Three CMEs Boost U.S. Aurora Odds Through Oct. 11 as NOAA Flags G2 Storm Risk

Q: With only a 15-minute warning from deep-space satellites, will the Northern Lights reach your backyard tonight or fizzle out completely?

Probably yes for northern-tier locations, but it is far from guaranteed anywhere farther south. The setup is favorable: three CMEs from AR4549 are due between late Oct. 8 and Oct. 11, and NOAA’s Space Weather Prediction Center has a G2, or moderate, geomagnetic storm watch for Oct. 9. That level has previously pushed auroras as far south as New York and Idaho, while the best odds remain in Alaska, Canada and the northern U.S. The catch is that aurora forecasts stay uncertain until the storm is almost on top of Earth. Spacecraft near the L1 point, such as ACE and DSCOVR, can measure the solar wind and the CME’s magnetic field only about 15 to 60 minutes before impact. The most important factor is whether the CME’s magnetic field turns southward. If it does, it couples efficiently with Earth’s field and the auroral oval can expand quickly. If it does not, the display can underperform or fizzle. So whether the lights reach your backyard tonight depends on two things: where you are and what the CME looks like when it arrives. If you are in the northern states, your chances are real. If you are farther south, you need the storm to reach the upper end of G2 or stronger, plus clear, dark skies and a low northern horizon. The smartest approach is to watch NOAA’s real-time aurora and Kp updates this evening. If Kp climbs to 5 or 6 and stays there, northern U.S. viewers have a credible shot.

3 articles · Updated · Space.com · Oct 8

NOAA expects the strongest of three Earth-bound coronal mass ejections to arrive Oct. 9, raising the chance of brighter northern lights across northern U.S. states through the weekend.
Three eruptions from sunspot region AR4549 on Oct. 6-8 are approaching in quick succession, with forecasters saying one CME may deliver only a glancing blow while another could extend activity into Oct. 10-11.
G2 geomagnetic storm conditions are forecast for Oct. 9, with NOAA's current windows showing G1 activity late Oct. 8 into early Oct. 9 and a possible G2 peak around 5-8 a.m. EDT.
How far south the aurora reaches remains uncertain because visibility depends on how the CMEs' magnetic fields interact with Earth's; during past G2 storms, auroras have reached as far south as New York and Idaho.
AR4549 is still facing Earth and remains magnetically complex, leaving room for additional solar activity that could further alter weekend aurora prospects.