Low-flying satellites running into denser air than usual may lose energy and fall. High-flying telecommunications and weather satellites in geostationary orbits may suffer in a different way. If a gust in the solar wind squeezes the shield of the magnetosphere severely, the satellites may find themselves outside the shield, and more exposed to damaging particles. In one respect the solar storms themselves shield the Earth. They reduce the intensity of cosmic rays, energetic particles reaching the Earth from the Galaxy.
Major storms can cause a big drop in the cosmic-ray count for a day or two.
Six of the spacecraft have been built in Europe for joint ESA-NASA missions.