Discrete mass ejections in Be stars

HeI lines are currently used to study the atmospheric activity of Be stars, in particular their non radial pulsation phenomena. Moreover, the HeI 6678 line is quite sensitive to mass ejections, as revealed by the presence of emission components in the wings. In the present paper we show that the highly variable aspect of the emission in the HeI 6678 line, as well as the changes of the photospheric like absorption component, can be due to orbiting clouds ejected by the star. The modeling of the variability of the HeI 6678 line could then help to estimate the strength of the magnetic field needed to maintain the ejected clouds, as it is meant, in nearly rigid rotation with the underlying star.