title: Atmospheric impacts of the strongest known solar particle storm of 775 AD.
abstract: Sporadic solar energetic particle (SEP) events affect the Earth's atmosphere and environment, in particular leading to depletion of the protective ozone layer in the Earth's atmosphere, and pose potential technological and even life hazards. The greatest SEP storm known for the last 11 millennia (the Holocene) occurred in 774-775 AD, serving as a likely worst-case scenario being 40-50 times stronger than any directly observed one. Here we present a systematic analysis of the impact such an extreme event can have on the Earth's atmosphere. Using state-of-the-art cosmic ray cascade and chemistry-climate models, we successfully reproduce the observed variability of cosmogenic isotope10Be, around 775 AD, in four ice cores from Greenland and Antarctica, thereby validating the models in the assessment of this event. We add to prior conclusions that any nitrate deposition signal from SEP events remains too weak to be detected in ice cores by showing that, even for such an extreme solar storm and sub-annual data resolution, the nitrate deposition signal is indistinguishable from the seasonal cycle. We show that such a severe event is able to perturb the polar stratosphere for at least one year, leading to regional changes in the surface temperature during northern hemisphere winters.
authors.affiliation: Physikalisch-Meteorologisches Observatorium Davos World Radiation Center, Davos, Switzerland.|Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland.
authors.forename: Timofei
authors.initials: T
authors.lastname: Sukhodolov
authors.affiliation: Space Climate Research group, University of Oulu, Finland.|Sodankylä Geophysical Observatory, University of Oulu, Finland.
authors.forename: Ilya
authors.initials: I
authors.lastname: Usoskin
authors.affiliation: Physikalisch-Meteorologisches Observatorium Davos World Radiation Center, Davos, Switzerland.|Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland.
authors.forename: Eugene
authors.initials: E
authors.lastname: Rozanov
authors.affiliation: Space Climate Research group, University of Oulu, Finland.
authors.forename: Eleanna
authors.initials: E
authors.lastname: Asvestari
authors.affiliation: Physikalisch-Meteorologisches Observatorium Davos World Radiation Center, Davos, Switzerland.|Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland.
authors.forename: William T
authors.initials: WT
authors.lastname: Ball
authors.affiliation: Department of the Environment, Australian Antarctic Division, Kingston, Australia.|Antarctic Climate and Ecosystem Cooperative Research Centre, University of Tasmania, Hobart, Australia.
authors.forename: Mark A J
authors.initials: MA
authors.lastname: Curran
authors.affiliation: Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland.
authors.forename: Hubertus
authors.initials: H
authors.lastname: Fischer
authors.affiliation: Ioffe Physical-Technical Institute RAS, St. Petersburg, Russia.
authors.forename: Gennady
authors.initials: G
authors.lastname: Kovaltsov
authors.affiliation: Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan.
authors.forename: Fusa
authors.initials: F
authors.lastname: Miyake
authors.affiliation: Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology Zurich, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Peter
authors.affiliation: Antarctic Climate and Ecosystem Cooperative Research Centre, University of Tasmania, Hobart, Australia.|Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Plummer
authors.affiliation: Physikalisch-Meteorologisches Observatorium Davos World Radiation Center, Davos, Switzerland.
authors.forename: Werner
authors.initials: W
authors.lastname: Schmutz
authors.affiliation: Dept. of Chemistry "Ugo Schiff", University of Florence, Florence, Italy.
authors.forename: Mirko
authors.initials: M
authors.lastname: Severi
authors.affiliation: Dept. of Chemistry "Ugo Schiff", University of Florence, Florence, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Traversi