Regional and Seasonal Effects of Geomagnetic Storms on Terrestrial Weather

Abstract It has long been a mystery why small Total Solar Irradiation changes have significant effects on Earth's climate. Solar cycle correlation studies abound but cannot conclusively point to a viable physical mechanism. Here, I show that geomagnetic storms have a profound terrestrial weather impact. Using 67 years of hourly Disturbance storm time (Dst) index and ERA5 atmosphere data over North America, I find geomagnetic storm impacts up to two orders of magnitude larger than the long‐term global mean surface temperature impact attributed to solar activity. Particle precipitation effects such as from cosmic rays, solar energetic particles, or magnetospheric electrons are least consistent with my results. In particular, the cosmic ray–cloudiness hypothesis is falsified by my results. A top‐down mechanism operating directly through the ionosphere or through stratospheric chemistry and the polar vortex appears to be more likely.