Study of Schumann resonances based on magnetotelluric records from the western Mediterranean and Antarctica

Toledo‐Redondo, Sergio; Salinas, Alfonso; Portí, J.A.; Morente, Juan A.; Fornieles, Jesús; Méndez, Alfredo; Galindo-Zaldı́var, Jesús; Pedrera, Antonio; Ruíz-Constán, Ana; Anahnah, Farida

doi:10.1029/2010jd014316

Cited by 22 publications

(19 citation statements)

References 30 publications

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“…SR corresponds to standing waves of the radial Transverse Magnetic (TM r ) mode; and therefore, for a source conveniently located at θ = 0, the primary magnetic field will be in the ϕ component and the electric field in the r component, [e.g., Toledo‐Redondo et al , ]. The ϕ coordinate of the outputs is irrelevant for this study, due to the symmetry of the cavity in this direction.…”

Section: The Tlm Methodsmentioning

confidence: 60%

Full 3‐D TLM simulations of the Earth‐ionosphere cavity: Effect of conductivity on the Schumann resonances

et al. 2016

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Schumann resonances can be found in planetary atmospheres, inside the cavity formed by the conducting surface of the planet and the lower ionosphere. They are a powerful tool to investigate both the electric processes that occur in the atmosphere and the characteristics of the surface and the lower ionosphere. Results from a full 3‐D model of the Earth‐ionosphere electromagnetic cavity based on the Transmission‐Line Modeling (TLM) method are presented. A Cartesian scheme with homogeneous cell size of 10 km is used to minimize numerical dispersion present in spherical schemes. Time and frequency domain results have been obtained to study the resonance phenomenon. The effect of conductivity on the Schumann resonances in the cavity is investigated by means of numerical simulations, studying the transition from resonant to nonresonant response and setting the conductivity limit for the resonances to develop inside the cavity. It is found that the transition from resonant to nonresonant behavior occurs for conductivity values above roughly 10−9 S/m. For large losses in the cavity, the resonances are damped, but, in addition, the peak frequencies change according to the local distance to the source and with the particular electromagnetic field component. These spatial variations present steep variations around each mode's nodal position, covering distances around 1/4 of the mode wavelength, the higher modes being more sensitive to this effect than the lower ones. The dependence of the measured frequency on the distance to the source and particular component of the electric field offers information on the source generating these resonances.

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Section: The Tlm Methodsmentioning

confidence: 60%

Full 3‐D TLM simulations of the Earth‐ionosphere cavity: Effect of conductivity on the Schumann resonances

et al. 2016

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“…It indicates random nature of the time series when H=0.5, while a reinforcing trend can be assumed when the value of H > 0.5 (e.g. Nickolaenko et al, 2000;Rasheed, 2004, 2007;Redondo, et al, 2010). Table 4 gives the estimated spectral indices and the corresponding Hurst exponents.…”

Section: Vlbi Data and Analysismentioning

confidence: 99%

Large-Scale Present-Day Plate Boundary Deformations in the Eastern Hemisphere Determined from VLBI Data: Implications for Plate Tectonics and Indian Ocean Growth

Akilan

Azeez

Schuh

et al. 2014

Pure Appl. Geophys.

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Dynamics of the planet Earth is the manifestation of the diverse plate tectonic processes, which have been operational since the Archean period of Earth evolution and continue to deform the plate boundaries. Very Long Baseline Interferometry (VLBI) is an efficient space geodetic method that allows the precise measurement of plate motions and associated deformations. We analyze here the VLBI measurements made during a period of about three decades at five locations on the Eastern hemisphere of the globe, which are geographically distributed over five continents (plates) around the Indian Ocean. The computed baseline length rates show the deformation pattern and its rate at the boundaries between the major tectonic plates constituting the Eastern Earth hemisphere. The African 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 (Nubian) and Antarctic plates are moving apart at 13.5 mm/yr, which is mostly attributed to South West Indian Ridge spreading. Similarly, a spreading rate of 59.0 mm/yr is observed for the South East Indian Ridge that separates the Antarctic and Australian plates. Shortening at the rate of 3.9 mm/yr is estimated across the subduction boundary between Africa (Nubia) and Eurasia. Similar kind of convergence process is evident between the Australian and Sunda blocks (of the Eurasian plate). The associated deformation of -54.8 mm/yr appears to be chiefly accommodated along the Banda arc system, where the Australian plate is subducting under the Sunda block. VLBI sites within the Eurasian plate, Wettzell in Germany and Seshan on the South China block, are moving apart at a rate of 3.6 mm/yr. This relative motion between locations on the same plate is interpreted to be due to the deformation process along a large strike-slip fault, which is identified as the Western boundary of South China block. Indian Ocean expansion, at the rate of +91.5 m 2 /yr, is also estimated from the deformation rate estimated within the five baselines studied here. From the Hurst exponent values, which is an indicator of the future trend of a time series data, we predict the deceleration of the various tectonic processes that are operational at present.

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“…The measurement process starts at the two magnetometers, north-south and east-west oriented, which can induce a voltage in the range of mV for fields in the range of pT (see section 3). This is the typical order of magnitude for natural electromagnetic noise in the atmosphere, such as is found in the SRs [Toledo-Redondo et al, 2010]. The preamplifiers are placed at a distance of less than 1 m from the sensors, connected by a double-shielded coaxial cable of very low losses, to deal with the low signal level at the sensor output.…”

Section: The Measurement Stationmentioning

confidence: 99%

“…The sensor noise figure, N s , subdivided into thermal and magnetic (Barkhausen) noise [Skrotskii et al, 1966], can be expressed as in section 4, is the sensor series resistance, and Im( rv ) is the imaginary part of the complex magnetic permeability of the sensor core, whose value is approximately eff for the configuration described.…”

Section: Noise Of the Systemmentioning

confidence: 99%

“…Mechanical vibrations of any kind, trees moving due to wind, etc., may introduce a significant amount of noise into the detection system. Moreover, the system itself introduces noise: thermal noise due to the finite conductivity of the coil, Barkhausen noise in the magnetic core [Skrotskii et al, 1966], voltage and intensity noise in the amplifiers, variations with temperature, etc.…”

Section: Introductionmentioning

confidence: 99%

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Extremely low frequency band station for natural electromagnetic noise measurement

et al. 2015

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A new permanent ELF measurement station has been deployed in Sierra Nevada, Spain. It is composed of two magnetometers, oriented NS and EW, respectively. At 10 Hz, their sensitivity is 19 μV/pT and the signal-to-noise ratio (SNR) is 28 dB for a time-varying signal of 1 pT, the expected field amplitude in Sierra Nevada. The station operates for frequencies below 24 Hz. The magnetometers, together with their corresponding electronics, have been specifically designed to achieve such an SNR for small signals. They are based on high-resolution search coils with ferromagnetic core and 10 6 turns, operating in limited geometry configuration. Different system noise sources are considered, and a study of the SNR is also included. Finally, some initial Schumann resonance measurements are presented in order to validate the performance of the measurement station, including 1 h length spectra, daily variations of resonance amplitudes and frequencies for the different seasons, and a 3 day spectrogram.

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Study of Schumann resonances based on magnetotelluric records from the western Mediterranean and Antarctica

Cited by 22 publications

References 30 publications

Full 3‐D TLM simulations of the Earth‐ionosphere cavity: Effect of conductivity on the Schumann resonances

Full 3‐D TLM simulations of the Earth‐ionosphere cavity: Effect of conductivity on the Schumann resonances

Large-Scale Present-Day Plate Boundary Deformations in the Eastern Hemisphere Determined from VLBI Data: Implications for Plate Tectonics and Indian Ocean Growth

Extremely low frequency band station for natural electromagnetic noise measurement

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