We have analyzed all the observations of BP Tauri taken by the International Ultraviolet Explorer in the low resolution ( \bigtriangleup \lambda \sim 6 \AA ) , long wavelength ( from \lambda = 1850 \AA to \lambda = 3350 \AA ) range .
This dataset contains 61 spectra .
We observe variability in the ultraviolet continuum of \bigtriangleup m _ { cont . } \sim 1 magnitude and variability in the Mg ii line flux of \bigtriangleup m _ { MgII } \sim 0.8 magnitudes .
Moreover , these spectra do not show any correlation between the continuum flux and the Mg ii line flux , thus resolving a standing controversy in the literature concerning the origin of the Mg ii line flux .
There is no correlation between the color temperature of the UV continuum and the average value of its flux .
Using models of the accretion process developed by Calvet & Gullbring ( 1998 ) , we obtain energy fluxes , accretion spot sizes , and accretion rates from the IUE observations of BP Tauri .
We find average energy fluxes of 5.0 10 ^ { 11 } { ergs cm ^ { -2 } s ^ { -1 } } , average spot sizes of 4.4 10 ^ { -3 } times the stellar surface , and average accretion rates of 1.6 10 ^ { -8 } { { M _ { \odot } / yr } } .
Our analysis shows that the particle energy flux and the UV flux in the stellar surface are proportional to each other .
Most strikingly , we observe a correlation between accretion rate and spot size , with the spot size increasing as the square of the accretion rate .
Based on the results of a simulation , we conclude that geometrical effects ( i.e .
the varying inclination of the spot with respect to the observer ) are not enough to account for this effect .
Current models of the accretion process fail to reproduce such an effect , suggesting the need of using more realistic descriptions of the stellar field when treating magnetospheric accretion .
There may also be an unmodelled efficiency factor that determines how matter is loaded into the field lines .
Non-dipole fields , geometry , oblique shocks and the possibility of “ limb brightening ” should be taken into account when creating models and explaining the results of observations of T-Tauri stars .