Coronal lines and the structure of an upper atmosphere of T Tauri type stars

The relations are obtained, allowing to determine the parameters of stellar coronae from intensities of the strongest forbidden coroanal lines. A joint analysis of the UV and X-ray observations together with the results of searches of coronal lines in the case of T Tau stars is performed. It is shown that thermal conductivity plays a negligible role in the energy balance in the atmospheres of these stars at T> or approximately 2x105 K. The prospects for the search of coronal lines in the spectra of T Tau stars are discussed. It is expedient to look for Si 8 1445.8 A and Fe 19 1118.1 A lines in UV range according to spectrograms obtained under condtions of high resolution. The value of equivalent width on the order of 20-30 mA can be expected for Fe 13 107456 A line in infrared range. Reliable conclusions about the structure of the upper atmosphere of T Tauri type stars and the properties of near-star shell can be obtained only after synchronous observation in all spectral ranges using the best of available instruments