You may want to keep one eye to the sky overnight into early Thursday morning.
Wednesday the sun unleashed a significant earthward directed coronal mass ejection. The burst of solar energy triggered an impressive display of northern lights as it collided with earth’s magnetosphere in the predawn hours Wednesday morning.
Minnesota based storm chaser and photographer Doug Kiesling captured the show in this impressive time lapse video.
Earth is passing through the wake of the CME where a region of high-speed solar wind continues to buffet our planet’s magnetic field. NOAA forecasters, who suspect that a second CME might arrive on Oct. 9th, estimate a 65% chance of polar geomagnetic storms during the next 24 hours. High-latitude sky watchers should remain alert for auroras.
If we get a repeat performance overnight, the best place to witness the aurora is away from city lights. Look in the northern sky, but a potent display can shoot overhead at times.
What triggers auroras?
Auroras can be a relatively rare, beautiful and mysterious sight. Most of the usual NASA explainer sites are dark due to the shutdown, but here’s a great explanation of how auroras happen from How Stuff Works.
The auroras, both surrounding the north magnetic pole (aurora borealis) and south magnetic pole (aurora australis) occur when highly charged electrons from the solar wind interact with elements in the earth’s atmosphere. Solar winds stream away from the sun at speeds of about 1 million miles per hour. When they reach the earth, some 40 hours after leaving the sun, they follow the lines of magnetic force generated by the earth’s core and flow through the magnetosphere, a teardrop-shaped area of highly charged electrical and magnetic fields.
As the electrons enter the earth’s upper atmosphere, they will encounter atoms of oxygen and nitrogen at altitudes from 20 to 200 miles above the earth’s surface. The color of the aurora depends on which atom is struck, and the altitude of the meeting.
- Green – oxygen, up to 150 miles in altitude
- Red – oxygen, above 150 miles in altitude
- Blue – nitrogen, up to 60 miles in altitude
- Purple/violet – nitrogen, above 60 miles in altitude
All of the magnetic and electrical forces react with one another in constantly shifting combinations. These shifts and flows can be seen as the auroras “dance,” moving along with the atmospheric currents that can reach 20,000,000 amperes at 50,000 volts. (In contrast, the circuit breakers in your home will disengage when current flow exceeds 15-30 amperes at 120 volts.)
Forecast: Weather perfection now, fall transition next week
Our postcard perfect September weather pattern hangs on into Friday in Minnesota. High in the upper 70s in October? That’s a weather bonus. You have to say Minnesota received a fair payback for our reluctant spring of 2013.
The next low pressure system winds up and tracks through the eastern Dakotas Friday. the system will pass to our west, meaning we’re on the dry warm side of the storm once again.
After a chance of a few light showers Friday night, a trailing cool front brings a cooler but mostly dry weekend. Here’s the Euro model take on temps into next week from Weatherspark.