Pre-main sequence dynamos and relic magnetic fields of solar-type stars

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29 Citations (Scopus)

Abstract

We argue that contemporary magnetic fields in the radiative cores of solar-type stars are relics of hydromagnetic dynamos operating over the pre-main sequence epoch when the core formed. Simulations of differential rotation and dynamos of a 1 M. star are performed for a sequence of evolutionary stages of the core-growth epoch. A big difference in the dynamo-generated field between the initial and final stages of the core formation is predicted. An axisymmetric and cyclic field similar to the present day Sun is excited in a star with a mature radiative zone. An infant Sun with its core just starting to grow generates a nonaxisymmetric global field which is steady in a rotating frame. A qualitative explanation for the nonaxisymmetry is suggested. A model for the field capturing by the growing core is designed. The internal field is most efficiently captured over the initial phase when the core grows most rapidly. A nonaxisymmetric global relic field with an amplitude somewhat below 1 G is predicted for a main-sequence star of solar mass. An interpretation of the active longitude phenomenon as observed on the Sun and stars in terms of the nonaxisymmetric relic field is suggested.

Original languageEnglish
Pages (from-to)250-258
Number of pages9
JournalAstronomy & Astrophysics
Volume374
DOIs
Publication statusPublished - Jul 2001

Keywords

  • stars : magnetic fields
  • stars : rotation
  • stars : interiors
  • stars : evolution
  • Sun : magnetic fields
  • MHD
  • STELLAR RADIATIVE ZONES
  • T-TAURI STARS
  • DIFFERENTIAL ROTATION
  • SPIN-DOWN
  • EVOLUTION
  • MODELS
  • STABILITY
  • CONVECTION
  • TRANSPORT

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