By Josh Smith BUSAN, South Korea (Reuters) -A U.S. aircraft carrier arrived in South Korea on Friday for the first time in about four years, set to join other military vessels in a show of force intended to send a message to North Korea. USS Ronald Reagan and ships from its accompanying strike group docked at a naval base in the southern port city of Busan ahead of joint drills with South Korean forces. Its arrival marks the most significant deployment yet under a new push to have more U.S. “strategic assets” operate in the area to deter North Korea. Strike group commander Rear Admiral Michael…