It has been previously demonstrated that an upgoing loss cone in the auroral electron population can be unstable to Z mode radiation. In this paper we propose that the specific electrons responsible for high-altitude (~4 RE, geocentric) Z mode radiation are diffuse auroral electrons which form an upgoing loss cone free energy region. These waves have frequencies &ohgr; greater than the local electron cyclotron frequency &OHgr;e, and based on previous growth rate calculations, have maximum growth rates &ggr;~10-3&OHgr;e. We employ a model of diffuse auroral electrons with a number density of (0.1 cm-3 and thermal energy of 1 keV. Assuming that the upgoing free energy region in velocity space is limited to electrons with energies of <10 keV, we show that the fastest growing Z mode waves have &OHgr;e<&ohgr;<1.02 &OHgr;e and are generated in regions where 0.2<&OHgr;pc/&OHgr;e<1.4. In addition, we estimate the amplification length of the fastest growing Z mode waves to be ~100 km, which is sufficient for Z mode radiation to grow to the intensities observed by satellites at 3--5 RE geocentric altitude in the auroral regions.