* Apple rallies, lifting S&P 500 and Nasdaq
* Weakness in Coca-Cola limits Dow's advance
* S&P 500 back above 200-day moving average
* Indexes up: Dow 0.6 pct, S&P 1.3 pct, Nasdaq 1.6 pct
By Ryan Vlastelica
NEW YORK, Oct 21 (Reuters) - U.S. stocks rallied on Tuesday, with the S&P 500 on track for a fourth straight session of gains as Apple and Texas Instruments jumped following their results.
The results gave an outsized boost to the tech-heavy Nasdaq index, but the Dow's gains were limited by a selloff in Coca-Cola shares.
The S&P 500 has gained 3.5 percent over the past four sessions, rebounding after a four-week decline that took the benchmark index down nearly 10 percent from its intraday record.
In a sign that momentum is turning more positive, the S&P returned back above its 200-day and 14-day moving averages, while the CBOE Volatility index fell 10 percent to 16.71. The VIX was below one-month VIX futures for the first time since Oct. 8.
Apple Inc rose 2.4 percent to $102.20 in heavy trading a day after revenue topped expectations, helped by strong sales of its iPhone line. It also gave a strong outlook for the holiday quarter.
"Apple gave a good guidance. Any fund manager who is underweight on Apple is probably rethinking that position today," said Michael Binger, senior portfolio manager at Minneapolis-based Gradient Investments, which owns Apple stock.
Chipmaker Texas Instruments' shares rose 3.4 percent to $45.91 after its revenue beat forecasts, easing concerns about weak industry demand following IBM's results.
On the downside, Dow components Coca-Cola Co and McDonald's Corp both fell following their results, with currency exchange rates a concern for both. Coca-Cola fell 6.2 percent to $40.61 in its biggest one-day decline since October 2008. McDonald's lost 0.5 percent to $91.15.
"The earnings season is kind of average so far, and we're starting to see the strong dollar hurt stocks like McDonald's and Coke," Binger said. "The world is a little different because of slowing overseas, but I'd use any pullback as a buying opportunity."
While earnings have largely come in strong so far this quarter, concerns continue to swirl over the pace of global economic growth. China's gross domestic product grew 7.3 percent in the third quarter, the slowest pace since the first quarter of 2009.
At 11:12 a.m. the Dow Jones industrial average rose 103.85 points, or 0.63 percent, to 16,503.52, the S&P 500 gained 24.05 points, or 1.26 percent, to 1,928.06 and the Nasdaq Composite added 69.72 points, or 1.62 percent, to 4,385.80.
U.S. existing home sales rose 2.4 percent in September, above expectations, hitting their highest level in a year. The PHLX Housing index rose 1.3 percent.
Advancing issues outnumbered declining ones on the NYSE by 2,422 to 540, for a 4.49-to-1 ratio on the upside; on the Nasdaq, 1,884 issues rose and 623 fell for a 3.02-to-1 ratio favoring advancers.
The benchmark S&P 500 index was posting 13 new 52-week highs and 1 new low; the Nasdaq Composite was recording 30 new highs and 17 new lows. (Editing by Nick Zieminski)