Again, we just don't know. IF the gravitational field collapses, then is recreated, that could very well happen. The Earth's gravitational field is what keeps a lion's share of the radiation and cosmic wind from reaching the surface, so if it collapsed, it would be somewhat similar to being in the inside of a nuclear reactor (not quite as intense, but similar). But we don't know if the field just reverses, or if it does actually collapse first. The sun's field merely flip flops without collapsing. But the sun's magnetic field is created by a different process than ours, and it also reverses much more often...11 years compared to a couple hundred thosand years.