Besides potential health impacts, what visible, immediate effect of a massive solar event is easily observed?

Answer

The spectacular aurora borealis

The immediate and easily observed visible effect associated with massive solar events, preceding the less certain health impacts, is the spectacular display of the aurora borealis.

Besides potential health impacts, what visible, immediate effect of a massive solar event is easily observed?
effectsspace weathergeomagnetic stormsEarth's magnetic fieldhuman behavior