Records of the past solar activity in terrestrial and meteorite archives

Abstract

Time series of cosmogenic radioisotopes in tree rings, sedimentary deposits on sea beds and ice cores form the polar ice caps show a large number of periodicities. Many of them can be attributed to changes in galactic cosmic ray flux due to solar modulation and in this way the past activity of the sun can be determined. However, since the effects of the geomagnetic field and the climatic processes are superimposed on these records, these periodicities, particularly their amplitudes, may not be wholly due to solar activity changes. The meteorite records, acquired outside the terrestrial influence, reflect the solar modulation more faithfully. Specifically, a century scale periodicity, related to the Gleissberg cycle, is supported by the observed ⁴⁴Ti activity variation in meteorites.