Laboratory Simulation of the Effect of Volcanic Material on the Formation of Transient Phenomena Near the Boundary betwe
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TICAL INSTRUMENTATION
Laboratory Simulation of the Effect of Volcanic Material on the Formation of Transient Phenomena Near the Boundary between the Middle and Lower Atmosphere E. A. Sosnina, b, *, V. S. Kuznetsova, V. A. Panarina, V. S. Skakuna, and V. F. Tarasenkoa, b aInstitute
of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055 Russia b Tomsk State University, Tomsk, 634050 Russia *e-mail: [email protected] Received November 13, 2019; revised January 27, 2020; accepted February 10, 2020
Abstract—It is ascertained that heating of volcanic material from the Etna volcano (Italy) by an apokampic discharge reduces the voltage at which a positive streamer (apokamp) starts from the discharge channel and increases its propagation speed. The luminescence spectra show these processes to be accompanied by the emission of easily ionizable K and Na, which is consistent with data on the elemental composition of Etna samples. A hypothesis is suggested about an increase in the appearance probability of blue jets and starters over sites of high volcanic activity at altitudes of 10–18 km (at the level of the troposphere). Keywords: apokampic discharge, volcanic material, blue stream, transient light phenomena DOI: 10.1134/S1024856020040168
INTRODUCTION Transient luminous events, or transients, are various large-scale luminous structures observed under conditions of high electric activity typical for thunderstorms, storms, and hurricanes in the middle and upper Earth’s atmosphere. Transients of the middle atmosphere include blue jets, starters, and red sprites. Blue jets are upward “fountains” of blue and/or light blue light from the top of a thundercloud. They originate at average altitudes of 12–18 km, reach altitudes of 40–45 km, propagate in a vertical direction at a speed of 100– 150 km/s, and exist for 60–400 ms [1–4]. Transients are studied from the Earth’s surface, airplanes, and satellites, in experiments with laboratory discharges, and in theoretical simulation. It is important that the results of laboratory experiments can be compared with the results of field observations, which allows suggesting new hypotheses about the development of transients and then taking them into account in theoretical simulation. Streamer discharges have been recently used in laboratory studies of transients of the middle atmosphere [5–7]. They help to elaborate ideas about the development of transients by means of introducing in experiments one or another physical factor which acts in the real atmosphere. In this work, we introduce volcanic material into a streamer discharge and analyze its effect on the initiation and propagation of a positive streamer at the air pressure similar to the natural conditions for blue jet and starter initiation. An apokam-
pic discharge is used to produce a streamer [8–14]. It is formed in open air and has the form of a long glowing structure (apokamp) oriented perpendicular to the bending point of the channel of a pulse-periodic highvoltage discharge. An apokampic d
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