Simulating Solar Cycles in Northern and Southern Hemispheres by Assimilating Magnetic Data into a Calibrated Flux-Transport Dynamo

Abstract

We use the flux-transport dynamo prediction scheme introduced by Dikpati, de Toma, and Gilman (Geophys. Res. Lett. 33, L05102, 2006) to make separate simulations and predictions of sunspot cycle peaks for northern and southern hemispheres. Despite the division of the data, the skill level achieved is only slightly lower than that achieved for the sum of both hemispheres. The model shows skill at simulating and predicting the difference in peaks between North and South, provided that difference is more than a few percent. The simulation and prediction skill is achieved without adjustment to any parameters of the model that were used when peaks for the sum of North and South sunspot areas was simulated. The results are also very insensitive to the averaging length applied to the input data, provided the simulations and predictions are for peaks defined by averaging the observations over at least 13 rotations. However, in its present form, the model is not capable of skillfully simulating or predicting short-time-scale features of individual solar cycles.

On the role of asymmetries in the reversal of the solar magnetic field

“…Actually with such a degree of asymmetry we find that the North pole reverses more than 1 yr ahead of the South pole. This is compatible with solar observations, that clearly show that one hemisphere can be ahead of the other one by up to 2 yr (Dikpati et al 2007, Shiota et al 2012, Tsuneta et al 2012 this proceedings). Here we did not tune the amplitude nor the sign of the asymmetry parameter to reproduce the sequence of reversals and time lag between the Northern and Southern hemispheres seen in the Sun but we intend to do so in the near future.…”

“…We have shown that by modifying the ingredients of the standard dynamo models by introducing a certain degree of asymmetry in the flow both families are coupled more efficiently. We find that we can qualitatively reproduce the ratio between the quadrupole and the dipole observed in the Sun and also explain the origin of the time lag seen in the reversal of the magnetic field between the North and the South poles (Dikpati et al 2007, Shiota et al 2012, Tsuneta et al 2012). …”

Difference between even- and odd-numbered cycles in the predictability of solar activity and prediction of the amplitude of cycle 25

“…Belucz and Dikpati (2013), who conducted simulations of solar cycles by changing properties of meridional circulation only in the south, obtained results that the Northern Hemisphere experienced virtually no change in spite of all the changes that occurred in the Southern Hemisphere. These results of simulations suggest that the north and the south are linked very weakly and that many of solar cycle characteristics within a hemisphere can be reproduced from information from previous cycles only from that hemisphere (Dikpati et al, 2007).…”

“…Having made separate simulations of sunspot cycles for Northern and Southern hemispheres by using the fluxtransport dynamo prediction scheme , Dikpati et al (2007) found that the skill level was only slightly lowered. Belucz and Dikpati (2013), who conducted simulations of solar cycles by changing properties of meridional circulation only in the south, obtained results that the Northern Hemisphere experienced virtually no change in spite of all the changes that occurred in the Southern Hemisphere.…”

Derivation of stochastic differential equations for sunspot activity

“…It is now generally accepted that magnetic cycles in the Sun are generated by a solar dynamo produced through nonlinear interactions between solar plasmas and magnetic fields as reviewed by Choudhuri (2000). It appears that the average or large-scale features of the solar cycle can be explained by solar dynamo models (Cameron & Schüssler 2007;Charbonneau 2005;Choudhuri 2000;Dikpati et al 2006Dikpati et al , 2007or Passos 2008). However, as pointed out, for example by Passos (2008), the variation in the amplitude and period in the 11-year cycle is still difficult to understand.…”