Jeudi 16 mai 2013
Mean-field electrodynamics was conceived as a model of dynamo action on large
scales due to small scale velocity fields. The model equations for the mean field,
which can give growing solutions in axisymmetric geometries (thus circumventing
Cowling’s Theorem), have led to a very large number of analytical and numerical
studies, and have produced plausible descriptions of the solar magnetic cycle. The
underlying theory is undoubtedly correct in some parameter ranges but problems
arise when there is the possibility of dynamo action on the smallest scales. In addition
there are difficulties in extending the models into the nonlinear regime, where
Lorentz forces affect the flow. I will review the history of the model, investigate its
theoretical underpinning and will discuss the implications of recent work.
RECRUTEMENT ACCES DIRECT
Le département de physique
Fête de la Science 2018 