The S&P 500 was up 0.8% in midday trading to 2,057.16.
The Dow Jones Industrial Average was up 0.8% to 17,704.10.
The NASDAQ was up 0.5% to 4,856.49.
The yield on a 10-year Treasury bond was up 2.8% to 1.77%.
The price of gold was up 0.1% to $1,259.
Aliso Viejo-based Microsemi Corp. was down 3% to a market cap of $4 billion. Juniper Networks, a key customer of the chipmaker, lowered current-quarter revenue and income estimates on lower demand for enterprise computing products.
Newport Beach-based American Vanguard Corp. was up 5% to $16 and a $467 million market cap on high volume.