The Origin of MHD Jets in T Tauri Stars

S. Cabrit, J. Ferreira, C. Dougados, N. Pesenti, P. J. V. Garcia

Resumo
In this contribution, we consider stationary MHD ejection models from the disk surface, the star-disk corotation region (``X-wind''), and the star itself. We compare their predicted angular momentum and poloidal speeds with recent observations of T Tauri jet kinematics, and review the resulting constraints on the launch radius, magnetic lever-arm, and heat deposition in the jet (see Ferreira et al. 2005 for more details).

Cold MHD disk winds are found to predict excessive rotation in T Tauri jets and are definitely excluded, while warm MHD disk winds (including heating at the disk surface) with moderate magnetic lever arms λ = (rA/r0)² ~= 6 - 20 reproduce very well both the observed rotation signatures and poloidal speeds, if launching radii extend to r0 ~= 0.1-3 AU. Both stellar winds and X-winds are challenged by the range of poloidal speeds in T Tauri jets: It should be checked if stellar winds can accelerate the observed jet mass-flux without excessive radiative losses, and if X-winds can sweep-up enough ambient gas to explain the intermediate-velocity components towards jet edges.

We also show that, contrary to common belief, warm self-similar disk winds are capable of reproducing the collimation, line profiles, and ejection/accretion ratio in T Tauri jets. Implications of the steady warm disk-wind hypothesis on physical conditions in T Tauri disks (e.g. the required magnetic flux) are recalled.

Magnetic Fields in the Universe: From Laboratory and Stars to Primordial Structures
(Eds.) E. Dal Pino, G. Lugones, A. Lazarian

AIP Conference Proceedings
Vol. 784, Página 215
2005

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