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The Earth's magnetic field can be decomposed into spherical harmonics, and the exact coefficients of the decomposition can be determined through a few measurements of its value at different locations. Using measurements from a magnetometer…

Geophysics · Physics 2025-08-20 Nuno Barros e Sá , Lourenço Faria , Bernardo Alves , Miguel Cymbron

There is mounting evidence that the ejection of magnetic helicity from the solar surface is important for the solar dynamo. Observations suggest that in the northern hemisphere the magnetic helicity flux is negative. We propose that this…

Astrophysics · Physics 2009-11-07 A. Brandenburg , E. G. Blackman , G. R. Sarson

Numerical experiments of dynamo action designed to understand the generation of Earth's magnetic field produce different regime branches identified within bifurcation diagrams. Notable are distinct branches where the resultant magnetic…

Geophysics · Physics 2025-08-11 Robert J. Teed , Emmanuel Dormy

We consider semi-infinite two-dimensional layered Ising models in the extreme anisotropic limit with an aperiodic modulation of the couplings. Using substitution rules to generate the aperiodic sequences, we derive functional equations for…

Statistical Mechanics · Physics 2009-10-22 L. Turban , F. Igloi , B. Berche

Glorified dimensional analysis is used to derive scaling rules for internal and external magnetic field strengths and various time scales. Naive dimensional analysis is inconclusive because of multiple time scales, but physical arguments…

Solar and Stellar Astrophysics · Physics 2016-03-31 Bertrand Barrois

A novel technique of the measurement data processing is developed which allows to apply the rotating coil method for measurement of a dynamic magnetic field, periodic in time. The developed technique allows to obtain time-dependent…

Accelerator Physics · Physics 2015-06-12 V. Marusov

The solar cycle is a complex phenomenon, a comprehensive understanding of which requires the study of various tracers. Here, we consider the solar cycle as manifested in the harmonics of the solar large-scale surface magnetic field,…

Solar and Stellar Astrophysics · Physics 2024-03-12 V. N. Obridko , A. S. Shibalova , D. D. Sokoloff

We consider possible geometries of magnetic fields in GRB outflows, and their evolution with distance from the source. For magnetically driven outflows, with an assumed ratio of magnetic to kinetic energy density of order unity, the field…

Astrophysics · Physics 2009-10-31 H. C. Spruit , F. Daigne , G. Drenkhahn

The turnover of interstellar gas on $\sim 10^9$yr timescales argues for the continuous operation of a galactic dynamo. The conductivity of interstellar gas is so high that the dynamo must be "fast" - i.e. the magnetic field must be…

Astrophysics · Physics 2008-05-06 Ellen G. Zweibel Fabian Heitsch

Theories of ion-scale microinstabilities in tokamaks and stellarators typically assume that the passing electrons respond adiabatically due to their fast propagation speed. However, when the magnetic shear becomes sufficiently small,…

Plasma Physics · Physics 2026-03-24 Richard Nies , Felix Parra

A simplified model for the stationary, axisymmetric structure of magnetized winds with a polytropic equation of state is presented. The shape of the magnetic surfaces is assumed to be known (conical in this paper) within the fast…

Astrophysics · Physics 2011-05-23 Thibaut Lery , J. Heyvaerts , S. Appl , C. A. Norman

We formulate a coarse-graining approach to the dynamics of magnetohydrodynamic (MHD) fluids at a continuum of length-scales. In this methodology, effective equations are derived for the observable velocity and magnetic fields…

Solar and Stellar Astrophysics · Physics 2017-04-05 Hussein Aluie

We consider the surface critical behaviour of diagonally layered Ising models on the square lattice where the inter-layer couplings follow some aperiodic sequence. The surface magnetisation is analytically evaluated from a simple formula…

Condensed Matter · Physics 2009-10-28 Ferenc Igloi , Peter Lajko

This paper proposes an efficient FDTD technique for determining electromagnetic fields interacting with a finite-sized 2D and 3D periodic structures. The technique combines periodic boundary conditions---modelling fields away from the edges…

Computational Engineering, Finance, and Science · Computer Science 2024-10-30 Aaron J. Kogon , Costas D. Sarris

We present a target field approach to analytically design magnetic fields using permanent magnets. We assume that their magnetisation is bound to a two-dimensional surface and is composed of a complete basis of surface modes. By posing the…

Applied Physics · Physics 2024-05-24 Peter J. Hobson , Chris Morley , Alister Davis , Thomas Smith , Mark Fromhold

The rapid rotation of planets causes cyclonic thermal turbulence in their cores which may generate the large-scale magnetic fields observed outside the planets. We consider the model which enables us reproduce the typical features of…

Fluid Dynamics · Physics 2020-01-29 M. Reshetnyak , P. Hejda

Dynamic compression of iron to Earth-core conditions is one of the few ways to gather important elastic and transport properties needed to uncover key mechanisms surrounding the geodynamo effect. Herein a new machine-learned ab-initio…

Dynamical extra dimensions break the conformal invariance of Maxwell's equations in four dimensions. A higher dimensional background with $n$ contracting extra dimensions and four expanding dimensions is matched to an effectively four…

High Energy Physics - Phenomenology · Physics 2010-04-05 Kerstin E. Kunze

The universe cools down monotonically following its expansion.This generates a sequence of phase transitions. If a second order phase transition happens during the radiation dominated era with a charged order parameter, spinodal…

Astrophysics · Physics 2009-11-10 D. Boyanovsky , H. J. de Vega

We calculate the critical magnetic fields for vortex expulsion for an infinitely long superconducting strip, using the Ginzburg-Landau formalism. Two critical fields can be defined associated with the disappearance of either the energetic…

Superconductivity · Physics 2009-11-13 P. Sanchez-Lotero , J. J. Palacios