Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24
Geophysical Research Letters
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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.
| 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 |
| Google Analytic Metrics | Metrics page |