Green flash, 2020 August 8th. An unusual sunset for several reasons... a thread 🧵 #GreenFlash #StormHour (1/10)
Here's a close-up of that green flash in real time... atmospheric turbulence makes the Sun appear to be in flames... (2/10)
A few minutes earlier, the Sun was already distorted in shape before reaching the horizon, due to atmospheric refraction, forming what's termed an Etruscan vase shape for sunsets like this... (3/10)
Thankfully this was not what it appears to be! Before reaching the horizon, the Sun started moving behind an inversion layer in the atmosphere, where warm air lay over cold air. This causes a mirror image -a 2nd image of part of the Sun under the main disk, but upside down.(4/10)
But under that upside-down image, was a 3rd one, right way up! How can you tell? On this occasion, a sunspot! There was only one that day - "small" region 12770 - shown here in @NASASun's SDO spacecraft data. Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams. (5/10)
This sunspot appeared as a single dot near the horizon as sunset approached (circled), but then it did something odd... (6/10)
It split into two - there was one sunspot, but two images of it, thanks to the refraction of light in the atmosphere... (7/10)
Here's a movie of it in real time - one spot moves up, and the other down... (8/10)
This can all be explained by the atmospheric conditions at the time: this was a Ducted Mock-Mirage sunset. Nice to be able to demonstrate these effects with a sunspot! More details of this type of sunset here: (9/10)
When I photographed this, I was 140m above sea level (Mynydd Parys, Anglesey, Wales), viewing the Sun setting over Dundalk, Ireland, about 95 km away over the Irish Sea. There were other weird atmospheric effects that evening, but I'll leave those for another time! (10/10)
(Oops, actually 95 miles / 150 km away!)
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