How can a solar storm affect satellites, GPS and trains?

A solar storm can hit satellites by heating the air they fly through, can scramble GPS by disturbing the layer of the atmosphere its signals cross, and has disturbed railway and telegraph lines with induced currents. None of these needs the storm to be a record: the best-documented satellite case came from a modest one.

On 3 February 2022, 49 Starlink satellites were launched, and the next day a G2-rated geomagnetic storm warmed the upper atmosphere and raised its density at the low altitude where the satellites were being released. More air means more drag. Predictions were that up to 40 of the 49 might be lost, and in the end 38 re-entered the atmosphere by 12 February, while the other 11 raised their orbits and avoided loss.

The mechanism is the same for any satellite in low orbit. Storms heat and expand the upper atmosphere, so the density at satellite orbits up to about 1,000 kilometres rises and the drag increases. In March 1989, four US Navy navigation satellites had to be taken out of service for up to a week. Skylab's 1979 destruction is an example of premature re-entry from higher-than-expected solar activity.

GPS is affected differently: signals scintillate, like a twinkling star, when solar activity makes the ionosphere's density vary suddenly. Trains are an old story. The May 1921 storm is called the New York Railroad Storm because its current sparked fires, including one near Grand Central Terminal.