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In a force-free magnetic field, there is no interaction of field and the plasma in the surrounding atmosphere i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of many magnetic…

Solar and Stellar Astrophysics · Physics 2015-05-20 Sanjiv Kumar Tiwari

Solar flares are intense bursts of electromagnetic radiation, which occur due to a rapid destabilization and reconnection of the magnetic field. While pre-flare signatures and trends have been investigated from magnetic observations prior…

Solar and Stellar Astrophysics · Physics 2025-06-18 Kara L. Kniezewski , Emily I. Mason , Daniel J. Emmons , Kyle E. Fitch , Seth H. Garland

The solar magnetic field is key to understanding the physical processes in the solar atmosphere. Nonlinear force-free codes have been shown to be useful in extrapolating the coronal field from underlying vector boundary data [see Schrijver…

Astrophysics · Physics 2008-01-21 T. Wiegelmann , J. K. Thalmann , C. J. Schrijver , M. L. DeRosa , T. R. Metcalf

In this paper, the statistical studies on the force-freeness of photosphere magnetic fields are given. The studies are based on the vector magnetic fields observed by Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) on board Hinode.…

Solar and Stellar Astrophysics · Physics 2019-02-04 S. Liu , J. Hao

The magnetic fields in the solar atmosphere structure the plasma, store free magnetic energy and produce a wide variety of active solar phenomena, like flare and coronal mass ejections(CMEs). The distribution and strength of magnetic fields…

Solar and Stellar Astrophysics · Physics 2015-06-12 Tilaye Tadesse , T. Wiegelmann , K. Olson , P. J. MacNeice

[..] The change in the magnetic configuration due to the increase/decrease of electric current for different force-free models (potential, linear and nonlinear force-free fields) has never been studied in detail before. Here we focus…

Solar and Stellar Astrophysics · Physics 2015-05-28 S. Regnier

We extend the foil winding homogenization method to magnetic field conforming formulations. We first propose a full magnetic field foil winding formulation by analogy with magnetic flux density conforming formulations. We then introduce the…

Computational Engineering, Finance, and Science · Computer Science 2026-05-19 Louis Denis , Elias Paakkunainen , Paavo Rasilo , Sebastian Schöps , Benoît Vanderheyden , Christophe Geuzaine

The coronal magnetic field evolution of 20 bipolar active regions (ARs) is simulated from their emergence to decay using the time-dependent nonlinear force-free field method of Mackay et al. A time sequence of cleaned photospheric…

Solar and Stellar Astrophysics · Physics 2021-01-13 Stephanie L. Yardley , Duncan H. Mackay , Lucie M. Green

A new method for reconstruction of coronal magnetic fields as force-free fields (FFFs) is presented. Our method employs poloidal and toroidal functions to describe divergence-free magnetic fields. This magnetic field representation…

Solar and Stellar Astrophysics · Physics 2022-10-04 Sibaek Yi , G. S. Choe , Kyung-Suk Cho , Sami K. Solanki , Jörg Büchner

We investigate in details properties of stationary force-free magnetosphere of aligned rotator assuming the last closed field line lying in equatorial plane at large distances from pulsar. The pulsar equations is solved numerically using…

Astrophysics · Physics 2009-11-11 A. N. Timokhin

Photospheric vector magnetograms from Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory are utilized as the boundary conditions to extrapolate both non-linear force-free and potential magnetic fields in solar corona.…

Solar and Stellar Astrophysics · Physics 2015-06-19 J. T. Su , J. Jing , S. Wang , T. Wiegelmann , H. M. Wang

Magnetic Particle Imaging (MPI) is a promising noninvasive in vivo imaging modality that makes it possible to map the spatial distribution of superparamagnetic nanoparticles by exposing them to dynamic magnetic fields. In the Field-Free…

Numerical Analysis · Mathematics 2025-08-08 Vladyslav Gapyak , Thomas März , Andreas Weinmann

In order to satisfy the symmetry between electric and magnetic fields in the source free Maxwell's equations, electric charges might have magnetic counterparts: magnetic monopoles. Many methods and techniques are proposed to search for the…

Solar and Stellar Astrophysics · Physics 2018-03-06 Jun Zhang , Ting Li

In an experiment on a magnetic dipole interacting with a laser-produced plasma the generation of an intense field aligned current (FAC) system was observed for the first time in a laboratory. The detailed measurements of the total value and…

A solar flare releases magnetic energy by reconnecting field lines across a current sheet, thereby allowing their relaxation to a lower energy state. The maximum possible energy is released if all field lines relax to a current-free…

Solar and Stellar Astrophysics · Physics 2025-11-03 Drake Osaben , Jiong Qiu , Dana W. Longcope

We report an analytical investigation of the force and torque acting upon a magnetic dipole placed in the vicinity of a moving electrically conducting nonmagnetic plate. This problem is relevant to contactless electromagnetic flow…

Fluid Dynamics · Physics 2011-03-14 Evgeny V. Votyakov , Andre Thess

Although it is generally believed that the solar photosphere is not magnetically force-free owning to its high plasma $\beta$, the estimations of force-freeness using observed magnetograms have produced disputable results. Some studies…

Solar and Stellar Astrophysics · Physics 2023-09-28 Mei Zhang , Haocheng Zhang

We explore the photospheric and chromospheric magnetic field in an emerging flux region. An image of the equivalent width of the He I 10830 A red blended component shows the presence of filamentary structures that might be interpreted as…

Solar and Stellar Astrophysics · Physics 2010-01-14 A. Asensio Ramos , J. Trujillo Bueno

In this review, I focus on the structure and evolution of the coronal magnetic fields modelled from observations. The development of instruments measuring the photospheric and chromospheric magnetic fields with a high spatial and time…

Solar and Stellar Astrophysics · Physics 2011-01-18 Stephane Regnier

The evolution of nonpotential characteristics of magnetic fields in AR 5747 is presented using Mees Solar Observatory magnetograms taken on Oct. 20, 1989 to Oct. 22, 1989. The active region showed such violent flaring activities during the…

Astrophysics · Physics 2007-05-23 Y. -J. Moon , H. S. Yun , G. S. Choe , Y. D. Park , D. L. Mickey
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