A geomagnetic storm watch is in effect through the weekend as solar eruptions barrel toward Earth, with up to 28 US states potentially in line for a rare Northern Lights display.
The National Oceanic and Atmospheric Administration (NOAA) has forecast a G2 (Moderate) geomagnetic storm, with peak activity now expected between 2 p.m. And 8 p.m. EDT on Friday, several hours later than initially predicted. That timing could place the strongest space weather right around nightfall for the northern tier of the country.
NOAA’s forecast states: “G1-G2 (Minor-Moderate) geomagnetic storms are likely on 09 Oct due to the anticipated arrival of a CME from 06 Oct.”
The trigger is a trio of coronal mass ejections, eruptions of solar material and magnetic fields from the sun, that could reach Earth across Friday through Sunday. The first followed an M1.4-class solar flare on Tuesday, Oct. 6. Called a full-halo CME, it appears to surround the sun in images from NASA’s SOHO spacecraft.
According to the UK Met Office, a glancing blow from a CME launched on Wednesday, Oct. 7 could bring G1 (Minor) storms on Saturday, with a slight chance of G2. A third eruption, tied to an M6.7-class solar flare on Thursday, Oct. 8, could arrive on Sunday, with the Met Office forecasting active to G1 conditions, a chance of G2 and a slight chance of G3 (Strong).
Across the weekend, the Met Office forecasts G1, G2 and possibly even G3 storms, the latter a potential Kp 7 event that could push aurora farther south than usual. However, it notes ‘significant uncertainty in the timing of these features’.
At G1 strength, Alaska and states across the northern tier, Washington, Idaho, Montana, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, Maine, Vermont and New Hampshire, could have chances, particularly from dark spots near the Canadian border.
At G2, the lights could stretch farther south, potentially allowing photographers in Oregon, Wyoming, Nebraska, Iowa, Illinois, Indiana, Ohio, Colorado, Pennsylvania and New York to capture faint displays.
At the less likely G3 level, parts of Kansas, Missouri, Kentucky, West Virginia, Virginia and Maryland could see them, especially from dark locations with unobstructed views north.
A new moon on Saturday, Oct. 10 leaves skies virtually free of moonlight, ideal wherever conditions are clear. If the aurora reaches the northern US, a smartphone camera may pick up faint colors that are hard to see with the naked eye, most likely low on the northern horizon.
Nothing is guaranteed though. Cloud cover, light pollution and the magnetic direction of the incoming solar material, known as Bz, all matter. A sustained southward Bz can mean aurora farther south than expected, while a northward Bz may mean a weak display limited to higher latitudes.
Apps such as Aurora Now, My Aurora Forecast and Glendale Aurora offer up-to-the-minute alerts and live solar wind data for those hoping to catch the show.
Parts of Canada and northern Europe could also see the Northern Lights during the three-day window.