Problems in lightning physics - the role of polarity asymmetry

Many outstanding problems in lightning physics are linked with a difference in macroscopic behaviour between positive and negative polarity. Such differences are referred to broadly as 'polarity asymmetry'. As specific examples, the positive and negative ends of lightning propagate at different speeds, with different degrees of steadiness, and with different radiated electromagnetic energy. Positive and negative flashes to ground transfer their charge in markedly different ways - negative flashes with multiple discrete strokes (often) and positive flashes with single strokes followed by continuing current. Positive ground flashes cause sprites and negative flashes do not (generally). Positive intracloud flashes send gamma radiation upward to space and negative intracloud flashes do not (generally). Speculative arguments are presented that all of these macroscopic asymmetries are rooted in the microscopic asymmetry in mobility for free electrons and positive ions.