Tohoku earthquake which devastated Japan on 11 March. Their results, although preliminary, are eye-opening.

They say that before the M9 earthquake, the total electron content of the ionosphere increased dramatically over the epicentre, reaching a maximum three days before the quake struck.

At the same time, satellite observations showed a big increase in infrared emissions from above the epicentre, which peaked in the hours before the quake. In other words, the atmosphere was heating up.

These observations help to support the hypothesis of the “Lithosphere-Atmosphere-Ionosphere Coupling mechanism”, which the paper describes primarily as “the ionization of the air produced by an increased emanation of radon (and other gases) from the Earth’s
crust in the vicinity of active fault… The increased radon emanation launches the chain of physical processes, which leads to changes in the conductivity of the air and a latent heat release (increasing air temperature)”.

Fascinating findings, and perhaps a first step towards earthquake prediction (not to mention another possible physical mechanism explaining animal ‘earthquake precognition’?).

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