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The modern Doppler Imaging (DI) technique allows the reconstruction of different stellar surface structures based on accurate calculation of spectra of specific intensity. New applications like the mapping of the magnetic field vector put…

Astrophysics · Physics 2007-05-23 N. Piskunov

The magnetic activity of the Sun changes with the solar cycle. Similar cycles are found in other stars as well, but their details are not known to a similar degree. Characterising stellar magnetic cycles is important for the understanding…

Solar and Stellar Astrophysics · Physics 2022-05-11 T. Willamo , J. J. Lehtinen , T. Hackman , M. J. Käpylä , O. Kochukhov , S. V. Jeffers , H. Korhonen , S. C. Marsden

We aim to characterise the surface magnetic fields of a sample of 8 T Tauri stars from high-resolution near-IR spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetric studies. Our…

Solar and Stellar Astrophysics · Physics 2019-10-02 Alexis Lavail , Oleg Kochukhov , Gaitee Hussain

Inversion techniques applied to the radiative transfer equation for polarized light are capable of inferring the physical parameters in the solar atmosphere (temperature $T$, magnetic field ${\bf B}$, and line-of-sight velocity $v_{\rm…

Solar and Stellar Astrophysics · Physics 2021-04-07 J. M. Borrero , A. Pastor Yabar , B. Ruiz Cobo

We present our analysis aimed at inferring average magnetic fields in slowly-rotating solar-like stars. Using the spectral line inversion code SPINOR, we perform high-accuracy line profile fitting and investigate whether Zeeman broadening…

Solar and Stellar Astrophysics · Physics 2010-12-15 Richard I. Anderson , Ansgar Reiners , Sami K. Solanki

For the observational modeling of horizontal abundance distributions and of magnetic geometries in chemically peculiar (CP) stars, Zeeman Doppler mapping (ZDM) has become the method of choice. Comparisons between abundance maps obtained for…

Solar and Stellar Astrophysics · Physics 2021-04-13 M. J. Stift , F. Leone

The degree to which the formation and evolution of clouds and filaments in the interstellar medium is regulated by magnetic fields remains an open question. Yet the fundamental properties of the fields (strength and 3D morphology) are not…

Astrophysics of Galaxies · Physics 2020-10-21 Stefan Reissl , Amelia M. Stutz , Ralf S. Klessen , Daniel Seifried , Stefanie Walch

We present a temperature and a magnetic-field surface map of the K2 subgiant of the active binary II Peg. Employed are high resolution Stokes IV spectra obtained with the new Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI)…

Solar and Stellar Astrophysics · Physics 2019-05-15 K. G. Strassmeier , T. A. Carroll , I. V. Ilyin

We investigate the possibility of measuring magnetic field strength in G-band bright points through the analysis of Zeeman polarization in molecular CH lines. To this end we solve the equations of polarized radiative transfer in the G band…

Astrophysics · Physics 2009-11-10 H. Uitenbroek , E. Miller-Ricci , A. Asensio Ramos , J. Trujillo Bueno

This study focuses on the stratification patterns and dynamic evolution of reservoir water temperatures, aiming to estimate and reconstruct the temperature field using limited and noisy local measurement data. Due to complex measurement…

Machine Learning · Computer Science 2025-02-21 Qianyu He , Huaiwei Sun , Yubo Li , Zhiwen You , Qiming Zheng , Yinghan Huang , Sipeng Zhu , Fengyu Wang

In this paper we describe and evaluate new spectral line polarisation observations obtained with the goal of mapping the surfaces of magnetic Ap stars in great detail. One hundred complete or partial Stokes IQUV sequences, corresponding to…

Solar and Stellar Astrophysics · Physics 2015-06-05 J. Silvester , G. A. Wade , O. Kochukhov , S. Bagnulo , C. P. Folsom , D. Hanes

The (Zeeman-)Doppler imaging studies of solar-type stars very often reveal large high-latitude spots. This also includes F stars that possess relatively shallow convection zones, indicating that the dynamo operating in these stars differs…

Solar and Stellar Astrophysics · Physics 2015-01-21 S. P. Järvinen , R. Arlt , T. Hackman , S. C. Marsden , M. Küker , I. V. Ilyin , S. V. Berdyugina , K. G. Strassmeier , I. A. Waite

This review discusses the problem of reconstruction of surface magnetic field topologies of early-type stars with a focus on mapping methods utilising information content of high-resolution spectropolarimetric observations. Basic principles…

Solar and Stellar Astrophysics · Physics 2019-12-17 Oleg Kochukhov

The spectral window, containing Fraunhofer lines formed in the solar photosphere, around the magnetically sensitive Cr I lines at 5780.9, 5781.1, 5781.7, 5783.0, and 5783.8 \r{A}, with Land\'e g-factors between 1.6 and 2.5, is explored. The…

Context. Investigations of the magnetism of the quiet Sun are hindered by extremely weak polarization signals in Fraunhofer spectral lines. Photon noise, straylight, and the systematically different sensitivity of the Zeeman effect to…

Strong, globally-organized magnetic fields are found for a small fraction of O, B, and A stars. At the same time, many theoretical and indirect observational studies suggested ubiquitous presence of weak localized magnetic fields at the…

Solar and Stellar Astrophysics · Physics 2015-06-15 O. Kochukhov , N. Sudnik

With the recent advent of circular polarization capabilities at the Atacama Large Millimeter/submillimeter Array (ALMA), Zeeman effect measurements of spectral lines are now possible as a means to directly probe line-of-sight magnetic…

Solar and Stellar Astrophysics · Physics 2020-11-04 Renato Mazzei , L. Ilsedore Cleeves , Zhi-Yun Li

Quantitative thermodynamical, dynamical and magnetic properties of the solar and stellar plasmas are obtained by interpreting their emergent non-polarized and polarized spectrum. This inference requires the selection of a set of spectral…

Solar and Stellar Astrophysics · Physics 2016-05-25 A. Asensio Ramos , J. de la Cruz Rodriguez , M. J. Martinez Gonzalez , A. Pastor Yabar

We use the POLARIS radiative transport code to generate predictions of the two main observables directly sensitive to the magnetic field morphology and strength in filaments: dust polarization and gas Zeeman line splitting. We simulate…

Astrophysics of Galaxies · Physics 2018-09-19 Stefan Reissl , Amelia M. Stutz , Robert Brauer , Eric W. Pellegrini , Dominik R. G. Schleicher , Ralf Klessen

Measurements of interplanetary magnetic fields have long relied on spacecraft measurements, which provide only in-situ sampling and therefore cannot capture the global magnetic structure. Faraday rotation of radio signals extends in-situ…

Space Physics · Physics 2026-05-28 Chuanpeng Hou , Huirong Yan , Siqi Zhao