The sun has been active this week as two large solar flares have aurora photographers reaching for their cameras.
A geomagnetic storm watch is in effect for Friday as a coronal mass ejection (CME) from Tuesday is expected to have a potent impact on Earth’s magnetic field. This storm could produce aurora’s grander than what we’ve seen over the past few weeks during storms less intense than this one.
Spaceweather.com describes Tuesday’s CME origins:
[On Tuesday], the magnetic canopy of sunspot AR2158 erupted, producing an explosion that lasted more than 6 hours. The flare peaked on Sept. 9th at 00:30 UT with a classification of M4 on the Richter Scale of Solar Flares. Long-duration flares tend to produce bright CMEs, and this one was no exception. Coronagraphs onboard the Solar and Heliospheric Observatory observed a CME racing out of the blast site at nearly 1,000 km/s (2.2 million mph)
According to NOAA’s Space Weather Prediction Center (SWPC), Friday’s geomagnetic storm is expected to be moderate — a G2 on the scale of intensity from G1 to G5. Storms of this magnitude typically set off voltage alarms of high-latitude power systems, and could cause transformer damage if the storm lasts long enough.
The relatively high predicted intensity of the storm also means it could be possible to see the aurora as far south as the northern U.S. states, including Wisconsin, Michigan, and New York.
Fortunately for aurora watchers in the Northwest and Northeast, the weather should be playing along as skies are expected to be clear. However, the Upper Midwest could be fighting the clouds on Thursday and Friday night, though there will likely be some breaks.
In addition to Tuesday’s ejection, scientists noted another flare on Wednesday afternoon from the same active region (AR2158). This flare was classified as X1. The X-class solar flares are the strongest classification on the scale, and can produce strong to extreme radio blackouts on the daylight side of Earth when they occur. They are also known to produce long-lasting geomagnetic storming when the associated CME arrives.
The SWPC was expecting impacts to high-frequency radio from this flare. While it’s likely that a CME was associated with this event, it’s not yet clear whether it will cause another geomagnetic storm over Earth in the coming days.