Aurora chasers are on alert after NOAA's Space Weather Prediction Center (SWPC) issued a moderate (G2) geomagnetic storm watch for Friday (Aug. 28), as coronal mass ejections (CMEs) launched from the sun yesterday (Aug. 25) head toward Earth.
The CME arrival follows a powerful M6.9 solar flare from restless sunspot region 4513 on Aug. 25. NOAA's SWPC has also issued a minor (G1) geomagnetic storm watch for Thursday (Aug. 27), as a stream of fast solar wind from a coronal hole is expected to buffet Earth ahead of the incoming CMEs
The M6.98 solar flare erupted from the active sunspot region 4513 and peaked at 6 a.m. EDT (1000 GMT), according to SpaceWeatherLive. 4513 has been particularly active over the previous 24 hours, firing off a barrage of solar flares including five powerful M-class eruptions. Solar flares are ranked by strength into five classes — A, B, C, M and X — with each class 10 times more powerful than the one before it. M-class flares are the second-strongest category, sitting just below the most powerful X-class eruptions.
The eruption also triggered a moderate (R2) radio blackout across the sunlit side of Earth, affecting high-frequency radio communications over parts of Africa, Europe and the Arctic.
CME incoming and possible northern lights?
The M6.9 flare wasn't the only eruption to launch material into space on Aug. 25. Several CMEs left the sun that day and NOAA's SWPC now anticipates their arrival at Earth.
NOAA's SWPC has issued a moderate (G2) geomagnetic storm watch for Aug. 28.
Before then, a coronal hole high-speed stream is forecast to reach Earth, prompting a minor (G1) geomagnetic storm watch for Aug. 27. NOAA forecasts isolated G1 to G2 conditions across Aug. 27-28 due to the combined influence of the high-speed solar wind stream and the incoming CME activity.
During G2 geomagnetic storm conditions, the northern lights can push farther south than usual, potentially becoming visible across parts of the northern U.S. and northern Europe.
If the glancing CME arrival coincides with the high-speed solar wind stream, the two influences could work together to ramp up geomagnetic activity and potentially enhance aurora activity.
How much of an impact the CME ultimately has will depend on its exact arrival time and, crucially, the orientation of its magnetic field when it reaches Earth. A strong southward magnetic field would interact more effectively with Earth's magnetic field, increasing the chances of stronger geomagnetic activity.
We'll be keeping a close eye on the latest models and space weather forecasts as Friday approaches and will update this story as more information becomes available.
Editor's note: This story was updated on Aug. 26 at 4:00 a.m. EDT (0800 GMT) to include NOAA's latest forecast and geomagnetic storm watches for Aug. 27 and Aug. 28.