HYSTERESIS BETWEEN DISTINCT MODES OF TURBULENT DYNAMOS

ABSTRACT Nonlinear mean-field models of the solar dynamo show long-term variability, which may be relevant to different states of activity inferred from long-term radiocarbon data. This paper is aimed at probing the dynamo hysteresis predicted by the recent mean-field models of Kitchatinov & Ole...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2015-04, Vol.803 (2), p.1-7
Main Authors: Karak, Bidya Binay, Kitchatinov, Leonid L., Brandenburg, Axel
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Computer simulation
COMPUTERIZED SIMULATION
dynamo
Field strength
HELICITY
HYSTERESIS
Initial conditions
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
magnetohydrodynamics (MHD)
Mathematical models
MEAN-FIELD THEORY
NONLINEAR PROBLEMS
PRANDTL NUMBER
PROBES
RANDOMNESS
Rotating generators
SHEAR
SOLAR ACTIVITY
SUN
Sun: activity
Sun: magnetic fields
Three dimensional
THREE-DIMENSIONAL CALCULATIONS
TURBULENCE
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:ABSTRACT Nonlinear mean-field models of the solar dynamo show long-term variability, which may be relevant to different states of activity inferred from long-term radiocarbon data. This paper is aimed at probing the dynamo hysteresis predicted by the recent mean-field models of Kitchatinov & Olemskoy with direct numerical simulations. We perform three-dimensional (3D) simulations of large-scale dynamos in a shearing box with helically forced turbulence. As an initial condition, we either take a weak random magnetic field or we start from a snapshot of an earlier simulation. Two quasi-stable states are found to coexist in a certain range of parameters close to the onset of the large-scale dynamo. The simulations converge to one of these states depending on the initial conditions. When either the fractional helicity or the magnetic Prandtl number is increased between successive runs above the critical value for onset of the dynamo, the field strength jumps to a finite value. However, when the fractional helicity or the magnetic Prandtl number is then decreased again, the field strength stays at a similar value (strong field branch) even below the original onset. We also observe intermittent decaying phases away from the strong field branch close to the point where large-scale dynamo action is just possible. The dynamo hysteresis seen previously in mean-field models is thus reproduced by 3D simulations. Its possible relation to distinct modes of solar activity such as grand minima is discussed.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.1088/0004-637X/803/2/95