Astron. Astrophys. 358, 1027-1034 (2000)

X-ray activity in T-Tauri stellar magnetospheres

G.T. Birk, D. Schwab, H. Wiechen and H. Lesch

Institut für Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, 81679 München, Germany

Received 18 January 2000 / Accepted 13 April 2000

Abstract

X-ray flares belong to magnetic activity phenomena that are characteristic for T-Tauri stars. The relatively strong magnetic fields of T-Tauri magnetospheres can be regarded as the primary energy source for the flares. The energy can be converted to particle acceleration and plasma heating by reconnection events in twisted flux tubes that connect the central object and the circumstellar disk. Considering the whole range of the dynamic plasma parameters involved, i.e. the partially ionized dusty plasma regime, the partially ionized dust-free one and eventually, the totally ionized one, it becomes obvious that the localized dissipation of free magnetic energy is efficient and fast enough to overcome the radiative cooling. Model results that take into account ionization as well as dust evaporation/sublimation and the temporal varying resistivity indicate that in course of the dynamics of the resistive tearing instability the plasma in magnetospheric flux tubes can be heated up to X-ray temperatures.

Key words: X-rays: stars stars: flare stars: magnetic fields

Send offprint requests to: G.T. Birk

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Contents

• 1. Introduction
• 2. Energy conversion caused by magnetic reconnection: heating versus cooling
  • 2.1. First step: the dusty plasma regime
  • 2.2. Second step: the dust-free regime
  • 2.3. Model results
• 3. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000
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