The solid curves denote the accretion radii for different eccentricities (e = 0.1,0.3,0.5,0.7). Dashed curves show the variations of the clump sizes in the same systems. Phase 0 corresponds to apastron passages. The orbital period is fixed as P_orb = 15 d. With this P_orb, the clump size is larger than that of the accretion radius when the eccentricity is low. Hence, flares rarely occur for these low e cases. On the other hand, when e is higher, the size of accretion radius becomes larger than clump size and the outburst may occur. This size-relation is reflected in Fig. 1.