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Energetics of Elves

Elves have been described by models as heating from the EMP from tropospheric lightning (Pasko et al.(1998),Inan et al.(1997)). The optical emissions of elves have been identified as originating from N2(1PG) (Heavner(2000)). The short duration of elves suggests that individual elves are less important energetically than sprites or jets. However, elves (optical emissions) may represent only the high energy component of the effect of lightning discharges transferring energy to the middle atmosphere. Lower energy lightning discharges may not cause optical emissions, but the majority of tropospheric lightning discharges can still cause neutral heating in the middle and upper atmosphere but do not stimulate optical emissions. Before the documentation of elves, the neutral heating of the upper atmosphere by lightning was proposed as a mechanism for creating a long-term (hour time scale) infrared glow above thunderstorms (Picard et al.(1997),Inan et al.(1991)). The mechanism described the vibrational excitation of ground state N2 by electron impact followed by energy transfer via N2(X1Su+) -> CO2. Because elves are observed to occur above both positive and negative CG's they may occur more frequently than sprites.

Matt Heavner 2002-02-13