NOAA says a coronal mass ejection from AR4549 could reach Earth early on Oct. 9 and briefly strengthen the Aurora Borealis later this week. The eruption followed an M1.4-class solar flare from the same sunspot region, which sat close to the center of the Earth-facing side of the sun.
The timing gives skywatchers a narrow window. NOAA modeling points to an early Oct. 9 arrival, which means the change in the northern lights could come quickly if the CME holds its course toward Earth.
AR4549 on Oct. 6
Early on Oct. 6, the sun unleashed the eruption that launched the CME. The source places the event in AR4549, a region near the center of the Earth-facing side, so the outburst came from a part of the sun aimed more directly at Earth than areas near the limb.
For readers watching the sky, that geometry is the practical detail. A CME sent from a sunspot region facing Earth has a better chance of reaching our planet than one thrown from the far side, and this one was modeled as Earth-bound from the start.
NOAA and the Oct. 9 window
NOAA modeling is what narrows the forecast to early Oct. 9. The projection does not give an exact minute of arrival, only a window, so the best reading is that the disturbance could show up sometime early in the day rather than on a fixed schedule.
The link between the arrival window and the aurora forecast is straightforward: if the CME reaches Earth as modeled, the northern lights could become brighter or visible over a wider area than usual later this week. For skywatchers, that means the useful step is to watch for the change on Oct. 9 rather than waiting for a precise hour.
Scott Sutherland's G1 watch forecast also points to a possible Northern Lights boost, lining up with NOAA's timing for the CME.
The source leaves the strength of the aurora unquantified, so the safer expectation is a short-lived boost rather than a guarantee of a dramatic display. If the CME arrives early on Oct. 9, the people most likely to notice are the skywatchers already tracking the northern lights later this week.
