Schumann Resonances as a Means of Investigating the Electromagnetic Environment in the Solar System

Abstract

The propagation of extremely low frequency (ELF, 3 Hz to 3 kHz) radio waves and resonant phenomena in the spherical Earth-ionosphere cavity has been studied for almost fifty years. When such a cavity is excited by naturally occurring broadband electromagnetic radiation, resonances can develop if the equatorial circumference is approximately equal to an integral number of wavelengths of the propagating electromagnetic waves; these are termed Schumann resonances. They provide information not only about thunderstorm and lightning activity on the Earth, and their relation to climate, but also on the properties of the low ionosphere. Similar investigations can be performed for any other planet or satellite, provided that it has an ionosphere. F. Simões ( ) Centre d'Etude des Environnements Terrestre et Planétaires, F. Simões et al.There are important differences between the Earth and other celestial bodies regarding, for example, the surface conductivity, the atmospheric conductivity profile, the geometry of the ionospheric cavity, and the sources of excitation. To a first approximation, the size of the cavity defines the fundamental resonant frequency, the atmospheric electron density profile controls the wave attenuation, the nature of the sources influences the electromagnetic field distribution in the cavity, and the body surface conductivity indicates to what extent the subsurface can be explored. The frequencies and attenuation rates of the principal eigenmodes depend upon the electrical properties of the cavity. Instruments that monitor the electromagnetic environment in the ELF range on the surface, on balloons, or on descent probes provide unique information on the cavity.In this paper, we present Schumann resonance models for selected inner planets, some gaseous giant planets and a few of their satellites. We review the crucial parameters of ELF electromagnetic waves in their atmospheric cavities, namely the electric and magnetic field spectra, their eigenfrequencies, and the associated Q-factors (damping factors). Then we present important information on theoretical developments, on a general model that uses the finite element method and on the parameterization of the cavity. Next we show the distinctiveness of each planetary environment, and discuss how ELF radio wave propagation can contribute to an assessment of the major characteristics of those planetary environments.

Ionization of the venusian atmosphere from solar and galactic cosmic rays

“…While positive detections of radio wave emissions due to venusian lightning have been reported (Ksanfomaliti et al, 1979;Russell et al, 2007;Taylor et al, 1979), radio observations by Cassini during two close flybys has not confirmed this and a lack of optical detections by Venus Express as well as ground-based observers leaves the question of venusian lightning unresolved (Yair, 2012;Yair et al, 2008). Lightning in the venusian atmosphere may be inferred by searching for Schumann resonances, Extremely Low Frequency (ELF) waves which are excited by electrical discharges within the surface-ionosphere cavity (Aplin et al, 2008;Simões et al, 2008b). The predicted signatures of such ELF waves within the venusian surface-ionosphere cavity has been studied theoretically by Simões et al (2008a) by incorporating the conductivity profile produced by the cosmic ray modeling work of Borucki et al (1982).…”

Schumann Resonance for Tyros

“…Rabinowicz 1982, 1987;Sentman 1990;Molina-Cuberos et al 2001, 2004Tokano et al 2001;Nickolaenko et al 2003;Pechony and Price 2004;Béghin et al 2007;Navarro et al 2007;Simões et al 2007Simões et al , 2008aMorente et al 2008;Fischer and Gurnett 2011 and references therein). Rabinowicz 1982, 1987;Sentman 1990;Molina-Cuberos et al 2001, 2004Tokano et al 2001;Nickolaenko et al 2003;Pechony and Price 2004;Béghin et al 2007;Navarro et al 2007;Simões et al 2007Simões et al , 2008aMorente et al 2008;Fischer and Gurnett 2011 and references therein).…”

An Overview of Earth’s Global Electric Circuit and Atmospheric Conductivity

“…These standing wave signals at ∼10 Hz excite the resonant cavity formed between the Earth and the ionosphere; these are the so-called Schumann resonances (Schumann 1952). Details of Schumann resonance phenomena are dealt with by Simoes et al (2008).…”