Effective Plasma Radiators for Satellite-Based Geological Prospecting pra-0088

Full Title Development of Effective Plasma Radiators of Low-frequency Electromagnetic Waves for Satellite-Based Geological Prospecting (Theory, Numerical Simulation, and Laboratory Modelling) Tech Area / Field

• PHY-PLS: Physics / Plasma Physics

• OBS-NAT: Other Basic Sciences / Natural Resources and Earth Sciences

• INF-SOF: Information and Communications / Software

Brief Description of Technology The proposed project is devoted to the development of plasma radiators of VLF electromagnetic waves for “sounding” the Earth from geospace.

Diagnostics of the Earth's near-surface layer by the VLF waves incoming from space is based on the fact that VLF field structures near the Earth's surface depend on both accident and distribution of the electrodynamical characteristics at a depth of the order of a typical scale of low-frequency wave penetration. Using these dependencies, one can draw up maps of the ground surface’s electrodynamical impedance, and then utilize them for geological prospecting and forecasting earthquakes.

To realize such activities, it is necessary to first develop effective VLF radiators to be located in geospace. In our opinion, the most promising prospects are associated with so-called plasma antennas (i.e. various plasma structures artificially created in the radiator vicinity) that allow an appreciable increase in the radiation power of customary elementary dipoles in the VLF/ELF bands. These structures possess a form of field aligned density enhancements arising due to ionization of the released gas, or the heating of the surrounding medium by the radiator near-zone field. Under optimal conditions, the appearance of such structures in the antenna vicinity provides a considerable increase in the radiation power, and allows for control of the radiation pattern.

In the course of carrying out this project, the great attention will be paid to considering the formation of optimal plasma-waveguide antenna systems (PWAS), modelling their operation in laboratory plasmas with similarity parameters appropriate to those of the ionosphere and magnetosphere, and working out the packages of computer programs for calculation of the electrodynamical characteristics of the proposed antennas and their fields of radiation. The laboratory experiments are presumed to be made in the large-scale devices that already exist at IAP, and require only slight adaptation for project activities. In the experiments, additional ionization of the released gas will be used in the radiator near-zone field to produce the PWAS. Computing and design activities will be carried out at OKBM.

At the final stage of the project’s execution, we anticipate presenting both a theoretical foundation and an experimental verification of the feasibility in developing effective and compact VLF antennas suitable for arranging aboard a satellite. In the course of the project’s execution, scientific collaboration is expected with French researchers whose interests involve similar problems.

Special Facilities in Use and Their Specifications IAP provides the following equipment in support of the project:

The laboratory’s large-scale set, "Ionosfera" (150 cm in length, 80 cm in diameter), has a quasi-uniform column of magnetized plasma. An ambient magnetic field directed along the column axis achieves the value of 1000 Oe. The plasma is created with rf inductance discharge. The most convenient regime for experimental investigations is that of a decaying plasma. Among the main and most important advantages at this facility is a large volume of a quasi-uniform plasma, within which a study of nonlinear resonance phenomena can be provided without the influence of a "plasma-chamber wall" interface. Moreover, a wide range of possible variations in the value of a static magnetic field allows both weak and strong plasma magnetization.

The wide-purpose laboratory set, "Krot," consists of a large-scale vacuum chamber (10 m in length, 3 m in diameter), a plasma source, a diagnostic complex, a system of automated data gathering and processing and a source of ambient magnetic field that includes a superpowerful VHF generator operating on the basis of a heavy-current relativistic electron accelerator. This facility is intended for the study of the nonlinear interaction of intensive electromagnetic fields with plasmas, laboratory modeling of space phenomena and the testing and tuning of both satellite equipment and on-board antenna systems.

Powerful generators of rf signals, suitable for studying various nonlinear phenomena in plasmas, are also present.

Scientific Papers A.V.Kostrov, A.V.Kudrin, G.V.Permitin, A.A.Shaykin, A.I.Smirnov, T.M.Zaboronkova, “Radiation and propagation of whistler range waves in ionosphere and magnetosphere plasma (laboratory modelling and theory),” Turkish Journal of Physics, v.18, N11, pp.1187-1193 (1994).

A.V.Kostrov, A.A.Shaikin, A.I.Smirnov,T.M.Zaboronkova, “Radiation of whistler range waves in ionosphere and magnetosphere plasma,” Proc. 2-st Int. Workshop "Strong Microwaves in Plasmas" (Ed. A.G.Litvak), Nizhny Novgorod, p.531 (1994).

G.Yu. Golubyatnikov, S.V.Egorov, A.V.Kostrov, E.A.Mareev, Yu.V.Chugunov, “Trapping of quasi-electrostatic waves in a thermal channel formed by the near field of a magnetic antenna in a magnetized plasma,” Zh. Eksp. Teor. Fiz., V.96, No. 6(12), p. 2009 (1989) [Sov. Phys. JETP].

T.M.Zaboronkova, A.V.Kostrov, A.V.Kudrin, S.V.Tikhonov, A.V.Tronin, A.A.Shaikin, “Channelling of waves in the whistler range within nonuniform plasma structures,” Zh. Eksp. Teor. Fiz., V.101, No. 4(10), pp.1151-1166 (1992) [Sov. Phys. JETP].

T.M.Zaboronkova, I.G.Kondrat'ev, A.V.Kudrin, “Radiation of waves in the whistler range in a magnetoactive plasma,” I, Izv. VUZov-Radiofizica, V.34, No. 9, pp.990-1000 (1991) [Radiophys. Quantum Electr.].

I.G.Kondrat'ev, A.V.Kudrin, T.M.Zaboronkova, “Radiation of whistler waves in magnetoactive plasma,” Radio Sci., v.27, N2, pp.315-324 (1992).

T.M.Zaboronkova, I.G.Kondrat'ev, A.V.Kudrin, “Radiation of waves in the whistler range in a magnetoactive plasma. II,” Izv. VUZov-Radiofizika, V.35, No.8, pp.631-640 (1992) [Radiophys. Quartum Electr].

T.M.Zaboronkova, I.G.Kondrat'ev, A.V.Kudrin, “On the radiation pattern of annular electric currents in a magnetoactive plasma in the whistler range,” Radiotekhnika i Electronika, V.38, No 8, pp.1451-1460 (1993).

T.M.Zaboronkova, A.V.Kudrin, G.A. Markov, “Whistler waves directed by channels with enhanced plasma density,” Fizika plazmy, V.19, No. 6, pp.769-780 (1993) [Sov. J. Plasma Phys.].

T.M.Zaboronkova, I.G.Kondrat'ev, A.V.Kudrin, “Radiation of given currents in the presence of a cylindrical plasma column immersed in a magnetoplasma,” Preprint NIRFI No. 375, Nizhny Novgorod, p.1-68 (1993).

T.M.Zaboronkova, A.V.Kudrin, “Influence of artificial plasma inhomogeneities on excitation of whistlers in a magnetoactive plasma,” Izv. VUZov - Radiofizika, V.33, No. 1, pp.118-120 (1990).

T.M.Zaboronkova, I.G.Kondrat'ev, A.V.Kudrin, “Radiation of whistler waves in magnetoactive plasma medium in the presence of density ducts,” Izv. VUZov-Radiofizika, V. 37, No. 7, pp.887-908 (1994) [Radiophys. Quantum Electr.].