Thursday, June 20, 2013

1306.4561 (Sabrina Maite Sanchez et al.)

On the predictability limit of a mean-field flux transport solar dynamo model and its implications for solar activity forecasting    [PDF]

Sabrina Maite Sanchez, Alexandre Fournier, Julien Aubert
Space weather is a matter of practical importance in our modern society. Predictions of forecoming solar cycles mean amplitude and duration are currently being made based on mean-field numerical models of the solar dynamo. Interested in the forecast horizon of such studies, we quantify the predictability window of a representative mean-field dynamo model by investigating its sensitivity to initial conditions and control parameters through a perturbation analysis. We measure the rate associated with the exponential growth of an initial perturbation of the model trajectory, which yields a characteristic time scale known as the e-folding time {\tau_e}. The e-folding time is shown to decrease with the strength of the {\alpha}-effect, and to increase with the magnitude of the imposed meridional circulation. Comparing the e-folding time with the solar cycle periodicity, we obtain an average estimate for {\tau_e} equal to 2.76 solar cycle durations. From a practical point of view, the perturbations analysed in this work can be interpreted as uncertainties affecting either the observations or the physical model itself. After discussing these, we conclude that the main properties of the solar cycle may be predicted, using mean-field models of the solar dynamo, up to 3 solar cycles ahead.
View original: http://arxiv.org/abs/1306.4561

No comments:

Post a Comment