AGU: Geophysical Research Letters

 

Editors' Highlight

Transient currents after lightning flashes

Within the Earth system, the ocean, land, and ionosphere are highly conductive. Conductivity of the atmosphere is low near sea level but increases rapidly with height up to the ionosphere. This difference gives rise to the global electric circuit (GEC) through the presence of electrical generators in the atmosphere–thunderstorms, shower clouds, dust storms, and snowstorms. Important contributors to the GEC are cloud-to-ground (CG) and intracloud lightning flashes. CG flash charges are quickly distributed over the surface and thereby contribute to the Earth's total charge and to charging or discharging of the GEC. After this fast process, a slow transient stage occurs, caused by redistribution of charge in the atmosphere. Noting that contributions of transient currents to the GEC are poorly understood, Mareev et al. (2008) used a numerical model of the transient electric field due to CG and intracloud flashes. They found that because the slow transients counteract the flashes, only a portion of the charge neutralized by a flash contributes to the GEC, with efficiency depending on the altitudes of the lightning charges.

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