Meteoritic evidence for the Maunder minimum in solar activity

Concentrations of argon-39 (t/sub 1/2/=269 years, production threshold about 400 MeV) produced by cosmic rays in the metal in 30 meteorites are remarkably similar, but they are slightly higher than expected for the present solar-cycle averaged flux of cosmic rays. This supports the idea suggested by Eddy (1976a) that there were prolonged minima in solar activity before 1715 which caused the deVries maximum in carbon-14 in the earth's atmosphere by reducing the amount of cosmic ray modulation in interplanetary space. Our observations are easily consitent with 180 years of ''sunspot minimum'' modulation during the Maunder and Spoerer minima, and possibly with virtually no solar modulation at all, during that time. This would indicate the solar wind then contained very little magnetic turbulence, or whatever it is in the solar wind that causes the modulation of galactic cosmic rays