As the event lasted only 4 hours, does that mean it would have had different levels of effect on different regions of the planet? Countries on the far side would be better shielded.
I don't see mention of 4 hours, but presumably that's how long it took to either erupt or transit through empty space.
If it hit the earth it would have slowed down and stayed longer.
The charged particles interacting with the magnetic field of the earth would have produced a planet wide EMP (larger than even a nuke could do). The charged particles would have induced electric current in any large wire and would have acted on the whole planet.