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Alfv\'en-wave-driven 3D magnetohydrodynamic (MHD) models, which are increasingly used to predict stellar wind properties, contain unconstrained parameters and rely on low-resolution stellar magnetograms. We explore the effects of the input…

Solar and Stellar Astrophysics · Physics 2020-04-08 S. Boro Saikia , M. Jin , C. P. Johnstone , T. Lüftinger , M. Güdel , V. S. Airapetian , K. G. Kislyakova , C. P. Folsom

We describe the energy budget of a coronal mass ejection (CME) observed on 1999 May 17 with the Ultraviolet Coronagraph Spectrometer (UVCS). We constrain the physical properties of the CME's core material as a function of height along the…

The efficacy of fast/slow MHD mode conversion in the surface layers of sunspots has been demonstrated over recent years using a number of modelling techniques, including ray theory, perturbation theory, differential eigensystem analysis,…

Astrophysics · Physics 2009-11-13 P. S. Cally , M. Goossens

There is observational evidence of the presence of small-amplitude transverse magnetohydrodynamic (MHD) waves with a wide range of frequencies in the threads of solar prominences. It is believed that the waves are driven at the photosphere…

Solar and Stellar Astrophysics · Physics 2021-06-09 Llorenc Melis , Roberto Soler , Jose Luis Ballester

Global coronal waves (CWs) and their interaction with coronal holes (CHs) result, among other effects, in the formation of reflected and transmitted waves. Observations of such events provide us with measurements of different CW parameters,…

Solar and Stellar Astrophysics · Physics 2020-09-02 I. Piantschitsch , J. Terradas , M. Temmer

Magnetohydrodynamic (MHD) waves and/or the braiding of magnetic field lines are largely thought to be responsible for heating the solar corona, both being mechanisms which are driven by the Sun's photospheric magnetic field. Recent…

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

Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO…

Solar and Stellar Astrophysics · Physics 2015-06-22 G. Q. Zhao , D. J. Wu , C. B. Wang

The solar wind emanates from the hot and tenuous solar corona. Earlier studies using 1.5 dimensional simulations show that Alfv\'{e}n waves generated in the photosphere play an important role in coronal heating through the process of…

Solar and Stellar Astrophysics · Physics 2015-05-30 Takuma Matsumoto , Takeru Ken Suzuki

To simulate the energy balance of coronal plasmas on macroscopic scales, we often require the specification of the coronal heating mechanism in some functional form. To go beyond empirical formulations and to build a more physically…

Solar and Stellar Astrophysics · Physics 2016-12-14 Cooper Downs , Roberto Lionello , Zoran Mikić , Jon A. Linker , Marco Velli

The aim of this work is to investigate and characterise non-thermal particle behaviour in a three-dimensional (3D) magnetohydrodynamical (MHD) model of unstable multi-threaded flaring coronal loops. We have used a numerical scheme which…

Solar and Stellar Astrophysics · Physics 2018-03-21 J. Threlfall , A. W. Hood , P. K. Browning

The magnetic processes associated with the non-thermal broadening of optically thin emission lines appear to carry enough energy to heat the corona and accelerate the solar wind. We investigate whether non-thermal motions in cool stars…

Solar and Stellar Astrophysics · Physics 2023-06-28 S. Boro Saikia , T. Lueftinger , V. S. Airapetian , T. Ayres , M. Bartel , M. Guedel , M. Jin , K. G. Kislyakova , P. Testa

Context. High energy electrons accelerated during solar flare are abundant in the solar corona and in the interplanetary space. Commonly, the number and the energy of non-thermal electrons at the Sun is estimated using hard X-ray (HXR)…

Solar and Stellar Astrophysics · Physics 2015-06-03 E. P. Kontar , H. Ratcliffe , N. H. Bian

Coronal loops, constituting the basic building blocks of the active Sun, serve as primary targets to help understand the mechanisms responsible for maintaining multi-million Kelvin temperatures in the solar and stellar coronae. Despite…

Solar and Stellar Astrophysics · Physics 2017-01-11 S. Krishna Prasad , D. B. Jess , J. A. Klimchuk , D. Banerjee

Context. Coronal heating is currently thought to proceed via the mechanism of nanoflares, small-scale and possibly recurring heating events that release magnetic energy. Aims. We investigate the effects of a periodic high-energy electron…

Solar and Stellar Astrophysics · Physics 2016-04-27 Elena Dzifcakova , Jaroslav Dudik , Simon Mackovjak

Four different approximate approaches used to model the stressing of coronal magnetic fields due to an imposed photospheric motion are compared with each other and the results from a full time-dependent magnetohydrodynamic (MHD) code. The…

Solar and Stellar Astrophysics · Physics 2018-02-28 E. E. Goldstraw , A. W. Hood , P. K. Browning , P. J. Cargill

We study the modes and stability of non - isothermal coronal loop models with different intensity values of the equilibrium magnetic field. We use an energy principle obtained via non - equilibrium thermodynamic arguments. The principle is…

Astrophysics · Physics 2008-11-26 Andrea Costa , Rafael Gonzalez

Super-Alfv\'enic shock waves associated with coronal mass ejections (CMEs) can produce radio emission known as Type II bursts. In the absence of direct imaging, accurate estimates of coronal electron densities, magnetic field strengths and…

Solar and Stellar Astrophysics · Physics 2014-05-08 Pietro Zucca , Eoin P. Carley , D. Shaun Bloomfield , Peter T. Gallagher

Transverse magnetohydrodynamic (MHD) waves have been shown to be ubiquitous in the solar atmosphere and can in principle carry sufficient energy to generate and maintain the Sun's million-degree outer atmosphere or corona. However, direct…

Solar and Stellar Astrophysics · Physics 2015-08-19 Takenori J. Okamoto , Patrick Antolin , Bart De Pontieu , Han Uitenbroek , Tom Van Doorsselaere , Takaaki Yokoyama

We present a technique which predicts the energy dependent fractional r.m.s for linear correlated variations of a pair of spectral parameters and apply it to an XMM-Newton observation of Mrk 335. The broadband X-ray spectrum can be…

High Energy Astrophysical Phenomena · Physics 2025-01-24 K. Akhila , Ranjeev Misra , Rathin Sarma , Savithri H. Ezhikode , K. Jeena