Experimental observations of the optical and electromagnetic fields generated by lightning flashes during the last 50 years have significantly advanced our knowledge concerning the mechanism of the lightning flash. Nevertheless, this knowledge is not as exhaustive as that of long laboratory sparks due to our inability to observe lightning flashes under controlled conditions. Thus, the mathematical description of the mechanism of a lightning flash is relatively poor at present even though the main features of lightning flashes themselves are well known. The main goal of this chapter is to provide the reader with the important features of the mechanism of the lightning flash. No attempt is made to provide an exhaustive list of the literature since this can be found elsewhere. Nomenclature: in this chapter a positive discharge is defined in such a way that the direction of motion of electrons in such a discharge is opposite to that of the discharge itself; a negative discharge is defined as one in the opposite sense. According to this definition a negative return stroke is a positive discharge and a positive return stroke is a negative discharge. A positive field is defined in terms of a negative charge being lowered to ground or positive charge being raised. According to this definition a lightning flash that transports negative charge to ground gives rise to a positive field change.

Inspec keywords: sparks; lightning

Other keywords: optical field; electromagnetic field; positive discharge; lightning flash; spark

Subjects: Atmospheric electricity