  The Halpha line emission formation region in the circumstellar disc of alpha
Eri is: a) extended with a steep outward matter density decline during low
H$\alpha$ emission phases; b) less extended with rather constant density
distribution during the strong Halpha emission. The long-term variation of the
Halpha emission has a 14-15 year cyclic B-Be phase transition. The disc
formation time scales agree with the viscous decretion model. The time required
for the disc dissipation is longer than expected from the viscous disc model.
