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A new model of cosmogenic tritium (3H) production in the atmosphere is presented. The model belongs to the CRAC (Cosmic Ray Atmospheric Cascade) family and is named as CRAC:3H. It is based on a full Monte Carlo simulation of the cosmic ray induced atmospheric cascade using the Geant4 toolkit. The CRAC:3H model is able, for the first time, to compute tritium production at any location and time, for any given energy spectrum of the primary incident cosmic ray particles, explicitly treating, also for the first time, particles heavier than protons. This model provides a useful tool for the use of 3H as a tracer of atmospheric and hydrological circulation. A numerical recipe for practical use of the model is appended. Key Points: A new CRAC:3H model of cosmogenic tritium (3H) production in the atmosphere is presentedFor the first time, it provides 3‐D production, also explicitly treating particles heavier than protonsThis model provides a useful tool for the use of 3H as a tracer of atmospheric and hydrological circulation [ABSTRACT FROM AUTHOR]

This paper presents the results of a comparative wavelet coherence analysis of a multimillennial nitrate record with a number of climatic and solar activity proxies. Distinguishing between these factors is important in the view of a possibility of nitrate deposited in a polar region to represent galactic cosmic ray flux and, consequently, solar activity. We used the data from the TALDICE drilling project (Talos Dome, Antarctica), which covers the age range 12,000–700 BP (years before present, i.e. before 1950) and includes records of nitrate as well as climatic proxies, such as Na + , Ca 2+ , MSA (methanesulphonic acid), δ 18 O, SO 4 2 − . The solar activity series is represented by reconstructions of the heliospheric modulation parameter from the 14 C and 10 Be data. We found (1) a confirmation of multimillennial relation between nitrate and galactic cosmic ray flux; (2) no clear signature of long-term variations of nitrate transport from lower latitudes. We suggest that variations in the nitrate record in the time scale of hundreds–thousands years are most likely caused by local production, deposition and post-deposition processes. [ABSTRACT FROM AUTHOR]

The amplitude of the 11-year cycle measured in the cosmogenic isotope Be during the Maunder Minimum is comparable to that during the recent epoch of high solar activity. Because of the virtual absence of the cyclic variability of sunspot activity during the Maunder Minimum this seemingly contradicts an intuitive expectation that lower activity would result in smaller solar-cycle variations in cosmogenic radio-isotope data, or in none, leading to confusing and misleading conclusions. It is shown here that large 11-year solar cycles in cosmogenic data observed during periods of suppressed sunspot activity do not necessarily imply strong heliospheric fields. Normal-amplitude cycles in the cosmogenic radio-isotopes observed during the Maunder Minimum are consistent with theoretical expectations because of the nonlinear relation between solar activity and isotope production. Thus, cosmogenic-isotope data provide a good tool to study solar-cycle variability even during grand minima of solar activity. [ABSTRACT FROM AUTHOR]