| Name: Chitradeep Saha |
| Affiliation: University of Reading, United Kingdom |
| Conference ID: ASI2026_135 |
| Title: A new millennial scale reconstruction of solar magnetic activity from 14C data |
| Abstract Type: Poster |
| Abstract Category: Sun, Solar System, Exoplanets, and Astrobiology |
| Author(s) and Co-Author(s) with Affiliation: Chitradeep Saha(University of Reading, Reading - RG6 6ET, UK), Mathew Owens(University of Reading, Reading - RG6 6ET, UK) |
| Abstract: The modulation in solar magnetic activity over the decadal timescales and beyond governs the heliospheric magnetic field and space climate conditions. These variations also modulate the flux of galactic cosmic rays reaching Earth, which in turn regulates the production of cosmogenic isotopes in the Earth's atmosphere. By harnessing the record of these radio-isotope proxies archived in natural terrestrial reservoirs over multiple millennia, it is therefore possible to reconstruct past solar magnetic activity. However, existing regression-based semi-empirical methods for estimating sunspot numbers (SSN) from radiocarbon data often produce negative SSN, which are physically implausible. Here, we employ a newly developed inverse modelling framework based on a Monte Carlo random search strategy, which combines a sequence of physics-based and semi-empirical forward models to reconstruct the open solar flux, SSN from the cosmogenic isotope production rates. We reconstruct yearly averaged SSN at annual resolution over the past millennia. The resulting SSN remains strictly non-negative throughout the entire record and shows excellent agreement with direct observations of the International Sunspot Number during the telescopic era. We further identify epochs of extremely high and low solar activity and examine their physical properties. These results offer new insights into long-term solar variability and its impact on the Earth’s climate. They also provide improved constraints for long-term solar dynamo modelling. |
