A Babcock-Leighton solar dynamo model with multi-cellular meridional circulation in advection- and diffusion-dominated regimes
A Babcock-Leighton solar dynamo model with multi-cellular meridional circulation in advection- and diffusion-dominated regimes
Abstract:
Babcock-Leighton type solar dynamo models with single cell
meridional circulation are successful in reproducing many solar
cycle features, and recently such a model was applied for solar
cycle 24 amplitude prediction. It seems that cycle 24 amplitude
forecast may not be validated. One of the reasons is the assumption
of a single cell meridional circulation. Recent observations and
theoretical models of meridional circulation do not indicate a single-celled
flow pattern. So it is nessecary to examine the role of complex
multi-cellular circulation patterns in a Babcock-Leighton solar
dynamo model in the advection and diffusion dominated regimes.
By simulating a Babcock-Leighton solar dynamo model with multi-cellular
flow, we show that the presence of a weak, second, high-latitude
reverse cell speeds up the cycle and slighty enhances the poleward branch
in the butterfly diagram, whereas the presence of a second cell
in depth reverses the tilt of the butterfly wing and leads to an
anti-solar type feature. If, instead, the butterfly diagram is
constructed from the middle of the convection zone in that case,
a solar-like pattern can be retrieved. All the above cases behave
qualitatively similar in advection and diffusion-dominated regimes.
However, our dynamo with a meridional circulation containing four
cells in latitude behaves distinctly different in the two regimes,
producing a solar-like butterfly diagram with fast cycles in
diffusion-dominated regime, and a complex branches in the butterfly
diagram in the advection-dominated regime. Another interesting
finding from our studies is that a four-celled flow pattern
containing two in radius and two in latitude always produces
quadrupolar parity as the relaxed solution.
meridional circulation are successful in reproducing many solar
cycle features, and recently such a model was applied for solar
cycle 24 amplitude prediction. It seems that cycle 24 amplitude
forecast may not be validated. One of the reasons is the assumption
of a single cell meridional circulation. Recent observations and
theoretical models of meridional circulation do not indicate a single-celled
flow pattern. So it is nessecary to examine the role of complex
multi-cellular circulation patterns in a Babcock-Leighton solar
dynamo model in the advection and diffusion dominated regimes.
By simulating a Babcock-Leighton solar dynamo model with multi-cellular
flow, we show that the presence of a weak, second, high-latitude
reverse cell speeds up the cycle and slighty enhances the poleward branch
in the butterfly diagram, whereas the presence of a second cell
in depth reverses the tilt of the butterfly wing and leads to an
anti-solar type feature. If, instead, the butterfly diagram is
constructed from the middle of the convection zone in that case,
a solar-like pattern can be retrieved. All the above cases behave
qualitatively similar in advection and diffusion-dominated regimes.
However, our dynamo with a meridional circulation containing four
cells in latitude behaves distinctly different in the two regimes,
producing a solar-like butterfly diagram with fast cycles in
diffusion-dominated regime, and a complex branches in the butterfly
diagram in the advection-dominated regime. Another interesting
finding from our studies is that a four-celled flow pattern
containing two in radius and two in latitude always produces
quadrupolar parity as the relaxed solution.