Why might the subjective feeling of poor sleep lag behind the initial announcement of a powerful solar flare?

Answer

Because the timing corresponds to the arrival of the slower plasma cloud causing the geomagnetic storm

The noticeable effects are linked to the arrival of the plasma cloud creating the geomagnetic storm, which takes one to three days, not the immediate arrival of the flare's light.

Why might the subjective feeling of poor sleep lag behind the initial announcement of a powerful solar flare?
sunhumanSleepradiationsolar flare