SAR arc outbreak over the Baltics and Russia

A coronal mass ejection (CME) that hit Earth on March 3, 2024, sparked G2 – Moderate geomagnetic storming with widespread Stable Auroral Red (SAR) arcs over the Baltics and Russia.

SAR arcs were widely observed, from Latvia to eastern Russia during the last G2 geomagnetic storm, as reported by Dr. Tony Phillips of SpaceWeather.com.

“Glowing with some of the purest red light nature can produce, these arcs look like auroras but are produced by a completely different process,” Phillips said.

While auroras appear when charged particles rain down from space, hitting the atmosphere and causing it to glow, SARs are a sign of heat energy leaking into the upper atmosphere from Earth’s ring current system, a donut-shaped circuit carrying millions of amps around our planet.

“During the geomagnetic storm of March 3, this ring current sprang a significant leak,” Phillips explained.

“It emerged from the trees and passed right by the Pleiades… the red color was so pure,” said Vladimir Nerush, who photographed the SAR arc (above) just east of Moscow.

SAR arcs are among the reddest things in the sky, with a monochromatic glow at 6300 Å that comes from atomic oxygen in the upper atmosphere. While the human eye is relatively insensitive to light at this wavelength cameras catch them easily. Phillips also shared a pro tip for those who want to capture them in all their beauty: use a 6300 Å filter.

References:

¹ These red lights are not auroras – SpaceWeather – March 8, 2024

Featured image: SAR arc over Kiia küla, Estonia. Credit: Märt Varatu via SpaceWeather