Preliminary study of cosmic rays, geomagnetic field changes and possible climate changes

Abstract

The possibility of a connection between cosmic radiation and climate has intrigued scientists for the past several decades. The studies of Friis-Christensen and Svensmark reported a variation of 3–4% in the global cloud cover between 1980 and 1995 that appeared to be directly correlated with the change in galactic cosmic radiation flux over the solar cycle. However, not only the solar cycle modulation of cosmic radiation must be considered, but also the changes in the cosmic radiation impinging at the top of the atmosphere as a result of the long-term evolution of the geomagnetic field. We present preliminary results of an on-going study of geomagnetic cutoff rigidities over a 400-year interval. These results show: (1) the change in cutoff rigidity is sufficiently large over this 400-year period that the change in cosmic radiation flux impacting the earth is approximately equal to the relative change in flux over a solar cycle, and (2) the changes in cutoff rigidity are non-uniform over the globe with both significant increases and decreases at mid-latitude locations.