title: Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields.
abstract: We consider the generation of a magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass antidynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, 24 rue Lhomond, 75005 Paris, France.
authors.forename: F
authors.initials: F
authors.lastname: Pétrélis
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, 24 rue Lhomond, 75005 Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Alexakis
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, 24 rue Lhomond, 75005 Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Gissinger