Correlation Between Cosmic-Ray Intensity and Total Solar Irradiance during the last three Solar Cycles

For reconstructions of the total solar irradiance (TSI) into the past it is important to understand the relation between the production of cosmogenic isotopes and TSI. The production rate is a function of the cosmic-ray intensity reaching the Earth, which is well represented by the neutron monitors. As theses data are available since well before the start of cycle 21 a direct comparison with the PMOD composite of TSI can be performed. For the correlation different lags of the cosmic-ray intensity for the odd and even cycles have to be taken into account, as well as different amplitudes. Both the cosmic-ray intensity and TSI are modulated by the solar activity related magnetic fields. While the cosmic ray intensity depends only on the open fields a major question is still how the open fields are related to the weak fields in the network on the Sun which seem to be responsible for the solar-cycle modulation of TSI. The much stronger fields on the solar surface on the other hand are responsible for the short-term variation related to sunspots and faculae. The implications of this comparison for the understanding of the relation between the production of cosmogenic isotopes and TSI will be discussed.