solar radiation.

kaiserkarl, thanks for those links. This information opened a whole new realm of possibilities and.... complexity.

Not solar radiation per se, but how atmospheric radiation is affected by solar activity. The data was gathered at ~65000 feet (~20000 meters).

Atmospheric Radiation Increasing from Coast to Coast in the USA
https://spaceweatherarchive.com/2018/10/24/atmospheric-radiation-increasing-from-coast-to-coast-in-the-usa/