  Buoyancy of the fossil magnetic field in the accretion disks of young stars
is investigated. It is assumed that the Parker instability leads to the
formation of slender flux tubes of toroidal magnetic field in the regions of
effective magnetic field generation. Stationary solution of the induction
equation is written in the form in which buoyancy is treated as the additional
mechanism of the magnetic flux escape. We calculate the fossil magnetic field
intensity in the accretion disks of young T Tauri stars for the cases when
radius of the magnetic flux tubes $a_{\mathrm{mft}} = 0.1H$, $0.5 H$ or $1H$,
where $H$ is the accretion disk height scale. Calculations show that the
buoyancy limits toroidal magnetic field growth, so that its strength is
comparable with the vertical magnetic field strength for the case
$a_{\mathrm{mft}}=0.1H$.
