Tree-rings reveal two strong solar proton events in 7176 and 5259 BCE

• Published in: Nature Communications
• Main Authors: Brehm, Nicolas, Christl, Marcus, Knowles, Timothy, Casanova, Emmanuelle, Evershed, Richard, Adolphi, Florian, Muscheler, Raimund, Synal, Hans-Arno, Mekhaldi, Florian, Paleari, Chiara, Leuschner, Hanns-Hubert, Bayliss, Alex, Nicolussi, Kurt, Pichler, Thomas, Schlüchter, Christian, Pearson, Charlotte, Salzer, Matthew, Fonti, Patrick, Nievergelt, Daniel, Hantemirov, Rashit, Brown, David, Usoskin, Ilya, Wacker, Lukas
• Other Authors: Ion Beam Physics ETH Zürich, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), Organic Geochemistry Unit - OGU (Bristol, United Kingdom), University of Bristol Bristol, Archéozoologie, archéobotanique : sociétés, pratiques et environnements (AASPE), Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), Alfred Wegener Institute Potsdam, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI), Helmholtz-Gemeinschaft = Helmholtz Association-Helmholtz-Gemeinschaft = Helmholtz Association, Skane University Hospital Lund, Georg-August-University = Georg-August-Universität Göttingen, Historic England, Institute of Geography, Leopold Franzens Universität Innsbruck - University of Innsbruck, Universität Bremen, Universität Bern / University of Bern (UNIBE), University of Arizona, Laboratory of Tree-Ring Research University of Arizona (LTRR), Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Laboratory of Dendrochronology, Institute of Plant and Animal Ecology, Ural Branch of Russian Academy of Sciences, Sodankyla Geophysical Observatory, University of Oulu (SGO)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; ice core
• Online Access: https://hal.science/hal-03961929; https://doi.org/10.1038/s41467-022-28804-9

International audience The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as 14 C, 10 Be and 36 Cl have been found. Analyzing annual 14 C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14 C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric 14 C recorded for both events exceed all previously known 14 C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.