University of Oulu

Usoskin, I.G. A history of solar activity over millennia. Living Rev Sol Phys 20, 2 (2023).

A history of solar activity over millennia

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Author: Usoskin, Ilya G.1
Organizations: 1Space Physics and Astronomy Research Unit and Sodankylä Geophysical Observatory (Oulu unit), University of Oulu, 90014, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 7.1 MB)
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Language: English
Published: Springer Nature, 2023
Publish Date: 2023-10-02


Here we review present knowledge of the long-term behaviour of solar activity on a multi-millennial timescale, as reconstructed using the indirect proxy method. The concept of solar activity is discussed along with an overview of the dedicated indices used to quantify different aspects of variable solar activity, with special emphasis on sunspot numbers. Over long timescales, quantitative information about past solar activity is historically obtained using a method based on indirect proxies, such as cosmogenic isotopes ¹⁴C and ¹⁰Be in natural stratified archives (e.g., tree rings or ice cores). We give a historical overview of the development of the proxy-based method for past solar-activity reconstruction over millennia, as well as a description of the modern state of the art. Special attention is paid to the verification and cross-calibration of reconstructions. It is argued that the method of cosmogenic isotopes makes a solid basis for studies of solar variability in the past on a long timescale (centuries to millennia) during the Holocene (the past ∼12 millennia). A separate section is devoted to reconstructions of extremely rare solar eruptive events in the past, based on both cosmogenic-proxy data in terrestrial and lunar natural archives, as well as statistics of sun-like stars. Finally, the main features of the long-term evolution of solar magnetic activity, including the statistics of grand minima and maxima occurrence, are summarized and their possible implications, especially for solar/stellar dynamo theory, are discussed.

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Series: Living reviews in solar physics
ISSN: 2367-3648
ISSN-E: 1614-4961
ISSN-L: 2367-3648
Volume: 20
Issue: 1
Article number: 2
DOI: 10.1007/s41116-023-00036-z
Type of Publication: A2 Review article in a scientific journal
Field of Science: 115 Astronomy and space science
Funding: This work was partly supported by the Academy of Finland (Project ESPERA, No. 321882).
Academy of Finland Grant Number: 321882
Detailed Information: 321882 (Academy of Finland Funding decision)
Copyright information: © The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit