HR: 0830h
AN: AE21A-1100    [PDF]
TI: Modeling of Sprite Optical Emissions From Runaway and Conventional Breakdown and Comparison to Measurements
AU: * Triplett, L A
EM: ltriplett@lanl.gov
AF: Los Alamos National Laboratory, EES-2, MS F665, Los Alamos, NM 87545 United States
AU: Roussel-Dupre, R A
EM: rroussel-dupre@lanl.gov
AF: Los Alamos National Laboratory, EES-2, MS F665, Los Alamos, NM 87545 United States
AU: Symbalisty, E M
EM: emds@aftac.gov
AF: AFTAC/TTAD, 1030 S. Highway A1A, Patrick AFB, FL 32925-3002 United States
AU: Suszcynsky, D M
EM: dsuszcynsky@lanl.gov
AF: Los Alamos National Laboratory, NIS-1, MS D466, Los Alamos, NM 87545 United States
AU: Tierney, H E
EM: htierney@lanl.gov
AF: Los Alamos National Laboratory, EES-2, MS F665, Los Alamos, NM 87545 United States
AB: There has been much scientific interest in understanding the physical processes that lead to high-altitude optical transients (i.e. sprites). Are sprites formed through conventional breakdown, runaway breakdown, or a combination of both depending on conditions? In this paper, we describe the calculation of optical emissions associated with two different simulations performed with a 2-d fully electromagnetic discharge model (UNIMAX). Optical emissions driven by primary electrons (runaway breakdown) are calculated using measured fluorescence efficiencies and quenching rates for each wavelength of interest. For the secondary electrons (conventional breakdown and secondary electrons sustained in an electric field that lies below the conventional breakdown threshold), the emissivity of nitrogen bands as a function of electric field are used to estimate the optical emissions for the N$_{2}$ 1P, 2P, and N$_{2}$$^{+}$ 1N bands. We developed a methodology to split the band results into individual transitions. In addition, we include absorption from the source to an observer at a specified height. We present simulated camera images, line ratios, and spectra for a typical sprite and a carrot-type sprite. We compare our model results in detail to measurements to identify more precisely what diagnostic information about the discharge plasma can be deduced from such observations. The differences between conventional breakdown models and those based on the simultaneous occurrence of both processes are delineated.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting