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Measurements of the magnetic field in the stellar coronae are extremely difficult. Recently, it was proposed that the magnetic-field-induced transition (MIT) of the Fe X 257 {\AA} line can be used to measure the coronal magnetic field of…

Solar and Stellar Astrophysics · Physics 2021-09-08 Yajie Chen , Xianyu Liu , Hui Tian , Xianyong Bai , Meng Jin , Wenxian Li , Yang Yang , Zihao Yang , Yuanyong Deng

Solar magnetic fields play a key role in understanding the nature of the coronal phenomena. Global coronal magnetic fields are usually extrapolated from photospheric fields, for which farside data is taken when it was at the frontside,…

Solar and Stellar Astrophysics · Physics 2022-04-28 Hyun-Jin Jeong , Yong-Jae Moon , Eunsu Park , Harim Lee

A plethora of coronal models, from empirical to more complex magnetohydrodynamic (MHD) ones, are being used for reconstructing the coronal magnetic field topology and estimating the open magnetic flux. However, no individual solution fully…

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

In solar physics, it is a big challenge to measure the magnetic fields directly from observations in the upper solar atmosphere, including the chromosphere and corona. Radio observations are regarded as the most feasible approach to…

Solar and Stellar Astrophysics · Physics 2022-06-22 Baolin Tan

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 recent third-order, essentially non-oscillatory central scheme to advance the equations of single-fluid magnetohydrodynamics (MHD) in time has been implemented into a new numerical code. This code operates on a 3-D Cartesian,…

Solar and Stellar Astrophysics · Physics 2012-04-18 Jens Kleimann , Andreas Kopp , Horst Fichtner , Rainer Grauer

This paper describes a new and efficient method of defining an annular region of a curl-free magnetic field with specific physics and coil properties that can be used in stellarator design. Three statements define the importance: (1) Codes…

Plasma Physics · Physics 2020-01-08 Allen H. Boozer

We estimated the accuracy of coronal magnetic fields derived from radio observations by comparing them to potential field calculations and the DEM measurements using EUV observations. We derived line of sight component of the coronal…

Solar and Stellar Astrophysics · Physics 2016-02-17 Shun Miyawaki , Kazumasa Iwai , Kiyoto Shibasaki , Daikou Shiota , Satoshi Nozawa

We derived the coronal magnetic field, plasma density, and temperature from the observation of polarization and intensity of radio thermal free-free emission using the Nobeyama Radioheliograph (NoRH) and extreme ultraviolet (EUV)…

Solar filament are commonly thought to be supported in magnetic dips, in particular, of magnetic flux ropes (FRs). In this Letter, from the observed photospheric vector magnetogram, we implement a nonlinear force-free field (NLFFF)…

Solar and Stellar Astrophysics · Physics 2015-06-19 Chaowei Jiang , S. T. Wu , Xueshang Feng , Qiang Hu

Force-free electrodynamics is the theoretical paradigm used to describe electromagnetic fields in a region where the inertia of plasma is negligible compared to the strength of the electromagnetic field. While these fields are studied…

General Relativity and Quantum Cosmology · Physics 2024-03-18 Rakshak Adhikari , Govind Menon , Mikhail V. Medvedev

[..] 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

The dynamics of magnetic fields in closed regions of solar and stellar coronae are investigated with a reduced magnetohydrodynamic (MHD) model in the framework of Parker scenario for coronal heating. A novel analysis of reduced MHD…

Solar and Stellar Astrophysics · Physics 2015-12-04 A. F. Rappazzo

One proposed resolution to the long-standing problem of solar coronal heating involves the buildup of magnetic energy in the corona due to turbulent motions at the photosphere that braid the coronal field, and the subsequent release of this…

Solar and Stellar Astrophysics · Physics 2015-05-27 D. I. Pontin , G. Hornig

The solar coronal magnetic field produces solar activity, including extremely energetic solar flares and coronal mass ejections (CMEs). Knowledge of the structure and evolution of the magnetic field of the solar corona is important for…

Solar and Stellar Astrophysics · Physics 2015-06-22 Tilaye Tadesse , Thomas Wiegelmann , Peter MacNeice

The minimum-energy configuration for the magnetic field above the solar photosphere is curl-free (hence, by Ampere's law, also current-free), so can be represented as the gradient of a scalar potential. Since magnetic fields are divergence…

Solar and Stellar Astrophysics · Physics 2016-06-20 Brian T. Welsch , George H. Fisher

The three-dimensional (3D) coordinates of stereoscopically triangulated loops provide strong constraints for magnetic field models of active regions in the solar corona. Here we use STEREO/A and B data from some 500 stereoscopically…

Solar and Stellar Astrophysics · Physics 2015-06-05 Markus J. Aschwanden , Jean-Pierre Wuelser , Nariaki V. Nitta , James R. Lemen , Marc L. DeRosa , Anna Malanushenko

We study the link between an expanding coronal shock and the energetic particles measured near Earth during the Ground Level Enhancement (GLE) of 17 May 2012. We developed a new technique based on multipoint imaging to triangulate the 3-D…

Solar eruptive phenomena, like flares and coronal mass ejections(CMEs) are governed by magnetic fields. To describe the structure of these phenomena one needs information on the magnetic flux density and the electric current density vector…

Solar and Stellar Astrophysics · Physics 2015-06-17 Tilaye Tadesse , T. Wiegelmann , Pevtsov A Alexei , P. Macneice , S. Gosain