Context : Classical T Tauri stars ( CTTS ) are surrounded by actively accreting disks .
According to current models material falls along the magnetic field lines from the disk with more or less free-fall velocity onto the star , where the plasma heats up and generates X-rays .

Aims : We want to quantitatively explain the observed high energy emission and measure the infall parameters from the data .
Absolute flux measurements allow to calculate the filling factor and the mass accretion rate .

Methods : We use a numerical model of the hot accretion spot and solve the conservation equations .

Results : A comparison to data from XMM-Newton and Chandra shows that our model reproduces the main features very well .
It yields for TW Hya a filling factor of 0.3 % and a mass accretion rate 2 \times 10 ^ { -10 } M _ { \sun } \mathrm { yr } ^ { -1 } .

Conclusions :