Dynamics of slender magnetic flux tubes ( MFT ) in the accretion discs of T Tauri stars is investigated .
We perform simulations taking into account buoyant , aerodynamic and turbulent drag forces , radiative heat exchange between MFT and ambient gas , magnetic field of the disc .
The equations of MFT dynamics are solved using Runge-Kutta method of the fourth order .
The simulations show that there are two regimes of MFT motion in absence of external magnetic field .
In the region r < 0.2 au , the MFT of radii 0.05 \leq a _ { 0 } \leq 0.16 H ( H is the scale height of the disc ) with initial plasma beta of 1 experience thermal oscillations above the disc .
The oscillations decay over some time , and MFT continue upward motion afterwards .
Thinner or thicker MFT do not oscillate .
MFT velocity increases with initial radius and magnetic field strength .
MFT rise periodically with velocities up to 5-15 km s ^ { -1 } and periods of 0.5 - 10 yr determined by the toroidal magnetic field generation time .
Approximately 20 % of disc mass and magnetic flux can escape to disc atmosphere via the magnetic buoyancy over characteristic time of disc evolution .
MFT dispersal forms expanding magnetized corona of the disc .
External magnetic field causes MFT oscillations near the disc surface .
These magnetic oscillations have periods from several days to 1-3 months at r < 0.6 au .
The magnetic oscillations decay over few periods .
We simulate MFT dynamics in accretion discs in the Chameleon I cluster .
The simulations demonstrate that MFT oscillations can produce observed IR-variability of T Tauri stars .