Spaceweather.com Time Machine - February 20th, 2021

CIR HITS EARTH, SPARKS ARCTIC AURORAS: Last night, a co-rotating interaction region (CIR) hit Earth’s magnetic field. High above Norway, “it looked like the sky split open,” says aurora tour guide Marianne Bergli, who sent this picture from Kvaløya, Tromsø.

“The auroras dancing over our heads were unbelievably beautiful,” says Bergli.

A CIR is like a mini-CME (coronal mass ejection). It’s a transition zone between slow- and fast-moving streams of solar wind. Density gradients inside CIRs can mimic the shock fronts of CMEs, and often do a good job sparking auroras.

A good job? “It was great,” says Markus Varik, also in Tromsø. “The pinks and reds were the best we’ve seen in years.”