By using a two-dimensional magnetized electron plasma simulation model it is found that an X mode which is presumed to be the dominant component of auroral kilometric radiation can parametrically decay into an electrostatic whistler and a Z mode. The electrostatic whistler grows to large amplitude, and the associated parallel electric field accelerates electrons to several kiloelectron volts. It is proposed that this mechanism is a possible origin of Z mode radiation, broadband electrostatic noise, and energetic parallel electron beams. ¿ American Geophysical Union 1993