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We show that the r-mode instability can generate strong toroidal fields in the core of accreting millisecond quark stars by inducing differential rotation. We follow the spin frequency evolution on a long time scale taking into account the…

High Energy Astrophysical Phenomena · Physics 2015-05-27 L. Bonanno , C. Cuofano , A. Drago , G. Pagliara , J. Schaffner-Bielich

Observations of dwarf galaxies suggest the presence of large-scale magnetic fields. However the size and slow rotation of these galaxies appear insufficient to support a mean-field dynamo action to excite such fields. Here we suggest a new…

Astrophysics of Galaxies · Physics 2017-02-08 David Moss , Dmitri Sokoloff

Magnetic confinement of stellar winds leads to the formation of magnetospheres, which can be sculpted into Centrifugal Magnetospheres (CMs) by rotational support of the corotating plasma. The conditions required for the CMs of magnetic…

Magnetars have inferred polar field strengths in excess of the Schwinger limit, where non-linear electromagnetic effects can be significant. Their internal fields may be even stronger, suggesting that Maxwellian characterizations of…

High Energy Astrophysical Phenomena · Physics 2025-05-12 Arthur G. Suvorov , José A. Pons

The magnetic fields of spiral galaxies are so strong that they cannot be primordial. Their typical values are over one billion times higher than any value predicted for the early Universe. Explaining this immense growth and incorporating it…

Astrophysics of Galaxies · Physics 2020-09-30 Evangelia Ntormousi , Konstantinos Tassis , Fabio Del Sordo , Francesca Fragkoudi , Rüdiger Pakmor

The gas from which stars form is magnetized, and strong magnetic fields can efficiently transport angular momentum. Most theoretical models of this phenomenon find that it should prevent formation of large (>100 AU), rotationally-supported…

Solar and Stellar Astrophysics · Physics 2015-06-12 Mark R. Krumholz , Richard M. Crutcher , Charles L. H. Hull

The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 Ioannis Contopoulos , Dimitris M. Christodoulou , Demosthenes Kazanas , Denise C. Gabuzda

A significant fraction of isolated white dwarfs host magnetic fields in excess of a MegaGauss. Observations suggest that these fields originate in interacting binary systems where the companion is destroyed thus leaving a singular,…

Solar and Stellar Astrophysics · Physics 2022-03-14 Gabriel Guidarelli , Jason Nordhaus , Jonathan Carroll-Nellenback , Luke Chamandy , Eric G. Blackman , Adam Frank

For Sun-like stars, the generation of toroidal magnetic field from poloidal magnetic field is an essential piece of the dynamo mechanism powering their magnetism. Previous authors have estimated the net toroidal flux generated in each…

Solar and Stellar Astrophysics · Physics 2024-01-23 Adam J. Finley , Sacha A. Brun , Antoine Strugarek , Robert Cameron

In this paper we review the current status of research on the observational and theoretical characteristics of isolated and binary magnetic white dwarfs (MWDs). Magnetic fields of isolated MWDs are observed to lie in the range 10^3-10^9G.…

Solar and Stellar Astrophysics · Physics 2015-06-03 Lilia Ferrario , Domitilla de Martino , Boris Gaensicke

We initiate numerical studies of differentially rotating magnetised (proto) neutron stars by studying - through construction from first principles - the coupling between an assumed differential rotation and an impressed magnetic field. For…

Astrophysics · Physics 2007-05-23 A. V. Thampan

Understanding the origin of the magnetic fields in white dwarfs (WDs) has been a puzzle for decades. A scenario that has gained considerable attention in the past years assumes that such magnetic fields are generated through a dynamo…

Solar and Stellar Astrophysics · Physics 2019-12-25 Diogo Belloni , Matthias R. Schreiber

We investigate whether the recently suggested rotation and crystallization driven dynamo can explain the apparent increase of magnetism in old metal polluted white dwarfs. We find that the effective temperature distribution of polluted…

Solar and Stellar Astrophysics · Physics 2021-07-14 Matthias R. Schreiber , Diogo Belloni , Boris T. Gaensicke , Steven G. Parsons

As another step towards understanding the long-term evolution of the magnetic field in neutron stars, we provide the first simulations of ambipolar diffusion in a spherical star. Restricting ourselves to axial symmetry, we consider a…

High Energy Astrophysical Phenomena · Physics 2017-07-17 F. Castillo , A. Reisenegger , J. A. Valdivia

We present 3D MHD simulations of purely toroidal and mixed poloidal-toroidal magnetic field configurations to study the behavior of the Tayler instability. For the first time the simultaneous action of rotation and magnetic diffusion are…

Solar and Stellar Astrophysics · Physics 2015-05-27 Juan C. Ibañez-Mejia , Jonathan Braithwaite

Weak magnetic fields have recently been detected in a number of A-type stars, including Vega and Sirius. At the same time, space photometry observations of A- and late B-type stars from Kepler and TESS have highlighted the existence of…

Solar and Stellar Astrophysics · Physics 2019-10-02 Matteo Cantiello , Jonathan Braithwaite

Massive, highly magnetized white dwarfs with fields up to $10^9$ G have been observed and theoretically used for the description of a variety of astrophysical phenomena. Ultramagnetized white dwarfs with uniform interior fields up to…

Solar and Stellar Astrophysics · Physics 2014-09-29 J. G. Coelho , R. M. Marinho , M. Malheiro , R. Negreiros , D. L. Cáceres , J. A. Rueda , R. Ruffini

We revise a magnetic buoyancy model that has recently been proposed as a mechanism for extra mixing in the radiative zones of low-mass red giants. The most important revision is our accounting of the heat exchange between rising magnetic…

Astrophysics · Physics 2011-02-11 Pavel A. Denissenkov , Marc Pinsonneault , Keith B. MacGregor

Total magnetic fields in spiral galaxies, as observed through their total synchrotron emission, are strongest (up to \simeq 30\mu G) in the spiral arms. The degree of radio polarization is low; the field in the arms must be mostly turbulent…

Astrophysics · Physics 2009-11-11 Rainer Beck