Northern Lights Now – The large coronal hole that was pointed directly towards Earth on May 12th and 13th combined with recent solar disturbances prompted space weather forecasters to predict there will be an extended period of aurora activity the third week of May. The Space Weather Prediction Center (SWPC) issued storm watches for three consecutive days with a G1 watch posted for May 16, and G2 watches posted for both May 17 and 18. A G1 storm watch means KP values will likely exceed 4.67 during the 24 hour period, a G2 storm watch means the KP will likely exceed 5.67.
The coronal hole responsible for the expected activity stretched from North to South on the solar disk on May 13. In the image below, the coronal hole is the outlined darker area at the time it was directed towards Earth. High speed solar wind exiting from that region should arrive at Earth around May 16. As it arrives, expect solar wind speed readings from DSCOVR to increase, possibly to as high as 600 km/s. As the higher wind pushes on Earth’s magnetosphere, KP will read higher and any aurora will be stronger during periods of negative Bz.
After the initial coronal hole impact, there are two additional features that should impact Earth this week. Part two of this storm will be the arrival of a slow moving CME that launched from the southern hemisphere of the Sun on May 13. This CME is visible on LASCO C2 and C3 imagery, but it is faint. There is a decent chance it will miss Earth entirely to the south and we may see nothing from it. But it may also arrive at Earth as a glancing blow. This is a low confidence forecast, but if it does hit there could be G2 storming due the the magnetosphere already being activated by the initial coronal hole. Here’s an animatedGIF of the CME lauching as seen by LASCO C3:
Finally the third portion of this storm is most promising and is expected to impact Earth on 5/19 and 5/20. This second coronal hole produced great activity on the previous rotation in April. NLN will keep you updated with more information about this CH as it’s structure becomes evident.
Update – The storm watch has been continued to a second day. Solar wind speeds arrived later than predicted. Aurora will continue to be possible over the next 24 hours:
Northern Lights Now – SWPC has issued a geomagnetic storm watch for Thursday, February 23. This means KP values could exceed 5 with aurora visible in higher latitudes. Viewing conditions will be favorable with an almost new waning crescent Moon. The confidence on this storm is a little lower than other recent storms, but is high enough to merit a watch.
The potential aurora is due to the combination of a coronal hole that was pointed towards the Earth on February 20, and a filament eruption that produces a CME from just North of the coronal hole.
The coronal hole, pictured below, is likely to produce solar wind speeds at Earth in the 500-550 km/s range. The winds could pick up anytime between 20:00 GMT on the 22nd and 8:00am GMT on the 23rd. Once wind speeds increase, if the Bz shifts southward (negative), it will indicate northern lights activity is about to increase. Monitor solar wind speed and current Bz on NLN’s DSCOVR Solar Wind Data Page to know when aurora activity is about to increase.
The eruption was from a filament just to the north of center disk and February 19th. Watch the eruption in the animatedGIF below. The plasma cloud is visible shooting out, mostly northward, from the location of the filament. If the material from that cloud is pulled into the solar wind, it will be accelerated and pushed toward Earth. If that happened (forecasters can’t know for sure until the solar wind arrives) it could enhance the aurora activity by increasing the plasma density and accentuating the shifts in the Bz.
This is a slightly lower confidence prediction because the predicted solar wind speed is moderate, and there is a good chance that none of the plasma directed was toward Earth. The plasma may move off into space well above Earth’s North Pole. The image above showing the eruption does appear to show most of the material ejected moving to the north.
Northern Lights Now – A large coronal hole that crosses the Solar equator will produce conditions conducive to aurora Thursday through Saturday this week. The expected enhanced solar winds could reach 700km/s and as a result SWPC has issued a three day G1 geomagnetic storm watch. This means KP values are likely to be enhanced and there is a good chance they will exceed KP=4.67.
This coronal hole is the return of a system that produced G1 storming on previous rotations in early October and November. Looking at the form and location of the coronal hole over the last four rotations, it is clear that it is a little farther north and bigger for this rotation. Each rotation takes about 27 days. Past experience has shown that the more of the coronal hole that passes through the center of the earth strike zone, the portion of the Solar disk pointed towards Earth, the longer the period of enhanced solar winds.
Close NLN readers and aurora hunters will recognize that this is a different coronal hole than the large system that has been producing storming in the second half of the month September, October and November. That system appeared to have been falling losing definition in the previous rotation, so when it rotates into view over the next couple weeks, watch it to see if it has regained organization or has continued to dissapate.
For this storm, the current expect timing of G1 storming conditions is just at the beginning of each UTC day during the watch period. The timing on these specific forecasts is difficult to predict but is often a good indicator of when it is worth keeping an eye on DSCOVR Solar wind data and the current KP.