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Despite its prediction over two decades ago, the detection of faint, high-temperature ("hot") emission due to nanoflare heating in non-flaring active region cores has proved challenging. Using an efficient two-fluid hydrodynamic model, this…

Solar and Stellar Astrophysics · Physics 2016-12-28 W. T. Barnes , P. J. Cargill , S. J. Bradshaw

We present the results of 1D hydrodynamic simulations of coronal loops which are subject to nanoflares, caused by either in-situ thermal heating, or non-thermal electrons (NTE) beams. The synthesized intensity and Doppler shifts can be…

Solar and Stellar Astrophysics · Physics 2018-04-18 V. Polito , P. Testa , J. Allred , B. De Pontieu , M. Carlsson , T. M. D. Pereira , M. Gošić , F. Reale

A full 3-dimensional compressible magnetohydrodynamic (MHD) simulation is conducted to investigate the thermal responses of a coronal loop to the dynamic dissipation processes of MHD waves. When the foot points of the loop are randomly and…

Solar and Stellar Astrophysics · Physics 2018-03-14 Takuma Matsumoto

We study a 2D cellular automaton (CA) model for the evolution of coronal loop plasmas. The model is based on the idea that coronal loops are made of elementary magnetic strands that are tangled and stressed by the displacement of their…

Solar and Stellar Astrophysics · Physics 2017-03-22 Marcelo López Fuentes , James A. Klimchuk

Quasi-periodic propagating intensity disturbances (PDs) have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves. However, spectroscopic observations from Hinode/EIS…

Solar and Stellar Astrophysics · Physics 2014-04-24 Tongjiang Wang , Leon Ofman , Joseph M. Davila

We use the cellular automaton model described in L\'opez Fuentes \& Klimchuk (2015, ApJ, 799, 128) to study the evolution of coronal loop plasmas. The model, based on the idea of a critical misalignment angle in tangled magnetic fields,…

Solar and Stellar Astrophysics · Physics 2016-09-21 Marcelo López Fuentes , James A. Klimchuk

The heating of the solar corona is one of the big questions in astrophysics. Rapid pulses called nanoflares are among the best candidate mechanisms. The analysis of the time variability of coronal X-ray emission is potentially a very useful…

Solar and Stellar Astrophysics · Physics 2012-01-27 S. Terzo , F. Reale , M. Miceli , R. Kano , S. Tsuneta , J. A. Klimchuk

The content of hot material in the corona is not constant. Soft X-ray and high-temperature EUV line observations show that new material, apparently heated and evaporated from the chromosphere, is frequently injected into the corona both in…

Astrophysics · Physics 2016-08-30 Arnold O. Benz , Paolo C. Grigis

Outflows perpendicular to the guide field are believed to be a possible signature of magnetic reconnection in the solar corona and specifically a way to detect the occurrence of ubiquitous small-angle magnetic reconnection. The aim of this…

Solar and Stellar Astrophysics · Physics 2025-03-05 G. Cozzo , P. Pagano , F. Reale , P. Testa , A. Petralia , J. Martinez-Sykora , V. Hansteen , B. De Pontieu

Recent imaging observations of EUV line emissions have shown evidence for frequent flare-like events in a majority of the pixels in quiet regions of the solar corona. The changes in coronal emission measure indicate impulsive heating of new…

Astrophysics · Physics 2009-11-07 Arnold O. Benz , Sam Krucker

It is extremely difficult to simulate the details of coronal heating and also make meaningful predictions of the emitted radiation. Thus, testing realistic models with observations is a major challenge. Observational signatures of coronal…

Solar and Stellar Astrophysics · Physics 2022-11-02 James A. Klimchuk , Kalman J. Knizhnik , Vadim M. Uritsky

Nanoflares, which are consequences of braids in tangled magnetic fields, are an important candidate to heat the solar corona to million degrees. However, their observational evidence is sparse and many of their observational characteristics…

Solar and Stellar Astrophysics · Physics 2025-04-18 Xiuhui Zuo , Zhenghua Huang , Hengyuan Wei , Chao Zhang , Boyu Sun , Youqian Qi , Hui Fu , Weixin Liu , Mingzhe Sun , Ming Xiong , Lidong Xia

It has been proposed that the million degree temperature of the corona is due to the combined effect of barely-detectable energy releases, so called nanoflares, that occur throughout the solar atmosphere. Alas, the nanoflare density and…

Solar and Stellar Astrophysics · Physics 2015-05-27 M. R. Bareford , P. K. Browning , R. A. M. Van der Linden

Advanced 3D radiative MHD simulations now reproduce many properties of the outer solar atmosphere. When including a domain from the convection zone into the corona, a hot chromosphere and corona are self-consistently maintained. Here we…

Solar and Stellar Astrophysics · Physics 2015-10-07 Viggo Hansteen , Nuno Guerreiro , Bart De Pontieu , Mats Carlsson

Aims. The goal is to employ a 3D magnetohydrodynamics (MHD) model including spectral synthesis to model the corona in an observed solar active region. This will allow us to judge the merits of the coronal heating mechanism built into the 3D…

Solar and Stellar Astrophysics · Physics 2017-09-19 Ph. -A. Bourdin , S. Bingert , H. Peter

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

Context. Multi-dimensional solar flare simulations have not yet included detailed analysis of the lower atmospheric responses such as down-flowing chromospheric compressions and chromospheric evaporation processes. Aims. We present an…

Solar and Stellar Astrophysics · Physics 2024-02-02 Malcolm Druett , Wenzhi Ruan , Rony Keppens

We investigate several key questions of plasma heating in open-field regions of the corona that connect to the solar wind. We present results for a model of Alfven-wave-driven turbulence for three typical open magnetic field structures: a…

Solar and Stellar Astrophysics · Physics 2015-10-07 Lauren N. Woolsey , Steven R. Cranmer

Nanoflares are impulsive energy releases by magnetic reconnection in the braided coronal magnetic field, which is a potential mechanism for heating the corona. However, there are still sporadic observations of the interchange of braiding…

Solar and Stellar Astrophysics · Physics 2023-11-01 Y. Bi , J. J. Yang , Y. Qin , Z. P. Qiang , J. C. Hong , B. Yang , Z. Xu , H. Liu , K. F. Ji

We report on the formation of small solar flares produced by patchy magnetic reconnection between interacting magnetic loops. A three-dimensional (3D) magnetohydrodynamic (MHD) numerical experiment was performed, where a uniform magnetic…

Solar and Stellar Astrophysics · Physics 2015-06-19 V. Archontis , V. Hansteen