  Plasma emission (PE), i.e., electromagnetic radiation at the plasma frequency
and its second harmonic, is a general process occurring in both astrophysical
and laboratory plasmas. The prevailing theory presents a multi-stage process
attributed to the resonant coupling of beam-excited Langmuir waves with
ion-acoustic waves. Here we examine another possibility of the fundamental PE
induced by the resonant coupling of Z-mode and whistler (W) waves. Earlier
studies have been controversial in the plausibility and significance of such
process in plasmas. In this study we show that the matching condition of three
wave resonant interaction (Z+W ! O) can be satisfied over a wide regime of
parameters based on the magnetoionic theory, demonstrate the occurrence of such
process and further evaluate the rate of energy conversion from the pumped Z or
W mode to the fundamental O mode with particle-in-cell (PIC) simulations of
wave pumping. The study presents an alternative form of the fundamental PE,
which could possibly play a role in various astrophysical and laboratory
scenarios with both Z and W modes readily excited through the electron
cyclotron maser instability.
