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By comparing a magneto-frictional model of the low coronal magnetic field to a potential-field source-surface model, we investigate the possible impact of non-potential magnetic structure on empirical solar-wind models. These empirical…

Solar and Stellar Astrophysics · Physics 2015-12-09 S. J. Edwards , A. R. Yeates , F. -X. Bocquet , D. H. Mackay

The adopted WSA model embedded in EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is compared to EUV observations. According to the standard paradigm coronal holes are sources of open flux thus we use remote sensing EUV…

Solar and Stellar Astrophysics · Physics 2020-01-08 Eleanna Asvestari , Stephan G. Heinemann , Mannuela Temmer , Jens Pomoell , Emilia Kilpua , Jasmina Magdalenic , Stefaan Poedts

In this review, our present day understanding of the Sun's global photospheric and coronal magnetic fields is discussed from both observational and theoretical viewpoints. Firstly, the large-scale properties of photospheric magnetic fields…

Solar and Stellar Astrophysics · Physics 2015-06-12 D. H. Mackay , A. R. Yeates

Coronal rain is the well-known phenomenon in which hot plasma high in the Sun's corona undergoes rapid cooling (from > 10^6 K to < 10^4 K), condenses, and falls to the surface. Coronal rain appears frequently in active region coronal loops…

Solar and Stellar Astrophysics · Physics 2019-04-22 E. I. Mason , S. K. Antiochos , N. M. Viall

An application of active contours without edges is presented as an efficient and effective means of extracting and characterizing coronal holes. Coronal holes are regions of low-density plasma on the Sun with open magnetic field lines. As…

Solar and Stellar Astrophysics · Physics 2016-10-05 L. E. Boucheron , M. Valluri , R. T. J. McAteer

Aims. We aim to infer information about the magnetic field in the low solar corona from coronal rain clumps using high-resolution spectropolarimetric observations in the Ca ii 8542 A line obtained with the Swedish 1-m Solar Telescope.…

Solar and Stellar Astrophysics · Physics 2021-06-09 M. Kriginsky , R. Oliver , P. Antolin , D. Kuridze , N. Freij

Waves are thought to play a significant role in the heating of the solar atmosphere and the acceleration of the wind. Among the many types of waves observed in the Sun, the so-called p-modes with a 3 mHz frequency peak dominate the lower…

We study the height variations of the sizes of chromospheric and transition-region features in a small coronal hole and the adjacent quiet Sun, considering images of the intensity, Doppler shift, and non-thermal motion of ultraviolet…

Solar and Stellar Astrophysics · Physics 2011-08-31 H. Tian , E. Marsch , C. -Y. Tu , L. -D. Xia , J. -S. He

Context. The Sun's complex corona is the source of the solar wind and interplanetary magnetic field. While the large scale morphology is well understood, the impact of variations in coronal properties on the scale of a few degrees on…

A major challenge in solar and heliospheric physics is understanding how highly localized regions, far smaller than 1 degree at the Sun, are the source of solar-wind structures spanning more than 20 degrees near Earth. The Sun's atmosphere…

Space Physics · Physics 2017-05-10 A. K. Higginson , S. K. Antiochos , C. R. DeVore , P. F. Wyper , T. H. Zurbuchen

New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer sub-structures within coronal loop cross sections, in order to…

Solar and Stellar Astrophysics · Physics 2015-06-22 Eamon Scullion , Luc Rouppe van der Voort , Sven Wedemeyer , Patrick Antolin

The prominent blue shifts of Ne viii associated with the junctions of the magnetic network in the quiet Sun are still not well understood. By comparing the coronal magnetic-field structures as obtained by a potential-field reconstruction…

Solar and Stellar Astrophysics · Physics 2014-11-20 Hui Tian , Eckart Marsch , Werner Curdt , Jiansen He

The solar magnetic field is the primary agent that drives solar activity and couples the Sun to the Heliosphere. Although the details of this coupling depend on the quantitative properties of the field, many important aspects of the corona…

Astrophysics · Physics 2009-11-13 S. K. Antiochos , C. R. DeVore , J. T. Karpen , Z. Mikic

Potential Field Source Surface (PFSS) models are widely used to simulate coronal magnetic fields. PFSS models use the observed photospheric magnetic field as the inner boundary condition and assume a perfectly radial field beyond a ``Source…

Solar and Stellar Astrophysics · Physics 2024-08-30 Luke Fushimi Benavitz , Benjamin Boe , Shadia Rifai Habbal

Observations of surface magnetic fields are now within reach for many stellar types thanks to the development of Zeeman-Doppler Imaging. These observations are extremely useful for constraining rotational evolution models of stars, as well…

Solar and Stellar Astrophysics · Physics 2015-09-24 Victor Réville , Allan Sacha Brun , Antoine Strugarek , Sean P. Matt , Jérôme Bouvier , Colin P. Folsom , Pascal Petit

Faraday rotation measures (RMs) of the polarized emission from extragalactic radio sources occulted by the coronal plasma were used to infer the radial profile of the inner heliospheric magnetic field near solar minimum activity. By…

Solar and Stellar Astrophysics · Physics 2013-05-20 S. Mancuso , M. V. Garzelli

Two states of the slow solar wind are identified from in-situ measurements by Parker Solar Probe (PSP) inside 50 solar radii from the Sun. At such distances the wind measured at PSP has not yet undergone significant transformation related…

Solar and Stellar Astrophysics · Physics 2021-04-07 Léa Griton , Alexis P. Rouillard , Nicolas Poirier , Karine Issautier , Michel Moncuquet , Rui Pinto

The shapes of solar coronal loops are sensitive to the presence of electrical currents that are the carriers of the nonpotential energy available for impulsive activity. We use this information in a new method for modeling the coronal…

Solar and Stellar Astrophysics · Physics 2021-06-29 A. Malanushenko , C. Schrijver , M. L. DeRosa , M. S. Wheatland

We use full-disk, SOHO/EIT 195 $\AA$ calibrated images to measure latitudinal and day to day variations of area and average photon fluxes of the near equatorial coronal holes. In addition, energy emitted by the coronal holes with their…

Solar and Stellar Astrophysics · Physics 2022-04-12 K. M. Hiremath , Manjunath Hegde

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