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R.C. Altrock (Air Force Research Lab. at NSO/SP)
Prediction of the exact time of solar-cycle maximum is a matter of disagreement among solar scientists and of some importance to satellite operators, space-system designers, etc. Most predictions are based on physical conditions occurring at or before the long-term minimum of activity preceding the maximum in question. However, another indicator of the timing of the maximum occurs early in the rise phase of the solar activity cycle. A study of the variation over two previous solar cycles of coronal emission features in Fe XIV from the National Solar Observatory at Sacramento Peak has shown that, prior to solar maximum, emission features appear near 55 degrees latitude in both hemispheres and begin to move towards the poles at a rate of 9 to 13 degrees of latitude per year. This motion is maintained for a period of 3 or 4 years, at which time the emission features disappear near the poles. This phenomenon has been referred to as the "Rush to the Poles". These observations show that the maximum of solar activity, as seen in the sunspot number, occurs approximately 15 +/- 1 months before the features reach the poles.
In 1997, Fe XIV emission features appeared near 55 degrees latitude, and began to move towards the poles. Using the above historical data from cycles 21 and 22, we will see how the use of progressively more data from cycle 23 affects the prediction of the time of solar maximum. For example, based on observations up through April 1999, the extrapolated Rush to the Poles is predicted to reach the poles in approximately June 2001, which results in a prediction for solar maximum of between January and April 2000. The actual smoothed sunspot number maximized in April 2000.
This work was supported by the Air Force Office of Scientific Research.
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The author(s) of this abstract have provided an email address for comments about the abstract: altrock@nso.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.