(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window.) * Alphabet rallies after results * Volatility index eases (Updates to close) Feb 3 (Reuters) - The S&P 500 ended higher on Wednesday, registering a third straight session of gains, with Alphabet Inc’s shares jumping following its strong quarterly results. Alphabet shares rose a day after its results, as it benefited from lockdowns that drove retail and other advertisers online. S&P 500 companies are on track to post earnings growth for the fourth quarter of 2020, data from Refinitiv showed on Wednesday, which would defy expectations for profits to drop 10% due to the pandemic. The Cboe Volatility index eased, and wild swings in stock prices of GameStop and other social media favorites subsided following a recent trading frenzy. “The broad tape continues to be strong,” said Michael O’Rourke, chief market strategist at JonesTrading in Stamford, Connecticut. The recent retail trading activity is likely “to be here for a while,” said O’Rourke. “I don’t know if it’s going to be here with the same intensity ... It’s hard to maintain that type of intensity. What we’ll probably see are coordinated movements in individual names by that crowd.” Amazon.com Inc shares eased as Jeff Bezos’ surprise move to step down as chief executive quashed optimism about bumper quarterly results. However, analysts were upbeat on the promotion of its cloud computing head to the top job. Unofficially, the Dow Jones Industrial Average rose 35.13 points, or 0.11%, to 30,722.61, the S&P 500 gained 3.77 points, or 0.10%, to 3,830.08 and the Nasdaq Composite dropped 2.23 points, or 0.02%, to 13,610.54. U.S. Treasury Secretary Janet Yellen is calling a meeting this week of top officials, including from the U.S. Securities and Exchange Commission and the Federal Reserve, to discuss market volatility driven by retail trading in shares of GameStop, silver and other stocks favored on social media. The SEC is reviewing social media posts for signs of potential fraud behind the recent trade frenzy in shares of GameStop and other companies, according to a Bloomberg News report, citing people familiar with the matter. U.S. President Joe Biden told congressional Democrats he would not back down on including $1,400 checks for struggling Americans in his COVID-19 relief plan but would consider tighter limits on who gets them, lawmakers and aides said. On the economic front, the ADP Report showed hiring by U.S. private employers rebounded by 174,000 in January after a drop in December. A more comprehensive jobs report is expected on Friday. A separate ISM survey showed U.S. services industry activity raced to its highest level in nearly two years in January. (Additional reporting by Devik Jain and Medha Singh in Bengaluru; Editing by Maju Samuel and Diane Craft)