A diffuse double is seen low in the northern sky at 9:30 p.m. CDT this evening September 11, 2014. The Big Dipper is off to the left. Credit: Bob King
(Scroll down for the latest update)
Just came in from a check on the northern lights and they’re out. Just a quiet start, but I can see a classic green arc low in the northern sky. Once my eyes were dark adapted, faint rays streaked the sky above the arc. No doubt they would have stood out more boldly were it not for the rising gibbous moon off to the east. Stay tuned for more updates during the night.
Faint rays streak either side of this photo taken at 9:35 p.m. Moonlight lowered the contrast but they were dimly visible with the naked eye. Credit: Bob King
Here are some links for you to check out to help you plan through the night:
The approximate extent of the auroral oval forecast for 10:30 p.m. CDT from Ovation. Credit: NOAA
* Ovation oval – shows the approximate extent of the auroral oval that looks like a cap centered on Earth’s geomagnetic pole. During storms, the oval extends south into the northern U.S. and farther.
* Kp index – indicator of magnetic activity high overhead and updated every three hours. A Kp index of “5″ means the onset of a minor storm; a Kp of “6″, a moderate storm.
* NOAA space weather forecast
* Advanced Composition Explorer (ACE) satellite plots - The magnetic field direction of the arriving wind from the sun. The topmost graph, plotting Bz, is your friend. When it drops into the negative zone that’s good! A prolonged stay at -10 or lower increases the chance of seeing the aurora.
* UPDATE 8:15 a.m. Saturday Sept. 13: Well, well, well. Yes, the effects of the solar blast did arrive and we did experience a G3 storm, only the best part happened before nightfall had settled over the U.S. and southern Canada. The peak was also fairly brief. All those arriving protons and electrons connected for a time with Earth’s magnetic field but then disconnected, leaving us with a weak storm for much of the rest of the night. More activity is expected tonight but the forecast calls for a lesser G1 geomagnetic storm.
* UPDATE 10:30 p.m. : Although the aurora has died back, I just got the NOAA forecast update which still calls for a strong storm overnight. Crossing my fingers it happens.
Graph of Bz from the ACE spacecraft shows the past 24 hours of solar wind direction changes. Far right is 11 p.m. CDT Credit: NOAA
* UPDATE 9:30 p.m. : Definite aurora seen through breaks in the clouds low in the northern sky here in Duluth, Minn. After a big surge late this afternoon and during early evening, activity’s temporarily dropped off. The ACE plot has “gone north”. Will keep tabs and report back.
* UPDATE Friday 7:30 p.m September 12: Wow! Kp=7 (G3 storm). Auroras should be visible now over the far eastern seaboard of Canada including New Brunswick and the Gaspe Peninsula. If I were a betting man, folks in Maine should see at least a low, glowing arc in the northern sky. Still dusk here in Duluth.
* UPDATE Friday 3 p.m.: The Kp index is now at “5″ or minor storm. If you live in the Scandinavian countries or Iceland, you’re getting a very good show right now.
* UPDATE Friday 9 a.m. September 12: Auroras did appear as forecast overnight beginning at nightfall and continuing through about 1 a.m. this morning. Then the action stopped. The Kp index reached “5″ during that time leading to a G1 or minor geomagnetic storm. It wasn’t a particularly bright aurora, remained low in the northern sky and had to compete with moonlight, so many of you may not have seen it.
The stronger G3 geomagnetic storm from the second and more Earth-directed solar blast is still forecast for tonight. This should bring a much better display and should begin right at nightfall. Peak is expected between 10 p.m. and 1 a.m. Central Daylight Time.
My forecast is good, so I’ll be updating during the night. Good luck and clear skies!