Non-linear mechanisms that regulate the solar cycle amplitude. (arXiv:2007.07069v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Jiang_J/0/1/0/all/0/1">Jie Jiang</a>
The solar magnetic activity cycle has an amplitude that varies within a wide,
but limited range of values. This implies that there are non-linear mechanisms
that prevent runaway solutions. The purpose of this paper is to propose the
observable non-linear mechanisms in the framework of the
Babcock-Leighton(BL)-type dynamo. Sunspot emergences show systematic properties
that strong cycles tend to have higher mean latitudes and lower tilt angle
coefficients. We use the surface flux transport model to investigate effects of
the systematic properties on the expected final total dipolar moment, i.e.
cancellation plus generation of dipole moment by a whole solar cycle. We
demonstrate that the systematic change in latitude has similar nonlinear
feedback on the solar cycle (latitudinal quenching) as tilt does (tilt
quenching). Both forms of quenching lead to that the expected final total
dipolar moment is enhanced for weak cycles and saturates to a nearly constant
value for normal and strong cycles. This explains observed long-term solar
cycle variability, e.g., the Gnevyshev-Ohl rule, which, in turn, justifies the
non-linear mechanisms inherent in the BL-type dynamo. Our work paves the way
for understanding magnetic cycles of cool stars, especially how the properties
of stellar spots may determine their properties.
The solar magnetic activity cycle has an amplitude that varies within a wide,
but limited range of values. This implies that there are non-linear mechanisms
that prevent runaway solutions. The purpose of this paper is to propose the
observable non-linear mechanisms in the framework of the
Babcock-Leighton(BL)-type dynamo. Sunspot emergences show systematic properties
that strong cycles tend to have higher mean latitudes and lower tilt angle
coefficients. We use the surface flux transport model to investigate effects of
the systematic properties on the expected final total dipolar moment, i.e.
cancellation plus generation of dipole moment by a whole solar cycle. We
demonstrate that the systematic change in latitude has similar nonlinear
feedback on the solar cycle (latitudinal quenching) as tilt does (tilt
quenching). Both forms of quenching lead to that the expected final total
dipolar moment is enhanced for weak cycles and saturates to a nearly constant
value for normal and strong cycles. This explains observed long-term solar
cycle variability, e.g., the Gnevyshev-Ohl rule, which, in turn, justifies the
non-linear mechanisms inherent in the BL-type dynamo. Our work paves the way
for understanding magnetic cycles of cool stars, especially how the properties
of stellar spots may determine their properties.
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