Monday evening, Active Solar region 2158 (Beta-Delta-Gamma) produced a very long duration M4.57 Solar flare. A large, partially Earth-directed coronal mass ejection (CME) was associated. As a result, high latitude Aurora hunters should be on alert Thursday and Friday. The Space Weather Prediction Center (SWPC) has issued a geomagnetic storm watch for possible G2 (KP = 6) conditions on 9/12/2014 and a G1 (KP=5) watch for 9/13/2014.
Region 2158 had been relatively quiet since it rotated into view late last week. The region grew in magnetic complexity from Beta to Beta-Delta to Beta-Delta-Gamma over the week. On Sunday, it was Beta-Delta-Gamma, but did not produce any notable flares. Monday it produced a C-level flare about 4 hours before launching the longest duration M or X class flare of the year.
The flare was 140 minutes (2:20) in duration and x-ray measurements remained above M-Class for 2 hours 45 minutes. Generally the longer a flare continues the more likely it is to release a CME and the larger and more complex that CME will be. The next longest M or X class flare we have seen in 2014 was the February 4 M1.56 CME which lasted abuot 90 minutes. Most M-Class flares have a duration around 30 minutes.
The position of region 2158 at the time of the flare was good for potential Aurora activity but not ideal. In the image below, region 2158 is the large disturbed area in the mid-upper left.
Regions rotate from left to right across or view of the Sun as Earth orbits and the Sun rotates. It takes about 14 days for a region to cross the earth-facing portion of the Sun. The closer a flare occurs to the center point, the more likely the resulting CME is to have an Earth-directed component.
The CME that is approaching Earth is due is due to arrive in the first part of 9/12 UTC. This means somewhere between midnight and 6:00am EST +/- six hours. Aurora hunting weather looks good for most of the country Thursday night into Friday morning. Here’s a map of the cloudcover forecast during the expected peak of aurora Activity.
As always, monitor the KP at http://northernlightsnow.com/current-kp-realtime/