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NOAO Newsletter - National Solar Observatory - March 1999 - Number 57


New Method for Determining the Time and Amplitude of Solar Maximum

Long-term maxima of solar activity occur on the average approximately every 11 years. However, the exact timing 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 minimum of activity preceding the maximum in question. However, a perhaps more reliable indicator of the timing of the maximum occurs early in the rise phase of the solar cycle. This graph shows that coronal Fe XIV emission features observed with the NSO/SP Evans Solar Facility 40-cm coronagraph appear near 55 latitude in approximately 1978 and 1988 and begin to move towards the poles at a rate of 9 to 12 of latitude per year. This motion is maintained for a period of 3 or 4 years, at which time the emission features disappear at the poles. This phenomenon has been referred to as the "Rush to the Poles." The maximum of solar activity has been found to occur approximately 14 months before the features reach the poles. In early 1997, emission features appeared near 55 latitude, and they are moving towards the poles. This then is the Rush to the Poles that heralds the next solar maximum. Based on observations up through October 1998, these features will reach the poles in approximately October 2000, which results in a prediction for solar maximum of between June and August 1999, substantially earlier than many other predictions. A maximum smoothed sunspot number of approximately 160 is predicted following Bray and Loughhead (Sunspots, 1965, pp. 240ff).

Rush to the Poles

Dick Altrock, Todd Brown, Joe Elrod,
John Cornett, Tim Henry


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