All of the stochastic terms in Eqs. ͑25a͒-͑25c͒ consist of integrals of the noise process into the past ͑convolutions͒, as given by Eqs. ͑26͒ and ͑27͒. These memory integrals are fast-time processes. Since we are interested in the long term slow processes and since the expectation of G equals e −Ꭽ ‫ء‬ E͓͔, where E͓͔ = 0, we neglect the memory integrals and the higher-order multiplicative terms found in Eqs. ͑25a͒-͑25c͒ so that