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G2 Storm Watch: CME Speeds Toward Earth for Oct. 9 Aurora Show
By @sharedot · · 6 pages
- Science
- Space
- Aurora Borealis
- Geomagnetic Storm
NOAA issued a G2 storm watch for Oct. 9 as a CME speeds toward Earth, potentially pushing auroras as far south as New York.
A Solar Eruption Sets Its Sights on Earth
The sun unleashed a powerful eruption early on October 6, launching a coronal mass ejection (CME) toward Earth following an M1.4-class solar flare from sunspot region AR4549, which sits near the center of the Earth-facing side of the sun. NOAA's Space Weather Prediction Center (SWPC) has responded by issuing a moderate (G2) geomagnetic storm watch for October 9, when the CME is expected to reach our planet. According to Space, forecasters at Belgium's Solar Influences Data Analysis Center (SIDC) estimate the CME is traveling at roughly 560 km/s, with current models putting its arrival in the early hours of October 9 UTC. NOAA's WSA-ENLIL model indicates the leading edge could reach Earth around 05:00 UTC (1 a.m. EDT) on October 9. The U.K. Met Office predicts an arrival near midnight EDT, give or take six hours.
Why the Timing and Direction Remain Uncertain
Predicting when a solar storm will arrive is notoriously difficult, and forecasters are still refining their estimates. According to The Economic Times, solar eruptions travel across millions of miles, which makes precise timing nearly impossible, and arrival estimates can shift by several hours as the cloud approaches. Space reports that space weather forecasters are busy analyzing coronagraph observations and models to determine the CME's trajectory and speed. Even an Earth-directed CME does not guarantee an impressive geomagnetic storm — much depends on the strength and orientation of the magnetic field carried by the CME when it reaches Earth. A southward orientation connects efficiently with Earth's magnetic field, allowing more energy to enter the magnetosphere and intensify auroras, while a northward orientation may produce a much weaker response, The Economic Times notes.
How Far South Could the Northern Lights Reach?
If a substantial part of the CME is Earth-directed, it could trigger a geomagnetic storm and push auroras into lower latitudes than usual. Geomagnetic storms are ranked on a scale of 1 to 5, from G1 (minor) to G5 (extreme), and G2 conditions correspond to a Kp index of 6. According to Space, auroras have previously been seen as far south as New York and Idaho during storms of this strength, though this does not guarantee those states will see the lights this time. The Economic Times reports that Alaska and areas near Canada usually have the strongest odds, while northern states may also catch the display if the storm reaches its predicted strength. Cloud cover and city lights can erase a view, and a faint aurora may look grey to the eye while appearing green through a phone camera.
What to Watch For — and What Comes Next
NOAA's latest three-day forecast shows G1 conditions between 11 p.m. and 2 a.m. EDT on October 8-9, with a possible G2 peak between 5 a.m. and 8 a.m. EDT on October 9, though daylight will limit viewing during that later window across much of the United States, according to The Economic Times. And this might not be all the sun has in store: Space reports that AR4549 produced another M-class flare, an M1.8, just hours after the first eruption, and that sunspot regions AR4549 and AR4545 are both facing Earth with increasing flare activity. Coronal holes rotating across the Earth-facing side of the sun are expected to send further streams of fast solar wind our way, with another enhanced period of geomagnetic activity predicted around October 11. Aurora watchers should keep alerts switched on and treat every timing estimate as provisional.