FOREX-Dollar up vs yen on buy backs; yen's downtrend seen intact

SINGAPORE, Jan 24- The dollar rose against the yen on Thursday with traders attributing the move to position squaring by short-term players in the wake of the yen's bounce over the past couple of days. The yen had bounced earlier this week after the Bank of Japan was deemed to have disappointed by not immediately upsizing its asset-purchasing programme.