Alleviating alpha quenching by solar wind and meridional flow

Abstract

We study the ability of magnetic helicity expulsion to alleviate catastrophic $\alpha$-quenching in mean field dynamos in two--dimensional spherical wedge domains. Motivated by the physical state of the outer regions of the Sun, we consider ${\alpha }^2\Omega$ mean field models with a dynamical $\alpha$ quenching. We include two mechanisms which have the potential to facilitate helicity expulsion, namely advection by a mean flow ("solar wind") and meridional circulation. We find that a wind alone can prevent catastrophic quenching, with the field saturating at finite amplitude. In certain parameter ranges, the presence of a large-scale meridional circulation can reinforce this alleviation. However, the saturated field strengths are typically below the equipartition field strength. We discuss possible mechanisms that might increase the saturated field.

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Cited by in corpus (7)

• On the role of tachoclines in solar and stellar dynamos
• The asymmetry of sunspot cycles and Waldmeier relations as due to nonlinear surface-shear shaped dynamo
• Turbulent dynamo with advective magnetic helicity flux
• Current helicity of active regions as a tracer of large-scale solar magnetic helicity
• The origin of the helicity hemispheric sign rule reversals in the mean-field solar-type dynamo
• The fluctuating α-effect and Waldmeier relations in the nonlinear dynamo models
• The effect of a dynamo-generated field on the Parker wind