Solar cycle correlations of substorm and auroral occurrence frequency

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  • Finnish Meteorological Institute


Recent results of Newel eb al. [1998a] suggest that the polar cap integrated aurora occurrence frequency is independent of the solar cycle phase. This paper utilizes auroral all-sky camera observations from Northern Finland during 1974-1996 to show that although the total number of auroral observations shows only a weak solar cycle dependence, the number of quiet aurora! arcs is anticorrelated with the sunspot number, indicating that active auroral forms are less common during sunspot minima. A local index for geomagnetic substorm occurrence frequency and intensity is developed. It is shown that in long-term averages this index is highly correlated with the planetary aa index, and that both show strong correlation with the sunspot number. We further demonstrate a clear correlation between the active auroral forms and the local geomagnetic disturbances.


Original languageEnglish
Pages (from-to)3087-3090
Number of pages4
JournalGeophysical Research Letters
Issue number16
Publication statusPublished - 15 Aug 1998
MoE publication typeA1 Journal article-refereed

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