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The solar atmosphere may be heated by Alfven waves that propagate up from the convection zone and dissipate their energy in the chromosphere and corona. To further test this theory, we consider wave heating in an active region observed on…

Solar and Stellar Astrophysics · Physics 2015-06-16 M. Asgari-Targhi , A. A. van Ballegooijen , S. R. Cranmer , E. E. DeLuca

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

Using the quantum Markovian master equation, we show that convection in the stellar photosphere generates plasma waves by an irreversible process akin to Zeldovich superradiance and sonic booms. In the Sun, this mechanism is most efficient…

Solar and Stellar Astrophysics · Physics 2022-03-08 Robert Alicki , Alejandro Jenkins

Magnetic fields in the sun's outer atmosphere -- the corona -- control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly…

Routine ultraviolet imaging of the Sun's upper atmosphere shows the spectacular manifestation of solar activity; yet we remain blind to its main driver, the magnetic field. Here we report unprecedented spectropolarimetric observations of an…

In this paper we seek to understand the timescale on which the photospheric motions on the Sun braid coronal magnetic field lines. This is a crucial ingredient for determining the viability of the braiding mechanism for explaining the high…

Solar and Stellar Astrophysics · Physics 2018-09-19 Simon Candelaresi , David Pontin , Anthony Yeates , Paul Bushby , Gunnar Hornig

The heating of the lower solar corona is examined using numerical simulations and theoretical models of magnetohydrodynamic turbulence in open magnetic regions. A turbulent energy cascade to small length scales perpendicular to the mean…

Astrophysics · Physics 2009-11-07 P. Dmitruk , W. H. Matthaeus , L. J. Milano , S. Oughton , G. P. Zank , D. J. Mullan

Turbulence, magnetic reconnection, and shocks can be present in explosively unstable plasmas, forming a new electromagnetic environment, which we call here turbulent reconnection, and where spontaneous formation of current sheets takes…

High Energy Astrophysical Phenomena · Physics 2018-11-28 Loukas Vlahos , Heinz Isliker

This paper reviews our growing understanding of the physics behind coronal heating (in open-field regions) and the acceleration of the solar wind. Many new insights have come from the last solar cycle's worth of observations and theoretical…

Solar and Stellar Astrophysics · Physics 2010-02-02 Steven R. Cranmer , John L. Kohl , Mari Paz Miralles , Adriaan A. van Ballegooijen

Results from a realistic simulation of 3D radiative magneto-convection in a strong background magnetic field corresponding to the conditions in sunspot umbrae are shown. The convective energy transport is dominated by narrow upflow plumes…

Astrophysics · Physics 2009-11-11 M. Schuessler , A. Voegler

Parker (1983) suggested a mechanism for the formation of current sheets (CSs) in the solar atmosphere. His main idea was that the tangling of coronal magnetic field lines by photospheric random flows facilitates the continuous formation of…

Solar and Stellar Astrophysics · Physics 2021-08-05 Loukas Vlahos , Heinz Isliker , Nikos Sioulas

Even in the absence of resolved flares, the corona is heated to several million degrees. However, despite its importance for the structure, dynamics, and evolution of the solar atmosphere, the origin of this heating remains poorly…

The coronal magnetic field is the prime driver behind many as-yet unsolved mysteries: solar eruptions, coronal heating, and the solar wind, to name a few. It is, however, still poorly observed and understood. We highlight key questions…

A second emission enhancement in warm coronal extreme-ultraviolet (EUV) lines (about 2-7 MK) during some solar flares is known as the EUV late phase. Imaging observations confirm that the late phase emission originates from a set of longer…

Solar and Stellar Astrophysics · Physics 2019-06-19 Zhenjun Zhou , Xin Cheng , Lijuan Liu , Yu Dai , Yuming Wang , Jun Cui

In this study we report detailed observations of magnetic environment at four footpoints of two warm coronal loops observed on 5 May 2016 in NOAA AR 12542 (Loop I) and 17 Dec 2015 in NOAA AR 12470 (Loop II). These loops were connecting a…

Solar and Stellar Astrophysics · Physics 2019-03-29 Seray Şahin , Vasyl Yurchyshyn , Pankaj Kumar , Ali Kilcik , Kwangsu Ahn , Xu Yang

As one of the most spectacular energy release events in the solar system, solar flares are generally powered by magnetic reconnection in the solar corona. As a result of the re-arrangement of magnetic field topology after the reconnection…

Solar and Stellar Astrophysics · Physics 2021-03-29 Tanmoy Samanta , Hui Tian , Bin Chen , Katharine K. Reeves , Mark C. M. Cheung , Angelos Vourlidas , Dipankar Banerjee

We report on the results of four convective dynamo simulations with an outer coronal layer. The magnetic field is self-consistently generated by the convective motions beneath the surface. Above the convection zone, we include a polytropic…

Solar and Stellar Astrophysics · Physics 2013-11-14 Jörn Warnecke , Petri J. Käpylä , Maarit. J. Mantere , Axel Brandenburg

We present a series of numerical simulations of the quiet Sun plasma threaded by magnetic fields that extend from the upper convection zone into the low corona. We discuss an efficient, simplified approximation to the physics of optically…

Solar and Stellar Astrophysics · Physics 2015-05-27 William P. Abbett , George H. Fisher

We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by…

Solar and Stellar Astrophysics · Physics 2016-10-12 F. Reale , S. Orlando , M. Guarrasi , A. Mignone , G. Peres , A. W. Hood , E. R. Priest

Solar flares are one of the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ejection, both of…

Solar and Stellar Astrophysics · Physics 2017-02-08 Y. Li , X. Sun , M. D. Ding , J. Qiu , E. R. Priest
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