Now we know how a solar storm took out a fleet of Starlinks

On March 23, sky observers marveled at a gorgeous display of northern and southern lights. It was reminder that when our sun gets active, it can spark a phenomenon called “space weather.” Aurorae are among the most benign effects of this phenomenon.

At the other end of the space weather spectrum are solar storms that can knock out satellites. The folks at Starlink found that out the hard way in February 2022. On January 29th that year, the sun belched out a class M 1.1 flare and related coronal mass ejection. Material from the sun traveled out on the solar wind and arrived at Earth a few days later. On February 3, Starlink launched a group of 49 satellites to an altitude only 130 miles above Earth’s surface. They didn’t last long, and now solar physicists know why.

A group of researchers from NASA Goddard Space Flight Center and the Catholic University of America took a closer look at the specifics of that storm. Their analysis identified a mass of plasma that impacted our planet’s magnetosphere. The actual event was a halo coronal mass ejection from an active region in the northeast quadrant of the sun.

The material traveled out at around 690 kilometers per second as a shock-driving magnetic cloud. Think of it as a long ropy mass of material writhing its way through space. As it traveled, it expanded and at solar-facing satellites—including STEREO-A, which took a direct hit from it—made observations. Eventually, the cloud smacked into Earth’s magnetosphere creating a geomagnetic storm.

How Starlink satellites experienced the effects space weather

One of the side effects of space weather that can affect satellites is warming in a region called the “thermosphere.” That increased the density of the upper atmosphere over a short amount of time and caused it to swell up. A denser atmosphere causes a phenomenon called “atmospheric drag.” Essentially, the thicker atmosphere slows down anything moving through. It also heats things up.

The atmosphere thickened enough that it affected the newly launched Starlink stations. They started to experience atmospheric drag, which caused them to deorbit and burn up on the way down. It was an expensive lesson in space weather and provided people on Earth with a great view of what happens when satellites fall back to Earth. It was also that could have been avoided if they’d delayed their launch to account for the ongoing threat.

How does space weather work?

The sun constantly sends a stream of charged particles called the solar wind. This stream varies in density, speed, and temperature. Occasionally, the sun will also belch out clouds of plasma in what’s called a ‘coronal mass ejection.” Sometimes it also sends out solar flares. All the material it loses travels away on the solar wind.

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