Evidence from numerical simulations suggest that the nature of dynamo transition changes from sup... more Evidence from numerical simulations suggest that the nature of dynamo transition changes from supercritical to subcritical as the magnetic Prandtl number is decreased. To explore this interesting crossover we first use direct numerical simulations to investigate the hysteresis zone of a subcritical Taylor-Green dynamo. We establish that a well defined boundary exists in this hysteresis region which separates dynamo states from the purely hydrodynamic solution. We then propose simple dynamo models which show similar crossover from supercritical to subcritical dynamo transition as a function of the magnetic Prandtl number. Our models show that the change in the nature of dynamo transition is connected to the stabilizing or destabilizing influence of governing non-linearities.
Using direct numerical simulations we study dynamo action under the Taylor-Green forcing with Pra... more Using direct numerical simulations we study dynamo action under the Taylor-Green forcing with Prandtl number less than one. We observe bistability with a weak magnetic field branch and a strong magnetic field branch. Both the dynamo branches undergo subcritical dynamo transition. We also observe host of dynamo states including constant, periodic, quasiperiodic, and chaotic magnetic fields. One of the chaotic state originates through a quasiperiodic route with phase locking, while another chaotic attractor appears to follow Newhouse-Ruelle-Takens route to chaos. We also observe intermittent transitions among quasiperiodic and chaotic states for a given Taylor-Green forcing.
Evidence from numerical simulations suggest that the nature of dynamo transition changes from sup... more Evidence from numerical simulations suggest that the nature of dynamo transition changes from supercritical to subcritical as the magnetic Prandtl number is decreased. To explore this interesting crossover we first use direct numerical simulations to investigate the hysteresis zone of a subcritical Taylor-Green dynamo. We establish that a well defined boundary exists in this hysteresis region which separates dynamo states from the purely hydrodynamic solution. We then propose simple dynamo models which show similar crossover from supercritical to subcritical dynamo transition as a function of the magnetic Prandtl number. Our models show that the change in the nature of dynamo transition is connected to the stabilizing or destabilizing influence of governing non-linearities.
Using direct numerical simulations we study dynamo action under the Taylor-Green forcing with Pra... more Using direct numerical simulations we study dynamo action under the Taylor-Green forcing with Prandtl number less than one. We observe bistability with a weak magnetic field branch and a strong magnetic field branch. Both the dynamo branches undergo subcritical dynamo transition. We also observe host of dynamo states including constant, periodic, quasiperiodic, and chaotic magnetic fields. One of the chaotic state originates through a quasiperiodic route with phase locking, while another chaotic attractor appears to follow Newhouse-Ruelle-Takens route to chaos. We also observe intermittent transitions among quasiperiodic and chaotic states for a given Taylor-Green forcing.
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Papers by Rakesh Yadav