Published by Jamie JemmesonThe dollar soared against the yen in global forex trading this morning (September 15th) after the Bank of Japan (BOJ) began buying the greenback.Reuters reports that traders have witnessed the BOJ buying dollars intermittently as part of a direct strategy to stop the rise of the yen, which has traded at a 15-year high against the dollar once more this week.One trader told the news agency: "The immediate impact from the intervention looks very big, but then the yen will likely eventually go back to the strong side as the actual problem exists in the dollar."Early estimates as to the size of the BOJ's yen selloff differed considerably, with some analysts putting forward predictions as high as 500 billion yen, while others put the figure closer to 100 billion yen.Japanese policymakers have been hinting at currency intervention for some time, but there is considerable concern that attempts to deflate the yen would be ineffective without coordinated international support.For more information on international payments, visit our Smart FX site.