Green Emissions From Sprite Tops

Abstract

Although sprite discharges above thunderstorms have been studied for about 35 years, science enthusiasts reported the existence of long‐duration green light emissions from sprite tops only recently using commercial digital cameras and named these events green ghosts . In this work, we address the physics and chemistry associated with green emissions from atomic oxygen excited by upward streamers in sprites. An explicit 0‐D chemical kinetics model has been developed to capture the production of O( ¹ S) in the upper region of sprites. We show the consistency of the model with observations using the spectral sensitivity of the camera photosensor along with calculations of the atmospheric transmission and digital processing effects. It is found that the excitation of O( ¹ S) can explain green ghosts. We show that at sprite tops, O( ¹ S) is mostly produced through the dissociation of at altitudes below 90 km and energy transfer from (A) to O at altitudes above 90 km. We also propose an explanation for the elusiveness of green ghosts through the strong dependence of O( ¹ S) lifetime on temperature in the lower‐thermosphere.