HR: 1330h
AN: SH23B-03    [Abstracts]
TI: Sunspot fragmentation and total solar irradiance modelling
AU: * Crouch, A D
EM: ash@ASTRO.UMontreal.CA
AF: Département de Physique, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C3J7 Canada
AU: * Crouch, A D
EM: ash@ASTRO.UMontreal.CA
AF: Centre for Stellar and Planetary Astrophysics, Monash University, Wellington Road, Clayton, Melbourne, VIC 3800 Australia
AU: Charbonneau, P
EM: paulchar@ASTRO.UMontreal.CA
AF: Département de Physique, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C3J7 Canada
AU: Tapping, K F
EM: Ken.Tapping@nrc-cnrc.gc.ca
AF: Dominion Radio Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, P.O. Box 248, Penticton, BC V2A6J9 Canada
AU: Paquin-Ricard, D
EM: phy3030b@ASTRO.UMontreal.CA
AF: Département de Physique, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C3J7 Canada
AB: Observational evidence suggests that sunspot decay is due, at least in part, to a fragmentation process. We have developed a model for this, where the sunspot fragmentation produces an ensemble of small scale magnetic flux tubes, which themselves can remain at the surface for many days. The number of sunspots emerging at the solar surface varies over the 11 year solar activity cycle. Consequently, the size distribution of magnetic structures is also modulated by the cycle. The simplicity of our model allows us to track the evolution of this distribution over very long time scales (many solar cycles). There are several applications for such a model. For example, to the total solar irradiance, which also varies over the solar cycle. Broadly speaking, the irradiance contribution from different magnetic features depends on their size (large features, such as sunspots, are dark, whereas small flux tubes tend to be bright). By combining this property with our sunspot fragmentation model, we show that the resultant system can produce an irradiance contribution that behaves very much like the observed total solar irradiance. Our model has several input parameters (one crucial example is the actual relationship between the size of a magnetic feature and its brightness). We have used a genetic algorithm to adjust the parameters in order to optimize the agreement between our model and the observations. Will we discuss those results and also comment on the contribution our model makes to the weak field component of solar magnetic flux budget.
DE: 1650 Solar variability
DE: 7537 Solar and stellar variability
DE: 7538 Solar irradiance
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly