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Presently, many models of the coronal magnetic field rely on photospheric vector magnetograms but these data have been shown to be problematic as the sole boundary information for nonlinear force-free field (NLFFF) extrapolations. Magnetic…

Solar and Stellar Astrophysics · Physics 2021-06-29 A. Malanushenko , C. J. Schrijver , M. L. DeRosa , M. S. Wheatland , S. A. Gilchrist

This paper is the third in a series of papers working towards the construction of a realistic, evolving, non-linear force-free coronal field model for the solar magnetic carpet. Here, we present preliminary results of 3D time-dependent…

Solar and Stellar Astrophysics · Physics 2013-03-07 K. A. Meyer , D. H. Mackay , A. A. van Ballegooijen , C. E. Parnell

Routine measurements of the solar magnetic field are mainly carried out in the photosphere. Therefore, one has to infer the field strength in the higher layers of the solar atmosphere from the measured photospheric field based on the…

Solar and Stellar Astrophysics · Physics 2015-05-20 Tilaye Tadesse , T. Wiegelmann , B. Inhester , A. Pevtsov

With the development of new instrumentation providing measurements of solar photospheric vector magnetic fields, we need to develop our understanding of the effects of current density on coronal magnetic field configurations. The object is…

Astrophysics · Physics 2009-11-13 S. Regnier , E. R. Priest

Potential field extrapolations are widely used as minimum-energy models for the Sun's coronal magnetic field. As the reference to which other magnetic fields are compared, they have -- by any reasonable definition -- no global (signed)…

Solar and Stellar Astrophysics · Physics 2020-08-12 A. R. Yeates

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

In this work we provide an updated description of the Vertical Current Approximation Nonlinear Force-Free Field (VCA-NLFFF) code, which is designed to measure the evolution of the potential, nonpotential, free energies, and the dissipated…

Solar and Stellar Astrophysics · Physics 2016-07-25 Markus J. Aschwanden

In the quiet solar photosphere, the mixed polarity fields form a magnetic carpet, which continuously evolves due to dynamical interaction between the convective motions and magnetic field. This interplay is a viable source to heat the solar…

Solar and Stellar Astrophysics · Physics 2014-09-16 L. P. Chitta , R. Kariyappa , A. A. van Ballegooijen , E. E. DeLuca , S. K. Solanki

A more accurate analytical solution of the {\sl vertical-current approximation nonlinear force-free field (VCA3-NLFFF)} model is presented that includes besides the radial $(B_r)$ and the azimuthal $(B_\varphi)$ magnetic field components a…

Solar and Stellar Astrophysics · Physics 2020-01-08 Markus J. Aschwanden

Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present…

Astrophysics · Physics 2020-01-29 T. Wiegelmann , T. Neukirch

Knowledge regarding the coronal magnetic field is important for the understanding of many phenomena, like flares and coronal mass ejections. Because of the low plasma beta in the solar corona the coronal magnetic field is often assumed to…

Astrophysics · Physics 2008-11-26 Thomas Wiegelmann , Bernd Inhester , Takashi Sakurai

We aim at demonstrating the capabilities of a newly developed method for determining electric currents in the solar photosphere. We employ three-dimensional radiative magneto-hydrodynamic (MHD) simulations to produce synthetic Stokes…

Solar and Stellar Astrophysics · Physics 2021-12-22 A. Pastor Yabar , J. M. Borrero , C. Quintero Noda , B. Ruiz Cobo

Context. Understanding the 3D magnetic field as well as the plasma in the chromosphere and transition region is important. One way is to extrapolate the magnetic field and plasma from the routinely measured vector magnetogram on the…

Solar and Stellar Astrophysics · Physics 2021-01-04 Xiaoshuai Zhu , Thomas Wiegelmann , Bernd Inhester

It is an indisputable fact that solar magnetic fields are force-free in the corona, where force free fields means that current and magnetic fields are parallel and there is no Lorentz force in the fields. While the force-free extent of…

Solar and Stellar Astrophysics · Physics 2015-06-05 S. Liu , J. T. Su , H. Q. Zhang , Y. Y. Deng , Y. Gao , X. Yang , X. J. Mao

Extrapolation codes for modelling the magnetic field in the corona in cartesian geometry do not take the curvature of the Sun's surface into account and can only be applied to relatively small areas, \textit{e.g.}, a single active region.…

Solar and Stellar Astrophysics · Physics 2011-04-13 T. Tadesse , T. Wiegelmann , B. Inhester , A. Pevtsov

Extrapolation codes in Cartesian geometry for modelling the magnetic field in the corona do not take the curvature of the Sun's surface into account and can only be applied to relatively small areas, e.g., a single active region. We compare…

Solar and Stellar Astrophysics · Physics 2015-06-11 Tilaye Tadesse , T. Wiegelmann , B. Inhester , P. MacNeice , A. Pevtsov , X. Sun

We take a broad look at the problem of identifying the magnetic solar causes of space weather. With the lackluster performance of extrapolations based upon magnetic field measurements in the photosphere, we identify a region in the near UV…

Using the method of retarded potentials approximate formulas are obtained that describe the electromagnetic field outside the relativistic uniform system in the form of a charged sphere rotating at a constant speed. For the near, middle and…

Classical Physics · Physics 2021-12-30 Sergey G. Fedosin

Expanding on an earlier work that relied on linear force-free magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free…

Solar and Stellar Astrophysics · Physics 2015-06-11 M. K. Georgoulis , K. Tziotziou , N. -E. Raouafi

Extrapolations of solar photospheric vector magnetograms into three-dimensional magnetic fields in the chromosphere and corona are usually done under the assumption that the fields are force-free. The field calculations can be improved by…

Solar and Stellar Astrophysics · Physics 2015-05-20 M. Fuhrmann , N. Seehafer , G. Valori , T. Wiegelmann