Issuance of prime non-agency mortgage securities rose 8.1 percent in the third quarter of 2004, despite an overall downturn in primary market lending. According to a new ranking and analysis by Inside MBS & ABS, Countrywide Financial remained the top issuer in the prime non-agency MBS sector, which includes traditional jumbo private-label deals and the growing Alternative A market. Countrywide paced the market with $36.56 billion in year-to-date issuance through the first nine months of…