HR: 0800h
AN: AE31A-0161    [Abstracts]
TI: Influence of Gravity Wave Density Perturbations on the Sprite Generation Mechanism
AU: * S \~{a}o Sabbas, F T
EM: fsaosabbas@dae.inpe.br
AF: Instituto Nacional de Pesquisas Espaciais - INPE, Av. Astronautas 1758, C.P. 515, Sao Jose dos Campos, SP 12245-970 Brazil
AU: Fritts, D C
EM: dave@cora.nwra.com
AF: Colorado Research Associates - CoRA, 3380 Mitchel Lane, Boulder, CO 80301 United States
AU: Vadas, S
EM: vadas@cora.nwra.com
AF: Colorado Research Associates - CoRA, 3380 Mitchel Lane, Boulder, CO 80301 United States
AB: This paper is part of a new initiative towards understanding the coupling of mechanical/thermal, electrical energy deposition in the atmospheric system by gravity waves and by lightning, which are signaled by the occurrence of lightning induced optical phenomena, e.g. sprites. We have investigated the effects of neutral density perturbations specifically caused by gravity waves in determining electric breakdown locations in the mesosphere that initiate sprites. We adapted the model of {\it S\~{a}o Sabbas} [2003] to simulate the spatio-temporal evolution of the lightning induced quasi-electrostatic field in the mesosphere when gravity waves are present. Gravity wave density perturbations were computed for a number of representative convective plume geometries. Sprites are one of several optical observable components of electrical energy deposition in the middle/upper atmosphere by lightning. Multiple sprites are often observed to occur simultaneously, laterally displaced from the underlying causative cloud-to-ground (CG) discharge. {\it S\~{a}o Sabbas} [2003] showed that pockets of neutral density depletions have a lower electric breakdown threshold. This facilitates the development of the streamer channels constituting sprites at multiple locations offset from the causative discharge, in good agreement with observations. Gravity waves are the principal source of density inhomogeneities in the mesosphere. They transport energy and momentum from the troposphere into the middle and upper atmosphere being a major forcing in the general circulation of the middle atmosphere [{\it Fritts and Alexander}, 2003]. The vertical motion of strong convective thunderstorm plumes generates gravity waves with potentially steep phase slopes and density perturbations which are likely most important for sprite initiation.
DE: 3324 Lightning
DE: 3334 Middle atmosphere dynamics (0341, 0342)
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting