2023-04-19 22:55:14
On March 23, skywatchers marveled at a magnificent display of aurora borealis and australis. This spectacle reminded us that when the Sun activates, it can trigger a phenomenon called “space weather”. Auroras are among the most benign effects of this phenomenon. At the other end of the space weather spectrum are solar storms that can bring down satellites. Starlink officials found out the hard way in February 2022. On January 29 of that year, the Sun put out an M1.1 class flare and coronal mass ejection. Material from the Sun traveled in the solar wind and arrived on Earth a few days later. On February 3, 2022, Starlink launched a group of 49 satellites to an altitude of just 130 miles above the Earth’s surface. They didn’t last long, and solar physicists now know why.
A group of researchers from NASA’s Goddard Space Flight Center and the Catholic University of America took a closer look at the specifics of this storm. Their analysis made it possible to identify a mass of plasma which touched the magnetosphere of our planet. It was a halo-shaped coronal mass jet from an active region in the northeast quadrant of the Sun. The material propagated at a speed of approximately 690 kilometers per second in the form of a shock-generating magnetic cloud. It is actually a long mass of matter twisting in space. As it moved, it expanded and sun-facing satellites – including STEREO-A, which was directly hit by this cloud – made observations. The cloud ended up hitting the Earth’s magnetosphere, creating a geomagnetic storm.
The atmosphere has thickened enough to affect newly launched Starlink stations. They began to experience atmospheric drag, which caused them to desorb and burn as they descended. This lesson in space weather was expensive and allowed people on Earth to see what happens when satellites fall back to Earth. This accident could have been avoided if the launch had been delayed to take into account the threat to the satellite.
NASA presented the details of the phenomenon in a scientific article published online:
We report the solar origin of the moderate-strength geomagnetic storm of February 3, 2022 that contributed to the loss of 39 Starlink satellites.
The geomagnetic storm was caused by the coronal mass ejection (CME) of the halo on January 29, 2022, at a moderate speed (about 690 km/s), originating from NOAA’s active region 12936 located in the northern quadrant -east (N18E06) of the Sun. The eruption was marked by an M1.1 eruption, which began at 22:45 UT, peaked at 23:32 UT on January 29, and ended at 00:24 UT the following day. The CME has transformed into a magnetic cloud (MC) causing a shock, observed L1 Sun-Earth and STEREO-Ahead (STA), located approximately 34 degrees behind the Earth.
The geomagnetic storm was caused by a strong southern component of the magnetic cloud which was boosted by a high speed solar wind stream behind the magnetic cloud. Although Earth and STA are only separated by about 34 degrees, the MC appeared very different to Earth and L1. One possibility is that the MC has been distorted by reflecting the curved neutral line of the Sun. In situ observations suggest that the MC was heading closer to STA than to Earth due to its earlier STA arrival. However, the shock arrived at STA and Earth around the same time, suggesting a weaker shock to Earth due to the flank passage.
Sources: Researchers from NASA’s Goddard Space Flight Center and the Catholic University of America, Article titled “The Solar Cause of the 2022 February 3 Geomagnetic Storm that Led to the Demise of the Starlink Satellitespublished on arXiv.org
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