A popular gauge of volatility on Wall Street, known as the fear index, on Thursday jumped to its highest level since February as stocks tanked on the back of mounting global-growth fears. The CBOE Volatility Index VIX, +6.40% , which uses S&P 500 bullish and bearish options to calculate expectations for volatility over the coming 30 days, was at 25.73, up 24%, in recent trade, which would mark its highest level (on a closing basis) since Feb. 9, according to FactSet data. The volatility index, referring to its popular ticker symbol, tends to maintain an inverse correlation to equity prices, and the jump comes as stocks are in free-fall. The Dow Jones Industrial Average DJIA, -1.92% was down 655 points, or 2.5%, at 24,407, coming after the blue-chip benchmark shed 800 points on Tuesday. Markets were closed on Wednesday to mark a national day of mourning for 41st U.S. President George Herbert Walker Bush, who died at 94. Meanwhile, on Thursday, the S&P 500 index SPX, -2.37% was down 2.3% at 2,639, while the Nasdaq Composite Index COMP, -3.01% traded 1.7% lower at 7,037.