Indexes were up in midday trading as European markets closed higher yesterday ahead of the U.K.’s vote today on European Union membership.

The S&P 500 was up 0.9% to 2,103.89. The Dow Jones Industrial Average was up 0.9% to 17,934.87, and the NASDAQ was up 1.1% to 4,886.70.

The yield on a 10-year Treasury bond was up 2.8% to 1.73%.

The price of gold was down 0.6% to $1,263.

TECHNOLOGY

Irvine-based Western Digital Corp. was up 5.3% to $50.90 and a $14.2 billion market cap on moderate volume. The storage products maker’s shares are up about 40% since closing its acquisition of SanDisk Corp. last month.

FINANCE

Irvine-based Impac Mortgage Holdings Inc. was up 6.4% to $15.78 and a $194 million market cap on moderate volume. The company is a residential lender.