Aurora alert! Pair of CMEs to jolt Earth’s magnetic field

Aurora alert: Animated spacecraft image of the sun, with a giant arc of plasma erupting from it.
Aurora alert! A huge filament from a large sunspot region (AR 2860) erupted on August 28. Its resulting coronal mass ejection or CME – a bubble of superheated gas from our sun – joined an earlier CME, created in a solar flare from this same region on the sun earlier that same day. Now both CMEs are headed our way. They’re expected to cause a beautiful display of auroras. Image via

Aurora alert for high latitudes is saying this morning (September 1, 2021) that two enormous bubbles of superheated gas from our sun – otherwise known as coronal mass ejections or CMEs – are headed toward Earth. There’s no danger to us on Earth. And these CMEs aren’t strong enough to knock out satellites or power grids. But they are about to give a “jolt” to our planet’s magnetic field, causing a beautiful display of auroras at high latitudes. SpaceWeather said:

Estimated time of arrival: September 1-2. NOAA forecasters expect geomagnetic storms as strong as category G2. That means people as far south as Idaho and New York (geomagnetic latitude 55 degrees) could see auroras.

As early as late last week, sun-watchers began to notice that solar activity was picking up, as solar active region 12860 (AR 2860) produced 8 C-class solar flares. Then on Saturday, August 28, at 5:30 UTC (1:30 a.m. EDT) the region produced a larger M4.7 solar flare. The flare was easily visible in the 131 angstrom wavelength band from NASA’s Solar Dynamics Observatory. It showed solar plasma temperatures over 10 million degrees. The event created a minor radio blackout on the sun-facing side of Earth (see the illustration below). The event created a coronal mass ejection (CME) directed toward Earth. That single CME, however, wasn’t expected to cause a large effect on the region around Earth.

Now 2 CMEs headed our way

But, later that day, as SpaceWeather explained, a massive filament of magnetism erupted on the sun. And this huge arc of electrified gas in the sun’s atmosphere produced a second Earth-directed CME. Now, the two CMEs are moving across space in tandem toward Earth. SpaceWeather said:

NOAA forecasters expect the CMEs to deliver a double blow separated by hours. The first CME could spark a minor G1-class geomagnetic storm late on September 1. The second CME could intensify the storm, boosting it to a moderately strong G2-class event on September 2.

Storms like these do no damage to power grids or satellites. They can, however, produce beautiful auroras at high latitudes. A light show is possible in Scandinavia, Iceland, Canada, and even some northern-tier U.S. states.

Submit your aurora photos to EarthSky’s community page

Images from the August 28 event

Map of Earth's surface, with a large part centered on India covered by colorful concentric blobs: the blackout region.
The M4.7 solar flare from AR 2860 caused minor radio blackouts on August 28. That is, it caused a weak degradation of high frequency radio communication and low-frequency navigation signals. Sunspot data is SDO HMI visible light data from and the flare data is GOES x-ray provided by NOAA Space Weather Prediction Center (SWPC). The radio blackout region is from NOAA SWPC.
Diagram of the sun, with AR12860's location marked.
Solar active region 12860 produced large flares on August 28, and 2 subsequent Earth-directed coronal mass ejections (CMEs). The CMEs are expected to strike Earth’s magnetosphere together, creating a good display of auroras around September 1 and 2, 2021.

Aurora alert. Here’s AR 2860 on August 30

Image of a portion of the sun, showing a large sunspot.
View at EarthSky Community Photos. | Victor Rogus of Sedona, Arizona, caught AR 2860 on August 30, 2021. As the sun rotates, this region is edging closer to the limb, or edge, of the sun. Soon, the sun’s rotation will carry it out of view. Victor wrote: “As seen to me just now, through thin clouds, Sunspot AR 2860 is big … The sunspot group has more than a dozen dark cores sprawling across 200,000 km [125,000 miles] of starscape.” Thank you, Victor!

Bottom line: Aurora alert. Two CMEs from AR 12860 are crossing space toward Earth and are expected to create a beautiful display of auroras at high latitudes.

September 1, 2021

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