SWPC has issued a G2 geomagnetic storm watch for October 7th and 8th and a G1 geomagnetic storm watch for October 9th. A positive polarity equatorial coronal hole will be producing a high speed solar wind that should be arriving late on Wednesday October 7th. On the previous rotation (Sept 8) this coronal hole produced a 2 day period of G1 and G2 storming. Here’s an image of the coronal hole on the previous rotation, and on the current rotation (Click for larger view):
Coronal holes on the equator of the sun take roughly 27 days to make a full rotation. During that time they are constantly changing and evolving. It is clear this coronal hole – the dark areas on the AIA 211 images above – has become larger. It is generaly a safe bet that if the previous rotation created a strong solar stream, the current rotation will as well.
Like on the last rotation, the predicted storm is coming at a good time for aurora hunters. The Moon will be in a waning crescent phase, so there shouldn’t be much light pollution from the moon. For viewers in the northern hemisphere there is between 30 and 90 minutes of additional dark hours as the nights are longer and days are shorter since the last rotation. This is what the phase of the moon should look like:
Predicting the timing of Aurora that come from a coronal holes is a little easier than that from CMEs. It is hard to determine the speed and orientation of a CME, but with a coronal hole there is a narrower window. That said, predicting the exact timing of any geomagetic storm is difficult, and predictions can be off by as much as 6-12 hours. As of this writing, the current timeline calls for a peak of the G2 storming to happen starting at the end of October 7 and continuing through the early hours of Oct 8 – with G1 storming continuing for up to 6 more hours. For the East Coast Time zone, this means Wednesday evening from sunset through 3:00-6:00AM. NLN’s current infographic for the timing of the storm’s arrival:
The predicted timelines are updated twice daily, you can always find them on NLN’s three-day forecast page. You can also keep an eye on the current and near-term predicted KP and the ovation auroral oval on the NLN Current Current KP Real-Time page.