The unusual minimum of sunspot cycle 23 a consequence of Sun's meridional plasma flow variations

Abstract

Direct observations over the past four centuries show that the number of sunspots observed on the Sun's surface vary periodically, going through successive maxima and minima. Following sunspot cycle 23, the Sun went into a prolonged minimum characterized by a very weak polar magnetic field and an unusually large number of days without sunspots. Sunspots are strongly magnetized regions and are generated by a dynamo mechanism which recreates the solar polar field mediated via plasma flows. Here we report results from kinematic dynamo simulations which demonstrate that a fast meridional flow in the early half of a cycle, followed by a slower flow in the latter half, reproduces both the characteristics of the minimum of sunspot cycle 23 - a large number of spotless days and a relatively weak polar field. Our model predicts that, in general, very deep minima are associated with weak polar fields. Sunspots govern the solar radiative energy and radio flux, and in conjunction with the polar field, modulate the solar wind, heliospheric open flux and consequently cosmic ray flux at Earth; our results therefore provide a causal link between solar internal dynamics and the atypical values of these heliospheric forcing parameters during the recently concluded solar minimum.

References in corpus (6)

• Predicting solar cycle 24 with a solar dynamo model
• Exploring the Physical Basis of Solar Cycle Predictions: Flux Transport Dynamics and Persistence of Memory in Advection versus Diffusion Dominated Solar Convection Zones
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• Helioseismic data inclusion in solar dynamo models
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• Nonlinear mechanisms that regulate the solar cycle amplitude
• Meridional Flow in the Solar Convection Zone I: Measurements from GONG Data
• Evolution of active and polar photospheric magnetic fields during the rise of Cycle 24 compared to previous cycles
• Understanding solar torsional oscillations from global dynamo models
• A proposed paradigm for solar cycle dynamics mediated via turbulent pumping of magnetic flux in Babcock-Leighton type solar dynamos
• A 3D kinematic Babcock Leighton solar dynamo model sustained by dynamic magnetic buoyancy and flux transport processes
• Oscillator models of the solar cycle: Towards the development of inversion methods
• Ensemble Kalman filter data assimilation in a Babcock-Leighton solar dynamo model: an observation system simulation experiment for reconstructing meridional flow-speed
• Estimating the deep solar meridional circulation using magnetic observations and a dynamo model: a variational approach
• Time-dependent theory of solar meridional flows
• Reconstructed Total Solar Irradiance as a precursor for long-term solar activity predictions: a nonlinear dynamics approach