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Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24

Geophysical Research Letters

By:
,
DOI: 10.1029/2011GL050702

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Abstract

[1] Analysis is made of the geomagnetic-activityaaindex covering solar cycle 11 to the beginning of 24, 1868–2011. Autocorrelation shows 27.0-d recurrent geomagnetic activity that is well-known to be prominent during solar-cycle minima; some minima also exhibit a smaller amount of 13.5-d recurrence. Previous work has shown that the recent solar minimum 23–24 exhibited 9.0 and 6.7-d recurrence in geomagnetic and heliospheric data, but those recurrence intervals were not prominently present during the preceding minima 21–22 and 22–23. Using annual-averages and solar-cycle averages of autocorrelations of the historicalaadata, we put these observations into a long-term perspective: none of the 12 minima preceding 23–24 exhibited prominent 9.0 and 6.7-d geomagnetic activity recurrence. We show that the detection of these recurrence intervals can be traced to an unusual combination of sectorial spherical-harmonic structure in the solar magnetic field and anomalously low sunspot number. We speculate that 9.0 and 6.7-d recurrence is related to transient large-scale, low-latitude organization of the solar dynamo, such as seen in some numerical simulations.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24
Series title:
Geophysical Research Letters
DOI:
10.1029/2011GL050702
Volume
39
Year Published:
2012
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
Geologic Hazards Science Center
Description:
L04102
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysical Research Letters
Country:
United States