Projects per year
Abstract
Nonlinear Hallmagnetohydrodynamic dynamos associated with coherent structures in subcritical shear flows are investigated by using unstable invariant solutions. The dynamo solution found has a relatively simple structure, but it captures the features of the typical nonlinear structures seen in simulations, such as current sheets. As is well known, the Hall effect destroys the symmetry of the magnetohydrodynamic equations and thus modifies the structure of the current sheet and mean field of the solution. Depending on the strength of the Hall effect, the generation of the magnetic field changes in a complex manner. However, a too strong Hall effect always acts to suppress the magnetic field generation. The hydrodynamic/magnetic Reynolds number dependence of the critical ion skin depth at which the dynamos start to feel the Hall effect is of interest from an astrophysical point of view. An important consequence of the matched asymptotic expansion analysis of the solution is that the higher the Reynolds number, the smaller the Hall current affects the flow. We also briefly discuss how the above results for a relatively simple shear flow can be extended to more general flows such as infinite homogeneous shear flows and boundary layer flows. The analysis of the latter flows suggests that interestingly a strong induction of the generated magnetic field might occur when there is a background shear layer.
Original language  English 

Article number  A46 
Number of pages  29 
Journal  Journal of Fluid Mechanics 
Volume  932 
DOIs  
Publication status  Published  10 Feb 2022 
Keywords
 bifurcation
 dynamo theory
 nonlinear instability
Projects
 1 Finished

Towards a mathematical description of magnetohydrodynamic turbulence
Australian Research Council (ARC)
1/04/17 → 31/03/21
Project: Research