The SAR and the Milky Way (Astronomy Picture of the Day)

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Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2023 November 11

See Explanation. Clicking on the picture [at link] will download the highest resolution version available.

The SAR and the Milky Way

Image Credit & Copyright: Julien Looten

Explanation: This broad, luminous red arc was a surprising visitor to partly cloudy evening skies over northern France. Captured extending toward the zenith in a west-to-east mosaic of images from November 5, the faint atmospheric ribbon of light is an example of a Stable Auroral Red (SAR) arc. The rare night sky phenomenon was also spotted at unusually low latitudes around world, along with more dynamic auroral displays during an intense geomagnetic storm. SAR arcs and their relation to auroral emission have been explored by citizen science and satellite investigations. From altitudes substantially above the normal auroral glow, the deep red SAR emission is thought to be caused by strong heating due to currents flowing in planet Earth's inner magnetosphere. Beyond this SAR, the Milky Way arcs above the cloud banks along the horizon, a regular visitor to night skies over northern France.