Short-Circuiting Civilization: Predicting the Disruptive Potential of a Solar Storm Is More Art Than Science
Predicting the severity of the effects of a particular solar storm is presently impossible. Scientists do not have the tools needed to say whether or not a particular coronal mass ejection will damage and shut down the power grid.
We can know a day or so in advance the direction and intensity of the charged particles. So the potential for damage can be predicted. But the orientation of the resulting magnetic field cannot be predicted. Consequently, when a powerful coronal mass ejection is directed toward earth, the strength of induced voltages in transmission lines can be either small or large.
Alan Detwiler, self sufficiency advocate and author. Bio at http://www.smashwords.com/profile/view/alandetwiler