Blowout bifurcations and the onset of magnetic activity in turbulent dynamos

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

Volumn 63, Issue 6, 2001, Pages

  Sweet, David ^a   Ott, Edward ^a   Finn, John M ^b   Antonsen, Thomas M ^a   Lathrop, Daniel P ^a  

^a Bldg 142   (United States)

^b LOS ALAMOS NATIONAL LABORATORY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BOUNDARY CONDITIONS; DC GENERATORS; MAGNETIC FIELDS; REYNOLDS NUMBER; TURBULENT FLOW;

BLOWOUT BIFURCATION; MAGNETIC FIELD SELF GENERATION; TURBULENT DYNAMOS;

MAGNETOHYDRODYNAMICS;

EID: 0035363417     PISSN: 1063651X     EISSN: None     Source Type: Journal    
DOI: 10.1103/PhysRevE.63.066211     Document Type: Article

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35. The expectation of similar behavior in the simulations and the much higher R experiments is also supported by the following argument. At onset, (Formula presented) the tendency to self-generate magnetic field is balanced by magnetic diffusion [the term (Formula presented) in Eq. (2)]. Shorter spatial magnetic-field scales are more rapidly damped by diffusion. Consequently, we expect that, at onset, the magnetic field varies predominantly at large spatial scales L. Thus low-pass spatial filtering of (Formula presented) for wave numbers (Formula presented) (Formula presented), leaves (Formula presented) approximately unchanged. Applying such a filter to Eq. (2) approximately reproduces Eq. (2) with (Formula presented) replaced by its filtered version (Formula presented). High fluid Reynolds number R is characterized by the creation, via turbulent cascade, of high wave-number components of (Formula presented) that are not present at lower R. The point is that high R dynamo action is essentially driven by the spatial low-pass filtered flow component (Formula presented) whose spatial variation is similar to that of flows with much lower R. Consequently, we expect our simulations to exhibit magnetic-field behavior similar to that of experiments at much higher R.
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