Mursula, K., Qvick, T., Holappa, L., & Asikainen, T. (2022). Magnetic storms during the space age: Occurrence and relation to varying solar activity. Journal of Geophysical Research: Space Physics, 127, e2022JA030830. https://doi.org/10.1029/2022JA030830
Magnetic storms during the space age : occurrence and relation to varying solar activity
|Author:||Mursula, Kalevi1; Qvick, Timo1; Holappa, Lauri1;|
1Space Climate Group, Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
|Online Access:||PDF Full Text (PDF, 2.3 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe202301021125
American Geophysical Union,
|Publish Date:|| 2023-05-25
We study the occurrence of magnetic storms in space age (1957–2021) using Dst and Dxt indices. We find 2,526/2,743 magnetic storms in the Dxt/Dst index, out of which 45% are weak, 40% moderate, 12% intense and 3% major storms. Occurrence of storms in space age follows the slow decrease of sunspot activity and the related change in solar magnetic structure. We quantify the sunspot—coronal mass ejection (CME) storm relation in the five cycles of space age. We explain how the varying solar activity changes the structure of the heliospheric current sheet (HCS), and how this affects the high-speed solar wind stream (HSS)/corotating interaction region (CIR) storms. Space age started with a record number of storms in 1957–1960, with roughly one storm per week. Solar polar fields attained their maximum in cycle 22, which led to an exceptionally thin HCS, and a space age record of large HSS/CIR storms in 1990s. In the minimum of cycle 23, for the only time in space age, CME storm occurrence reduced below that predicted by sunspots. Weak sunspot activity since cycle 23 has weakened solar polar fields and widened the HCS, which has decreased the occurrence of large and moderate HSS/CIR storms. Because of a wide HCS, the Earth has spent 50% of its time in slow solar wind since cycle 23. The wide HCS has also made large and moderate HSS/CIR storms occur in the early declining phase in recent cycles, while in the more active cycles 20–22 they occurred in the late declining phase.
Journal of geophysical research. Space physics
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
The authors acknowledge financial support by the Academy of Finland to the Postdoctoral Researcher project of L. Holappa (No. 322459) and to the PROSPECT project (No. 321440) of T. Asikainen. T. Qvick was supported by University of Oulu Graduate School.
|Academy of Finland Grant Number:||
322459 (Academy of Finland Funding decision)
321440 (Academy of Finland Funding decision)
The Dxt index is maintained by the University of Oulu at http://dcx.oulu.fi/ (Karinen & Mursula, 2005). The Dst index is provided by the WDC for Geomagnetism, Kyoto, Japan at http://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html (Nose et al., 2015). Sunspot data are from the World Data Center SILSO, Royal Observatory of Belgium, Brussels, on-line catalog at https://www.sidc.be/silso/datafiles. The WSO source surface maps are available at http://wso.stanford.edu/synsourcel.html.
© 2022. American Geophysical Union. All Rights Reserved.