Hole In Sun’s Corona Could Spark Auroras

One big, one medium and one small hole in the sun's corona (called coronal holes) darken the sun's disk this morning as viewed in ultraviolet light by the Solar Dynamics Observatory. Credit: NASA
One big, one medium and one small hole in the sun’s corona (called coronal holes) darken the sun’s disk this morning as seen in ultraviolet light by the Solar Dynamics Observatory. Credit: NASA

The sun’s atmosphere is like Swiss cheese at times. It develops these big holes that while not visible with regular filters on amateur telescopes stand out boldly in ultraviolet light. NASA’s orbiting Solar Dynamics Observatory keeps a constant watch on the sun in many wavelengths or colors of light, where the holes stand out like giant black continents on its otherwise scintillating solar disk.

The holes are regions in the sun’s corona or atmosphere where billions of tons of material streams freely into space. Nearly all of it a swarm of single protons — basically hydrogen without its buzzing cloud of electrons — mingled with free electrons and stamped with the sun’s magnetic field. Just like a bar magnet, this cloud of minute particles has a north and a south pole within it. Whooshing away into the solar system at a million miles an hour, you might liken it to a giant, expanding amoeba carrying the sun’s magnetic force across the solar system as the interplanetary magnetic field. Wow, now there’s a mouthful!

Because the sun is so brilliant, we can't see the corona except when the moon blocks the solar disk during a total solar eclipse. Then it stands out in beautiful, feathery detail. Credit: Miloslav Druckmuller / SWNS
Because the sun is so brilliant, we can’t see the corona except when the moon cover the sun’s face during a total solar eclipse. Then it stands out in beautiful, feathery detail. Credit: Miloslav Druckmuller / SWNS

Tomorrow afternoon (Nov. 22) and through about 3 a.m. Wednesday morning the 23rd, the amoeba may either slide right past Earth, protected as we are by our planet’s own magnetic field, or link into that field to make a conduit for all those crazy electrons and protons to come streaming down into our atmosphere, strike the atoms there and light up and aurora.

The NOAA space weather center predicts a minor or G1 geomagnetic storm during that time, so skywatchers in the northern U.S., Canada and northern Europe should keep watch for the aurora Tuesday night (Nov. 22) as soon as it gets dark. This would be a good time to watch for northern lights because there’s no moon to contend with. Watch the northern horizon tomorrow for greenish arcs!