NEW YORK (AP) — Gripped by fear of a new recession, the stock market suffered its worst day Thursday since the financial crisis in the fall of 2008. The Dow Jones industrial average fell more than 500 points, its ninth-steepest decline.The sell-off wiped out the Dow’s remaining gains for 2011. It put the Dow and broader stock indexes into what investors call a correction — down 10 percent from their highs in the spring.“We are continuing to be bombarded by worries about the global economy,” said Bill Stone, the chief investment strategist for PNC Financial.Across the financial markets, the day was reminiscent of the wild swings that defined the financial crisis in September and October three years ago.