GROUP A

PREDICTION ON TIMESCALES OF YEARS TO DECADES - SOLAR CYCLE VARIABILITY

Most forms of solar activity are well correlated with the solar cycle as measured by the 10.7 cm flux or the sunspot number. Presently, predictions of the smoothed level of these activity indicators over the course of an individual sunspot cycle become reliable about 2-3 years after sunspot minimum (when the size of the cycle can be ascertained). Earlier predictions are needed but are currently much less reliable. Recent advances in dynamo theory and in our understanding of the solar cycle indicate new avenues for predicting the amplitude of a solar cycle well before minimum. Physical mechanisms for producing solar variability on timescales of 1-3 years have also been identified. The occurrence of super active regions relative to the amplitude and phase of the activity cycle needs to be addressed. This group will discuss advances in understanding and modeling of solar cycle variability and its impact on mission planning for the Space Exploration Initiative.