  We demonstrate the differences in hot electron absorption mechanisms dominant
in the interaction of femtosecond laser pulse with intensities 1e18 W/cm2 and
1e21 W/cm2 on fully ionized target with steep density profile and preplasma
with moderate scale length (3 microns). We show that acceleration of each
electron starts at the moment when magnetic component of standing
electromagnetic wave changes its polarity in regime without preplasma. In the
presence of preplasma the stochastic heating is the dominant absorption
mechanism along with the longitudinal electric field. It is observed, that
wave's energy is absorbed only if standing wave is already created at the
position of electron during the interaction with the pulse with intensity 1e18
W/cm2. In the case with intensity 1e21 W/cm2, part of electrons is
pre-accelerated in front of the target before the reflection and following
stochastic heating. The presence of preplasma results in electron temperatures
close to or even exceeding ponderomotive scaling. At higher intensity, the
re-injection of electrons previously repelled by incident wave's ponderomotive
force into high-field regions is allowed if standing wave is created.
