| Issue |
A&A
Volume 433, Number 2, April II 2005
|
|
|---|---|---|
| Page(s) | 707 - 712 | |
| Section | The Sun | |
| DOI | https://doi.org/10.1051/0004-6361:20041833 | |
| Published online | 22 March 2005 | |
What causes the 24-day period observed in solar flares?
1
Institute of Physics/IGAM, Universität Graz, Universitätsplatz 5, 8010 Graz, Austria e-mail: mat@igam.uni-graz.at
2
Astronomical Institute/SAS, 05960 Tatranská Lomnica, Slovak Republic
Received:
11
August
2004
Accepted:
3
December
2004
Previous studies report a ~24-day (synodic) period
in the occurrence rate of solar flares for each of the solar
cycles studied, Nos. 19–22 (Bai 1987, ApJ, 314, 795;
Temmer et al. 2004, Sol. Phys. 221, 325). Here we study
the 24-day period in the solar flare occurrence for solar cycles 21 and 22
by means of wavelet power spectra together with the solar flare
locations in synoptic magnetic maps. We find that the 24-day
peak revealed in the power spectra is just the result of a particular
statistical clumping of data points, most probably caused
by a characteristic longitudinal separation
of about 
to 
of activity complexes in
successive Carrington rotations. These complexes appear as parallel,
diverging or converging branches in the synoptic magnetic maps and are
particularly flare-productive.
Key words: Sun: flares / Sun: activity / Sun: magnetic fields
© ESO, 2005
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