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In this paper, we present a systematic study of the force-free field equation for simple axisymmetric configurations in spherical geometry and apply it to the solar active regions. The condition of separability of solutions in the radial…

Solar and Stellar Astrophysics · Physics 2014-05-07 A. Prasad , A. Mangalam , B. Ravindra

We derive an analytical approximation of nonlinear force-free magnetic field solutions (NLFFF) that can efficiently be used for fast forward-fitting to solar magnetic data, constrained either by observed line-of-sight magnetograms and…

Solar and Stellar Astrophysics · Physics 2014-03-27 Markus J. Aschwanden

Electromagnetic fields which solve the vacuum Maxwell equations in one spacetime are well-known to also be solutions in all spacetimes with conformally-related metrics. This provides a sense in which electromagnetism alone cannot be used to…

General Relativity and Quantum Cosmology · Physics 2017-04-13 Abraham I. Harte

Rotating magnetic structures are common in astrophysics, from vortex tubes and tornados in the Sun all the way to jets in different astrophysical systems. The physics of these objects often combine inertial, magnetic, gas pressure and…

Solar and Stellar Astrophysics · Physics 2018-08-29 Manuel Luna , Eric Priest , Fernando Moreno-Insertis

We study non-resonant circles for strong magnetic fields on a closed, connected, oriented surface and show how these can be used to prove the existence of trapping regions and of periodic magnetic geodesics with prescribed low speed. As a…

Dynamical Systems · Mathematics 2021-04-15 L. Asselle , G. Benedetti

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on…

Solar and Stellar Astrophysics · Physics 2015-05-20 Ioannis Contopoulos , Constantinos Kalapotharakos , Manolis Georgoulis

We show that a large class of null electromagnetic fields are immune to any modifications of Maxwell's equations in the form of arbitrary powers and derivatives of the field strength. These are thus exact solutions to virtually any…

High Energy Physics - Theory · Physics 2018-03-09 Marcello Ortaggio , Vojtěch Pravda

Dipole fields are common in electromagnetism and may be viewed as the result of a positive and negative charge (or pole) which are close together. A dipole field in gravity is not expected to exist because negative mass has never been…

General Relativity and Quantum Cosmology · Physics 2020-06-02 Richard T Hammond

Covariant Lagrangian formulation for free bosonic massless fields of arbitrary mixed-symmetry type in (A)dS(d) space-time is presented. The analysis is based on the frame-like formulation of higher-spin field dynamics [1] with higher-spin…

High Energy Physics - Theory · Physics 2009-11-11 K. B. Alkalaev , O. V. Shaynkman , M. A. Vasiliev

The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the…

Solar and Stellar Astrophysics · Physics 2021-03-24 Thomas Wiegelmann , Takashi Sakurai

The coronal magnetic field is an important quantity because the magnetic field dominates the structure of the solar corona. Unfortunately direct measurements of coronal magnetic fields are usually not available. The photospheric magnetic…

Astrophysics · Physics 2009-06-25 T. Wiegelmann

It is shown that conformal symmetry exists in force-free electrodynamics (FFE) in Minkowski spacetime, a foundational framework for describing magnetospheres around astronomical objects. In force-free magnetospheres, charges are constrained…

General Relativity and Quantum Cosmology · Physics 2026-03-27 Huiquan Li , Jianyong Wang

Dupin cyclides are interesting algebraic surfaces used in geometric design and architecture to join canal surfaces smoothly and to construct model surfaces. Dupin cyclides are special cases of Darboux cyclides, which in turn are rather…

Algebraic Geometry · Mathematics 2025-03-27 Jean Michel Menjanahary , Raimundas Vidunas

In this paper, we establish an equivalence between force-free fields and conformally geodesic fields, and between harmonic fields and conformally eikonal fields in the context of conformal geometry. In contrast to previous work, our…

Differential Geometry · Mathematics 2025-08-05 Albert Chern , Oliver Gross

A recent research presented a solution for a Schwarzschild black hole with a force-free magnetic field showing how the canonical form of background metric changes, Found. Phys. 52 (2022) 4, 93. Therefore, it is logical that this research…

General Relativity and Quantum Cosmology · Physics 2023-11-01 Haidar Sheikhahmadi

Force-Free Electrodynamics (FFE) is known to describe the highly magnetized plasma around pulsars and astrophysical black holes. The equations describing FFE are highly non-linear and the task of finding a well-defined analytical solution…

General Relativity and Quantum Cosmology · Physics 2023-12-14 Rakshak Adhikari , Govind Menon , Mikhail V. Medvedev

The static electrogravitational equations are studied and it is shown that an aligned type D metric which has a Weyl-type relationship between the gravitational and electric potential has shearfree geodesic lines of force. All such fields…

General Relativity and Quantum Cosmology · Physics 2015-06-25 Brendan S. Guilfoyle

A scalar field method to obtain transverse solutions of the vector Laplace and Helmholtz equations in spherical coordinates for boundary-value problems with azimuthal symmetry is described. Neither scalar nor vector potentials are used.…

Classical Physics · Physics 2007-05-23 Ernesto A. Matute

We compare magnetic field extrapolations from a photospheric magnetogram with the observationally inferred structure of magnetic loops in a newly developed active region. This is the first time that the reconstructed 3D-topology of the…

Astrophysics · Physics 2009-06-25 T. Wiegelmann , A. Lagg , S. K. Solanki , B. Inhester , J. Woch

In this work, expanded solutions of force-free magnetospheres on general Kerr black holes are derived through a radial distance expansion method. From the regular conditions both at the horizon and at spatial infinity, two previously known…

High Energy Astrophysical Phenomena · Physics 2017-08-02 Huiquan Li , Jiancheng Wang