Magnetic Field Amplification Via Protostellar Disc Dynamos

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We numerically investigate the generation of a magnetic field in a protostellar disc via an αΩ-dynamo and the resulting magnetohydrodynamic (MHD) driven outflows. We find that for small values of the dimensionless dynamo parameter αd, the poloidal field grows exponentially at a rate σ∝ΩKαd−−√, before saturating to a value αd−−√. The dynamo excites dipole and octupole modes, but quadrupole modes are suppressed, because of the symmetries of the seed field. Initial seed fields too weak to launch MHD outflows are found to grow sufficiently to launch winds with observationally relevant mass fluxes of the order of 10−9M⊙yr−1 for T Tauri stars. This suggests that αΩ-dynamos may be esponsible for generating magnetic fields strong enough to launch observed outflows.


Accretion; Accretion discs; Dynamo; MHD; Stars: Magnetic Field; Stars; Protostars; Stars: Winds, outflows


Astrophysics and Astronomy

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