UPDATE: 20:00UTC December 31
The New Year’s Aurora of 2016 is playing out as expected in the “slower CME, longer storm” forecast scenario. There have been a few periods of G1-G2 storming. Wing-KP was overestimating the Kp and calling for 7+ earlier in the day. About 2 hours ago, Bz shifted strongly to the south and it has been in the -15nT to -17nT range since. It’s likely that the Wing-Kp model is now underestimating the actual extend of the aurora. The next 1-4 hours could produce some very good aurora. It even look likes there may be some clearing around sunset for downeast Maine, if the storm lasts another 6 hours, the upper Midwest may see northern lights around sunset as well
UPDATE: 04:00UTC December 31
The CME arrived! It arrived shortly after the previous update. so far Solar wind speed have been in the 425-475 km/s range, which is fairly low for a CME. The Bz component of the magnetic field has switched a couple times between negative and positive. There was a 45 minute period of sustained south orientation that pushed the KP to 5, but it has since subsided. It’s likely there will be more periods of high KP over the coming hours. Here’s is what the ACE data looked at at the moment the CME first arrived:
There are a lot of articles being posted about the ongoing storm. NLN has started a live updated post that contains links to those articles.
UPDATE: 00:00UTC December 31
8 hours after the official forecasted arrival of the CME, it hasn’t arrived yet. Not to worry, it is still on it’s way.
As noted in the original post, this means that it’s more likely the NASA Enlil model is closer to correct than the SWPC model. That means a wider, slower moving CME. It will bring a slightly weaker storm with slower solar wind speeds, but it also should make for a longer duration storm. This will give aurora hunters on the west coast and in Australia/NewZealand a better chance. If the storm lasts long enough, some new year’s revelers in Europe, Iceland and the East coast of the United states could be ringing in the new year under a dancing sky. Here’s the updated forecast graphic from SWPC:
UPDATE: 03:00UTC December 30
As the watch period begins, SWPC has updated the storm watch to G3. This means that KP=7+ is expected. There have only been a couple storms of this magnitude during this solar cycle. The timing of the start of the storm has stayed the same, roughly around 3pm UTC (10:00am EST). The duration prediction was extended to 15 hours, which should give north american viewers a better chance of seeing northern lights.
EPAM will continue to rise as the CME approaches Earth. Once the shock hits, EPAM should spike up, then start to decline. When the CME arrives at the ACE satellite, watch the Bz, if it is negative, this storm could be really good. If the Bz stays positive, this storm could top out at just KP=5, so keep your fingers crossed.
Also keep an eye on the arrival time of the CME. The later it arrives the weaker the storm will be, but the longer it will last (because the CME was moving slower than expected.
Original Post: 06:00UTC December 29
The Earth-directed Coronal Mass Ejection (CME) from Monday’s long duration solar flare is predicted to arrive on December 20. The Space Weather Prediction Center has issued a G2 geomagnetic storm watch for Wednesday and a G1 watch for Thursday. Aurora hunters with clear skies should get a nice show. For clouded-in skywatchers, keep an eye on the NLN Twitter feed for images of the northern lights.
Monday’s M1.86 originated from active region 2473 (Beta-Delta), the same region that produced a couple M-class flares as it rotated onto the disk about a week ago. The region was beyond the center of the Earth-strike zone during for this eruption, but was close enough for a nice CME signature on LASCO. In the CACTus image below, see the partial halo ejection:
The two main models that are used to predict the timelines of the storm are in disagreement. The official forecast model shows a stronger faster moving storm arriving around noon eastern time and lasting 6-12 hours. The NASA model shows a slower moving storm, that would be weaker, arrive later and last longer. It will be exciting to see which model proves correct. Here is the current predicted timeline for the KP according to the SWPC models.
NLN will continue to post updates on the twitter feed as this storm progresses.