  We demonstrate that laser reflection acts as a catalyst for
superponderomotive electron production in the preplasma formed by relativistic
multipicosecond lasers incident on solid density targets. In 1D
particle-in-cell simulations, high energy electron production proceeds via two
stages of direct laser acceleration, an initial stochastic backward stage, and
a final non-stochastic forward stage. The initial stochastic stage, driven by
the reflected laser pulse, provides the pre-acceleration needed to enable the
final stage to be non-stochastic. Energy gain in the electrostatic potential,
which has been frequently considered to enhance stochastic heating, is only of
secondary importance. The mechanism underlying the production of high energy
electrons by laser pulses incident on solid density targets is of direct
relevance to applications involving multipicosecond laser-plasma interactions.
