Northern Lights Now – Just a couple days before the 2017 total eclipse in the United States, there will be another exciting astonomical event. There is a chance for Aurora on August 17 and 18. The Space Weather Prediction Center (SWPC) has issued a G1 geomagnetic storm watch for Wednesday and Thursday. Global aurora activity levels could reach KP=5 on the 0-9 scale.
The expected activity is the result of a activity from a solar sector boundary crossing during high speed solar wind stream arriving from a coronal hole. The northern hemisphere coronal hole (below) pointed towards Earth on August 15th is releasing solar winds in excess of 650 km/s. The winds, and the plasma and solar particles carried on them will start to arrive early on 8/17
Embedded in the solar wind there will be disturbance along the solar sector boundary. This is basically a line on the in space between a positively charged region and a negatively charged region. As the boundary passes Earth, there will be enhanced geomagnetic activity leading to Northern Lights.
Northern Lights Now – A large polar-connected coronal hole will bring high speed solar wind to Earth starting August 4th and SWPC has posted a G2 geomagnetic storm watch. The watch means it is possible that aurora activity as measured by KP may reach 5.67 during the August 4th UTC day (from 8pm EST on 8/3 through 8pm EST on 8/4). The watch period extends into August 5th at a slightly lower activity level with G1 storming predicted.
The coronal hole responsible for this activity is large. It extends from the polar region to the Southern Hemisphere of the Sun:
Earth is expected to travel through the area of high speed solar winds sometime on Friday. Any disturbances carried on the wind stream with a negative oriented Bz could make for strong aurora activity. Keep any eye on the solar wind data, there should be a period of increased activity in Bt and Bz before the actual arrival.
The current timing and forecast for this storm calls for the G1 and G2 storming late on the 4th followed by G1 storming through midday on the 5th as winds subside. As always, these forecasts can be +/-12 hours, so the best bet is to keep an eye on the data or the Northern Lights Now Twitter feed, to know when it is best to go out.
The Moon is waxing gibbous – which means it will be visible and bright in the evening and set after midnight. The best aurora viewing times will be in the wee hours after the Moon sets.
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.