Göttingen 2025 – wissenschaftliches Programm
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EP: Fachverband Extraterrestrische Physik
EP 2: Sun and Heliosphere I
EP 2.3: Vortrag
Montag, 31. März 2025, 17:30–17:45, ZHG101
Towards a reconstruction of the annual solar Irradiance over the past 9 millennia — •Duresa Temaj1, Natalie Krivova1, Sami Solanki1, Illya Usoskin2, and Bernhard Hofer1 — 1Max planck institute for solar system research, Goettingen, Germany — 2Space Climate Research Unit, University of Oulu, Finland
Space-based observations of solar irradiance since the 1970s revealed its variability, but these records are too short to reliably assess solar impact on Earth's climate. Therefore, irradiance reconstructions are needed, which requires proxies of past solar activity. The longest direct proxy is the sunspot number, recorded for the past 400 years. We employ the Spectral And Total Irradiance REconstructions (SATIRE) model, using the sunspot number as input, while also accounting for the emergence of small-scale magnetic features, to reconstruct solar irradiance from direct sunspot observations.
Furthermore, concentrations of cosmogenic isotopes, e.g. 14C and 10Be, in terrestrial archives, allow reconstructions of sunspot numbers over nine millennia, albeit at a decadal resolution, except the last millennium. Thus, solar cycles remain unresolved. Based on previous findings that cycle strength and length correlate well with the mean solar activity, we study the relationships between the decadally averaged sunspot numbers and solar cycle parameters. We validate this approach using synthetic records constructed from telescopic data and find a fair agreement with the observed record. We apply the derived relationships to reconstruct the annual sunspot number and then irradiance over the nine Millennia.
Keywords: Sun; Solar Activity; Sunspots; Solar Irradiance; Magnetic fields