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Small-scale magnetic fields are major contributors to the solar irradiance variations. Hence, the continuum intensity contrast of magnetic elements in the quiet Sun (QS) network and in active region (AR) plage is an essential quantity that…

Solar and Stellar Astrophysics · Physics 2015-05-28 P. Kobel , S. K. Solanki , J. M. Borrero

Sunspots are regions of decreased brightness on the visible surface of the Sun (photosphere) that are associated with strong magnetic fields. They have been found to be locations associated with solar flares, which occur when energy stored…

Solar and Stellar Astrophysics · Physics 2013-01-24 Sophie A. Murray

Nanoflares, short and intense heat pulses within spatially unresolved magnetic strands, are now considered a leading candidate to solve the coronal heating problem. However, the frequent occurrence of nanoflares requires that flare-hot…

Solar and Stellar Astrophysics · Physics 2011-02-11 Fabio Reale , Paola Testa , James A. Klimchuk , Susanna Parenti

{We report on the first of a series of studies on coronal bright points investigating the physical mechanism that generates these phenomena.} {The aim of this paper is to understand the magnetic-field structure that hosts the bright…

Solar and Stellar Astrophysics · Physics 2017-10-11 K. Galsgaard , M. S. Madjarska , F. Moreno-Insertis , Z. Huang , T. Wiegelmann

Context: Studying the problem of active region heating requires precise measurements of physical plasma parameters such as electron density, temperature etc. It is also important to understand the relationship of coronal structures with the…

Astrophysics · Physics 2009-11-13 D. Tripathi , H. E. Mason , P. R. Young , G. Del Zanna

Several coronal bright points identified in a quiet region of the Sun from SOHO/EIT Fe XII images are found to have a time evolution from birth to decay which is extremely well correlated with the rise and fall of magnetic flux as…

Astrophysics · Physics 2009-10-31 Paweł Preś , Kenneth J. H. Phillips

We examine the hypothesis that multipolar magnetic fields advected by photospheric granules can contribute heating to the active chromosphere and corona. On 28 September 2020 the GRIS and HiFI+ instruments at the GREGOR telescope obtained…

Solar and Stellar Astrophysics · Physics 2024-05-14 Philip Judge , Lucia Kleint , Christoph Kuckein

We compare the coronal magnetic energy and helicity of two solar active regions (ARs), prolific in major eruptive (AR~11158) and confined (AR~12192) flaring, and analyze the potential of deduced proxies to forecast upcoming flares. Based on…

Solar and Stellar Astrophysics · Physics 2020-01-08 J. K. Thalmann , K. Moraitis , L. Linan , E. Pariat , G. Valori , K. Dalmasse

To understand the physical mechanisms for activity and heating in the solar atmosphere, the magnetic coupling from the photosphere to the corona is an important piece of information from the Hinode observations, and therefore precise…

It is generally agreed that small impulsive energy bursts called nanoflares are responsible for at least some of the Sun's hot corona, but whether they are the explanation for most of the multi-million degree plasma has been a matter of…

Solar and Stellar Astrophysics · Physics 2015-05-28 Sergio Terzo , Fabio Reale , Marco Miceli , James A. Klimchuk , Ryouhei Kano , Saku Tsuneta

Aims. We analyze observational data from 4 instruments to study the correlations between chromospheric emission, spanning the heights from the temperature minimum region to the middle chromosphere, and photospheric magnetic field. Methods:…

Solar and Stellar Astrophysics · Physics 2014-11-20 Maria A. Loukitcheva , Sami K. Solanki , Stephen M. White

Recently, it has been proposed that the magnetic-field-induced transition (MIT) in Fe X can be used to measure coronal magnetic field strengths. Several techniques, the direct line ratio technique and the weak and strong magnetic field…

Solar and Stellar Astrophysics · Physics 2023-03-08 Yajie Chen , Xianyong Bai , Hui Tian , Wenxian Li , Feng Chen , Zihao Yang , Yang Yang

Adopting the thermal free-free emission mechanism, the coronal and chromospheric magnetic fields are derived from the polarization and spectral observations with the Nobeyama Radioheliograph at 1.76 cm. The solar active regions (AR) located…

Solar and Stellar Astrophysics · Physics 2018-02-14 A. Mouner , Abdelrazek M. K. Shaltout , M. M. Beheary , K. A. K. Gadallah , K. A. Edris

For all involved in astronomy, the importance of monitoring and determining astrophysical magnetic field strengths is clear. It is also a well-known fact that the corona magnetic fields play an important part in the origin of solar flares…

Atomic Physics · Physics 2020-08-18 Ran Si , Tomas Brage , Wenxian Li , Jon Grumer , Meichun Li , Roger Hutton

Solar activity can be witnessed in the form of sunspots and active regions, where the magnetic field is enhanced by up to a factor 1000 as compared to that of the quiet Sun. In addition, solar activity manifests itself in terms of flares,…

Solar and Stellar Astrophysics · Physics 2025-07-25 Gottfried Mann , Frédéric Schuller

Stellar dynamos generate magnetic fields that are of fundamental importance to the variability and evolution of Sun-like and low-mass stars, and for the development of their planetary systems. We report measurements of surface-average…

Strong coronal magnetic field, when present, manifests itself as bright microwave sources at high frequencies produced by gyroresonant (GR) emission mechanism in thermal coronal plasma. The highest frequency at which this emission is…

Solar and Stellar Astrophysics · Physics 2023-02-15 V. V. Fedenev , S. A. Anfinogentov , G. D. Fleishman

We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager sounding rocket payload. FOXSI has performed the first…

We have measured line widths in active region coronal loops in order to determine whether the non-thermal broadening is anisotropic with respect to the magnetic field direction. These non-thermal velocities are caused by unresolved fluid…

Solar and Stellar Astrophysics · Physics 2023-08-09 Michael Hahn , Mahboubeh Asgari-Targhi , Daniel Wolf Savin

With the recent launch of the Hinode satellite our view of the nature and evolution of quiet-Sun regions has been improved. In light of the new high resolution observations, we revisit the study of the quiet Sun's topological nature.…

Astrophysics · Physics 2009-11-13 S. Regnier , C. E. Parnell , A. L. Haynes