Transient luminous events (TLEs) are various brief optical emissions between the top of the thunderclouds and the lower boundary of the ionosphere. These emissions are consequences of occasional, intensive flow of electromagnetic energy and charge in the upper atmosphere up to 90-100 km height. More details you can find here: Wikipedia
Video sequence of the captured sprites on 17.7.2015. at 22:43:27
Video sequence of the captured sprites on 17.7.2015. at 22:53:17