Launching of conical winds and axial jets from the disc–magnetosphere boundary: axisymmetric and 3D simulations

By M. Romanova, G. V. Ustyugova, Alexander V. Koldoba, R. Lovelace. 2009

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We investigate the launching of outflows from the disc-magnetosphere boundary of slowly and rapidly rotating magnetized stars using axisymmetric and exploratory 3D magnetohydro-dynamic simulations. We find long-lasting outflows in the following cases. (1) In the case of slowly rotating stars, a new type of outflow, a conical wind, is found and studied in simulations. The conical winds appear in cases where the magnetic flux of the star is bunched up by the disc into an X-type configuration. The winds have the shape of a thin conical shell with a half-opening angle θ ∼ 30°-40°. About 10-30 per cent of the disc matter flows from the inner disc into the conical winds. The conical winds may be responsible for episodic as well as long-lasting outflows in different types of stars. There is also a low-density, higher velocity component (a jet) in the region inside the conical wind. (2) In the case of rapidly rotating stars (the 'propeller regime'), a two-component outflow is observed. One component is similar to the conical winds. A significant fraction of the disc matter may be ejected into the winds. The second component is a high-velocity, low-density magnetically dominated axiaL jet where matter flows along the opened polar field lines of the star. The jet has a mass flux of about 10 per cent of that of the conical wind, but its energy flux (dominantly magnetic) can be larger than the energy flux of the conical wind. The jet's angular momentum flux (also dominantly magnetic) causes the star to spin down rapidly. Propeller-driven outflows may be responsible for the jets in protostars and for their rapid spin-down. The jet is collimated by the magnetic force while the conical winds are only weakly collimated in the simulation region. Exploratory 3D simulations show that conical winds are axisymmetric about the rotational axis (of the star and the disc), even when the dipole field of the star is significantly misaligned.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2d9994be8336c2cf977189e7b82006f5e4c79cc7

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Citations in the corpus

Formation of Double Neutron Star Systems (2017, background): “For example, some of it may be lost from the system due to ejector or propeller effects, accretion disk instabilities and direct irradiation of the donors atmosphere from the pulsar (e.g. Illarionov & Sunyaev 1975; van Paradijs 1996; Dubus et al. 1999; Romanova et al. 2009).”
Episodic accretion on to strongly magnetic stars (2010, methodology): “…picture of a small interaction region with some reconnection was first proposed by Lovelace et al. (1995) and has been supported by 2D and 3D simulations of accretion discs interacting with a magnetic field (e.g. Hayashi et al. 1996; Goodson et al. 1997; Miller & Stone 1997; Romanova et al. 2009).”
MHD simulations of accretion onto a dipolar magnetosphere - II. Magnetospheric ejections and stellar spin-down (2012, background): “More recently, Romanova et al. (2009) developed both axisymmetric and three dimensional non-axisymmetric simulations that describe the formation of uncollimated outflows (“conical winds”) coming from the boundary of the closed magnetosphere, both for slowly and fast rotating stars.”
THE INTERPLAY OF MAGNETIC FIELDS, FRAGMENTATION, AND IONIZATION FEEDBACK IN HIGH-MASS STAR FORMATION (2010, background): “…& Tomisaka 2004; Machida et al. 2004; Banerjee & Pudritz 2006, 2007) or interactions between the disk field and protostellar magnetosphere, either at an X-point (Najita & Shu 1994; Shu et al. 1994, 2007; Cai et al. 2008) or in more general geometries (Lovelace et al. 1999; Romanova et al. 2009).”
Accretion dynamics and disk evolution in NGC 2264: a study based on the Corot photometric observations (2010, methodology): “Like AA Tau, the star-disk interaction is seen to be very dynamic on a rotational timescale, as predicted by MHD models of young magnetized star-disk systems (Goodson et al., 1999; Matt etl., 2002; Romanova et al., 2009; Zanni, 2009).”