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The characteristic electron densities, temperatures, and thermal distributions of 1MK active region loops are now fairly well established, but their coronal magnetic field strengths remain undetermined. Here we present measurements from a…

Solar and Stellar Astrophysics · Physics 2021-07-14 David H. Brooks , Harry P. Warren , Enrico Landi

We present a new method for direct measurement of magnetic fields on ultracool stars and brown dwarfs. It takes advantage of the Wing-Ford band of FeH, which are seen throughout the M and L spectral types. These molecular features are not…

Astrophysics · Physics 2009-11-11 Ansgar Reiners , Gibor Basri

Accurate estimates of the horizontal electric field on the Sun's visible surface are important not only for estimating the Poynting flux of magnetic energy into the corona but also for driving time-dependent magnetohydrodynamic models of…

Solar and Stellar Astrophysics · Physics 2017-02-22 A. R. Yeates

Here we present a systematic study of force-free field equation for simple axisymmetric configurations in spherical geometry. The condition of separability of solutions in radial and angular variables leads to two classes of solutions:…

Solar and Stellar Astrophysics · Physics 2014-04-03 A. Prasad , A. Mangalam

A new model has been proposed for magnetic field determination at different distances from the Sun during different solar cycle phases. The model depends on the observed large-scale non-polar photospheric magnetic fields and that measured…

Solar and Stellar Astrophysics · Physics 2018-08-08 Irina A. Bilenko

We looked at the orbital motions of test particles according to the External Field Effect (EFE) predicted by the MOdified Newtonian Dynamics (MOND) in the Oort cloud which falls in the deep MONDian regime (r\approx 50-150 kAU). Concerning…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Lorenzo Iorio

We describe a new scheme for evolving the equations of force-free electrodynamics, the vanishing-inertia limit of magnetohydrodynamics. This pseudospectral code uses global orthogonal basis function expansions to take accurate spatial…

High Energy Astrophysical Phenomena · Physics 2015-06-03 Kyle Parfrey , Andrei M. Beloborodov , Lam Hui

In this paper a new technique for modeling non-linear force-free fields directly from line of sight magnetogram observations is presented. The technique uses sequences of magnetograms directly as lower boundary conditions to drive the…

Solar and Stellar Astrophysics · Physics 2011-02-28 Duncan H. Mackay , L. M. Green , Aad van Ballegooijen

The force-free limit of magnetohydrodynamics (MHD) is often a reasonable approximation to model black hole and neutron star magnetospheres. We describe a general relativistic force-free (GRFFE) formulation that allows general relativistic…

Astrophysics · Physics 2009-11-11 Jonathan C. McKinney

We examine the nonlinear magnetofrictional extrapolation scheme using the solar active region model by Titov and D\'emoulin as test field. This model consists of an arched, line-tied current channel held in force-free equilibrium by the…

Solar and Stellar Astrophysics · Physics 2015-05-18 G. Valori , B. Kliem , T. Török , V. S. Titov

We describe the numerical algorithms of a global magnetohydrodynamic (MHD) code utilizing the Yin-Yang grid, called the Yin-Yang Magnetic Flux Eruption (Yin-Yang-MFE) code, suitable for modeling the large-scale dynamical processes of the…

Solar and Stellar Astrophysics · Physics 2025-09-23 Hongyang Luo , Yuhong Fan

The open solar flux, that is, the total magnetic flux escaping the Sun, is one of the most important parameters connecting solar activity to the Earth. The open solar flux is commonly estimated from photospheric magnetic field measurements…

Solar and Stellar Astrophysics · Physics 2024-08-23 Ismo Tähtinen , Timo Asikainen , Kalevi Mursula

The photospheric response to solar flares, also known as coronal back reaction, is often observed as sudden flare-induced changes in vector magnetic field and sunspot motions. However, it remains obscure whether evolving flare ribbons, the…

Solar and Stellar Astrophysics · Physics 2018-12-19 Chang Liu , Wenda Cao , Jongchul Chae , Kwangsu Ahn , Debi Prasad Choudhary , Jeongwoo Lee , Rui Liu , Na Deng , Jiasheng Wang , Haimin Wang

By measuring the geometrical properties of the coronal mass ejection (CME) flux rope and the leading shock observed on 2010 June 13 by the Solar Dynamics Observatory (SDO) mission's Atmospheric Imaging Assembly (AIA) we determine the…

Solar and Stellar Astrophysics · Physics 2015-05-30 Nat Gopalswamy , Nariaki Nitta , Sachiko Akiyama , Pertti Mäkelä , Seiji Yashiro

The solar coronal magnetic field is a pivotal element in the study of eruptive phenomena, and understanding its dynamic evolution has long been a focal point in solar physics. Numerical models, driven directly by observation data, serve as…

Solar and Stellar Astrophysics · Physics 2024-10-15 Zhi-Peng Liu , Chao-Wei Jiang , Xin-Kai Bian , Qing-Jun Liu , Peng Zou , Xue-Shang Feng

In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure…

Solar and Stellar Astrophysics · Physics 2022-11-30 Michaela Brchnelova , Błażej Kuźma , Barbara Perri , Andrea Lani , Stefaan Poedts

Our aim is to model the 3D magnetic field structure of the upper solar atmosphere, including regions of non-negligible plasma beta. We use high-resolution photospheric magnetic field measurements from SUNRISE/IMaX as boundary condition for…

Solar and Stellar Astrophysics · Physics 2015-12-09 T. Wiegelmann , T. Neukirch , D. H. Nickeler , S. K. Solanki , V. Martinez Pillet , J. M. Borrero

The coronal magnetic field plays a fundamental role in governing coronal activities, driving space-weather events, and shaping the heliosphere. Due to a lack of direct observations, extrapolation models such as the Potential Field Source…

Solar and Stellar Astrophysics · Physics 2026-04-02 Ziqi Wu , Jiansen He , Chuanpeng Hou , Tom van Doorsselaere , Rui Zhuo , Tianhang Chen , Liping Yang , David Pontin , Daniel Verscharen , Fang Shen

Using solar wind observation near PSP perihelions as constraints, we have investigated the parameters in various PFSS model methods. It's found that the interplanetary magnetic field extrapolation with source surface height $R_\mathrm{SS} =…

Solar and Stellar Astrophysics · Physics 2023-05-23 Yuechun Song