>>11699473Solar activity in the sense of solar flares (which were called "magnetic storms" in the USSR), the 7 year cycle, and the more seasonal variations you mentioned. Strictly electromagnetically however, Soviets found magnetic storms affected animals, and looking into it more closely, they found various elements correlated strongly with these shifts.
Unfortunately I only have a few declassified reports on the topic. It's been covered otherwise from various angles. Structure of water, etc.
