Are you sure that's from Tunguska, and not the solar storm of 1859?
I'm kind of leaning towards a volcanic eruption, particularly when an alleged scientist proclaims "would have been out
of all proportion to ones we see in recent times".
This is now, that was then. Maybe Tambora erupted spectacularly a number of times in human history, before
the early 19th Century blast.
"The first reports of a strange glow in the sky came from across Europe. Shortly after midnight on 1 July 1908, Londoners were intrigued to see a pink phosphorescent night sky over the capital. People who had retired awoke confused as the strange pink glow shone into their bedrooms. The same ruddy luminescence was reported over Belgium. The skies over Germany were curiously said to be bright green, while the heavens over Scotland were of an incredible intense whiteness which tricked the wildlife into believing it was dawn. Birdsong started and cocks crowed - at two o'clock in the morning. The skies over Moscow were so bright, photographs were taken of the streets without using a magnesium flash. A captain on a ship on the River Volga said he could see vessels on the river two miles away by the uncanny astral light. One golf game in England almost went on until four in the morning under the nocturnal glow, and in the following week The Times of London was inundated with letters from readers from all over the United Kingdom to report the curious 'false dawn'. A woman in Huntingdon wrote that she had been able to read a book in her bedroom solely by the peculiar rosy light."