The bunching of giant planets at a distance of several stellar radii may be explained by the disruption of the inner part of the disk by the magnetosphere of the star during the T Tauri stage of evolution .
The rotating magnetic field of the star gives rise to a low density magnetospheric gap where stellar migration is strongly suppressed .
We performed full 3D magnetohydrodynamic simulations of the disk-magnetosphere interaction and examined conditions for which the magnetospheric gap is “ empty ” , by changing the misalignment angle between magnetic and rotational axes of the star , \Theta , and by lowering the adiabatic index \gamma , which mocks up the effect of heat conductivity and cooling .
Our simulations show that for a wide range of plausible conditions the gap is essentially empty .
However , in the case of large misalignment angles \Theta , part of the funnel stream is located in the equatorial plane and the gap is not empty .
Furthermore , if the adiabatic index is small ( \gamma \sim 1.1 ) and the rotational and magnetic axes are almost aligned , then matter penetrates through the magnetosphere due to 3D instabilities forming high-density equatorial funnels .
For these two limits there is appreciable matter density in the equatorial plane of the disk so that a planet may migrate into the star .