  We have studied the hard X-ray variability of the soft X-ray transient GRO
J0422+32 with BATSE in the 20-100 keV energy band. Our analysis covers 180 days
following the first X-ray detection of the source on 1992 August 5, fully
covering its primary and secondary X-ray outburst. We computed power density
spectra (PDSs) in the 20-50, 50-100, and 20-100 keV energy bands, in the
frequency interval 0.002-0.488 Hz. The PDSs of GRO J0422+32 are approximately
flat up to a break frequency, and decay as a power law above, with index ~1.
The canonical anticorrelation between the break frequency and the power density
at the break, observed in Cyg X-1 and other BHCs in the low state, is not
observed in the PDSs of GRO J0422+32. We compare our results with those of
similar variability studies of Cyg X-1. The relation between the spectral slope
and the amplitude of the X-ray variations of GRO J0422+32 is similar to that of
Cyg X-1; however, the relation between the hard X-ray flux and the amplitude of
its variation is opposite to what has been found in Cyg X-1. Phase lags between
the X-ray flux variations of GRO J0422+32 at high and low photon energies,
could only be derived during the first 30 days of its outburst. During this
period, the variations in the 50-100 keV lag those in the 20-50 keV energy band
by an approximately constant phase difference of 0.039(3) rad in the frequency
interval 0.02-0.20 Hz.
