Rayleigh-Taylor-Unstable Accretion and Variability of Magnetized Stars: Global Three-Dimensional Simulations

Journal Article · Wed Oct 29 00:00:00 EDT 2008 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3031212· OSTI ID:21251786

Kulkarni, A K; Romanova, M M ^[1]

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1. Dept. of Astronomy, Cornell University, Ithaca, NY 14853 (United States)

We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It produces tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the tongues changes with time on the inner-disk dynamical timescale. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator. The instability appears for relatively small misalignment angles, {theta} < or approx. 30 deg., between the star's rotation and magnetic axes, and is associated with higher accretion rates. The hot spots and light curves during accretion through instability are generally much more chaotic than during stable accretion. The unstable state of accretion has possible implications for quasi-periodic oscillations and intermittent pulsations from accreting systems.

• OSTI ID: 21251786
• Journal Information: AIP Conference Proceedings, Vol. 1068, Issue 1; Conference: Workshop on a decade of accreting millisecond X-ray pulsars, Amsterdam (Netherlands), 14-18 Apr 2008; Other Information: DOI: 10.1063/1.3031212; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

97 MATHEMATICAL METHODS AND COMPUTING
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ACCRETION DISKS
CHAOS THEORY
EQUATOR
HOT SPOTS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
PERIODICITY
POLAR REGIONS
PULSATIONS
RAYLEIGH-TAYLOR INSTABILITY
ROTATION
SIMULATION
STARS
THREE-DIMENSIONAL CALCULATIONS