Numerical Study of Global ELF Electromagnetic Wave Propagation with Respect to Lithosphere–Atmosphere–Ionosphere Coupling

Before and after earthquakes, abnormal physical and chemical phenomena can be observed by gathering ground-based and satellite data and interpreted by the lithosphere–atmosphere–ionosphere coupling (LAIC) mechanism. In this study, we focused on the mechanism of LAIC electromagnetic radiation and investigated the seismic electromagnetic (EM) wave generated in the lithosphere by earthquakes and its global propagation process from the lithosphere through the atmosphere and into the bottom of ionosphere, in order to analyze the abnormal disturbance of ground-based and space-based observation results. First, analytic formulas of the electrokinetic effect were used to simulate the generation and propagation process of the seismic EM wave in the lithosphere, interpreted as the conversion process of the seismic wave and EM wave in porous media. Second, we constructed a three-dimensional Earth–ionosphere waveguide by applying the finite-difference time-domain (FDTD) algorithm to model the global propagation process of the seismic EM wave into the atmosphere and cavity between the bottom of the ionosphere and the surface of the Earth. By combining the model of the electrokinetic effect in the lithosphere with the numerical model of the Earth–ionosphere waveguide in the atmosphere and ionosphere, we numerically simulated the global transmission process of extremely low-frequency (ELF: 3 Hz–3000 Hz) EM waves which are related to earthquakes. The propagation parameters of coseismic ELF EM waves with different duration times and center frequencies were analyzed and summarized. The simulation results demonstrate that the distribution characteristics of an electric field along longitude, latitude and altitude with time are periodic and the time interval during which an EM wave travels around the whole Earth is approximately 0.155 s when adopting the conductivity of the knee profile. We also compared the observation data with the simulation results and found that the attenuating trends of the ELF electric field are consistent. This proposed ELF EM wave propagation model of lithosphere–atmosphere–ionosphere coupling is very promising for the explanation of abnormal disturbances of ground-based and space-based observation results of ELF EM fields which are associated with earthquakes.

Influence of direct electric field on PMCG-alginate-based microcapsule

In this study, the influence of direct electric current on a microcapsule was investigated. The microcapsule consisted of a core from a calcium ion and sodium alginate (SA) complex and the microcapsule membrane was formed by the polyionic complexation of poly(methylene-co-guanidine) (PMCG) and cellulose sulfate (CS). Microcapsules showed swelling and decreasing mechanical properties under the applied electric current, and the microcapsule membrane showed anisotropic swelling on the electrode side. The effect is attributed to an electrokinetic phenomenon, predominant formation of hydroxyl ions, and the diffusion of hydrated ions. The swelling degree of the microcapsule and microcapsule membrane at different pH and the applied electric current under alkali and acidic conditions was investigated. The swelling degree was influenced by the dissociation of the membrane, which was observed after applying the electric field, which was caused by the electrokinetic effect and the neutralization of the polycation (under alkali conditions) or polyanionic (under acidic conditions) segment during membrane formation.

Thermo-fluidic transport of electromagnetohydrodynamic flow of sodium alginate based Casson nano fluid passing through a porous microtube under the effect of streaming potential

Thermal transport characteristics of Casson nanofluid through a porous microtube is analyzed under the effect of streaming potential and constant pressure gradient with electrokinetic effect associated with applied magnetic field. An analytical solution of the velocity and temperature distribution of Casson-nano fluid through the porous microtube related to combining effects of electromagnetohydrodynamics forces under the effect of streaming potential have been obtained. The significant influences of various non-dimensional parameters on velocity and temperature profiles are discussed in this study. Also, it is revealed the impact of nano particles on flow transport and heat transfer phenomenon. Furthermore, the Nusselt number is calculated analytically. The variations of pertinent parameters such as Hartmann number, Darcy number,Casson parameter, volume friction parameter of nanoparticles, joule heating parameter are delineated graphically and discussed in details.

Electrokinetic effect and H2O2 boosting in synthetic graphene/α-FeOOH aerogel films for the generation of electricity

Novel catalytic α-FeOOH/graphene aerogel films for high performance hydrovoltaic power generation devices have been developed with an exceptionally high power density of 47 mW m−2 upon the addition of H2O2 to the saline solution.

Coseismic electric and magnetic signals observed during 2017 Jiuzhaigou Mw 6.5 earthquake and explained by electrokinetics and magnetometer rotation

SUMMARY Very clear coseismic electric and magnetic signals accompanying seismic waves were observed during the 2017 Mw 6.5 Jiuzhaigou earthquake, which took place in western China. In order to understand the generation mechanism of these observed signals, we simulate electric and magnetic responses to this specific earthquake based on three mechanisms, namely, the electrokinetic effect, the motional induction effect and the rotation effect of the coil-type magnetometer. We conduct the simulations using a point source model and a realistic layered earth model and compare to the observed data in the frequency band 0.05–0.3 Hz. Our results show that the electrokinetic effect can explain the observed electric fields in both waveform and amplitude, but it cannot explain the magnetic signals accompanying the Rayleigh wave. The motional induction effect cannot explain either the coseismic electric or magnetic data because it predicts much weaker coseismic electric and magnetic fields than the observed data. The magnetic fields resulting from the rotation of the magnetometer agree with the observed data in the waveforms though their amplitudes are two to four times smaller than the observed data. Our simulations suggest that the electrokinetic effect is responsible for the generation of coseismic electric fields and that rotation of the coil magnetometer is likely the main cause of coseismic magnetic fields. The results improve our interpretation of the coseismic electromagnetic (EM) phenomenon and are useful for understanding other kinds of earthquake-associated EM phenomena.

Numerical simulations to explain the coseismic electromagnetic signals: a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake

Coseismic electromagnetic (EM) signals that appear from the P arrival were observed in a volcanic area during the 2016 Kumamoto earthquake. In this study, we conduct numerical simulations to explain the coseismic EM signals observed for a M5.4 aftershock of the earthquake. Initially, we adopt a water-saturated half-space model, and its simulation result for a receiver with a depth of 0.1 m suggests that the magnetic signals do not show up at the arrivals of P, refracted SV–P and Rayleigh waves because the evanescent EM waves just counterbalance the localized magnetic signals that accompany P, refracted SV–P and Rayleigh waves. Then, we conduct numerical simulations on a seven-layer half-space model in which the second layer corresponds to an aquifer analogy and the six other layers refer to air-saturated porous media. When only the electrokinetic effect is considered, the simulated coseismic magnetic signals still appear from the S arrival. The combination of electrokinetic effect and surface-charge assumption is also tested. We find that signals before the S arrival are missing on the transverse seismic, transverse electric, radial magnetic and vertical magnetic components, although the situation on horizontal magnetic components is improved to an extent. Then, we introduce an artificial scattering effect into our numerical simulations given that the scattering effect should exist in the volcanic area. New numerical result shows good agreement with the observation result on the signal appearance time. Hence, the combination of electrokinetic and scattering effects is a plausible explanation of coseismic EM signals. Further investigations indicate that coseismic electric and/or magnetic signals are more sensitive to the scattering effect and the aquifer thickness than seismic signals.

Boehmite and Akaganeite 1D and 2D Mesostructures: Synthesis, Growth Mechanism, Ageing Characteristics and Surface Nanoscale Roughness Effect on Water Purification

The role of surface nanoscale roughness on the charging behavior of nanostructured γ-AlOOH (Boehmite) and β-FeOOH (Akaganeite)/γ-AlOOH (Boehmite) mesostructures deposited onto siliceous substrates has been investigated. Two-dimensional (2D) quantum-sized and one-dimensional (1D) nanometer size γ-AlOOH (Boehmite) structures and 2D atomically-thin β-FeOOH (Akaganeite) nanobelts with a mean width of approximately 10 nm were deposited onto siliceous substrates in aqueous processes at moderate temperatures. Low cost and large scale manufacturing of siliceous substrates coated with 2D and 1D γ-AlOOH (Boehmite) crystallites of 2.7 ± 0.5 nm in diameter, with an average length of 2.9 ± 0.9 nm and 250 ± 50 nm, respectively, that were further functionalized with atomically thin 2D β-FeOOH (Akaganeite) nanobelts was demonstrated. Zeta potentials of surfaces have been characterized by direct measurement of streaming potentials in NaCl aqueous electrolyte. A model explaining the pH dependent behavior of the zeta potential was proposed. The isoelectric point values of rough nanostructured surfaces are three pH units higher as compare to the flat crystalline γ-AlOOH (Boehmite) and β-FeOOH (Akaganeite) surfaces, resulting in a high removal efficacy of submicron particles from aqueous suspension by the surfaces with combined microscale and nanoscale structures. This suggests the existence of a coupling electrokinetic effect of the local electrical double layer (EDL) fields with the local flow fields.