>Honest question: do we have any idea of the biological impact of these?

Probably not too much[0], although some folks claim[1] that an increase in cardiovascular events (myocardial infarctions and the like) are increased[1] during geomagnetic storms.

Here's[2] a higher level overview.

[0] https://www.health.com/condition/stroke/solar-flare-health-e...

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739933/#CR29

[2] https://www.sfchronicle.com/health/article/geomagnetic-solar...