| AMS Citation: |
Love, J. J., E. J. Rigler, and , 2012: Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24. Geophysical Research Letters, 39, L04102, doi:10.1029/2011GL050702. |
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| Date: | 2012-02-28 |
| Resource Type: | article |
| Title: | Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24 |
| Abstract: | Analysis is made of the geomagnetic-activity aa index 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 historical aa data, 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. |
| Subject(s): | Magnetic observatory, Recurrent geomagnetic activity, Solar-terrestrial interaction |
| Peer Review: | Refereed |
| Copyright Information: | Copyright 2012 American Geophysical Union. |
| OpenSky citable URL: | ark:/85065/d78g8mcv |
| Publisher's Version: | 10.1029/2011GL050702 |
| Author(s): |
