#sar arc

[kestarren]

SAR arc over Agawa Bay, Ontario, Canada. Photo by Jeffery Dixon, 12 Sept '24.

[of-stars-and-dust]

Astronomy Picture of the Day

2025 January 7

A New Year's Aurora and SAR Arc

A star field appears above a town at night. The left part of the sky shows a pinkish-red glow that is an aurora, while the right part of the sky shows a smoother and darker glow that is a SAR arc.

Image Credit & Copyright: Alessandra Masi

It was a new year, and the sky was doubly red. The new year meant that the Earth had returned to its usual place in its orbit on January 1, a place a few days before its closest approach to the Sun. The first of the two red skyglows, on the left, was a red aurora, complete with vertical rays, caused by a blast from the Sun pushing charged particles into Earth's atmosphere. The second red glow, most prominent on the far right, was possibly a SAR arc caused by a river of charged particles flowing across Earth's atmosphere. Although both appear red, the slight color difference is likely due to the aurora being emitted by both oxygen and nitrogen, whereas the higher SAR arc was possibly emitted more purely by atmospheric oxygen. The featured image was taken on January 1 from near Pieve di Cadore in Italy.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.