Computer Science
Scientific paper
Oct 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002esasp.505..453k&link_type=abstract
In: SOLMAG 2002. Proceedings of the Magnetic Coupling of the Solar Atmosphere Euroconference and IAU Colloquium 188, 11 - 15 Jun
Computer Science
2
Solar Magnetic Fields, Magnetic Cycle, Spherical Harmonics, Time Series Analysis
Scientific paper
The temporal variations of the global magnetic field in the Sun's photosphere have been investigated through a harmonic analysis of the zonal (m=0) as well as the non-axisymmetric (m≠0) modes. A 25 yr time series of magnetic maps, recorded at the Kitt Peak Observatory (Tucson, AZ) on a daily basis, was used to calculate the spherical coefficients of the radial magnetic field. Subsequently, we applied Fourier analysis as well as wavelet analysis to deduce the temporal variations. A complex structure of resonant modes has been revealed. Besides the obvious 22 yr magnetic cycle, shorter-lived fluctuations have been detected, e.g. with periods of approx. 6-7 yr and 2-3 yr. The latter is most accentuated during the solar maxima. However, we cannot yet verify a systematic correlation between the spherical degree of the even zonal modes and their resonance frequencies, which is in contrast to earlier analyses of low-resolution synoptic charts. What we can confirm is the previously found parity selection rule that the 22 yr cycle is the dominating feature of the odd zonal modes and we can extend this rule to non-axisymmetric modes.
Knaack R.
Stenflo Jan Olof
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