A model is developed for magnetic, "propeller"-driven outflows that cause a rapidly rotating magnetized star accreting from a disk to spin-down. Energy and angular momentum lost by the star goes into expelling most of the accreting disk matter. The theory gives an expression for the effective Alfvén radius RA (where the inflowing matter is effectively stopped), which depends on the mass accretion rate, the star's mass and magnetic moment, and the star's rotation rate. The model points to a mechanism for "jumps" between spin-down and spin-up evolution and for the reverse transition, which are changes between two possible equilibrium configurations of the system. In, for example, the transition from spin-down to spin-up states, the Alfvén radius RA decreases from a value larger than the corotation radius to one that is smaller. In this transition the "propeller" goes from being "on" to being "off." The ratio of the spin-down to spin-up torque (or the ratio for the reverse change) in a jump is shown to be of order unity.
CITATION STYLE
Lovelace, R. V. E., Romanova, M. M., & Bisnovatyi‐Kogan, G. S. (1999). Magnetic Propeller Outflows. The Astrophysical Journal, 514(1), 368–372. https://doi.org/10.1086/306945
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