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GEOPHYSICAL RESEARCH LETTERS,
VOL. 32,
L01104,
doi:10.1029/2004GL021664,
2005
Sunspot cycle 24: Smallest cycle in 100 years?
Leif Svalgaard
Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan
Edward W. Cliver
Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AFB, Massachusetts, USA
Yohsuke Kamide
Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Japan
Abstract
Predicting the peak amplitude of the sunspot cycle is a key goal of solar-terrestrial physics. The precursor method currently
favored for such predictions is based on the dynamo model in which large-scale polar fields on the decline of the 11-year
solar cycle are converted to toroidal (sunspot) fields during the subsequent cycle. The strength of the polar fields during
the decay of one cycle is assumed to be an indicator of peak sunspot activity for the following cycle. Polar fields reach
their peak amplitude several years after sunspot maximum; the time of peak strength is signaled by the onset of a strong annual
modulation of polar fields due to the 7 ° tilt of the solar equator to the ecliptic plane. Using direct polar field measurements, now available for four solar cycles,
we predict that the approaching solar cycle 24 (∼2011 maximum) will have a peak smoothed monthly sunspot number of 75 ± 8,
making it potentially the smallest cycle in the last 100 years.
Received 3
October
2004;
accepted 9
December
2004;
published 11
January
2005.
Index Terms: 7500 Solar Physics, Astrophysics, and Astronomy; 7536 Solar Physics, Astrophysics, and Astronomy: Solar activity cycle (2162); 7537 Solar Physics, Astrophysics, and Astronomy: Solar and stellar variability (1650); 7900 Space Weather; 7924 Space Weather: Forecasting (2722).
Read Full Article (file size: 172422 bytes) Cited by
Citation: Svalgaard, L., E. W. Cliver, and Y. Kamide
(2005),
Sunspot cycle 24: Smallest cycle in 100 years?,
Geophys. Res. Lett.,
32,
L01104,
doi:10.1029/2004GL021664.
Copyright 2005 by the American Geophysical Union.
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