  Particle-in-cell code, EPOCH, is used for studying features of the wave
component evident to propagate backwards from the front of the non-gyrotropic,
relativistic beam of electrons injected in the Maxwellian, magnetised
background plasma with decreasing density profile. According to recent findings
presented in Tsiklauri (2011), Schmitz & Tsiklauri (2013) and Pechhacker &
Tsiklauri (2012), in a 1.5-dimensional magnetised plasma system, the
non-gyrotropic beam generates freely escaping electromagnetic radiation with
properties similar to the Type-III solar radio bursts. In this study the
backwards propagating wave component evident in the perpendicular components of
the elecromagnetic field in such a system is presented for the first time.
Background magnetic field strength in the system is varied in order to prove
that the backwards propagating wave's frequency, prescribed by the whistler
wave dispersion relation, is proportional to the specified magnetic field.
Moreover, the identified whistlers are shown to be generated by the normal
Doppler-shifted relativistic resonance. Large fraction of the energy of the
perpendicular electromagnetic field components is found to be carried away by
the whistler waves, while a small but sufficient fraction is going into L- and
R- electromagnetic modes.
