Video: Japan quake light unexplained

As well known the recent 7.1 magnitude Japan quake triggered an unusual effect: a light in the sky. The misterious phenomenon was filmed during the tremor and its image was widely debated. Of course that made the delight of the UFO passionate who are fermly convinced that some aliens are behind the weird lighting. Howeverer the scientist came up with several explanations regarding the flash and they reminded that previous instance had been recorded. Although the pizeoelectric effects of the radon emission might be placed as generating source of high atmosphere flashes, yet such phenomena are not completely understood.
Video and explanations: Japan earthquake light