This is a good question! There are several different ways the Sun can harm satellites. For example there is surface charging and increased atmospheric drag during geomagnetic storms, and high energy particles from solar storms can penetrate through shielding and harm sensitive electronics in spacecraft. I do not know the exact number how many satellites in total have been harmed by solar storms, the information is often difficult to gather, in particular for military missions. I found this webpage that has listed quite many spacecraft failures and problems due to solar effects: http://www.solarstorms.org/Sscope.html. For example, a communication satellite Telstar 401 was failed during a storm in January 1997.

Emilia