You would need a very large solar panel to power 12 volt incandescent rope light for any duration of time. However, 12 volt LED rope lights use far less energy to run and could most likely be rigged to some sort of reasonably sized solar panel. Another option is to use a 12 volt rechargeable battery and have a small solar cell recharge the battery during the day. Here is a site you might want to look at that sells solar panels:
http://www.siliconsolar.com/12-volt-solar-battery-chargers.php