The in-limbo markets finally got their answer: The Federal Reserve said today it will indeed try to juice the economy with an aggressive new round of bond-buying. The difference this time, explains the Wall Street Journal, is that it's not buying a set amount—this is "an open-ended program to buy bonds until the economy improves." Specifically, the Fed will purchase $40 billion in mortgage-backed securities each month. As expected, the Fed also plans to keep interest rates low for the foreseeable future. The Dow jumped 50 points in the first few minutes after the announcement and seemed on track for a strong day. (More Federal Reserve stories.)