Functionally the letter of submission accompanying an article submitted to a journal is promotional, but it does not have the form one would expect from e.g. Bhatia 1993. Instead it is extremely brief and uninformative. This reflects the so-called Utilitarian Discourse which is a shared feature of American culture and the subculture of science. Research published elsewhere (Okamura and Shaw 1999, ESPJ) shows that neither native speakers of English nor non-natives who were not practising scientists could produce the appropriate genre, while NNS scientists produced texts which only deviated slightly from those of NSE.
I E E E Transactions on Professional Communication, 1998, Vol 41, Issue 4, p. 277-279