Explained: Geomagnetic storm that killed Starlink satellites

The satellites were designed to burn up on reentry into the Earth’s atmosphere, and did not create debris in space. However, the loss of 40 satellites — most of a launch batch — in a single solar event has been described as “unheard of” and “huge”.

Solar storms/flares

Solar storms are magnetic plasma ejected at great speed from the solar surface. They occur during the release of magnetic energy associated with sunspots (‘dark’ regions on the Sun that are cooler than the surrounding photosphere), and can last for a few minutes or hours. The solar storm that deorbited the satellites occurred on February 1 and 2, and its powerful trails were observed on February 3.

“The emerging data suggest that the passing of the latter part of the storm, with its high density core, possessed speeds higher than what was recorded during the storm’s arrival — something we did not expect,” said physicist Prof Dibyendu Nandi, head of the Centre of Excellence in Space Sciences India (CESSI) at the Indian Institute of Science Education and Research (IISER), Kolkata.

The storm was unusual, an unexpectedly extended event and of a kind not seen in the recent past, Prof Nandi said.

Effect on Earth

Not all solar flares reach Earth, but solar flares/storms, solar energetic particles (SEPs), high-speed solar winds, and coronal mass ejections (CMEs) that come close can impact space weather in near-Earth space and the upper atmosphere.

Solar storms can hit operations of space-dependent services like global positioning systems (GPS), radio, and satellite communications. Geomagnetic storms interfere with high-frequency radio communications and GPS navigation systems. Aircraft flights, power grids, and space exploration programmes are vulnerable.

CMEs, with ejectiles loaded with matter travelling at millions of miles an hour, can potentially create disturbances in the magnetosphere, the protective shield surrounding the Earth. Astronauts on spacewalks face health risks from possible exposure to solar radiation outside the Earth’s protective atmosphere.

Predicting solar storms

Solar physicists and other scientists use computer models to predict solar storms and solar activities in general. The February 1-2 phenomenon that knocked out Starlink’s satellites was predicted on January 29.

“Current models are capable of predicting a storm’s time of arrival and its speed. But the storm’s structure or orientation still cannot be predicted,” Prof Nandi said.

Certain orientations of the magnetic field can produce a more intense response from the magnetosphere, and trigger more intense magnetic storms.

With the increasing global dependence on satellites for almost every activity, there is a need for better space weather forecasts and more effective ways to protect satellites.

Newsletter | Click to get the day’s best explainers in your inbox