AkaSci 🛰️
It's happening! Aurora sightings being reported from Europe.
Just search for "aurora" on twitter or Mastodon.
Visit this website for lots of images posted in real-time in Germany -
https://www.foto-webcam.eu/
Also, see posts and boosts by @AstroMigration
Kp index now above 8.
N. America is in for a treat in the next few hours.
AkaSci 🛰️
We are now in G5 territory! Both NOAA and the GFZ in Potsdam are reporting Kp index at 9 (G5). GFZ is the source of the index. This is happening far earlier than predicted. G5 conditions were first observed at Earth at 6:54 p.m. EDT (22:54 UTC).
Let's hope we get a terrific light show tonight and nothing more 🤞.
https://kp.gfz-potsdam.de/en/figures/kp-daily-plots
18/n
#SolarStorm
AkaSci 🛰️
Here is a more granular version of the geomagnetic Kp Index called Hp30.
It has a time resolution of 30 minutes instead of 3 hours and its value is not capped at 9.
The highest Hp30 value measured today was 11.3!
The Hpo index was developed in the H2020 project SWAMI. There is an Hp60 index as well with an averaging period of 60 minutes.
AkaSci 🛰️
The serene/ferocious Sun ... just moments ago ... as imaged by the NASA Solar Dynamics Observatory (SDO) in various wavelengths.
Any CMEs from region 3664 in the next few days will not strike earth as the region (at the 4 o'clock position) is rotating away from us. But other sunspot regions may become more active and start lobbing CMEs at us
hnapel
Some results from the Netherlands...
Kees Cook :tux:
AkaSci 🛰️
Did you know (I didn't 🙁) that the term aurora borealis was coined by Galileo in 1619?
The term was derived from Aurora, the Roman goddess of the dawn and Boreas, the Greek name for the north wind.
Galileo actually believed that auroras were due to sunlight reflecting from thin, high, vaporous clouds.
https://en.wikipedia.org/wiki/Aurora#cite_note-8
https://www.google.com/books/edition/Discorso_delle_comete/_EtbAAAAcAAJ?hl=en&gbpv=1&bsq=auro
25/n
AkaSci 🛰️
Sun and Earth, by XKCD.
And us Humans in between, enjoying its life-sustaining warmth. And Auroras.
Title text: "But we don't need to worry about the boiling masses sandwiching the thin layer in which we live, since we're so fragile and short-lived that it's unlikely to kill us before something else does! Wait, why doesn't that sound reassuring?"
https://xkcd.com/2004/
https://www.explainxkcd.com/wiki/index.php
23/n
AkaSci 🛰️
Here is an image of last night's aurora over N. America as seen from space at 0658 UTC.
The image was taken by the Visible Infrared Imaging Radiometer (VIIRS) instrument onboard the NOAA-20 satellite, using its Day Night Band sensor (DNB).
The VIIRS DNB can image at very low levels of light at night in wavelengths between 0.5 – 0.9 µm (visible and some near-IR).
Most aurora emissions are at 90-150 km, but the reds last night were likely from higher altitudes.
https://cimss.ssec.wisc.edu/satellite-blog/archives/59112
24/n
AkaSci 🛰️
It's been quite an experience for many who got to see and photograph the aurora borealis last night in shimmering magenta and green colors.
No major reports of damage or disruptions.
It's not over yet. The Kp index has stayed above 8 for over 15 hours. It hit 9 again (G5) this morning. It is forecast to decline steadily over the day but rise again to around 6 tonight.
Search for "aurora" and "solar storm" to see the wonderful images taken by the good folks here.
AkaSci 🛰️
There is still a lot of activity on the frothing surface of the Sun.
Here are two sets of images taken by the Solar Dynamics Observatory (SDO) 11 hours apart. Notice the new loop at the 10 o'clock position.
There was another high energy X5.4 flare last night from the 3664 sunspot region at the 4 o'clock position, but not directed at earth.
You can see near-real-time images and time-lapse videos of the Sun at
https://sdo.gsfc.nasa.gov/data/
22/n
AkaSci 🛰️
Why does this aurora have vivid pink colors?
Auroras are caused by emissions from O atoms and N2 molecules. Solar-origin electrons cause the energy states of O and N2 to rise which result in photon emissions at specific wavelengths.
O atoms below 200 km emit in the familiar green color. O atoms above 200 km emit in red. N2 near 200 km emits in blue, N2 below 100 km emits in reds and blues that mix to produce pink.
Intense solar storms like this one cause lower altitude N2 emissions.
26/n
AkaSci 🛰️
What's up with Atomic Oxygen emissions in red and green?
O is unusual in terms of its return to ground state after excitation: it takes ~0.7 sec to emit the green light and up to 2 mins for red.
- At low altitudes, collisions with other atoms or molecules absorb the excitation energy and prevent emissions.
- At high altitudes, O density is v low which allows time for oxygen to emit red light.
- At 100-200 km, O density is sufficiently low to allow green emission.
AkaSci 🛰️
Further reading on Aurora colors -
https://www.lwpetersen.com/science-and-nature/what-causes-the-aurora/
https://atoptics.co.uk/blog/glowing-gases-aurorae/
https://www.researchgate.net/publication/233408329_The_Colors_of_the_Aurora
https://auroraborealisobservatory.com/2020/11/24/have-you-ever-seen-blue-aurora-borealis/
https://www.nps.gov/articles/-articles-aps-v8-i1-c9.htm
https://en.wikipedia.org/wiki/Aurora
http://ffden-2.phys.uaf.edu/webproj/212_spring_2015/Joyce_Dustin_Demientieff/joyce_dustindemientieff/colors.htmlhttp://ffden-2.phys.uaf.edu/webproj/212_spring_2015/Joyce_Dustin_Demientieff/joyce_dustindemientieff/colors.html
Note that 100 km is where space begins, aka the Kármán line. It is far above the highest clouds.
#Aurora
28/n
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