11 research outputs found
Oscillator models of the solar cycle: Towards the development of inversion methods
This article reviews some of the leading results obtained in solar dynamo
physics by using temporal oscillator models as a tool to interpret
observational data and dynamo model predictions. We discuss how solar
observational data such as the sunspot number is used to infer the leading
quantities responsible for the solar variability during the last few centuries.
Moreover, we discuss the advantages and difficulties of using inversion methods
(or backward methods) over forward methods to interpret the solar dynamo data.
We argue that this approach could help us to have a better insight about the
leading physical processes responsible for solar dynamo, in a similar manner as
helioseismology has helped to achieve a better insight on the thermodynamic
structure and flow dynamics in the Sun's interior.Comment: 28 pages; 16 figures, ISSI Workshop 11-15 November 2013 - The Solar
Cycle, http://www.issibern.ch/program/workshops.htm
On the compatibility of a flux transport dynamo with a fast tachocline scenario
The compatibility of the fast tachocline scenario with a flux transport
dynamo model is explored. We employ a flux transport dynamo model coupled with
simple feedback formulae relating the thickness of the tachocline to the
amplitude of the magnetic field or to the Maxwell stress. The dynamo model is
found to be robust against the nonlinearity introduced by this simplified fast
tachocline mechanism. Solar-like butterfly diagrams are found to persist and,
even without any parameter fitting, the overall thickness of the tachocline is
well within the range admitted by helioseismic constraints. In the most
realistic case of a time and latitude dependent tachocline thickness linked to
the value of the Maxwell stress, both the thickness and its latitude dependence
are in excellent agreement with seismic results. In the nonparametric models,
cycle related temporal variations in tachocline thickness are somewhat larger
than admitted by helioseismic constraints; we find, however, that introducing a
further parameter into our feedback formula readily allows further fine tuning
of the thickness variations.Comment: Accepted in Solar Physic
Surface Flux Transport on the Sun
We review the surface flux transport model for the evolution of magnetic flux
patterns on the Sun's surface. Our underlying motivation is to understand the
model's prediction of the polar field (or axial dipole) strength at the end of
the solar cycle. The main focus is on the "classical" model: namely, steady
axisymmetric profiles for differential rotation and meridional flow, and
uniform supergranular diffusion. Nevertheless, the review concentrates on
recent advances, notably in understanding the roles of transport parameters and
- in particular - the source term. We also discuss the physical justification
for the surface flux transport model, along with efforts to incorporate radial
diffusion, and conclude by summarizing the main directions where researchers
have moved beyond the classical model.Comment: 35 pages, 11 figures, accepted for publication in Space Science
Review