10Be as a Proxy Indicator of Variations in Solar Activity and Geomagnetic Field Intensity During the Last 10,000 Years

Abstract

The study of the concentration of long lived cosmogenic (cosmic ray produced) isotopes in various natural reservoirs is a potentially powerful method for investigating time variations in cosmogenic production rates (Raisbeck and Yiou, 1984), In principle at least, these variations can then be interpreted in terms of a temporal record of the parameters which affect cosmogenic production rate, including, in the context of the present meeting, solar activity and the geomagnetic field intensity. The study of 14C in tree rings is the most developed example of such an application, and is treated in detail elsewhere in this volume. The technique of accelerator mass spectrometry (AMS) offers the possibility of extending such studies to a number of other cosmogenic isotopes, and in particular to 10Be (half-life 1.5 My). Indeed the first published measurements of 10Be by AMS emphasized the potential of this type of application (Raisbeck et al. 1978), and one of the first AMS profiles of 10Be in a natural reservoir included a tentative identification of an enhanced production rate associated with reduced solar activity during the Maunder Minimum (Raisbeck et al., 1981).