Electric Field Perturbations Research Articles

Domain Dynamics Response to Polarization Switching in Relaxor Ferroelectrics.

Nanoscale polar regions, or nanodomains (NDs), are crucial for understanding the domain structure and high susceptibility of relaxors. However, unveiling the evolution and function of NDs during polarization switching at the microscopic level is of great challenge. The experimental in situ characterization of NDs under electric-field perturbations, and computational accurate prediction of the dipole switching within a sufficiently large supercell, are notoriously tricky and tedious. These difficulties hinder a full understanding of the link between micro domain dynamics and macro polarization switching. Herein, the real-time evolution of NDs at the nanoscale is observed and visualized during polarization switching in an exemplary relaxor system of Bi5- xLaxMg0.5Ti3.5O15. Two fundamentally different domain switching pathways and dynamic characteristics are revealed: one steep, bipolar-like switching between two degenerate polarization states; and another flat, multi-step switching process with a thermodynamically stable non-polar mesophase mediating the degenerate polarization states. The two are determined by the distinct Landau energy landscapes that are strongly dependent on the intrinsic domain configurations and interdomain interactions. This work bridges the gap between micro domain dynamics and macro polarization switching, providing a guiding principle for the strategic design and optimization of relaxors.

The Ionospheric Electric Field Perturbation with an Increase in Radon Emanation

The Ionospheric Electric Field Perturbation with an Increase in Radon Emanation

Electromagnetic ULF Fields from an Underground Seismic Source on the Earth’s Surface and in the Ionosphere

A theoretical formalism has been developed to calculate the electromagnetic fields generated in the atmosphere–ionosphere system by a finitelength underground horizontal current source. A numerical model with a realistic profile of the ionosphere in a vertical geomagnetic field has been designed based on this theory. It is shown that the apparent impedance of the electromagnetic field created by an underground source on the Earth’s surface is one order of magnitude higher than the Earth’s impedance, which can be used to discriminate perturbations from seismogenic sources. The presented results of numerical modeling allow us to relate perturbations created by a large-scale underground source in the Earth surface magnetic field and in the electric field in the ionosphere. Based on these model estimates it is concluded that many of the ULF electric field perturbations detected in satellite data before earthquakes cannot be attributed to direct emission from seismogenic sources.

An Active Site Tyr Residue Guides the Regioselectivity of Lysine Hydroxylation by Nonheme Iron Lysine-4-hydroxylase Enzymes through Proton-Coupled Electron Transfer.

Lysine dioxygenase (KDO) is an important enzyme in human physiology involved in bioprocesses that trigger collagen cross-linking and blood pressure control. There are several KDOs in nature; however, little is known about the factors that govern the regio- and stereoselectivity of these enzymes. To understand how KDOs can selectively hydroxylate their substrate, we did a comprehensive computational study into the mechanisms and features of 4-lysine dioxygenase. In particular, we selected a snapshot from the MD simulation on KDO5 and created large QM cluster models (A, B, and C) containing 297, 312, and 407 atoms, respectively. The largest model predicts regioselectivity that matches experimental observation with rate-determining hydrogen atom abstraction from the C4-H position, followed by fast OH rebound to form 4-hydroxylysine products. The calculations show that in model C, the dipole moment is positioned along the C4-H bond of the substrate and, therefore, the electrostatic and electric field perturbations of the protein assist the enzyme in creating C4-H hydroxylation selectivity. Furthermore, an active site Tyr233 residue is identified that reacts through proton-coupled electron transfer akin to the axial Trp residue in cytochrome c peroxidase. Thus, upon formation of the iron(IV)-oxo species in the catalytic cycle, the Tyr233 phenol loses a proton to the nearby Asp179 residue, while at the same time, an electron is transferred to the iron to create an iron(III)-oxo active species. This charged tyrosyl residue directs the dipole moment along the C4-H bond of the substrate and guides the selectivity to the C4-hydroxylation of the substrate.

Multi-process driven unusually large equatorial perturbation electric fields during the April 2023 geomagnetic storm

The low latitude ionosphere and thermosphere are strongly disturbed during and shortly after geomagnetic storms. We use novel Jicamarca radar measurements, ACE satellite solar wind, and SuperMAG geomagnetic field observations to study the electrodynamic response of the equatorial ionosphere to the 23, 24 April 2023 geomagnetic storm. We also compare our data with results from previous experimental and modeling studies of equatorial storm-time electrodynamics. We show, for the first time, unusually large equatorial vertical and zonal plasma drift (zonal and meridional electric field) perturbations driven simultaneously by multi storm-time electric field mechanisms during both the storm main and recovery phases. These include daytime undershielding and overshielding prompt penetration electric fields driven by solar wind electric fields and dynamic pressure changes, substorms, as well as disturbance dynamo electric fields, which are not well reproduced by current empirical models. Our nighttime measurements, over an extended period of large and slowly decreasing southward IMF Bz, show very large, substorm-driven, vertical and zonal drift fluctuations superposed on large undershield driven upward and westward drifts up to about 01 LT, and the occurrence of equatorial spread F irregularities with very strong spatial and temporal structuring. These nighttime observations cannot be explained by present models of equatorial storm-time electrodynamics.

Instability of steady states with inhomogeneous field in electron–positron plasma diode

Instability features of steady states of the plasma diode with electron and positron counter flows are studied. There are several types of such states for each value of the inter-electrode distance. The case when charged particles moving in the diode plasma are not reflected from potential extrema is considered. We have solved an equation for the amplitude of the electric field perturbation for steady states with an inhomogeneous field distribution. Studying the dispersion equation has shown that all considered solutions are unstable. We have also confirmed this result when simulating small perturbation evolution of a steady-state solution.

Self-excited converging shock structure in a complex plasma medium.

We report the study of a self-excited converging shock structure observed in a complex plasma medium. A high-density dust cloud of melamine formaldehyde particles is created and horizontally confined by a circular ring in a dc glow discharge plasma at a particular discharge voltage and pressure. Later, as the discharge voltage is increased, a circular density crest is spontaneously generated around the outer boundary of the dust cloud. This nonlinear density structure is seen to propagate inward towards the center of the dust cloud. The properties of the excited structure are analyzed and found to follow the characteristics of a converging shock structure. A three-dimensional molecular dynamics simulation has also been performed in which a stable dust cloud is formed and levitated by the balance of forces due to gravity and an external electric field mimicking the cathode sheath electric field in the experiment. Particles are also horizontally confined by an external electric field, representing the sheath electric field of the circular ring present in the experiment. A circular shock structure has been excited by applying an external perturbation in the horizontal electric field around the outer boundary of the dust cloud. The characteristic properties of the shock are analyzed in the simulation and qualitatively compared with the experimental findings. This paper is not only of fundamental interest but has many implications concerning the study of converging shock waves excited in other media for various potential applications.

Evidence of an upper ionospheric electric field perturbation correlated with a gamma ray burst

Earth’s atmosphere, whose ionization stability plays a fundamental role for the evolution and endurance of life, is exposed to the effect of cosmic explosions producing high energy Gamma-ray-bursts. Being able to abruptly increase the atmospheric ionization, they might deplete stratospheric ozone on a global scale. During the last decades, an average of more than one Gamma-ray-burst per day were recorded. Nevertheless, measurable effects on the ionosphere were rarely observed, in any case on its bottom-side (from about 60 km up to about 350 km of altitude). Here, we report evidence of an intense top-side (about 500 km) ionospheric perturbation induced by significant sudden ionospheric disturbance, and a large variation of the ionospheric electric field at 500 km, which are both correlated with the October 9, 2022 Gamma-ray-burst (GRB221009A).

Periodic oscillations of Doppler frequency excited by the traveling ionospheric disturbances associated with the Tonga eruption in 2022

The explosive eruption of the Hunga Tonga-Hunga Ha’apai volcano on 15 January 2022 generated atmospheric waves traveling around the Earth, which caused ionospheric disturbances on various spatio-temporal scales. A HF Doppler sounding system in Japan detected characteristic ionospheric disturbances showing periodic oscillations in the Doppler frequency with a period of ~ 4 min. In this study, such periodic oscillations were examined by comparing Doppler frequency data with Total Electron Content data obtained by Global Navigation Satellite System. The observed periodic oscillations in the Doppler frequency were characterized by a sawtooth or S-letter shaped variation, implying the passage of the traveling ionospheric disturbances through the reflection points of the HF Doppler sounding system. It was also found that the periodic oscillations occurred prior to the arrival of the tropospheric Lamb wave excited by the Tonga eruption. From the total electron content data, the traveling ionospheric disturbances causing the periodic oscillations were excited by the tropospheric Lamb waves at the conjugate point in the southern hemisphere, namely, the electric field perturbations due to the Lamb waves in the southern hemisphere mapped onto the sensing area of the HF Doppler sounding system in the northern hemisphere along the magnetic field lines. The periodic oscillations were observed only in the path between Chofu transmitter and Sarobetsu receiver, whose the radio propagation path is almost aligned in the north–south direction. This suggests that the traveling ionospheric disturbance has a structure elongating in the meridional direction. The variation in the Doppler frequency was reproduced by using a simple model of the propagation of the traveling ionospheric disturbances and the resultant motion of the reflection point. As a result, the vertical motion of the reflection point associated with the periodic oscillations was estimated to be about 1 km. It is known that 4-min period variations are sometimes observed in association with earthquakes, which is due to resonances of acoustic mode waves propagating between the ground and the lower ionosphere. Therefore, a similar resonance structure in the southern hemisphere is a plausible source of the traveling ionospheric disturbances detected in the northern hemisphere.Graphical

Ion-acoustic waves in weakly ionized plasmas with charge-exchange collisions

Ion-neutral charge-exchange collisions in plasmas of laboratory, space, and astrophysical origins are fundamental to understanding wave dissipation and wave generation phenomena. This paper implements a charge-exchange collision operator in the Boltzmann–Poisson system equations for a weakly ionized plasma. When considering an electric field perturbation, the governing kinetic equations provide significant results concerning the plasma conductivity and the dielectric function, appearing in simple, sensible forms. The present analysis reveals a backward wave propagation phenomenon at maximum conductivity when the wavenumber of the plasma wave is smaller than the reciprocal of the ion-neutral collisions mean free path. In addition, it is shown that ion-neutral coupling resulting from charge-exchange collisions enhances ion-acoustic waves below and beyond the ion plasma frequency and leads to the onset of a fundamental instability that overcomes Landau damping under certain circumstances. The collisionless model is recovered as a limiting case, i.e., in the asymptotic limit of a long mean free path.

A novel computational technique to analyse the corona generated ionized field environment of EHV/UHV DC transmission lines

Abstact The corona-generated electromagnetic field environment under and nearer to the extra high dc potential conductors generates an ill health environment which causes serious electrical threats to living organisms present in the conductor corridor. The ionized electromagnetic field environment is characterizing with ionized ionic current flow and enhanced electric field perturbation at ground levels. The primary factors which affect the safe and economical design dimensions of high potential dc conductors are conductor diameter, altitude, applied potential and atmospheric parameters such as temperature, humidity, pressure, and aerosol pollution, etc. This remains a challenging task to design the HVDC transmission system at extended potential levels, as HVDC system employed for a large amount of power transfer barrier in the electrical system to meet inevitable power thrust. To obtain a safe and economical design configuration, multiple experimental design measurements are essential at various climatic seasons which incorporates the tedious process and significant economical expenditure. To obtain the safe and cost-effective design dimension configuration, computational-based numerical analysis with final experimental validation offers substantial support. Using various computational methodologies, many researchers have attempted to guide the critical line design proportions to establish a safe and economical electrical environment beneath the lines at ground levels. All these computational techniques are emphasizing the algorithm iterative-based complex solutions claim the lack of computational accuracy. Hence, this work aims to provide a unique computational technique to analyse the ionised electromagnetic field environment of a unipolar UHV dc transmission system using modelling of the physics of the corona discharge procedure in the active high electrostatic field zone. Modelling of the corona discharge includes the estimation of the amount of new ionized ions generated in the ionization region dynamically claims complex less equations offer a unique solution. To validate the accuracy of the proposed computational technique, multiple outdoor experimental measurements are carried out at HV/EHV/UHV potential applications and discussed. Also, the computed results are compared with the experimental findings, from the comparison outstanding computational accuracy was marked.

Significant Mid‐ and Low‐Latitude Ionospheric Disturbances Characterized by Dynamic EIA, EPBs, and SED Variations During the 13–14 March 2022 Geomagnetic Storm

AbstractThis work investigates mid‐ and low‐latitude ionospheric disturbances over the American sector during a moderate but geo‐effective geomagnetic storm on 13–14 March 2022 (π‐Day storm), using ground‐based Global Navigation Satellite System total electron content data, ionosonde observations, and space‐borne measurements from the Global‐scale Observations of Limb and Disk (GOLD), Swarm, the Defense Meteorological Satellite Program (DMSP), and the Ionospheric Connection Explorer (ICON) satellites. Our results show that this modest but geo‐effective storm created a number of large ionospheric disturbances, especially the dynamic multi‐scale electron density gradient features in the storm main phase as follows: (a) The low‐latitude equatorial ionization anomaly (EIA) exhibited a dramatic storm‐time deformation and reformation, where the EIA crests evolved into a bright equatorial band for 1–2 hr and then quickly separated back into the typical double‐crest structure with a broad crest width and deep equatorial trough. (b) Strong equatorial plasma bubbles (EPBs) occurred with an abnormally high latitude/altitude extension, reaching the geomagnetic latitude of ∼30°, corresponding to an Apex height of 2,600 km above the dip equator. (c) The midlatitude ionosphere experienced a conspicuous storm‐enhanced density (SED) plume structure associated with the subauroral polarization stream (SAPS). This SED/SAPS feature showed an unusual temporal variation that intensified and diminished twice. These distinct mid‐ and low‐latitude ionospheric disturbances could be attributed to the storm‐time electrodynamic effect of electric field perturbation, along with contributions from neutral dynamics and thermospheric composition change.

Predicting the electronic density response of condensed-phase systems to electric field perturbations.

We present a local and transferable machine-learning approach capable of predicting the real-space density response of both molecules and periodic systems to homogeneous electric fields. The new method, Symmetry-Adapted Learning of Three-dimensional Electron Responses (SALTER), builds on the symmetry-adapted Gaussian process regression symmetry-adapted learning of three-dimensional electron densities framework. SALTER requires only a small, but necessary, modification to the descriptors used to represent the atomic environments. We present the performance of the method on isolated water molecules, bulk water, and a naphthalene crystal. Root mean square errors of the predicted density response lie at or below 10% with barely more than 100 training structures. Derived polarizability tensors and even Raman spectra further derived from these tensors show good agreement with those calculated directly from quantum mechanical methods. Therefore, SALTER shows excellent performance when predicting derived quantities, while retaining all of the information contained in the full electronic response. Thus, this method is capable of predicting vector fields in a chemical context and serves as a landmark for further developments.

A dataset of field-aligned Poynting flux in the dayside polar cap of the northern hemisphere during 2014-2016

The transport of electromagnetic energy in the polar upper atmosphere and its spatial and temporal distribution are current hot issues and important topics for studying the polar upper atmospheric environment and space weather forecasting models. Researchers usually adopted the observations from low-altitude polar-orbiting satellites to estimate the magnitude and direction of electromagnetic energy. The continuous accumulation of electromagnetic energy data will be beneficial to the study on the transmission and variation characteristics of electromagnetic energy in the polar ionosphere in China. In this paper, we estimated the distribution of field-aligned Poynting flux, horizontal convection electric field and magnetic field perturbation in the dayside polar cap based on the plasma velocity and magnetic field data of DMSP F17 satellite in the northern hemisphere during 2014-2016. The initial DMSP F17 satellite data included in this dataset are of high quality. The estimation process is rigorous and reasonable, and the data records are complete. The dataset can provide important data support for the study on energy transport and dissipation in the ionosphere/thermosphere in the polar region.

Electric and magnetic conductivities in magnetized fermion systems

In Wigner function approach with relaxation time approximation, we calculate electric and magnetic conductivities of a fermion system in the strong magnetic field. The linear response has been calculated to the perturbation of electromagnetic fields on the background constant magnetic field. The Wigner function is separated into an equilibrium part in the background magnetic field and an off-equilibrium part induced by perturbative fields. The analytical expression for the equilibrium part and the corresponding equilibrium conditions are given. For the off-equilibrium part, we obtain the kinetic equation at the leading order in $\ensuremath{\hbar}$ from the master equation of the Wigner function. When perturbative fields only depend on the proper time, the off-equilibrium part can be analytically solved, from which the vector and axial vector currents are obtained. We obtain the longitudinal and transverse Ohm conductivities as well as Hall conductivity as the linear response of the vector current to the perturbative electric field. The behaviors of these conductivities as functions of the evolving time, relaxation time, particle mass, and strength of the background magnetic field are investigated both analytically and numerically.

Protected spin-orbit induced absorption divergence in distorted Landau levels

The effect of spin-orbit (and Darwin) interaction on a 2D electron gas subject to a radial symmetric, inhomogeneous $1/r$-magnetic field is discussed analytically in a perturbative and non-perturbative manner. For this purpose, we investigate the radial Hall conductivity that emerges from an additional homogeneous electric field perturbation perpendicular to the 2D electron gas, which solely interacts via spin-orbit coupling. Numerical calculations of the absorptive spin-orbit spectra show for an ideal InSb electron gas a behaviour that is dominated by the localized (atomic) part of the distorted Landau levels. In contrast, however, we also find analytically that a (non-local) divergent static response emerges for Fermi energies close to the ionization energy in the thermodynamic limit. The divergent linear response implies that the external electric field is entirely absorbed outside the 2D electron gas by induced radial spin-orbit currents, as it would be the case inside a perfect conductor. This spin-orbit induced polarization mechanism depends on the effective $g^*$-factor of the material for which it shows a critical behaviour at $g^*_c=2$, where it abruptly switches direction. The diverging absorption relies on the presence of degenerate energies with allowed selection rules that are imposed by the radial symmetry of our inhomogeneous setup. We show analytically the presence of a discrete Rydberg-like band structure that obeys these symmetry properties. In a last step, we investigate the robustness of the spectra by solving analytically the Dirac equation expanded up to order $1/(mc)^2$. We find that the distorted Landau-levels, and thus the divergent spin-orbit polarization, remain protected with respect to slow changes of the applied $1/r$-magnetic field.

Theoretical and Experimental Investigation of the Electronic Propensity Rule: A Linear Relationship between Radiative and Nonradiative Decay Rates of Molecules

The electronic propensity rule, which suggests a proportional relationship between radiative and nonradiative electronic coupling elements in fluorescent molecules, has been postulated for some time. Despite its potential significance, the rule has not been rigorously derived and experimentally validated. In this work, we draw upon the theoretical framework established by Schuurmans et al. for the relation between the radiative and nonradiative electronic coupling elements of the rare earth metal in the crystal at low temperature and extend their approach to the fluorescent molecules under external electric field perturbation at a fixed energy gap and varied temperatures, with a further single-electron approximation (Schuurmans, M. F. H., et al. Physica B & C 1984, 123, 131-155). We obtained a linear relation between the radiative decay rates and nonradiative decay rates for internal conversion, which is verified by experimental data from two types of dextran-dye complexes and the light-harvesting antenna complex in photosynthetic bacteria.

The Inner Structure of STEVE‐Linked SAID

AbstractWe found the inner electromagnetic structure of subauroral ion drifts (SAID) in the SAID‐STEVE events documented by the Swarm spacecraft and numerically simulated the ionospheric feedback instability (IFI) development for one of the four similar events. Good quantitative agreement of the modeling results with the observed features shows that the ionospheric feedback mechanism captures their basic underlying physics. Simulations require nonlinear saturation of the IFI‐generated dispersive Alfvén waves. That is, a strong driving field of STEVE‐linked SAID with a deep density trough leads to a nonlinear system of dispersive Alfvén waves coupled with the density perturbation and parallel electric fields. As shown earlier, these fields produce the suprathermal electron population and energy balance necessary for the STEVE and Picket Fence radiation. Therefore, our results predict their inner structure.

Global Observations of the Short‐Term Disturbances in the Geomagnetic Field and Induced Currents During the Supersubstorms Events of Solar Cycle 24

AbstractFour supersubstorms of the solar cycle 24 are analyzed to investigate the global variations in the H‐component and geomagnetically induced currents (GICs). The response to the storm sudden commencement (SSC) of the 2012 and 2017 events is observed differently over different latitude bands. Initially, the latitude band of 0°–45° shows a step‐like preliminary positive impulse (PPI), 45°–65° shows a Gaussian‐kind of PPI and 65°–90° shows a preliminary reverse impulse, followed by a main impulse all over. The H‐component variations during the supersubstorm periods show a strong north‐south asymmetry over the high latitudes which is attributed to the seasonal dependence of the growth and decay of ionospheric currents respectively in the summer and winter hemispheres. The co‐latitude band of ∼55°–65° shows a complete reversal of phase (i.e., global positive peak) of the H‐component compared to the maximum depression observed from the close‐by latitude bands and peak depressions in the SYM‐H, SML, and AE indices. The low latitude variations exhibit a dominant local time‐dependent control of the perturbation electric fields over the short and long terms during the geomagnetic events. The D‐component variations reflect complex ionospheric contributions during the SSC and the main phase with more asymmetries and variability. The GIC threat represented by the dB/dt peaks during the supersubstorms shows the highest magnitude (∼900 nT/min) in the latitude band of 60°–75° with a secondary peak over the dip equatorial regions. Further, some scattered and prominent peaks over the mid and high latitudes outside the supersubstorm periods are also observed.

Local electric field perturbations due to trapping mechanisms at defects: What random telegraph noise reveals

As devices scale closer to the atomic size, a complete understanding of the physical mechanisms involving defects in high-κ dielectrics is essential to improve the performance of electron devices and to mitigate key reliability phenomena, such as Random Telegraph Noise (RTN). In fact, crucial aspects of defects in HfO2 are still under investigation (e.g., the presence of metastable states and their properties), but it is well known that oxygen vacancies (V+s) and oxygen ions (O0s) are the most abundant defects in HfO2. In this work, we use simulations to gain insights into the RTN that emerges when a constant voltage is applied across a TiN/(4 nm)HfO2/TiN stack. Signals exhibit different RTN properties over bias and, thus, appear to originate from different traps. Yet, we demonstrate that they can be instead promoted by the same O0s which change their capture (τc) and emission (τe) time constants with the applied bias, which, in turn, changes the extent of their electrostatic interactions with the traps that assist charge transport (V+s). For a certain bias, RTN is given by the modulation of the trap-assisted current at V+s induced by trapping/detrapping events at O0s, which are, in turn, influenced by the bias itself and by trapped charge at nearby O0s. In this work, we demonstrate that accounting for the effect of trapped charge is essential to provide accurate estimation of the RTN parameters, which allow us to retrieve information about traps and to explain key mechanisms behind complex RTN signals.