Modeling of transient luminous events in Earth's middle atmosphere with apokamp discharge

We describe the recently discovered phenomenon of the formation of an extended luminous structure at the bend of the channel of a high-voltage pulse discharge. It is called the apokamp (from the Greek words $\alpha \pi {\acute {\rm o}}$—‘from’ and $\kappa {\acute \alpha }\mu \pi \eta $—‘bend’), and the discharge as a whole is referred to as apokampic. In the course of experimental and theoretical studies, it is shown that the apokamp is a narrow streamer channel that propagates at a characteristic speed of tens to hundreds of km/s, depending on the applied voltage, pressure, and gas type. The necessary conditions for apokamp formation are established. The apokamp discharge is used for laboratory studies of conditions for the formation of blue jets and red sprites—large-scale transient luminous events (transients) observed in Earth's atmosphere above areas with thunderstorm activity. The revealed signs of similarity between apokamps and blue jets are described. The proposed experimental setup can also be used for meaningful testing of hypotheses about the conditions of formation of transients in Earth's atmosphere and in the atmospheres of other planets.