MHD instabilities at the disk-magnetosphere boundary: 3D simulations

We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a large range of parameter values. It manifests itself in the form of tall, thin tongues of plasma that reach the star by penetrating through the magnetosphere in the equatorial plane. The tongues rotate around the star in the equatorial plane, and their shape and number changes with time on inner-disk dynamical timescales. In contrast with funnel flows, which deposit matter mainly in the polar region, the tongues deposit matter much closer to the stellar equator.