Aurora Australis

Okay, I thought I knew science, but after several days of researching this, all I've got is indecision and a headache.

Original fiction, unspecified not-too-far-future time.

My character is the pilot of a small cargo ship in the asteroid belt. (No FTL, no artificial gravity.) Said ship has sufficient radiation shielding to be safe under normal conditions. My idea is that there's an unusually strong solar event (solar flare? coronal mass ejection?), and he has to survive by positioning his ship on the shadowed side of an asteroid (rocks are good shielding), and use his excellent piloting skills to stay there until the storm passes.

1. Does this, theoretically, actually work?

2. I'd like the solar event to be a Coronal Mass Ejection, because some CMEs move relatively slowly, and that gives my character time to make a narratively interesting choice. But is it the CME itself that's hazardous to human life, or a sort of "bow wave" of radiation that precedes it? And if the latter, is that radiation moving at the speed of the CME, or the speed of light? (I keep thinking I have a grasp on this, and then the next source I read contradicts it.)

Guidance appreciated, fellow space enthusiasts!

ETA: Okay, based on comments and additional research the comments inspired, my takeaway is: (1) CMEs can happen with or without accompanying radiation, (2) the stuff in the CME itself is not dangerous to humans, (3) the dangerous-to-humans part of the radiation travels at the speed of light. Which means this story is probably dead; I really needed that longer warning time for the narratively-interesting parts, darn it.