  It is proposed that planetesimals perturbed by Jovian mean-motion resonances
are the source of shock waves that form chondrules. It is considered that this
shock-induced chondrule formation requires the velocity of the planetesimal
relative to the gas disk to be on the order of > 7 km/s at 1 AU. In previous
studies on planetesimal excitation, the effects of Jovian mean-motion resonance
together with the gas drag were investigated, but the velocities obtained were
at most 8 km/s in the asteroid belt, which is insufficient to account for the
ubiquitous existence of chondrules. In this paper, we reexamine the effect of
Jovian resonances and take into account the secular resonance in the asteroid
belt caused by the gravity of the gas disk. We find that the velocities
relative to the gas disk of planetesimals a few hundred kilometers in size
exceed 12 km/s, and that this is achieved around the 3:1 mean-motion resonance.
The heating region is restricted to a relatively narrow band between 1.5 AU and
3.5 AU. Our results suggest that chondrules were produced effectively in the
asteroid region after Jovian formation. We also find that many planetesimals
are scattered far beyond Neptune. Our findings can explain the presence of
crystalline silicate in comets if the scattered planetesimals include silicate
dust processed by shock heating.
