scholarly journals Doppler Imaging of stellar magnetic fields

2002 ◽  
Vol 381 (2) ◽  
pp. 736-756 ◽  
Author(s):  
N. Piskunov ◽  
O. Kochukhov
Keyword(s):  
Magnetic Fields ◽  
Doppler Imaging ◽  
Stellar Magnetic Fields

Stellar activity and winds shaping the atmospheres of Earth-like planets

2018 ◽  
Vol 14 (S345) ◽  
pp. 181-184
Author(s):  
Theresa Lueftinger ◽  
Manuel Güdel ◽  
Sudeshna Boro Saikia ◽  
Colin Johnstone ◽  
Beatrice Kulterer ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Extreme Environments ◽  
Doppler Imaging ◽  
Research Network ◽  
Theoretical Understanding ◽  
Stellar Activity ◽  
Active Stars ◽  
Earth Like Planets ◽  
Stellar Magnetic Fields ◽  
Host Stars

AbstractPlanets orbiting young, active stars are embedded in an environment that is far from being as calm as the present solar neighbourhood. They experience the extreme environments of their host stars, which cannot have been without consequences for young stellar systems and the evolution of Earth-like planets to habitable worlds. Stellar magnetism and the related stellar activity are crucial drivers of ionization, photodissociation, and chemistry. Stellar winds can compress planetary magnetospheres and even strip away the outer layers of their atmospheres, thus having an enormous impact on the atmospheres and the magnetospheres of surrounding exoplanets. Modelling of stellar magnetic fields and their winds is extremely challenging, both from the observational and the theoretical points of view, and only ground breaking advances in observational instrumentation and a deeper theoretical understanding of magnetohydrodynamic processes in stars enable us to model stellar magnetic fields and their winds – and the resulting influence on the atmospheres of surrounding exoplanets – in more and more detail. We have initiated a national and international research network (NFN): ‘Pathways to Habitability – From Disks to Active Stars, Planets to Life’, to address questions on the formation and habitability of environments in young, active stellar/planetary systems. We discuss the work we are carrying out within this project and focus on how stellar evolutionary aspects in relation to activity, magnetic fields and winds influence the erosion of planetary atmospheres in the habitable zone. We present recent results of our theoretical and observational studies based on Zeeman Doppler Imaging (ZDI), field extrapolation methods, wind simulations, and the modeling of planetary upper atmospheres.

scholarly journals Observational methods for stellar magnetism: from detection to cartography

2012 ◽  
Vol 8 (S294) ◽  
pp. 447-458 ◽  
Author(s):  
Klaus G. Strassmeier ◽  
Thorsten A. Carroll ◽  
Ilya Ilyin ◽  
Silva Järvinen
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Inverse Modeling ◽  
Doppler Imaging ◽  
Observational Methods ◽  
Related Data ◽  
Cool Stars ◽  
Stellar Magnetic Fields

AbstractWe review some of the currently used techniques to detect stellar magnetic fields on cool stars. Emphasis is put on spectropolarimetry with high-resolution spectrographs and its related data de-noising techniques and multi-line inverse modeling. Detections and results from Zeeman splittings and broadenings are briefly mentioned. We discuss some of our most recent Zeeman Doppler Imaging (ZDI) results and present a comparison of ZDI maps of the K-type WTTS V410 Tauri and the planet-hosting F8 star HD 179949 with results from other groups.

scholarly journals Stellar magnetic activity and their influence on the habitability of exoplanets

2014 ◽  
Vol 10 (S305) ◽  
pp. 333-339
Author(s):  
T. Lüftinger ◽  
M. Güdel ◽  
C. Johnstone
Keyword(s):  
Magnetic Fields ◽  
International Research ◽  
Planetary Systems ◽  
Magnetic Activity ◽  
Doppler Imaging ◽  
Research Network ◽  
Stellar Rotation ◽  
Theoretical Understanding ◽  
Points Of View ◽  
Stellar Magnetic Fields

AbstractStellar magnetism, explorable via polarimetry, is a crucial driver of activity, ionization, photodissociation, chemistry and winds in stellar environments. Thus it has an important impact on the atmospheres and magnetospheres of surrounding planets. Modeling of stellar magnetic fields and their winds is extremely challenging, both from the observational and the theoretical points of view, and only recent ground breaking advances in observational instrumentation - as were discussed during this Symposium - and a deeper theoretical understanding of magnetohydrodynamic processes in stars enable us to model stellar magnetic fields and winds and the resulting influence on surrounding planets in more and more detail. We have initiated a national and international research network (NFN): ‘Pathways to Habitability - From Disks to Active Stars, Planets to Life’, to address questions on the formation and habitability of environments in young, active stellar/planetary systems. In this contribution we discuss the work we are carrying out within this project and focus on how stellar magnetic fields, their winds and the relation to stellar rotation can be assessed observationally with relevant techniques such as Zeeman Doppler Imaging (ZDI), field extrapolation and wind simulations.

scholarly journals Doppler Imaging of stellar magnetic fields

2002 ◽  
Vol 389 (2) ◽  
pp. 420-438 ◽  
Author(s):  
O. Kochukhov ◽  
N. Piskunov ◽  
I. Ilyin ◽  
S. Ilyina ◽  
I. Tuominen
Keyword(s):  
Magnetic Fields ◽  
Doppler Imaging ◽  
Stellar Magnetic Fields

scholarly journals Zeeman Doppler Imaging

1993 ◽  
Vol 138 ◽  
pp. 247-257
Author(s):  
William Wehlau ◽  
John Rice
Keyword(s):  
Integral Equation ◽  
Magnetic Fields ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Spectral Lines ◽  
Doppler Imaging ◽  
Analytic Approximation ◽  
Line Profiles ◽  
Surface Mapping ◽  
Stellar Magnetic Fields

AbstractThe mapping of stellar surfaces using the observed profiles of spectral lines is described. The problem is expressed in terms of an integral equation to be solved, using Tikhonov’s method. The local line profiles may be given either by an analytic approximation or by the solution of the equation of transfer with a model atmosphere. The model atmospheres commonly used may not correctly represent the stellar atmosphere which may lead to errors in the derived surface maps. Tests of mapping programs and applications to real stars show the capabilities and limitations of surface mapping. Mapping stellar magnetic fields places more severe demands on the data and computational programs than mapping the abundance distributions.

scholarly journals Stellar magnetic fields from four Stokes parameter observations

2014 ◽  
Vol 9 (S307) ◽  
pp. 395-396
Author(s):  
N. Rusomarov ◽  
O. Kochukhov ◽  
N. Piskunov
Keyword(s):  
Magnetic Fields ◽  
Stokes Parameter ◽  
Doppler Imaging ◽  
Stokes Parameters ◽  
High Mass ◽  
Small Scale ◽  
Chemically Peculiar ◽  
New Information ◽  
Stellar Magnetic Fields ◽  
Ap Stars

AbstractMagnetic Doppler imaging (MDI) from observations of four Stokes parameters can uncover new information that is of interest to the evolution and structure of magnetic fields of intermediate and high-mass stars. Our MDI study of the chemically peculiar star HD 24712 from four Stokes parameter observations, obtained with the HARPSpol instrument at the 3.6-m ESO telescope, revealed a magnetic field with strong dipolar component and weak small-scale contributions. This finding gives evidence for the hypothesis that old Ap stars have predominantly dipolar magnetic fields.

scholarly journals The Evolution of Surface Magnetic Fields in Young Solar-type Stars

2015 ◽  
Vol 10 (S314) ◽  
pp. 113-116
Author(s):  
Colin P. Folsom ◽  
Pascal Petit ◽  
Jérôme Bouvier ◽  
Julien Morin ◽  
Agnès Lèbre ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Main Sequence ◽  
Open Clusters ◽  
Doppler Imaging ◽  
Clear Trend ◽  
Open Clusters And Associations ◽  
T Tauri ◽  
First Results ◽  
Solar Type ◽  
Stellar Magnetic Fields

AbstractSurface rotation rates of young solar-type stars display drastic changes at the end of the pre-main sequence through the early main sequence. This may trigger corresponding changes in the magnetic dynamos operating in these stars, which ought to be observable in their surface magnetic fields. We present here the first results of an observational effort aimed at characterizing the evolution of stellar magnetic fields through this critical phase. We observed stars from open clusters and associations, which range from 20 to 600 Myr, and used Zeeman Doppler Imaging to characterize their complex magnetic fields. We find a clear trend towards weaker magnetic fields for older ages, as well as a tight correlation between magnetic field strength and Rossby number over this age range. Comparing to results for younger T Tauri stars, we observe a very significant change in magnetic strength and geometry, as the radiative core develops during the late pre-main sequence.

scholarly journals Doppler Imaging of stellar magnetic fields

2002 ◽  
Vol 388 (3) ◽  
pp. 868-888 ◽  
Author(s):  
O. Kochukhov ◽  
N. Piskunov
Keyword(s):  
Magnetic Fields ◽  
Doppler Imaging ◽  
Stellar Magnetic Fields

scholarly journals Infrared Measurements of Stellar Magnetic Fields

1994 ◽  
Vol 154 ◽  
pp. 437-447 ◽  
Author(s):  
Steven H. Saar
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Pressure Support ◽  
Field Research ◽  
Future Directions ◽  
Rotation Rates ◽  
Infrared Measurements ◽  
Cool Stars ◽  
Rs Cvn Variables ◽  
Stellar Magnetic Fields

I review the advantages, techniques, and results of measurement of magnetic fields on cool stars in the infrared (IR). These measurements have generated several important results, including the following: the first data on the magnetic parameters of dMe and RS CVn variables; evidence for field strength confinement by photospheric gas pressure; support for the correlation between magnetic flux and rotation, with possible saturation at high rotation rates; indications of horizontal and/or vertical magnetic field structure; and evidence of spatial variations in B over a stellar surface. I discuss these results in detail, and suggest future directions for IR magnetic field research.

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