Thank you, Andrew, for your very comprehensive reply, and also for posting the graphic. The lightning caused by volcanic plumes is promising.<br /><br />And centsworth_II, what a great idea: lightning shooting from planet to planet, or from a planet to its moon. That would be so spectacular.<br /><br />I've gotten myself a bit stuck. I need some really spectacular lightning effects (scientifically feasible), but I don't want to mention the names of our planets in the solar system. <br /><br />Thanks for all your help -- it's appreciated.<br />