  The magnon gas created by spatially localized longitudinal parametric pumping
in an yttrium-iron-garnet film is probed by a traveling packet of spin waves
non-resonant with the pumping field. The analysis of the influence of the
magnon gas on the amplitude and phase of the propagating spin waves allows to
determine characteristic properties of the parametrically pumped magnon gas. A
simple theoretical model is proposed from which the magnon density in the
pumping region is calculated.
