Poster by Th.Ulich and K.Mursula
The Varying Length of the Solar Cycle
Determined by Different Methods
Thomas Ulich and Kalevi Mursula
Department of Physical Sciences, University of Oulu,
Linnanmaa, FIN-90570 Oulu, Finland
Introduction
The sunspot numbers have traditionally been used as a measure for the solar
activity (Fig. 1). The sunspot number is, e.g., well correlated to the
10.7cm radio flux emission rate (Fig. 2).
Recently, solar activity has been related to the long-term evolution of global
temperature (Friis-Christensen and Lassen, 1993; see ``Correlations''). The
key question is whether this connection dominates over the anthropogenic
effects on climate.
In this work we re-analyse the solar cycle lengths using traditional methods
and a novel technique based on determining the time (``median time'') of half
of the integrated sunspot number per cycle. While traditional methods are
sensitive to the different estimations of sunspot minima or maxima, the
median method is very stable to these differences.
