HR: 09:30h
AN: AE11A-07 INVITED     [Abstracts]
TI: Large Stratospheric Electric Fields Driven by Possible Upward Initiated Positive Lightning
AU: * Thomas, J N
EM: jnt@u.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195-1310 United States
AU: Holzworth, R H
EM: bobholz@ess.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195-1310 United States
AU: McCarthy, M P
EM: mccarthy@ess.washington.edu
AF: University of Washington, Box 351310, Seattle, WA 98195-1310 United States
AU: Solorzano, N N
EM: NSolorzano@uwb.edu
AF: University of Washington, Bothell, 18115 Campus Way NE, Bothell, WA 98011 United States
AU: Naccarato, K P
EM: kleberp@dge.inpe.br
AF: National Institute of Space Research (INPE), Av. dos. Astronautas, 178, Sao Jose dos Campos, SP 12201 Brazil
AU: Pinto, O
EM: osmar@dge.inpe.br
AF: National Institute of Space Research (INPE), Av. dos. Astronautas, 178, Sao Jose dos Campos, SP 12201 Brazil
AB: Thirty-seven vertical quasi-dc (<25~Hz) electric field changes greater than 10~V/m were measured at 30-35 km in altitude during Flight 1 of the Sprite Balloon Campaign in southeastern Brazil (December 6-7, 2002). These electric field changes were measured when the balloon payload was within 75 km horizontal distance of a thunderstorm that occurred above the Serra da Mantiqueira, a mountain range with peaks of 2000-2800 m in altitude. The majority (31/37) of these vertical electric field changes were negative (or towards the earth), which is consistent with either positive cloud-to-ground (+CG) lightning or cloud discharges. However, 25 of these negative vertical electric field changes were not detected by the Brazilian Integrated Lightning Network (BIN), which detects CG lightning with an efficiency of about 80-90% in this region. This suggests that these 25 field changes were driven by either cloud discharges or +CG lightning that did not fit the criteria for CG lightning used by BIN. Moreover, each of these negative electric fields changes usually were comprised of two slow field changes separated in time by 100s of ms that add to give the total field change. These field changes are consistent with previous measurements of upward +CG lightning initiated by tall structures that have multiple, slow electric fields changes and remove large amounts of positive cloud charge [Rakov and Uman, Lightning: Physics and Effects, Chpt.~6, 2003]. Thus, we discuss the possibility that the lightning that drove these 31 negative electric field changes (of which only 6 were detected by BIN as CG lightning) were upward +CG lightning that included upward negative leaders, initiated by the mountains, which allowed for large reservoirs of positive charge to be tapped. Finally, this leads us to speculate about how mountain ranges might trigger large charge moment upward +CG lightning that can drive the large quasi-electrostatic fields needed for sprite production.
UR: http://earthweb.ess.washington.edu/lnk/jnt/
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 6994 Instruments and techniques (1241)
SC: Atmospheric and Space Electricity [AE]
MN: Fall Meeting 2005