  In the solar atmosphere, the jets are ubiquitous and found to be at various
spatia-temporal scales. They are significant to understand energy and mass
transport in the solar atmosphere. Recently, the high-speed transition region
jets are reported from the observation. Here we conduct a numerical simulation
to investigate the mechanism in their formation. Driven by the supergranular
convection motion, the magnetic reconnection between the magnetic loop and the
background open flux occurring in the transition region is simulated with a
two-dimensional magnetohydrodynamics model. The simulation results show that
not only a fast hot jet, much resemble the found transition region jets, but
also a adjacent slow cool jet, mostly like classical spicules, is launched. The
force analysis shows that the fast hot jet is continually driven by the Lorentz
force around the reconnection region, while the slow cool jet is induced by an
initial kick through the Lorentz force associated with the emerging magnetic
flux. Also, the features of the driven jets change with the amount of the
emerging magnetic flux, giving the varieties of both jets. These results will
inspire our understanding of the formation of the prevalence of both the fast
hot jet and slow cool jet from the solar transition region and chromosphere.
