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Three CMEs Now Race Toward Earth for Weekend Auroras
By @sharedot · · 7 pages
- Science
- Aurora
- Space Weather
- Geomagnetic Storm
Sunspot AR4549 has fired three coronal mass ejections toward Earth, setting up G2 storm conditions Oct. 9 and renewed aurora chances into the weekend.
What happened: a busy week on the sun
It has been an unusually active stretch for the sun. A coronal mass ejection — a massive burst of charged particles embedded in a magnetic field — left the sun on Tuesday, Oct. 6, associated with a moderate solar flare, and NOAA's Space Weather Prediction Center responded with a moderate Geomagnetic Storm Watch beginning Thursday evening into Friday, Oct. 9, according to ABC News. space.com reports that three solar eruptions in total erupted from sunspot region AR4549 on Oct. 6 and Oct. 7, with a third CME erupting on Oct. 8, and all are hurtling toward Earth. Northern lights were already observed earlier this week from New England to Iowa and northward into Canada, WWMT reports.
Why it's surprising: a one-two-then-three punch
The surprise is not a single CME but the stack of them. space.com notes space weather physicist Tamitha Skov's observation that the two Oct. 6 CMEs could reach Earth in relatively quick succession, delivering a 'one-two punch' to Earth's magnetic field, while the third, which erupted Oct. 8, could arrive around Oct. 10-11. WWMT's forecast goes further, projecting a Kp index value of six for Thursday night — a level the station says is usually good enough to incite auroras in West Michigan, where a Kp of 5 typically suffices for northern Lower Michigan and the Upper Peninsula. With AR4549 still magnetically complex and facing Earth, space.com reports more solar activity could be on the way.
The evidence: NOAA watches and forecast windows
NOAA's Space Weather Prediction Center is the anchor for the numbers. Its aurora forecast suggests activity could be enhanced across northern North America, and the agency's alert states aurora may be seen as low as New York to Wisconsin to Washington state, per ABC News. space.com reports NOAA's 3-day forecast calls for minor (G1) conditions between 11 p.m. and 2 a.m. EDT on Oct. 8-9, followed by a possible G2 (moderate) peak between 5-8 a.m. EDT on Oct. 9 — during G2 storms, auroras have previously been observed as far south as New York and Idaho. The UK Met Office adds there is even a slight chance of strong G3 levels, according to ABC News, while WWMT says the best window runs from 11 p.m. through 5 or 6 a.m. Friday morning.
The stakes: manageable impacts, rare southern views
Beyond pretty skies, geomagnetic storms matter for technology. The SWPC says the solar activity could create minor impacts to technological infrastructure but that it is 'mainly manageable,' ABC News reports. NOAA defines a geomagnetic storm as a major disturbance of Earth's magnetosphere occurring when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. The upside is that when geomagnetic activity strengthens, auroras can appear farther south than usual — potentially in areas that don't normally experience them, including states along a New York-to-Washington line. space.com cautions that even an Earth-directed CME doesn't guarantee a spectacular display.
What comes next: weekend waves and uncertainty
The show may not end Thursday night. WWMT reports two CMEs are inbound per spaceweather.com, with the first arriving Thursday night and the second Saturday night into Sunday morning, while space.com says a third CME could deliver a glancing blow late on Oct. 10 or early Oct. 11, potentially prolonging unsettled geomagnetic activity and aurora prospects into the weekend. The catch: exact arrival times carry uncertainty of several hours, depend on the surrounding solar wind, and hinge on how the CMEs' magnetic fields orient when they meet Earth's, space.com explains. Skywatchers at mid-latitudes are advised to keep aurora alerts on and camera batteries charged, using apps like My Aurora Forecast & Alerts or Space Weather Live.