title: Long-term memory in experiments and numerical simulations of hydrodynamic and magnetohydrodynamic turbulence.
abstract: We analyze time series stemming from experiments and direct numerical simulations of hydrodynamic and magnetohydrodynamic turbulence. Simulations are done in periodic boxes, but with a volumetric forcing chosen to mimic the geometry of the flow in the experiments, the von Kármán swirling flow between two counterrotating impellers. Parameters in the simulations are chosen to (within computational limitations) allow comparisons between the experiments and the numerical results. Conducting fluids are considered in all cases. Two different configurations are considered: a case with a weak externally imposed magnetic field and a case with self-sustained magnetic fields. Evidence of long-term memory and 1/f noise is observed in experiments and simulations, in the case with weak magnetic field associated with the hydrodynamic behavior of the shear layer in the von Kármán flow, and in the dynamo case associated with slow magnetohydrodynamic behavior of the large-scale magnetic field.
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
authors.forename: P
authors.initials: P
authors.lastname: Mininni
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
authors.forename: P
authors.initials: P
authors.lastname: Dmitruk
authors.affiliation: Laboratoire de Physique - UMR 5672 Ecole Normale Suprieure de Lyon / CNRS 46 Allée d'Italie, 69007 Lyon, France.
authors.forename: P
authors.initials: P
authors.lastname: Odier
authors.affiliation: Laboratoire de Physique - UMR 5672 Ecole Normale Suprieure de Lyon / CNRS 46 Allée d'Italie, 69007 Lyon, France.
authors.forename: J-F
authors.initials: JF
authors.lastname: Pinton
authors.affiliation: Laboratoire de Physique - UMR 5672 Ecole Normale Suprieure de Lyon / CNRS 46 Allée d'Italie, 69007 Lyon, France.
authors.forename: N
authors.initials: N
authors.lastname: Plihon
authors.affiliation: Aix-Marseille Université, IRPHE - UMR 7342, CNRS, Marseille, France.
authors.forename: G
authors.initials: G
authors.lastname: Verhille
authors.affiliation: Laboratoire de Physique - UMR 5672 Ecole Normale Suprieure de Lyon / CNRS 46 Allée d'Italie, 69007 Lyon, France.
authors.forename: R
authors.initials: R
authors.lastname: Volk
authors.affiliation: Laboratoire des Écoulements Géophysiques et Industriels, UMR5519 CNRS/UJF/Grenoble-INP/Université de Grenoble, BP53, 38041, Grenoble cedex 9, France.
authors.forename: M
authors.initials: M
authors.lastname: Bourgoin