Solar Hole Could Kick Up Auroras Tonight

Auroras have been few and far between this winter. On the night of Feb. 17-18, I caught this little glow show low in the northern sky not far from my house. Credit: Bob King

The aurora’s been practically out of sight the past couple months unless you live in central Canada and points north. For U.S. observers, only a couple of weak displays — usually a mustache of pale green light just above the northern horizon — have been sighted. The scene might get livelier soon with a minor G1 storm forecast for this evening. Skywatchers living in the northern states with clear skies in the forecast should step outside tonight, allow 5-10 minutes for night vision to take hold and then scan the sky for a greenish arc or two a fist or more above the northern horizon.

See that big gash on the sun? That’s a coronal hole, an opening in the sun’s atmosphere that allows high stream plasma (a mix of electrons and protons) to gush into space. Sometimes the material finagles its way past Earth’s magnetic defenses to spark auroras. The stream arrives later this afternoon U.S. time. The photo was taken on Feb. 20 by NASA’s Solar Dynamics Observatory. Credit: NASA

This latest opportunity for northern lights comes to us courtesy of a big coronal hole (see above) that was aimed directly at the Earth earlier this week. When the material in the hole sweeps by Earth later today and its magnetic “compass” happens to be pointing south at the time, it could link into our planet’s magnetic field. There it would be directed into the upper atmosphere where the particles would excite air molecules to bring forth a modest display of northern lights.