  We confirm the principal difference of the initiation phase between the
impulsive and gradual CME motion trajectory revealed earlier in preliminary
studies. Based on studying the dynamics of two impulsive CME (25 March 2008 and
13 June 2010), and also the MHD-approximation computations, we have come to a
conclusion that forming impulsive CME starts under the solar photosphere and
may be associated with supersonic emergence of magnetic tubes from the
convective region. A radial velocity of such tubes at the photosphere level can
reach hundreds of km s$^{-1}$, and their angular size $d\approx$ (1-3)$^\circ$.
A probable reason of their rise from the convective region is the "slow wave"
instability (the Parker instability).

Solar and Stellar Astrophysics