HR: 1330h
AN: AE42A-0788    [PDF]
TI: Dynamics of Positive and Negative Streamers in Weak Uniform Electric Fields Between Thunderstorm Tops and the Lower Ionosphere
AU: * Liu, N
EM: nul105@psu.edu
AF: The Pennsylvania State University, 204 EE East, University Park, PA 16802 United States
AU: Pasko, V P
EM: vpasko@psu.edu
AF: The Pennsylvania State University, 204 EE East, University Park, PA 16802 United States
AB: It is well established by now that transient luminous events (TLEs) observed at different altitudes above thunderstorms commonly consist of large numbers of needle-shaped filaments of ionization, called streamers [e.g., Gerken and Inan, JASTP, 65, 567, 2003; Su et al., Nature, 423, 974, 2003; Pasko, Nature, 423, 927, 2003; and references cited therein]. One of the important questions of the current TLEs research, which directly relates to the evaluation of the total volumes of atmosphere affected by these phenomena and possible role of some of the TLEs (i.e., sprites, jets and gigantic jets) in establishing a direct path of electrical contact between the tropospheric and mesospheric/lower ionospheric regions, is related to the determination of the minimum electric fields required for the propagation of streamers in air at different pressures [Pasko and George, JGR, 107, 1458, 2002]. The minimum field required for the propagation of positive streamers in air at ground pressure has been extensively documented experimentally and usually stays close to the value 4.4 kV/cm [Allen and Ghaffar, J. Phys. D Appl. Phys., 28, 331, 1995], in agreement with recent results of numerical simulations of positive streamers [Babaeva and Naidis, IEEE Trans. Plasma Sci., 25, 375, 1997; Morrow and Lowke, J. Phys. D Appl. Phys., 30, 614, 1997]. The information about the absolute value of the similar field for the negative streamers at present is very limited. The existing sources indicate that this field is a factor of 2-3 higher than the corresponding field for the positive streamers [e.g., Raizer, Gas Discharge Physics, 1991, p. 361; Babaeva and Naidis, 1997]. We note that although from the streamer similarity laws one generally would expect the minimum fields required for streamer propagation to scale with altitude proportionally to the air neutral density N, the actual scaling for the altitude range of sprites, jets and gigantic jets has not yet been verified experimentally, and a limited amount of data currently available in the literature [Griffiths and Phelps, Q.J.R. Meteorol. Soc., 102, 419, 1976; Bazelyan and Raizer, Spark Discharge, 1998, p. 216] indicate possible deviations from the N scaling. In this talk we will discuss conditions required for the propagation of streamers in air at different pressures and will present corresponding results from a new two-dimensional model, which has recently been developed at Penn State for studies of dynamics of streamers in weak uniform electric fields, documenting the minimum electric field magnitudes required for the propagation of positive and negative streamers at TLE altitudes.
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting