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In the solar atmosphere, Alfv\'en waves are believed to play an important role in the transfer of energy from the photosphere to the corona and solar wind, and in the heating of the chromosphere. We perform numerical computations to…

Solar and Stellar Astrophysics · Physics 2019-01-23 Roberto Soler , Jaume Terradas , Ramon Oliver , Jose Luis Ballester

With a test-particle simulation, we investigate the effect of large-scale coronal magnetic fields on electron acceleration at an outward-propagating coronal shock with a circular front. The coronal field is approximated by an analytical…

Solar and Stellar Astrophysics · Physics 2016-04-20 Xiangliang Kong , Yao Chen , Fan Guo , Shiwei Feng , Guohui Du , Gang Li

The impulsive phase of a solar flare is known to generate strong turbulence and to transfer magnetic energy into accelerated electrons. Recognizing the importance of angular diffusion on the dynamics of the accelerated electrons, we extend…

Solar and Stellar Astrophysics · Physics 2026-03-30 A. Gordon Emslie , Eduard P. Kontar

Extreme-ultraviolet images from the Solar Dynamics Observatory often show looplike fine structure to be present where no minority-polarity flux is visible in magnetograms, suggesting that the rate of ephemeral region (ER) emergence inside…

Solar and Stellar Astrophysics · Physics 2021-04-14 Y. -M. Wang

We develop a model of particle energization and emission from strongly turbulent black-hole coronae. Our local model is based on a set of 2D radiative particle-in-cell simulations with an electron-ion plasma composition, injection and…

High Energy Astrophysical Phenomena · Physics 2026-04-07 Daniel Groselj , Alexander Philippov , Andrei M. Beloborodov , Richard Mushotzky

Solar flares are known to be prolific electron accelerators, yet identifying the mechanism(s) for such efficient electron acceleration in solar flare (and similar astrophysical settings) presents a major challenge. This is due in part to a…

Solar and Stellar Astrophysics · Physics 2023-04-18 Eduard P. Kontar , A. Gordon Emslie , Galina G. Motorina , Brian R. Dennis

The transition region is a thin inhomogeneous region where Alfven waves' energy fluxes generated elsewhere in the solar atmosphere are effectively converted. Large-scale kinetic Alfven wave propagations, transmission, and reflection…

Solar and Stellar Astrophysics · Physics 2026-05-12 Petko Nenovski

The problem of explaining observed soft X-ray fluxes during solar flares, which invokes acceleration of large fraction of electrons, if the acceleration takes places at the solar coronal loop-top, can potentially be solved by postulating…

Solar and Stellar Astrophysics · Physics 2023-12-25 D. Tsiklauri

The large temperature gradients in the solar transition region present a significant challenge to large scale numerical modelling of the Sun's atmosphere. In response, a variety of techniques have been developed which modify the…

Solar and Stellar Astrophysics · Physics 2023-09-13 Thomas Howson , Cosima Breu

We report the properties of electron distributions and turbulence during a Coronal Mass Ejection (CME) in April 2023 observed by Magnetospheric Multiscale (MMS). The CME exhibits a clear sheath and magnetic cloud (MC), and within the MC,…

The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations…

We develop a model for stochastic acceleration of electrons in solar flares. As in several previous models, the electrons are accelerated by turbulent fast magnetosonic waves ("fast waves") via transit-time-damping (TTD) interactions. (In…

Solar and Stellar Astrophysics · Physics 2015-06-19 Peera Pongkitiwanichakul , Benjamin D. G. Chandran

Magnetic reconnection in solar flares can efficiently generate non-thermal electron beams. The energetic electrons can, in turn, cause radio waves through microscopic plasma instabilities as they propagate through the ambient plasma along…

Solar and Stellar Astrophysics · Physics 2022-07-27 Xin Yao , Patricio Muñoz , Jörg Büchner , Jan Benáček , Siming Liu , Xiaowei Zhou

We propose a new model for explaining the observations of more than mass proportional heating of heavy ions in the polar solar corona. We point out that a large number of small scale intermittent shock waves can be present in the solar…

Solar and Stellar Astrophysics · Physics 2010-12-13 Gaetano Zimbardo

In the parts of the solar corona and solar wind that experience the fewest Coulomb collisions, the component proton, electron, and heavy ion populations are not in thermal equilibrium with one another. Observed differences in temperatures,…

Solar and Stellar Astrophysics · Physics 2015-06-05 Steven R. Cranmer , Adriaan A. van Ballegooijen

The collisionless dissipation of anisotropic Alfv\'enic turbulence is a promising candidate to solve the solar wind heating problem. Extensive studies examined the kinetic properties of Alfv\'en waves in simple Maxwellian or bi-Maxwellian…

Solar and Stellar Astrophysics · Physics 2015-05-12 Yuguang Tong , Stuart D. Bale , Christopher H. K. Chen , Chadi S. Salem , Daniel Verscharen

The origin of solar transition region redshifts is not completely understood. Current research is addressing this issue by investigating three-dimensional magneto-hydrodynamic models that extend from the photosphere to the corona. By…

Solar and Stellar Astrophysics · Physics 2015-05-28 Pia Zacharias , Sven Bingert , Hardi Peter

The X-ray emission of coronal flare sources can be explained considering the kappa electron distribution. Motivated by this fact, we study the problem of how hot plasma with the kappa distribution of electrons is confined in these sources.…

Solar and Stellar Astrophysics · Physics 2020-06-09 Jan Benáček , Marian Karlický

The brightness of the emission from coronal loops in the solar atmosphere is strongly dependent on the temperature and density of the confined plasma. After a release of energy, these loops undergo a heating and upflow phase, followed by a…

Solar and Stellar Astrophysics · Physics 2019-03-20 C. D. Johnston , S. J. Bradshaw

During solar flares fast electron beams generated in the solar corona are non-thermal radio sources in terms of type III bursts. Sometimes they can enter into the interplanetary space, where they can be observed by in-situ measurements as…

Solar and Stellar Astrophysics · Physics 2011-12-23 H. Önel , G. Mann , E. Sedlmayr