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Title: A SHELL MODEL TURBULENT DYNAMO

Abstract

Turbulent dynamo phenomena, observed almost everywhere in astrophysical objects and also in the laboratory in the recent VKS2 experiment, are investigated using a shell model technique to describe magnetohydrodynamic turbulence. Detailed numerical simulations at very high Rossby numbers ({alpha}{sup 2} dynamo) show that as the magnetic Reynolds number increases, the dynamo action starts working and different regimes are observed. The model, which displays different large-scale coherent behaviors corresponding to different regimes, is able to reproduce the magnetic field reversals observed both in a geomagnetic dynamo and in the VKS2 experiment. While rough quantitative estimates of typical times associated with the reversal phenomenon are consistent with paleomagnetic data, the analysis of the transition from oscillating intermittent through reversal and finally to stationary behavior shows that the nature of the reversals we observe is typical of {alpha}{sup 2} dynamos and completely different from VKS2 reversals. Finally, the model shows that coherent behaviors can also be naturally generated inside the many-mode dynamical chaotic model, which reproduces the complexity of fluid turbulence, as described by the shell technique.

Authors:
; ;  [1]
  1. Universita della Calabria, Dipartimento di Fisica and Centro Nazionale Interuniversitario Struttura della Materia, Unita di Cosenza, I-87030 Arcavacata di Rende (Italy)
Publication Date:
OSTI Identifier:
21578429
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 735; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/735/2/73; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPUTERIZED SIMULATION; MAGNETIC FIELD REVERSAL; MAGNETIC REYNOLDS NUMBER; MAGNETOHYDRODYNAMICS; SHELL MODELS; TURBULENCE; DIMENSIONLESS NUMBERS; FLUID MECHANICS; HYDRODYNAMICS; MAGNETIC FIELD CONFIGURATIONS; MATHEMATICAL MODELS; MECHANICS; NUCLEAR MODELS; REYNOLDS NUMBER; SIMULATION

Citation Formats

Perrone, D., Nigro, G., and Veltri, P. A SHELL MODEL TURBULENT DYNAMO. United States: N. p., 2011. Web. doi:10.1088/0004-637X/735/2/73.
Perrone, D., Nigro, G., & Veltri, P. A SHELL MODEL TURBULENT DYNAMO. United States. doi:10.1088/0004-637X/735/2/73.
Perrone, D., Nigro, G., and Veltri, P. Sun . "A SHELL MODEL TURBULENT DYNAMO". United States. doi:10.1088/0004-637X/735/2/73.
@article{osti_21578429,
title = {A SHELL MODEL TURBULENT DYNAMO},
author = {Perrone, D. and Nigro, G. and Veltri, P.},
abstractNote = {Turbulent dynamo phenomena, observed almost everywhere in astrophysical objects and also in the laboratory in the recent VKS2 experiment, are investigated using a shell model technique to describe magnetohydrodynamic turbulence. Detailed numerical simulations at very high Rossby numbers ({alpha}{sup 2} dynamo) show that as the magnetic Reynolds number increases, the dynamo action starts working and different regimes are observed. The model, which displays different large-scale coherent behaviors corresponding to different regimes, is able to reproduce the magnetic field reversals observed both in a geomagnetic dynamo and in the VKS2 experiment. While rough quantitative estimates of typical times associated with the reversal phenomenon are consistent with paleomagnetic data, the analysis of the transition from oscillating intermittent through reversal and finally to stationary behavior shows that the nature of the reversals we observe is typical of {alpha}{sup 2} dynamos and completely different from VKS2 reversals. Finally, the model shows that coherent behaviors can also be naturally generated inside the many-mode dynamical chaotic model, which reproduces the complexity of fluid turbulence, as described by the shell technique.},
doi = {10.1088/0004-637X/735/2/73},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 735,
place = {United States},
year = {2011},
month = {7}
}