A Theoretical Study of the Build-Up of the Sun’s Polar Magnetic Field by Using a 3d Kinematic Dynamo Model

Abstract

We develop a three-dimensional kinematic self-sustaining model of the solar dynamo in which the poloidal field generation is from tilted bipolar sunspot pairs placed on the solar surface above regions of strong toroidal field by using the SpotMaker algorithm, and then the transport of this poloidal field to the tachocline is primarily caused by turbulent diffusion. We obtain a dipolar solution within a certain range of parameters. We use this model to study the build-up of the polar magnetic field and show that some insights obtained from surface flux transport (SFT) models have to be revised. We present results obtained by putting a single bipolar sunspot pair in a hemisphere and two symmetrical sunspot pairs in two hemispheres.We find that the polar fields produced by them disappear due to the upward advection of poloidal flux at low latitudes, which emerges as oppositely-signed radial flux and which is then advected poleward by the meridional flow. We also study the effect that a large sunspot pair, violating Hale's polarity law would have on the polar field. We find that there would be some effect-especially if the anti-Hale pair appears at high latitudes in the mid-phase of the cycle-though the effect is not very dramatic.

Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock–Leighton Solar Dynamo Model

“…Tilts of these pairs are given by Joys law and no seed magnetic field is given in this simulation. (This study is very similar to the one presented in Section 4.2 of Hazra et al (2017).) Then we perform two more simulations.…”

“…Because of this random component, the actual tilt angle in our model has a considerable variation. Since the poloidal field generated by the BL mechanism depends sensitively on the BMR tilt (Dasi-Espuig et al 2010;Jiang et al 2014;Hazra et al 2017), its random scatter gives rise to cycle variability. This greatly enhances the relatively modest cycle variability arising just from the random time delay (MT16).…”

“…In comparison to previous publications (MD14, MT16, Hazra et al 2017), here we have some changes in order to make a close connection with observations. In the previous model, the BMR flux was directly related to the toroidal field at the base of the CZ while in this model, it is obtained from the observed distribution.…”

Improvement of solar-cycle prediction: Plateau of solar axial dipole moment

“…In the SFT model, the only effect of meridional flow is the horizontal (poleward) transport of the surface magnetic field. However, some studies indicated the possible role of the vertical (radial) component of the meridional circulation for the evolution of the surface magnetic field (e.g., Dikpati & Choudhuri 1994;Hazra et al 2017). On the other hand, suggested that the effect of the vertical flow of the meridional circulation is suppressed when sufficiently strong downward magnetic pumping exists near the solar surface.…”

The alpha effect of Babcock-Leighton in the in the surface layers of the Sun

“…Разом з тим, в останні роки наступив ренесанс щодо ви-вчення поверхневого α-ефекту Бебкока-Лейтона. Виявилося, що механізм Бебкока-Лейтона заслуговує не меншої уваги [11][12][13][14][15][16][17], оскільки його властивості можна оцінити з статистичних властивостей спостережених сонячних плям на відміну від необхідності теоретичних розрахунків кінетичного параметру Паркера-Штеєнбека-Краузе.…”