Northern Lights Now – SWPC has issued two geomagnetic storm watches for G2 storming (KP=6+) on August 2nd and G1 storming (KP=5+) on August 3rd. These watches are the result of a pair of solar features that will impact Earth starting midday UTC on August 2nd. The NLN AuroraCast shows the current predicted timing for the timing. As always, these can be within +/- 6 hours:
Please visit NLN’s live blog of this storm and follow out Twitter feed for the most up-to-date information.
The first solar event that will impact Earth is the arrival of a very slow moving CME (Coronal Mass Ejection) that was launched during the July 28th filament eruption. The eruption happened almost dead center (near N01E06) on the solar disk. The associated CME was estimated to be travelling at 125-150 km/s. At that speed, it could take as many as 7 days for the CME to arrive at Earth, but it should be pushed by the ambient solar wind to 350 km/s or so. Then, an even higher wind from a coronal hole high speed wind stream should push it even faster to 600-650 km/s. There are several factors making the timing on this forecast complex – current models show the CME arriving midday to late August 2nd, 5 days after it’s launch.
In the animated GIF below watch the filament eruption in a composite of AIA 211, 193 and 171 wavelengths. These frames are about 14 hours of images taken by the Solar Dynamic Observatory (SDO) cameras. Note that just to the east (left) of the eruption, the coronal hole rotating into center disk is visible as a darker area:
The second feature is a large coronal hole that rotated into geoeffective position on July 31. The high speed stream from this CH measured at STEREO Ahead indicated that winds could reach 650-750 km/s at L1. This very strong wind will likely start impacting Earth either with or just after the CME arrives. If it “pushes” the particles in the CME, they will arrive at the leading edge of the shock. Due to the elongated shape of the CH, the period of elevated winds could be extended in duration. Here is an image of the coronal hole from SDO in AIA 211 from July 31 as it rotated toward Earth:
Together these storms have the potential to arrive with a strong shock and an extended period of high solar wind and active geomagnetic conditions. If they do, it should be a very good couple of nights for aurora hunters worldwide. As an added bonus, the Moon will be waxing just past new, so skies should be dark.
Northern Lights Now – There is a slight chance for an aurora display on July 20 and July 21 UTC. The most likely times are in the evening, just after sunset and before moonrise, across the Northern United States. The chances aurora may be visible are higher at this time because a cloud of magnetically charged gas is moving toward Earth after an eruption on the Sun on Sunday. The chances are only slight because the cloud is moving slowly and when it arrives it may not have enough magnetic charge to activate the aurora bands. It will also be hard to see any aurora because the Moon will be full or near-full, which will make the sky fairly bright overnight.
That said – keep your cameras ready because there’s a chance!
Northern Lights Now – On July 16 NLN noted that there was a delta spot on active region 2567. The delta spot didn’t last long, but the active region interacted with AR 2565 to produce several C-class flares over the next 24-36 hours. Early on the 17th, between 5:39 and 9:27 UTC, there was a long duration C1 flare between the two with a period of coronal dimming. Coronal dimming is often a sign that a CME was launched – sure enough a large, but slow CME was launched AND the region was in the Earth strike zone. It get’s better, there is coronal hole pointed towards Earth that could enhance the incoming solar storm. Social media is abuzz with the prospect we might get a solar storm and an aurora show.
Not so fast! While the CME had an asymmetric halo signature, it was quite faint. It’s likely there was not a lot of material ejected. Subsequent WSA-Enlil model runs show a small impact from a slow moving CME early on July 21. The model indicate such a diffuse impact that SWPC has chosen not to post a storm watch. The max predicted KP is 4. In addition to that, the moon will be nearly full as a waning gibbous, so at best there will be an hour two of true dark just after sunset.
Bottom line – There is definitely a higher chance for aurora late on the 20th and early on the 21st than at other times. If the orientation of the CME is favorable, or if it is pushed faster than the models suggest by the high speed wind, we could easily see a period of G1 storming. This is a wait-and-see type event, have your cameras charged and ready just in case.