As I mentioned in today's edition of Options Update: Solarfun Power (SOLF), speculative investors are piling into call options on solar stocks today. Not only has SOLF attracted some bullish attention, but so has Canadian Solar (CSIQ), despite negative comments from several brokerage firms.

Two other solar-sector members receiving a wealth of call option activity today are Suntech Power Holdings (STP: sentiment, chart, options) and LDK Solar (LDK: sentiment, chart, options). Specifically, STP and LDK have both seen call volume more than quadruple their daily averages. For STP, traders are focusing on the stock's November 20 call, with more than 4,200 contracts changing hands on open interest of 3,076 contracts. Meanwhile, investors have zeroed in on LDK's November 30 call, with 5,800 contracts trading on open interest of 3,699 contracts. At last check, the STP November 20 call was $0.50 higher at $1.75, while the LDK November 30 call had risen $0.42 to $0.65.

This heavy call activity stands in stark contrast to current sentiment in the options pits for both securities. Schaeffer's put/call open interest ratio (SOIR) for STP stands at 1.14, as puts outnumber calls among near-term options. This ratio also ranks just 3 percentage points shy of an annual peak. Meanwhile, LDK's SOIR of 0.80 ranks in the 70th percentile of its annual range, and options traders have been more negative toward the shares only 30% of the time in the prior 52 weeks.

If today's rally continues, these call traders stand to make quite a profit. At last check, STP was up more than 1%, while LDK had surged more than 15%.