Giant Jets as Higher Transverse Modes of an Open Cavity
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INEAR PHENOMENA
Giant Jets as Higher Transverse Modes of an Open Cavity G. V. Sklizkova, * and A. V. Shelobolina, ** a
Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119333 Russia *e-mail: [email protected] **e-mail: [email protected] Received December 24, 2018; revised March 15, 2019; accepted March 25, 2019
Abstract—The spatial structure of giant blue jets in the upper atmospheric layers is considered on the basis of a nonlinear plasma waveguide model of electric gas breakdown. Laser analogues for such waves are proposed, and the azimuthally equidistant conical structure formed by the rays of a giant jet is explained. The field parameters and the electron density required for this process are estimated. Using the model proposed, requirements to the diagnostics of waves in the upper atmosphere are formulated. Similar models for analyzing thunderstorm phenomena in the lower atmosphere are offered. DOI: 10.1134/S1063780X19080099
1. INTRODUCTION In recent years, electric discharges in the upper atmosphere have received active study [1–7] due to the perfection of systems for high-speed photography of such discharges. The typical time resolution of these systems is about 17 ms [2, 3], which is the limiting resolution for reliable determination of the rate at which electric breakdown waves develop under these conditions. For the processes under consideration, the range of absolute altitudes above the ocean level is from 15 to 90 km, which corresponds to an air density from 1018 to 1014 cm–3 and a neutral gas temperature of 200–280 K. In ground-based measurements [2, 3], the distance from the optical recording equipment to the object under study was typically three to four times larger than the object altitude. In principle, a spatial resolution of ~1 m can be achieved under these conditions; however, judging from Figs. 1 and 2, in the abovementioned experiments, it was no better than ~10– 100 m. Nevertheless, this was sufficient, because, according to the estimates made in [2, 3], the diameters of the recorded breakdown waves was about 1 km. In this context, the question arises as to whether it is necessary to enhance the spatial resolution of the experiment or pay attention to improving its other parameters, e.g., time resolution. The answer to this question is related to the theoretical concepts of the considered phenomenon and problems of developing new-generation diagnostics. The main types of breakdown waves in the upper atmosphere, as well as the types of transit radiative phenomena (TRPs), were described in [4–7]. Giant blue jets (GBJs) are multichannel breakdown waves
starting from the upper edge of a thundercloud slightly below its boundary and propagating upward to the lower boundary of the ionosphere (see Figs. 1, 2). Such waves arise during thunderstorms in the coastal areas of the ocean, but the start of these waves is not associated with the discharge of a thundercloud to the ground. GBJs are observed only at equatorial latitudes. Kindreds of GBJs are single-channel blue jets
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