Simulations of the sun's polar magnetic fields during sunspot cycle 21

✍ Scribed by C. Richard DeVore; Neil R. Sheeley

• Publisher: Springer
• Year: 1987
• Tongue: English
• Weight: 675 KB
• Volume: 108
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00152076

✦ Synopsis

Regarding new bipolar magnetic regions as sources of flux, we have simulated the evolution of the radial component of the solar photospheric magnetic field during 1976-1984 and derived the corresponding evolution of the line-of-sight polar fields as seen from Earth. The observed timing and strength of the polar-field reversal during cycle 21 can be accounted for by supergranular diffusion alone, for a diffusion coefficient of 800 km 2 s -1. For an assumed 300 km 2 s -1 rate of diffusion, on the other hand, a poleward meridional flow with a moderately broad profile and a peak speed of 10 m s -1 reached at about 5 ~ latitude is required to obtain agreement between the simulated and observed fields. Such a flow accelerates the transport of following-polarity flux to the polar caps, but also inhibits the diffusion of leading-polarity flux across the equator. For flows faster than about 10 m s -1 the latter effect dominates, and the simulated polar fields reverse increasingly later and more weakly than the observed fields.