Effect of flow shear on the onset of dynamos
arXiv:2305.19796 · doi:10.1063/5.0170796
Abstract
Understanding the origin and structure of mean magnetic fields in astrophysical conditions is a major challenge. Shear flows often coexist in such astrophysical conditions and the role of flow shear on dynamo mechanism is only beginning to be investigated. Here, we present a direct numerical simulation (DNS) study of the effect of flow shear on dynamo instability for a variety of base flows with controllable mirror symmetry (i.e, fluid helicity). Our observations suggest that for helical base flow, the effect of shear is to suppress the small scale dynamo (SSD) action, i.e, shear helps the large scale magnetic field to manifest itself by suppressing SSD action. For non-helical base flows, flow shear has the opposite effect of amplifying the small-scale dynamo action. The magnetic energy growth rate () for non-helical base flows are found to follow an algebraic nature of the form, , where a, b > 0 are real constants and S is the shear flow strength and is found to be independent of scale of flow shear. Studies with different shear profiles and shear scale lengths for non-helical base flows have been performed to test the universality of our finding.
References in corpus (36)
- Simulations of small-scale turbulent dynamo
- Generation of magnetic field by dynamo action in a turbulent flow of liquid sodium
- Dynamo theories
- Magnetic diffusivity tensor and dynamo effects in rotating and shearing turbulence
- Electromotive Force and Large-Scale Magnetic Dynamo in a Turbulent Flow with a Mean Shear
- Direct magnetic field detection in the innermost regions of an accretion disc
- Nonlinear theory of a "shear-current" effect and mean-field magnetic dynamos
- Large-scale dynamos in turbulent convection with shear
- Generation of Magnetic Field by Combined Action of Turbulence and Shear
- Large-scale Dynamo Action Driven by Velocity Shear and Rotating Convection
- Numerical Simulations of Kinematic Dynamo Action
- Turbulent dynamos with shear and fractional helicity
- Numerical experiments on dynamo action in sheared and rotating turbulence
- Revisiting the ABC flow dynamo
- The helicity constraint in turbulent dynamos with shear
- Generation of large-scale magnetic fields by small-scale dynamo in shear flows
- On Large-Scale Dynamo Action at High Magnetic Reynolds Number
- The shear dynamo problem for small magnetic Reynolds numbers
- The alpha effect in rotating convection with sinusoidal shear
- Nonperturbative quasilinear approach to the shear dynamo problem
- Large-scale dynamo action due to fluctuations in a linear shear flow
- AccFFT: A library for distributed-memory FFT on CPU and GPU architectures
- Transport coefficients for the shear dynamo problem at small Reynolds numbers
- Epi-two-dimensional fluid flow: a new topological paradigm for dimensionality
- Shear dynamo problem: Quasilinear kinematic theory
- On the Structure of the Magnetic Field in a Kinematic ABC Flow Dynamo
- Coherent nonhelical shear dynamos driven by magnetic fluctuations at low Reynolds numbers
- Enhancement of small-scale turbulent dynamo by large-scale shear
- The Effect of Velocity Shear on Dynamo Action Due to Rotating Convection
- Magnetic field correlations in a random flow with strong steady shear
- Small-Scale Dynamo in Stably Stratified Turbulence
- On large-scale dynamos with stable stratification and the application to stellar radiative zones
- Dynamo efficiency with shear in helical turbulence
- Convection-driven kinematic dynamos with a self-consistent shear flow
- Long time fate of two-dimensional incompressible high Reynolds number Navier-Stokes turbulence: A quantitative comparison between theory and simulation
- Revisiting Kinematic Fast Dynamo in 3-dimensional magnetohydrodynamic plasmas: Dynamo transition from non-Helical to Helical flows