Voltage noise of the Bi 2 Sr 2 CaCu 2 O 8+x single crystal below T c is analysed by an asymptotic power spectrum method. The low-frequency noise power, S v (T ), shows a peak at T = T p . This peak is found to be closely related to the vortex lattice melting temperature. Near the peak T = T p the power spectrum, S v (f ), exhibits a power-law fall-off, while at much lower temperatures S v (f ) dramatically deviates from the power-law behaviour, showing some broad peaks which are superposed upon a background with an exponential-law characteristic. The estimated correlation dimension of the noise data reveals that the vortex motion is highly correlated at the early stage of melting, then develops into an extended dissipative dynamic system with self-organized criticality, showing a 1/f α behaviour. The correlated motion disappears when the lattice completely melts.

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