Aurora warning: Powerful geomagnetic storm could trigger northern lights in US, Europe on September 16

A combination of powerful solar phenomena has prompted the National Oceanic and Atmospheric (NOAA) Space Weather Prediction Center (SWPC) to issue a geomagnetic storm warning today (Sept. 16).

This is great news for those who northern lights the predicted geomagnetic storm could cause auroras deep into the mid-latitudes (around 50°) and if far to the south such as California, Missouri and Oregon.

This perpetrator? In this case, there are actually two.

The first is a large plume of plasma and magnetic field known as a coronal mass ejection (CME) released by the Sun during a colossal X-class solar flare, the most powerful class of solar flare — on September 14. The X4.5 solar flare peaked at 11:29 a.m. EDT (3:29 p.m. GMT) and was the fifth largest solar flare of the current solar cycle.

The CME released during the X-flare is currently hurtling toward Earth and is expected to arrive today (September 16). CMEs carry electrically charged atoms known as ions. When they collide with the Earth magnetospherethey can cause geomagnetic storms. During these storms the ions interact with gases in The Earth’s atmosphereradiating energy as light. It is this light that we see as the Northern Lights, or Aurora Borealis, in the Northern Hemisphere, and the Southern Lights, or Aurora Australia, in the Southern Hemisphere.

A close-up of the turbulent Sun shows a large, bright flare with a huge filament.

The X-flare outburst on September 14, 2024 was accompanied by a coronal mass ejection (CME). (Image credit: NASA/SDO and the AIA, EVE and HMI science teams)

The second culprit is a coronal hole on the side of the sun that faces Earth. Coronal holes appear as dark areas in the sun‘s corona (outer atmosphere). They have an open, unipolar magnetic field line structure that essentially solar wind to more easily escape into space. This stream of relatively fast solar wind and the influence of the incoming CME resulted in the issuance of the G3 geomagnetic storm warning.

NOAA classifies geomagnetic storms using a G scale that measures their intensity, ranging from G1 for minor storms to G5 for the most extreme. Strong G3 conditions are forecast for today (16th September), meaning we can expect a decent aurora show, as earlier “minor” G1 conditions on 29th/30th July still managed to stunning northern lights in the US and Canada.

graphical representation of the g3 geomagnetic storm alarm with possible effects.

Periods of G3 (strong) geomagnetic storms are likely on September 16, 2024 due to the influence of coronal holes and the expected arrival of a CME in combination with an X4.5 outburst. (Image credit: NOAA Space Weather Prediction Center)

When will the geomagnetic storm occur?

Current forecasts call for the G3 series geomagnetic storm conditions to arrive on September 16, but the exact timing is uncertain.

Similar to the weather on Earth, space weather is unpredictable and difficult to predict. Although geomagnetic storm warnings of this level are unusual, they can sometimes fail to materialize.

“NOAA & NASA forecasts call for the storm to arrive sometime between 06:00 UTC and 18:00 UTC on September 16. The storm will likely arrive late, possibly deflected further east by a fast solar wind stream,” space weather physicist Tamitha Skov wrote in a post on X.

The large #solarstorm launched during the X4.5 flare is headed for Earth. NOAA & NASA forecasts call for the storm to arrive sometime between 06:00 UTC and 18:00 UTC on September 16. The storm will likely arrive late, possibly deflected further east by a fast solar wind stream. My… pic.twitter.com/ifT4UZt6jUSeptember 16, 2024

If you use X, I recommend checking out space weather person Sara Housseal’s account for regular updates on “CME arrivals” and general space weather information.

“CME update: We have reached the point where we could expect the CME to arrive at any moment based on the model results, but there are still no signs that an arrival is imminent,” Houseeal said wrote in a message on X this morning (Sept. 16).

“Now the fun begins, will it arrive later than expected or not at all? Stay tuned!” Housseal continued.

CME Update: We’ve reached the point where we can expect the CME at any time based on model results, but there’s still no sign that an arrival is imminent. Usually, a noticeable surge of low-energy protons being pushed out of the way of the CME front can be a sign… pic.twitter.com/PDqNU0LbT6September 16, 2024

If you want to keep an eye on space weather conditions and know when (and where) to look for aurora, I recommend downloading a space weather app that will notify you of the forecasted conditions based on your location. I use an app called “My Aurora Forecast & Alerts” that is available on iOS And Android. But any similar app should do the job. I’ll pair this with the Space Weather Live app that’s available on iOS And AndroidThis app is great because it gives you more insight into whether space weather conditions are promising for aurora activity.