sentences:  They are triggered by the discharges of positive lightning between the thundercloud and the ground.The phenomena were named after the mischievous sprite, e.g., Shakespeare's Ariel or Puck, and is also an acronym for Stratospheric/mesospheric Perturbations Resulting from Intense Thunderstorm Electrification.They normally are colored reddish-orange or greenish-blue, with hanging tendrils below and arcing branches above.