STATISTICAL STUDY OF STRONG AND EXTREME GEOMAGNETIC DISTURBANCES AND SOLAR CYCLE CHARACTERISTICS

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Kilpua , E K J , Olspert , N , Grigorievskiy , A , Kapyla , M J , Tanskanen , E I , Miyahara , H , Kataoka , R , Pelt , J & Liu , Y D 2015 , ' STATISTICAL STUDY OF STRONG AND EXTREME GEOMAGNETIC DISTURBANCES AND SOLAR CYCLE CHARACTERISTICS ' , Astrophysical Journal , vol. 806 , no. 2 , 272 . https://doi.org/10.1088/0004-637X/806/2/272

Title: STATISTICAL STUDY OF STRONG AND EXTREME GEOMAGNETIC DISTURBANCES AND SOLAR CYCLE CHARACTERISTICS
Author: Kilpua, E. K. J.; Olspert, N.; Grigorievskiy, A.; Kapyla, M. J.; Tanskanen, E. I.; Miyahara, H.; Kataoka, R.; Pelt, J.; Liu, Y. D.
Other contributor: University of Helsinki, Department of Physics

Date: 2015-06-20
Language: eng
Number of pages: 7
Belongs to series: Astrophysical Journal
ISSN: 0004-637X
DOI: https://doi.org/10.1088/0004-637X/806/2/272
URI: http://hdl.handle.net/10138/183640
Abstract: We study the relation between strong and extreme geomagnetic storms and solar cycle characteristics. The analysis uses an extensive geomagnetic index AA data set spanning over 150 yr. complemented by the Kakioka magnetometer recordings. We apply Pearson correlation statistics and estimate the significance of the correlation with a bootstrapping technique. We show that the correlation between the storm occurrence and the strength of the solar cycle decreases from a clear positive correlation with increasing storm magnitude toward a negligible relationship. Hence, the quieter Sun can also launch superstorms that may lead to significant societal and economic impact. Our results show that while weaker storms occur most frequently in the declining phase, the stronger storms have the tendency to occur near solar maximum. Our analysis suggests that the most extreme solar eruptions do not have a direct connection between the solar large-scale dynamo-generated magnetic field, but are rather associated with smaller-scale dynamo and resulting turbulent magnetic fields. The phase distributions of sunspots and storms becoming increasingly in phase with increasing storm strength, on the other hand, may indicate that the extreme storms are related to the toroidal component of the solar large-scale field.
Subject: dynamo
solar-terrestrial relations
Sun: activity
Sun: coronal mass ejections (CMEs)
sunspots
STORMS
INTENSE
DYNAMO
JACKKNIFE
BOOTSTRAP
STRENGTH
DRIVERS
115 Astronomy, Space science
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