Diagnostics of Polar Field Reversal in Solar Cycle 23 Using a Flux Transport Dynamo Model

2004 ◽  
Vol 601 (2) ◽  
pp. 1136-1151 ◽  
Author(s):  
Mausumi Dikpati ◽  
Giuliana de Toma ◽  
Peter A. Gilman ◽  
Charles N. Arge ◽  
Oran R. White
Keyword(s):  
Solar Cycle ◽  
Polar Field ◽  
Dynamo Model ◽  
Flux Transport ◽  
Field Reversal ◽  
Solar Cycle 23

scholarly journals Does the mean-field α effect have any impact on the memory of the solar cycle?

2020 ◽  
Vol 642 ◽  
pp. A51
Author(s):  
Soumitra Hazra ◽  
Allan Sacha Brun ◽  
Dibyendu Nandy
Keyword(s):  
Solar Cycle ◽  
Mean Field ◽  
Solar Dynamo ◽  
Dynamo Model ◽  
Solar Cycles ◽  
Poloidal Field ◽  
Flux Transport ◽  
Solar Convection ◽  
The Mean ◽  
And Diffusion

Context. Predictions of solar cycle 24 obtained from advection-dominated and diffusion-dominated kinematic dynamo models are different if the Babcock–Leighton mechanism is the only source of the poloidal field. Some previous studies argue that the discrepancy arises due to different memories of the solar dynamo for advection- and diffusion-dominated solar convection zones. Aims. We aim to investigate the differences in solar cycle memory obtained from advection-dominated and diffusion-dominated kinematic solar dynamo models. Specifically, we explore whether inclusion of Parker’s mean-field α effect, in addition to the Babcock–Leighton mechanism, has any impact on the memory of the solar cycle. Methods. We used a kinematic flux transport solar dynamo model where poloidal field generation takes place due to both the Babcock–Leighton mechanism and the mean-field α effect. We additionally considered stochastic fluctuations in this model and explored cycle-to-cycle correlations between the polar field at minima and toroidal field at cycle maxima. Results. Solar dynamo memory is always limited to only one cycle in diffusion-dominated dynamo regimes while in advection-dominated regimes the memory is distributed over a few solar cycles. However, the addition of a mean-field α effect reduces the memory of the solar dynamo to within one cycle in the advection-dominated dynamo regime when there are no fluctuations in the mean-field α effect. When fluctuations are introduced in the mean-field poloidal source a more complex scenario is evident, with very weak but significant correlations emerging across a few cycles. Conclusions. Our results imply that inclusion of a mean-field α effect in the framework of a flux transport Babcock–Leighton dynamo model leads to additional complexities that may impact memory and predictability of predictive dynamo models of the solar cycle.

scholarly journals Flux-transport and mean-field dynamo theories of solar cycles

2012 ◽  
Vol 8 (S294) ◽  
pp. 37-47
Author(s):  
Arnab Rai Choudhuri
Keyword(s):  
Solar Cycle ◽  
Meridional Circulation ◽  
Mean Field ◽  
Dynamo Model ◽  
Solar Cycles ◽  
Poloidal Field ◽  
Flux Transport ◽  
Mean Field Model ◽  
Mean Field Models ◽  
Mean Field Dynamo

AbstractWe point out the difficulties in carrying out direct numerical simulation of the solar dynamo problem and argue that kinematic mean-field models are our best theoretical tools at present for explaining various aspects of the solar cycle in detail. The most promising kinematic mean-field model is the flux transport dynamo model, in which the toroidal field is produced by differential rotation in the tachocline, the poloidal field is produced by the Babcock–Leighton mechanism at the solar surface and the meridional circulation plays a crucial role. Depending on whether the diffusivity is high or low, either the diffusivity or the meridional circulation provides the main transport mechanism for the poloidal field to reach the bottom of the convection zone from the top. We point out that the high-diffusivity flux transport dynamo model is consistent with various aspects of observational data. The irregularities of the solar cycle are primarily produced by fluctuations in the Babcock–Leighton mechanism and in the meridional circulation. We summarize recent work on the fluctuations of meridional circulation in the flux transport dynamo, leading to explanations of such things as the Waldmeier effect.

scholarly journals Is meridional circulation important in modelling irregularities of the solar cycle?

2011 ◽  
Vol 7 (S286) ◽  
pp. 367-371 ◽  
Author(s):  
Bidya Binay Karak ◽  
Arnab Rai Choudhuri
Keyword(s):  
Solar Cycle ◽  
Convection Zone ◽  
Meridional Circulation ◽  
Dynamo Model ◽  
Turbulent Diffusivity ◽  
Flux Transport ◽  
Grand Minimum

AbstractWe explore the importance of meridional circulation variations in modelling the irregularities of the solar cycle by using the flux transport dynamo model. We show that a fluctuating meridional circulation can reproduce some features of the solar cycle like the Waldmeier effect and the grand minimum. However, we get all these results only if the value of the turbulent diffusivity in the convection zone is reasonably high.

scholarly journals Solar-cycle precursors and predictions

2012 ◽  
Vol 8 (S294) ◽  
pp. 49-60 ◽  
Author(s):  
Jie Jiang
Keyword(s):  
Solar Cycle ◽  
Polar Field ◽  
Magnetic Memory ◽  
Flux Transport ◽  
Geomagnetic Variations ◽  
Magnetic Diffusivity ◽  
Time Period ◽  
Set Up ◽  
Open Flux ◽  
Robust Prediction

AbstractThe sunspot number data during the past 400 years indicates that both the profile and the amplitude of the solar cycle have large variations. Some precursors of the solar cycle were identified aiming to predict the solar cycle. The polar field and the geomagnetic index are two precursors which are received the most attention. The geomagnetic variations during the solar minima are potentially caused by the solar polar field by the connection of the solar open flux. The robust prediction skill of the polar field indicates that the memory of the dynamo process is less than 11 yrs based on the frame of the Babcock-Leighton flux transport dynamo. One possible reason to get the short magnetic memory is the high magnetic diffusivity in the convective zone. Our recent studies show that the radial downward pumping is another possible reason. Based upon the mechanism, we well simulate the cycle irregularities during RGO time period. This opens the possibility to set up a standard dynamo based model to predict the solar cycle. In the end, the no correlation between the polar field and the preceding cycle strength due to two nonlinearities involved in the sunspot emergence will be stressed.

scholarly journals Predicting a Solar Cycle Before its Onset Using a Flux Transport Dynamo Model

2017 ◽  
Vol 13 (S335) ◽  
pp. 177-182
Author(s):  
Arnab Rai Choudhuri
Keyword(s):  
Solar Cycle ◽  
Meridional Circulation ◽  
Dynamo Model ◽  
Flux Transport ◽  
Successful Prediction ◽  
Cycle 24

AbstractWe begin with a review of the predictions for cycle 24 before its onset. After summarizing the basics of the flux transport dynamo model, we discuss how this model had been used to make a successful prediction of cycle 24, on the assumption that the irregularities of the solar cycle arise due to the fluctuations in the Babcock–Leighton mechanism. We point out that fluctuations in the meridional circulation can be another cause of irregularities in the cycle.

scholarly journals Solar cycle 24: An unusual polar field reversal

2018 ◽  
Vol 618 ◽  
pp. A148 ◽  
Author(s):  
P. Janardhan ◽  
K. Fujiki ◽  
M. Ingale ◽  
S. K. Bisoi ◽  
D. Rout
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Field Strength ◽  
Polar Field ◽  
Line Of Sight ◽  
Zero Field ◽  
Field Reversal ◽  
Reversal Process ◽  
Solar Cycle 24 ◽  
Cycle 24

Context. It is well known that the polarity of the Sun’s magnetic field reverses or flips around the maximum of each 11 year solar cycle. This is commonly known as polar field reversal and plays a key role in deciding the polar field strength at the end of a cycle, which is crucial for the prediction of the upcoming cycle. Aims. We aim to investigate solar polar fields during cycle 24, using measurements of solar magnetic fields in the latitude range 55°–90° and 78°–90°, to report a prolonged and unusual hemispheric asymmetry in the polar field reversal pattern in solar cycle 24. Methods. This study was carried out using medium resolution line-of-sight synoptic magnetograms from the magnetic database of the National Solar Observatory at Kitt Peak (NSO/KP), USA for the period between February 1975 and October 2017, covering solar cycles 21–24 and high-resolution line-of-sight synoptic magnetograms from the Michaelson Doppler Imager instrument onboard the Solar Heliospheric Observatory. Synoptic magnetograms using radial measurements from the Heliospheric Magnetic Imager instrument onboard the Solar Dynamics Observatory, covering solar cycle 23 and 24, were also used. Results. We show that the southern solar hemisphere unambiguously reversed polarity in mid-2013 while the reversal in the field in the northern solar hemisphere started as early as June 2012, was followed by a sustained period of near-zero field strength lasting until the end of 2014, after which the field began to show a clear rise from its near-zero value. While this study compliments a similar study carried out using microwave brightness measurements which claimed that the field reversal process in cycle 24 was completed by the end of 2015, our results show that the field reversal in cycle 24 was completed earlier that is, in late 2014. Signatures of this unusual field reversal pattern were also clearly identifiable in the solar wind, using our observations of interplanetary scintillation at 327 MHz which supported our magnetic field observations and confirmed that the field reversal process was completed at the end of 2014.

scholarly journals The need for active region disconnection in 3D kinematic dynamo simulations

2019 ◽  
Vol 627 ◽  
pp. A168 ◽  
Author(s):  
T. Whitbread ◽  
A. R. Yeates ◽  
A. Muñoz-Jaramillo
Keyword(s):  
Solar Cycle ◽  
Active Region ◽  
Convection Zone ◽  
Transport Model ◽  
Active Regions ◽  
Surface Flux ◽  
Dynamo Model ◽  
Flux Transport ◽  
Kinematic Dynamo ◽  
The Difference

In this paper we address a discrepancy between the surface flux evolution in a 3D kinematic dynamo model and a 2D surface flux transport model that has been closely calibrated to the real Sun. We demonstrate that the difference is due to the connectivity of active regions to the toroidal field at the base of the convection zone, which is not accounted for in the surface-only model. Initially, we consider the decay of a single active region, firstly in a simplified Cartesian 2D model and subsequently the full 3D model. By varying the turbulent diffusivity profile in the convection zone, we find that increasing the diffusivity – so that active regions are more rapidly disconnected from the base of the convection zone – improves the evolution of the surface field. However, if we simulate a full solar cycle, we find that the dynamo is unable to sustain itself under such an enhanced diffusivity. This suggests that in order to accurately model the solar cycle, we must find an alternative way to disconnect emerging active regions, whilst conserving magnetic flux.

scholarly journals Towards an algebraic method of solar cycle prediction

2020 ◽  
Vol 10 ◽  
pp. 50 ◽  
Author(s):  
Kristóf Petrovay ◽  
Melinda Nagy ◽  
Anthony R. Yeates
Keyword(s):  
Dipole Moment ◽  
Solar Cycle ◽  
Active Regions ◽  
Surface Flux ◽  
Algebraic Method ◽  
Meridional Flow ◽  
Activity Level ◽  
Dynamo Model ◽  
Flux Transport ◽  
Axial Dipole

We discuss the potential use of an algebraic method to compute the value of the solar axial dipole moment at solar minimum, widely considered to be the most reliable precursor of the activity level in the next solar cycle. The method consists of summing up the ultimate contributions of individual active regions to the solar axial dipole moment at the end of the cycle. A potential limitation of the approach is its dependence on the underlying surface flux transport (SFT) model details. We demonstrate by both analytical and numerical methods that the factor relating the initial and ultimate dipole moment contributions of an active region displays a Gaussian dependence on latitude with parameters that only depend on details of the SFT model through the parameter η/Δu where η is supergranular diffusivity and Δu is the divergence of the meridional flow on the equator. In a comparison with cycles simulated in the 2 × 2D dynamo model we further demonstrate that the inaccuracies associated with the algebraic method are minor and the method may be able to reproduce the dipole moment values in a large majority of cycles.

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