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In recent decades our understanding of solar active regions (ARs) has improved substantially due to observations made with better angular resolution and wider spectral coverage. While prior AR observations have shown that these structures…

Determining the heating mechanism (or mechanisms) that causes the outer atmosphere of the Sun, and many other stars, to reach temperatures orders of magnitude higher than their surface temperatures has long been a key problem. For decades…

Solar and Stellar Astrophysics · Physics 2012-06-27 Clare E. Parnell , Ineke De Moortel

The solar corona produces coronal rain, hundreds of times colder and denser material than the surroundings. Coronal rain is known to be deeply linked to coronal heating, but its origin, dynamics, and morphology are still not well…

Solar and Stellar Astrophysics · Physics 2023-07-05 Seray Şahin , Patrick Antolin , Clara Froment , Thomas A. Schad

Cool, dense material is frequently observed to permeate the hot, tenuous solar corona in the form of prominences, spicules and coronal rain. Both the cool material and surrounding corona exist at temperatures that are effectively thermally…

Solar and Stellar Astrophysics · Physics 2026-01-30 B. Snow , A. Hillier

We examine the hypothesis that ``cool loops'' dominate emission from solar transition region plasma below temperatures of $2\times10^5$K. We compare published VAULT images of H L$\alpha$, a lower transition region line, with…

Astrophysics · Physics 2009-11-13 Philip G. Judge , Rebecca Centeno

The EUI instrument on the Solar Orbiter spacecraft has obtained the most stable, high-resolution images of the solar corona from its orbit with a perihelion near 0.4 AU. A sequence of 360 images obtained at 17.1 nm, between 25-Oct-2022…

Solar and Stellar Astrophysics · Physics 2023-09-12 Philip G. Judge

Coronal rain, observed in 3D spine-fan magnetic configurations, results from thermal instability in the solar corona, where runaway in-situ cooling causes plasma to condense and drain along the magnetic lines. The reconnection of the…

Solar and Stellar Astrophysics · Physics 2025-06-18 Beatrice Popescu Braileanu , Rony Keppens

Determining the mechanisms responsible for the heating of the coronal plasma and maintaining and accelerating the solar wind are long standing goals in solar physics. There is a clear need to constrain the energy, mass and momentum flux…

Solar and Stellar Astrophysics · Physics 2016-11-21 R. J. Morton , E. Scullion , D. S. Bloomfield , J. A. McLaughlin , S. Regnier , S. W. McIntosh , S. Tomczyk , P. Young

Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time is well known, but it is unclear how much each source contributes to the solar wind. In this…

Solar and Stellar Astrophysics · Physics 2021-08-11 D. Stansby , L. M. Green , L. van Driel-Gesztelyi , T. S. Horbury

The Sun is a magnetic star, and the only spatio-temporally resolved astrophysical system displaying turbulent MHD thermal convection. This makes it a privileged object of study to understand fluid turbulence in extreme regimes and its…

Solar and Stellar Astrophysics · Physics 2025-04-16 F. Rincon , P. Barrère , T. Roudier

The magnetic field in the Sun's corona stores energy that can be released to heat the coronal plasma and drive solar eruptions. Measurements of the global coronal magnetic field have been limited to a few snapshots. We present observations…

Solar and Stellar Astrophysics · Physics 2024-10-23 Zihao Yang , Hui Tian , Steven Tomczyk , Xianyu Liu , Sarah Gibson , Richard J. Morton , Cooper Downs

The anomalous heating of the solar upper atmosphere is one of the eight key problems in modern astronomy. Moreover, the stratification of the solar atmosphere is an outstanding key-problem in solar physics. In this study, a hot…

Solar and Stellar Astrophysics · Physics 2022-09-29 K. J. Li , J. C. Xu , W. Feng

The phenomenon of solar "torsional oscillations" (TO) represents migratory zonal flows associated with the solar cycle. These flows are observed on the solar surface and, according to helioseismology, extend through the convection zone. We…

Solar and Stellar Astrophysics · Physics 2016-08-31 G. Guerrero , P. K. Smolarkiewicz , E. M. de Gouveia Dal Pino , A. G. Kosovichev , N. N. Mansour

Vortex flows have been found in the photosphere, chromosphere and low corona in observations and simulations. It has been suggested that vortices play an important role for channeling energy and plasma into the corona, but the impact of…

Solar and Stellar Astrophysics · Physics 2023-07-05 C. Breu , H. Peter , R. Cameron , S. K. Solanki

The solar convection zone exhibits a strong level of differential rotation, whereby the rotation period of the polar regions is about 25-30% longer than the equatorial regions. The Coriolis force associated with these zonal flows…

Solar and Stellar Astrophysics · Physics 2011-02-11 P. Garaud , L. Acevedo-Arreguin

The solar wind, a continuous flow of plasma from the sun, not only shapes the near Earth space environment but also serves as a natural laboratory to study plasma turbulence in conditions that are not achievable in the lab. Starting with…

Space Physics · Physics 2022-05-03 Tulasi N. Parashar , William H. Matthaeus

Solar dynamics and turbulence occur at all heights of the solar atmosphere and could be described as stochastic processes. We propose that finite lifetime transients recurring at a certain place could trigger quasi-periodic processes in the…

Solar and Stellar Astrophysics · Physics 2016-06-15 Ding Yuan , Jiangtao Su , Fangran Jiao , Robert W. Walsh

The profiles of emission lines formed in the corona contain information on the dynamics and the heating of the hot plasma. Only recently has data with sufficiently high spectral resolution become available for investigating the details of…

Solar and Stellar Astrophysics · Physics 2015-05-18 H. Peter

The problem of solar corona heating remains one of key puzzles in astrophysics for a few decades; but none of the proposed mechanisms can give a definitive answer to this question. As a result, the novel scenarios are still suggested. Here,…

Solar and Stellar Astrophysics · Physics 2020-05-15 Yurii V. Dumin

Microturbulence, i.e. enhanced fluctuations of plasma density, electric and magnetic fields, is of great interest in astrophysical plasmas, but occurs on spatial scales far too small to resolve by remote sensing, e.g., at ~ 1-100 cm in the…

Astrophysics · Physics 2009-11-13 Gelu M. Nita , Dale E. Gary , Gregory D. Fleishman