Sun activity: 3rd CME sideswipe in a week

The March 20, 2022, solar flare and filament eruption. The eruption produced an EIT wave, Type II radio burst, and a CME that should glance Earth on March 23, 2022. Image via helioviewer.org.

Another possible CME sideswipe coming

A CME is estimated to give Earth a glancing blow on March 23, 2022, with a possible uptick in auroral activity around that time. Sunspot region AR2971 launched a C4 solar flare and resulting CME at 7:45 UTC on March 20. As Spaceweather.com pointed out:

This will be the 3rd time in the past week that a CME has almost landed a direct hit.

This eruption also caused a filament to be ejected from the sun. Solar filaments are long ropes of solar material held down by magnetic fields. They’re the same pink-red structures you see around a darkened moon during total solar eclipses. In this case, the magnetic fields shifted in such a way that the filament detached from the sun, sending a CME our way.

Filaments on the sun can exist by themselves, or they can lie over a sunspot region. Here the filament was draped over region AR2971, giving us an especially energetic explosion.

A solar prominence (also known as a filament when viewed against the solar disk) is a large, bright feature extending outward from the sun’s surface. Prominences (filaments) are anchored to the sun’s surface in its photosphere. They extend outward into the sun’s hot outer atmosphere, called the corona. A prominence forms over timescales of about a day, and stable prominences may persist in the corona for several months, looping hundreds of thousands of miles into space. This image, from March 2010, shows a solar eruptive prominence, with Earth superimposed for a sense of scale. Image via NASA.

A March 20 EIT wave

During the March 20 solar flare and filament release, the eruption also created an EIT wave. EIT stands for Extreme-ultraviolet Imaging Telescope, an instrument aboard the SOHO sun observatory. This instrument first observed these waves, which are blast waves that ripple through the solar corona, the outermost part of the sun’s atmosphere. They’re visible only in wavelengths of extreme ultraviolet light.

If you look closely at the animated gif above, you can the wave moving away from the eruption. You can also see dark pieces of material leaving the area with the bright flash from the flare. This dark material is the filament, which is much cooler than the surrounding atmosphere, the corona. This makes the material appear darker.

The eruption also produced a Type II radio burst. These blasts of radio waves are most associated with CMEs and shock waves through the corona.

The CME itself is not expected to provide much of a disturbance to Earth’s magnetic field but it may be combined with the arrival of high-speed solar wind from a coronal hole. Together the two may create a minor geomagnetic disturbance or at least some heightened activity. This means the possibility for some heightened aurora from high latitudes and lots of beautiful pictures from aurora watchers.

Coronal hole detected in the SDO 193 wavelength. This coronal produced high-speed solar wind expected to reach Earth on March 23, 2022. Image via NASA iSWA.

Today’s sun

No sun activity today? Today’s sun appears relatively quiet, with no large sunspot regions easily visible in this March 21, 2022, image from NASA SDO. But some active regions are there, as evidenced by the solar flare and filament release on March 20, 2022. View this image with labels, via SpaceWeather.com.

Bottom line: Sun activity for the week of March 21, 2022. For the third time in a week, a CME may give our planet a glancing blow, with a possible uptick in auroras.

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