University of Oulu

Usoskin, I. G., Koldobskiy, S. A., Kovaltsov, G. A., Rozanov, E. V., Sukhodolov, T. V., Mishev, A. L., & Mironova, I. A. ( 2020). Revisited reference solar proton event of 23 February 1956: Assessment of the cosmogenic‐isotope method sensitivity to extreme solar events. Journal of Geophysical Research: Space Physics, 125, e2020JA027921.

Revisited reference solar proton event of 23 February 1956 : assessment of the cosmogenic‐isotope method sensitivity to extreme solar events

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Author: Usoskin, Ilya G.1,2; Koldobskiy, Sergey A.3; Kovaltsov, Gennady A.4;
Organizations: 1Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
2Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
3National Research Nuclear University MEPhI, Moscow, Russia
4Ioffe Physical-Technical Institute, St. Petersburg, Russia
5PMOD/WRC, Davos and IAC ETH, Zurich, Switzerland
6Department of Physics of Earth, Faculty of Physics, St. Petersburg State University, St. Petersburg, Russia
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.3 MB)
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Language: English
Published: American Geophysical Union, 2020
Publish Date: 2020-06-09


Our direct knowledge of solar eruptive events is limited to several decades and does not include extreme events, which can only be studied by the indirect proxy method over millennia, or by a large number of Sun‐like stars. There is a gap, spanning 1–2 orders of magnitude, in the strength of events between directly observed and reconstructed ones. Here, we study the proxy method sensitivity to identify extreme solar particle events (SPEs). First, the strongest directly observed SPE (23 February 1956), used as a reference for proxy‐based reconstructions, was revisited using the newly developed method. Next, sensitivity of the cosmogenic‐isotope method to detect a reference SPE was assessed against the precision and number of individual isotopic records, showing that it is too weak by a factor ≈30 to be reliably identified in a single record. Uncertainties of 10Be and 14C data are shown to be dominated by local/regional patterns and measurement errors, respectively. By combining several proxy records, a SPE 4–5 times stronger than the reference one can be potentially detected, increasing the present‐day sensitivity by an order of magnitude. This will allow filling the observational gap in SPE strength distribution, thus enriching statistics of extreme events from 3–4 presently known ones to several tens. This will provide a solid basis for research in the field of extreme events, both for fundamental science, namely solar and stellar physics, and practical applications, such as the risk assessments of severe space‐based hazards for modern technological society.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 125
Issue: 6
Article number: e2020JA027921
DOI: 10.1029/2020JA027921
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This work was partially supported by the Academy of Finland (Project 321882 ESPERA), MEPhI Academic Excellence Project (Contract 02.a03.21.0005), and the Russian Science Foundation (RSF Project No. 20‐67‐46016). TS and ER have been supported from the Swiss National ScienceFoundation (POLE (grant no.200020_182239)). IM acknowledges the support of St. Petesburg State University through the grant COLLAB2019_2 (Id:41167902 and Id:41167802).
Academy of Finland Grant Number: 321882
Detailed Information: 321882 (Academy of Finland Funding decision)
Copyright information: © 2020. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.