Solar activity forecast with a dynamo model

Jiang, Jie ; Chatterjee, Piyali ; Rai Choudhuri, Arnab (2007) Solar activity forecast with a dynamo model Monthly Notices of the Royal Astronomical Society, 381 (4). pp. 1527-1542. ISSN 0035-8711

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Although systematic measurements of the Sun's polar magnetic field exist only from mid-1970s, other proxies can be used to infer the polar field at earlier times. The observational data indicate a strong correlation between the polar field at a sunspot minimum and the strength of the next cycle, although the strength of the cycle is not correlated well with the polar field produced at its end. This suggests that the Babcock-Leighton mechanism of poloidal field generation from decaying sunspots involves randomness, whereas the other aspects of the dynamo process must be reasonably ordered and deterministic. Only if the magnetic diffusivity within the convection zone is assumed to be high (of order 1012 cm2 s−1), we can explain the correlation between the polar field at a minimum and the next cycle. We give several independent arguments that the diffusivity must be of this order. In a dynamo model with diffusivity like this, the poloidal field generated at the mid-latitudes is advected toward the poles by the meridional circulation and simultaneously diffuses towards the tachocline, where the toroidal field for the next cycle is produced. To model actual solar cycles with a dynamo model having such high diffusivity, we have to feed the observational data of the poloidal field at the minimum into the theoretical model. We develop a method of doing this in a systematic way. Our model predicts that cycle 24 will be a very weak cycle. Hemispheric asymmetry of solar activity is also calculated with our model and compared with observational data.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons.
Keywords:Sun: Activity; Sun: Magnetic Fields; Sunspots
ID Code:66548
Deposited On:24 Oct 2011 08:21
Last Modified:18 May 2016 14:02

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