Issue |
A&A
Volume 390, Number 2, August I 2002
|
|
---|---|---|
Page(s) | 707 - 715 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20020758 | |
Published online | 12 July 2002 |
Hemispheric Sunspot Numbers
and
:
Catalogue and N-S asymmetry
analysis*
Institut für Geophysik, Astrophysik und Meteorologie, Universität Graz, Universitätsplatz 5, 8010 Graz, Austria
Corresponding author: M. Temmer, manuela.temmer@uni-graz.at
Received:
18
December
2001
Accepted:
6
May
2002
Sunspot drawings are provided on a regular basis at the
Kanzelhöhe Solar Observatory, Austria, and the derived relative
sunspot numbers are reported to the Sunspot Index Data Center in
Brussels. From the daily sunspot drawings, we derived the
northern, Rn, and southern, Rs, relative sunspot numbers
for the time span 1975–2000. In order to accord with the
International Sunspot Numbers Ri, the Rn and Rs
have been normalized to the Ri, which ensures that the
relation is fulfilled. For validation, the
derived Rn and Rs are compared to the international
northern and southern relative sunspot numbers, which are
available from 1992. The regression analysis performed for the
period 1992–2000 reveals good agreement with the International
hemispheric Sunspot Numbers. The monthly mean and the smoothed
monthly mean hemispheric Sunspot Numbers are compiled into a
catalogue. Based on the derived hemispheric Sunspot Numbers, we
study the significance of N-S asymmetries and the rotational
behavior separately for both hemispheres. We obtain that
~60% of the monthly N-S asymmetries are significant at a
95% level, whereas the relative contributions of the northern and
southern hemisphere are different for different cycles. From the
analysis of power spectra and autocorrelation functions, we derive
a rigid rotation with ~27 days for the northern hemisphere,
which can be followed for up to 15 periods. Contrary to that, the
southern hemisphere reveals a dominant period of ~28 days,
whereas the autocorrelation is strongly attenuated after
3 periods. These findings suggest that the activity of the
northern hemisphere is dominated by an active zone, whereas the
southern activity is mainly dominated by individual long-lived
sunspot groups.
Key words: catalogs / Sun: activity / Sun: rotation / Sun: sunspots
© ESO, 2002
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