  This study investigates that a characteristic time scale on an exchange rate
market (USD/JPY) is examined for the period of 1998 to 2000. Calculating power
spectrum densities for the number of tick quotes per minute and averaging them
over the year yield that the mean power spectrum density has a peak at high
frequencies. Consequently it means that there exist the characteristic scales
which dealers act in the market. A simple agent model to explain this
phenomenon is proposed. This phenomena may be a result of stochastic resonance
with exogenous periodic information and physiological fluctuations of the
agents. This may be attributed to the traders' behavior on the market. The
potential application is both quantitative characterization and classification
of foreign currency markets.
