Here's a recent article in Science magazine about natural disasters, that covers solar storms: http://www.sciencemag.org/news/2016/07/here-s-how-world-could-en

Here's a recent article in Science magazine about natural disasters, that covers solar storms: http://www.sciencemag.org/news/2016/07/here-s-how-world-could-end-and-what-we-can-do-about-it http://www.sciencemag.org/news/2016/07/here-s-how-world-coul... In general, the author seems to believe that these storms are not likely to cause national-scale extreme hardships like the ones you mention. The experts admit being unsure, but nothing like 90% casualties seems probable. There are some much more problematic scenarios, such as the ever present rogue asteroid one, and the often overlooked super-volcano one. It seems Yellowstone is a likely trouble spot.