The lithium flash - Thermal instabilities generated by lithium burning in RGB stars

We present a scenario to explain the lithium-rich phase which occurs on the red giant branch at the so-called bump in the luminosity function. The hig h transport coefficients required to enhance the surface lithium abundance are obtained in the framework of rotation-induced mixing thanks to the impu lse of the important nuclear energy released in a lithium burning shell. Un der certain conditions a lithium ash is triggered off. The enhanced mass lo ss rate due to the temporary increase of the stellar luminosity naturally a ccounts for a dust shell formation.