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NASA Astronomy Picture of the Day:

What is that unusual red halo surrounding this aurora? It is a Stable Auroral Red (SAR) arc. SAR arcs are rare and have only been acknowledged and studied since 1954. The featured wide-angle photograph, capturing nearly an entire SAR arc surrounding more common green and red aurora, was taken earlier this month from Poolburn, New Zealand, during an especially energetic geomagnetic storm. Why SAR arcs form remains a topic of research, but is likely related to Earth's protective magnetic field, a field created by molten iron flowing deep inside the Earth. This magnetic field usually redirects incoming charged particles from the Sun's wind toward the Earth's poles. However, it also traps a ring of ions closer to the equator, where they can gain energy from the magnetosphere during high solar activity. The energetic electrons in this ion ring can collide with and excite oxygen higher in Earth's ionosphere than typical auroras, causing the oxygen to glow red. Ongoing research has uncovered evidence that a red SAR arc can even transform into a purple and green STEVE.

Photo by Tristian McDonald; Text: Tiffany Lewis (Michigan Tech U.)

A Repost

Posted by MFish Profile 01/03/24 at 05:11AM Share Poetry See more by MFish

Sometimes, reposting helps me with
this process of living. This is from December 23, 2017

A Comment by Loy

Your avatar
Loy • 01/03/2024 at 11:38PM • Like 1 Profile

Very touching and sweet poem.

The removal of the Great Works Dam on the Penobscot River in Old Town, Maine shows that when dams are removed, a river and its fish can recover with surprising speed. More at Reasons to be Cheerful ➜

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