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Measurements of magnetic fields on T Tauri stars

Published online by Cambridge University Press:  01 May 2007

Christopher M. Johns–Krull
Christopher M. Johns–Krull*
Affiliation:
Physics and Astronomy Department, Rice University, Houston, TX 77005, USA email: cmj@rice.edu
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Abstract

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Stellar magnetic fields including a strong dipole component are believed to play a critical role in the early evolution of newly formed stars and their circumstellar accretion disks. It is currently believed that the stellar magnetic field truncates the accretion disk several stellar radii above the star. This action forces accreting material to flow along the field lines and accrete onto the star preferentially at high stellar latitudes. It is also thought that the stellar rotation rate becomes locked to the Keplerian velocity near the radius where the disk is truncated. This paper reviews recent efforts to measure the magnetic field properties of low mass pre-main sequence stars, focussing on how the observations compare with the theoretical expectations. A picture is emerging indicating that quite strong fields do indeed cover the majority of the surface on these stars; however, the dipole component of the field appears to be alarmingly small. On the other hand, at least one accretion model which takes into account the non-dipole nature of the magnetic field provides predictions relating various stellar and accretion parameters which are present in the current data.

Keywords

Accretionaccretion disksstars: formationstars: magnetic fieldsstars: pre–main-sequence
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S243: Star-Disk Interaction in Young Stars , May 2007 , pp. 31 - 42
Copyright
Copyright © International Astronomical Union 2007

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