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Given its unchallenged capabilities in terms of sensitivity and spatial resolution, the combination of imaging spectropolarimetry and numeric Stokes inversion represents the dominant technique currently used to remotely sense the physical…

Instrumentation and Methods for Astrophysics · Physics 2019-11-05 Francisco A. Iglesias , Alex Feller

The solar surface and atmosphere are highly dynamic plasma environments, which evolve over a wide range of temporal and spatial scales. Large-scale eruptions, such as coronal mass ejections, can be accelerated to millions of kilometres per…

Spicules are intermittently rising above the surface of the Sun eruptions; EUV jets are now also reported in immediately above layers. The variation of spicule orientation with respect to the solar latitude, presumably reflecting the…

Solar and Stellar Astrophysics · Physics 2021-07-27 E. Tavabi , S. Koutchmy

Context: Solar active regions (ARs) are key manifestations of the Sun's magnetic activity, displaying diverse spatial and temporal characteristics. Their formation and evolution play a crucial role in understanding the solar dynamo and…

Solar and Stellar Astrophysics · Physics 2025-08-06 M. Švanda , J. Jurčák , M. Schmassmann

Sunspots are the longest-known manifestation of solar activity, and their magnetic nature has been known for more than a century. Despite this, the boundary between umbrae and penumbrae, the two fundamental sunspot regions, has hitherto…

Solar and Stellar Astrophysics · Physics 2018-03-28 Jan Jurčák , Reza Rezaei , Nazaret Bello González , Rolf Schlichenmaier , Jiří Vomlel

Three-dimensional magnetic reconnection is a fundamental plasma process crucial for heating the solar corona and generating the solar wind, but resolving and characterizing it on the Sun remains challenging. Using high-quality data from the…

The analyses of sunspot observations revealed a fundamental magnetic property of the umbral boundary, the invariance of the vertical component of the magnetic field. We aim to analyse the magnetic properties of the umbra-penumbra boundary…

Solar and Stellar Astrophysics · Physics 2020-07-01 Jan Jurcak , Markus Schmassmann , Matthias Rempel , Nazaret Bello Gonzalez , Rolf Schlichenmaier

It is generally believed that sunspots are the emergent part of magnetic flux tubes in the solar interior. These tubes are created at the base of the convection zone and rise to the surface due to their magnetic buoyancy. The motion of…

Solar and Stellar Astrophysics · Physics 2015-05-14 Franck Plunian , Graeme Sarson , Rodion Stepanov

Context: Sunspot penumbrae harbor highly structured magnetic fields and flows. The moving flux tube model offers an explanation for several observed phenomena, e.g. the Evershed effect and bright penumbral grains. Aims: A wealth of…

Astrophysics · Physics 2007-05-23 D. A. N. Mueller , R. Schlichenmaier , G. Fritz , C. Beck

We identify and examine the solar wind intervals near the sonic critical point (i.e., $M_S \sim 1$) observed by the Parker Solar Probe (PSP). The near subsonic wind intervals show similar properties: a low density, an extremely low…

Solar and Stellar Astrophysics · Physics 2024-04-16 Wenshuai Cheng , Ying D. Liu , Hao Ran , Yiming Jiao , Michael L. Stevens , Justin C. Kasper

Some models for the topology of the magnetic field in sunspot penumbrae predict the existence of field-free or dynamically weak-field regions in the deep Photosphere. To confirm or rule out the existence of weak-field regions in the deepest…

A new Stokes inversion technique that greatly reduces the effect of the spatial point spread function of the telescope is used to constrain the physical properties of umbral dots (UDs). The depth-dependent inversion of the Stokes parameters…

Solar and Stellar Astrophysics · Physics 2015-06-15 T. L. Riethmüller , S. K. Solanki , M. van Noort , S. K. Tiwari

In recent years, astronomical photometry has been revolutionised by space missions such as MOST, CoRoT and Kepler. However, despite this progress, high-quality spectroscopy is still required as well. Unfortunately, high-resolution spectra…

Solar and Stellar Astrophysics · Physics 2014-03-05 T. Van Reeth , A. Tkachenko , V. Tsymbal

The solar photosphere is the visible surface of the Sun, where many bright granules, surrounded by narrow dark intergranular lanes, are observed everywhere. The granular pattern is a manifestation of convective motion at the photospheric…

Solar and Stellar Astrophysics · Physics 2017-02-15 T. Oba , Y. Iida , T. Shimizu

Using turbulent MHD simulations (magnetic Reynolds numbers up to 8000) and Hinode observations, we study effects of turbulence on measuring the solar magnetic field outside active regions. Firstly, from synthetic Stokes V profiles for the…

Astrophysics · Physics 2011-02-11 Jonathan Pietarila Graham , Sanja Danilovic , Manfred Schuessler

Many previous studies have shown that magnetic fields as well as sunspot structures present rapid and irreversible changes associated with solar flares. In this paper we first use five X-class flares observed by SDO/HMI to show that not…

Solar and Stellar Astrophysics · Physics 2016-08-17 Yongliang Song , Mei Zhang

Sunspots are the most spectacular manifestation of solar magnetism, yet, 99% of the solar surface remains 'quiet' at any time of the solar cycle. The quiet sun is not void of magnetic fields, though; they are organized at smaller spatial…

Solar and Stellar Astrophysics · Physics 2015-05-18 M. J. Martinez Gonzalez , R. Manso Sainz , A. Asensio Ramos , L. R. Bellot Rubio

Magnetic bright points are small-scale magnetic elements ubiquitous across the solar disk, with the prevailing theory suggesting that they form due to the process of convective collapse. Employing a unique full Stokes spectropolarimetric…

Context. High-resolution observations of the solar photosphere reveal the presence of fine structures, in particular the so-called magnetic bright points (MBPs), which are small-scale features associated with strong magnetic field regions…

The magnetic fields, activity and dynamos of young solar-type stars can be empirically studied using time-series of spectropolarimetric observations and tomographic imaging techniques such as Doppler imaging and Zeeman Doppler imaging. In…