Electric Field Signal Research Articles

The Electric Field and Waves Instruments on the Radiation Belt Storm Probes Mission

The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ∼15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the “highest quality” events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing et al. Space Sci. Rev. 2013).

Radially polarized tip-enhanced near-field coherent anti-Stokes Raman scattering microscopy for vibrational nano-imaging

We report a radially polarized tip-enhanced near-field coherent anti-Stokes Raman scattering (RP-TE-CARS) microscopy technique for high-contrast vibrational imaging of subcellular organelles at nano-scale resolutions. The radially polarized pump and Stokes laser beams are tightly focused onto the sample while a gold-coated metallic probe is placed at the upper surface of the sample to enhance the electric field and CARS signals. The back-scattered CARS signal is measured with the gold-coated nano-tip being stationary at the focal region of laser beams. The RP-TE-CARS signal is ∼6-fold higher than that using linearly polarized laser excitation. We demonstrate the good performance of the RP-TE-CARS technique developed by imaging sub-micron polystyrene beads and mitochondria at nano-scale resolutions.

Poloidal ULF wave observed in the plasmasphere boundary layer

AbstractWe report on a rare ultra‐low‐frequency (ULF) wave generation event associated with the formation of a plasmasphere boundary layer (PBL), which was well observed by one of the THEMIS satellites, TH‐D, during subsequent outbound passes. On 13 September 2011, TH‐D observed a sharp plasmapause at L = 3.4. The plasmasphere started to expand and continued to be refilled on 14 September. On 15 September, a PBL was formed with two density gradients at L = 4.4 and 6.5, respectively. Within the two density gradients, strong radial magnetic field and azimuthal electric field oscillations were observed, suggesting poloidal ULF waves. Based on the phase delay between magnetic and electric field signals, as well as the comparison between the observed wave frequency and predicted harmonic eigenfrequency, we find that the observed oscillations are second harmonic poloidal waves. Further investigation shows that the observed waves are likely generated by drift‐bounce resonance with “bump‐on‐tail” plasma distributions at ~10 keV. We demonstrate that the waves are excited within the PBL where the eigenfrequency is close to the bounce frequency of these hot protons, but not outside the PBL where the eigenfrequency deviates from the bounce frequency. Finally, we suggest that cold plasma density seems to be a controlling factor for ULF wave generation as well, in addition to the bump‐on‐tail energy source, by altering eigenfrequency of the local field lines.

Study of Eddy Electromagnetic Fields Induced by Propeller Rotating in the Earth's Magnetic Field

A mathematical analytic expression is proposed to calculate the eddy electromagnetic fields induced by rotating simplified propeller model based on Faradays law. The simulation of this model gives the distribution characteristics of the induced electric field signals. The longitudinal characteristics and transit characteristics shows the transit characteristics is discrete and has apparent characteristics.

Research on the Charged Omni-Directional Spatial Electric Field Tester

The spatial electric field tester is mainly used for the measurement of high-altitude electrostatic field. The spatial electric field tester will be electrostatically charged during the period it is sent to a certain height by a micro-rocket. In order to study the charge characteristics, the paper analyzes the charging mechanism of the omni-directional spatial electric field tester and builds mathematics model for the friction charging, which is a main factor of the charging process. The numerical calculation and experimental research demonstrate that the friction introduces a slow charge accumulation process for the electric field instrument in the course of its campaign. Under the testing conditions in this paper, the charge amount is 10-11 C within the 6s duration. In order to improve the accuracy of the electric field measurement, a time-frequency analysis method can be adopted to remove the slow-varying electric field signal.

Volumetric Thermoacoustic Imaging over Large Fields of View

The thermoacoustic (TA) contrast mechanism relies on rapid tissue heating and subsequent thermal expansion. TA computerized tomography (TCT) is therefore inverse source imaging. The TA contrast mechanism provides information complementary to that revealed by current diagnostic imaging techniques, but has been limited to just a few centimeters depth penetration. In this article, whole organ TCT is demonstrated on a large swine kidney. TA sinograms show that TA signal generated by high-power, very high frequency (VHF) electromagnetic pulses is detectable after travel through 6 cm of soft tissue. Reconstructed images provide resolution sufficient to track progression of calyces throughout the kidney. Because VHF electromagnetic energy can easily penetrate the abdomen of large adults, our results indicate that whole organ TA imaging is feasible in vivo, provided an ultrasound array can be placed near the region of interest. Pulses of 22 to 25 kW with carrier frequency 108 MHz and 900 ns pulse width were applied at a 100-Hz pulse repetition frequency to generate a 13-kV/m electric field and TA signal. Only 2 to 5 mJ was absorbed in the kidney per pulse, causing temperature and pressure jumps of only 5e-6°C and 4 Pa averaged throughout the 141-g specimen. TA pulses were detected by focused, single-element transducers (V306, Panametrics), amplified by 54 dB and averaged 64 times to reduce electronic noise. Data were measured over a cylindrical measurement aperture of radius 5 cm and length 6 cm, by rotating the specimen 1.8 degrees between tomographic views and translating 2 mm between slices. Reconstruction via filtered backprojection yields in-plane resolution better than 5 mm, but suffers significant blurring between planes. Both in-plane resolution and slice sensitivity profile could be improved by applying shorter irradiation pulsewidths and using less directional transducers. Both hardware changes would be recommended for a clinical prototype.

The Design and Implementation of Ship Electric Field Measurement System Based on MSP430

The ship electric field has become a new physical field which is widely concerned at home and abroad in recent years. For the research of ship electric field, one of the most effective methods is to measure it underwater. According to the analysis of ship electric field signal’s characteristics, the ship electric field measurement system based on MSP430F149 was designed and the key technologies of software and hardware were also presented in this paper. The results of experiment demonstrated that the system could effectively measure the ship electric field signal in a low SNR. Meanwhile, it has the advantages of low power consumption, high accuracy and credible.

The Fluid Power Control Performance Comparison Study of Two-Type ER Valve Based on FLUENT

The current flow and pressure drop of ER valve which is a new type power control valve could be adjusted by the electric field signal directly .In this paper, the fluid power control performance of concentric cylindrical ER valve and parallel plate-type ER valve based on ER principal is comparative studied .First power control equation has been analysed, and then flow simulation of internal flow field of ER valve has been taken based on FLUENT software. The results show that with the increasing of the strength of excitation field, the flow through the two different type of ER valve decreases, the pressure drop between import and export is even greater; and the fluid power control performance of parallel plate-type ER valve is superior to concentric cylindrical ER valve under the same control volume.

Design and Application of Natural Audio Electric Field Frequency Selecting Instrument

An observation scheme, which is designed several frequencies suited over the natural audio electric field frequency range, is used to qualitatively understand the electrical structure of underground geological body. Weak signal detection technology has been used to amplify and filter the weak natural electric field signal, and read out them after selecting corresponding frequencies and integrating. This instrument can observe eight natural electric field signal at frequency of 8Hz, 16Hz, 32Hz, 64Hz, 128Hz, 256Hz, 512Hz, 1024Hz. Several reliable technologies have been used in the hardware design and software development to improve both the anti-interferences capability and system stability. Compared with field work instance, we conclude that natural audio electric field frequency selecting instrument can get the underground geological information within a certain depth, and therefore it can be used for fast survey in geology and mineral resources, and in engineering geophysical and water resources.

SU-E-I-177: Electric Field and Ionization Signal Simulation in Liquid Xenon Detectors for PET

Purpose: A liquid xenon (LXe) detector prototype was developed to assess the performance of LXe for use in positron emission tomography. In this prototype, the measurement of ionization signals was achieved by using a time projection chamber (TPC), and scintillation light was measured by large area avalanche photodiodes. This work is aimed to simulate the electric field and readout signals in the LXe TPC.Methods: The electric field inside a single sector of the prototype detector was calculated through the finite element method using the software of Opera‐3d, with focus given to determining the uniformity of the field. The simulation model consists of a cathode, an anode, and field cage strips, which were immersed in a liquid xenon volume. With the electric field map obtained by Opera‐3d, the signals simulation were implemented in the Garfield package. The detector responses, including the primary ionization, generation of electron clouds, electron drift, diffusion, induced current signals on induction wires, and collection signals on anodes, were simulated. Comparison of simulation signals and measurement signals was made.Results: Three‐dimensional simulation results for the prototype detector showed that the field was nearly uniform in the center, with electron drifts deviating by less than 1 mm between the cathode and anode. The region of dead space constitutes 2.9% of the total volume in this sector. The simulation signals were in a good agreement with measurements. Conclusions: The good uniformity inside the chamber guaranteed 3‐D sub‐millimeter position resolution across the entire field of view. Based on the 3D electric field map, we can assign correction factors to correct the non‐uniformity in the whole sector. We also correctly simulated the signals of the TPC.

Lightning-generated whistler waves observed by probes on the Communication/Navigation Outage Forecast System satellite at low latitudes

Direct evidence is presented for a causal relationship between lightning and strong electric field transients inside equatorial ionospheric density depletions. In fact, these whistler mode plasma waves may be the dominant electric field signal within such depletions. Optical lightning data from the Communication/Navigation Outage Forecast System (C/NOFS) satellite and global lightning location information from the World Wide Lightning Location Network are presented as independent verification that these electric field transients are caused by lightning. The electric field instrument on C/NOFS routinely measures lightning ]related electric field wave packets or sferics, associated with simultaneous measurements of optical flashes at all altitudes encountered by the satellite (401.867 km). Lightning ]generated whistler waves have abundant access to the topside ionosphere, even close to the magnetic equator.

Integrated optics magnetic sensor from 2 kHz to 9 GHz

A new type of integrated optical magnetic field sensor is presented in this paper. The proposed sensor consists of a Mach-Zehnder waveguide interferometer and a doubly loaded loop antenna. Such a structure can successfully avoid detection of the undesired electric field signal. The size of the sensor is 35 mm×6 mm×1 mm. The measurements show that the frequency response is from 2 kHz to 9 GHz, the dynamic range is 98 dB, and the minimum detectable magnetic field is 51.8 μA/m at 1 GHz. Therefore, this sensing system can be used in electromagnetic compatibility measurements.

Finite Size Scaling of Hysteresis Behavior: Monte Carlo Simulation on DIFFOUR Model

In this work, Monte Carlo simulation was used to study the size dependence of the dynamic hysteresis properties of 2 dimensional ferroelectric system. The DIFFOUR model and Metropolis algorithm were used to investigate the size effect on hysteresis properties. From the simulation, it was found that the competition between the electric field parameters and the system size plays a crucial role on the phase-lag between the polarization and the electric field signals, which defines particular hysteresis properties. In describing the hysteresis behavior qualitatively, finite size scaling formalism, in a power law form, was used to predict relations among the field parameters, system size, and hysteresis. The purpose was to establish phenomenological knowledge of how dynamic perturbations affect the hysteresis in finite ferroelectric system. Comparison with related experiments was also discussed.

A Method of Extracting Line Spectrum of Ship's Shift-Rate Electric Field Signal

The line spectrum of shift-rate electric field is an important characteristic of ship, so it is very useful to detect the harmonics in shift-rate signal to ship's subwater detection. In this paper the forth order cumulant MUSIC method is used to detect the harmonics’ line spectrum in shift-rate signal and then this method is improved so that the line spectrum can be extracted from colored Gaussian noise even when the harmonics number is unknown. At last the actrually measured data detection have all proved that this improved method can precisily detect the harmonics frequency and the frequency resolution is very high.

Object size effect on the contact potential difference measured by scanning Kelvin probe method

Contact potential difference (CPD) was measured by macroscopic Kelvin probe instrument and scanning Kelvin probe microscope on Al, Ni and Pt on ITO substrates at ambient conditions. CPD values measured by scanning Kelvin probe microscope and macroscopic Kelvin probe are close within the error of about 10–30% for large studied objects, whereas scanning Kelvin probe microscope signal decreases, when the object size becomes smaller than 1.4 μm. CPD and electric field signals measured using many-pass technique allowed us to estimate the influence of electrostatic field disturbance, especially, in the case of small objects.

AC Electric Field Communication for Human-Area Networking

We have proposed a human-area networking technology that uses the surface of the human body as a data transmission path and uses an AC electric field signal below the resonant frequency of the human body. This technology aims to achieve a “touch and connect” intuitive form of communication by using the electric field signal that propagates along the surface of the human body, while suppressing both the electric field radiating from the human body and mutual interference. To suppress the radiation field, the frequency of the AC signal that excites the transmitter electrode must be lowered, and the sensitivity of the receiver must be raised while reducing transmission power to its minimally required level. We describe how we are developing AC electric field communication technologies to promote the further evolution of a human-area network in support of ubiquitous services, focusing on three main characteristics, enabling-transceiver technique, application-scenario modeling, and communications quality evaluation. Special attention is paid to the relationship between electro-magnetic compatibility evaluation and regulations for extremely low-power radio stations based on Japan's Radio Law.

The CGR4 lightning sensor

The design of the CGR4 lightning sensor is based on several observed characteristics of the electric field changes caused by nearby lightning, and the radiofrequency noise bursts from lightning. The electric field signals from lightning are detected by a simple aerial, and processed by a combination of analogue and digital circuitry under microprocessor control to determine if there is a nearby lightning flash, and, if so, to assign the type of flash as negative ground flash (NGF), positive ground flash (PGF), or cloud flash (CF). These types have distinctive features in their electric field change waveforms, enabling an assignment of type of lightning to be made by obtaining several measures of the waveform characteristics and applying an appropriate set of rules. A method of estimating the sensor's effective range and area has been developed using data for a set of nearby lightning events. This involves the recording of the variation of electric field with time, the response of a lightning sensor, and the distance to the lightning flash using thunder ranging. As the sensor is able to apply different threshold overall field changes for each type of lightning detected, a single effective range of 11.3 km (effective area 400 km) for all types of lightning was achieved by using threshold field changes of 520 volts per metre (V/m) for CF, 760 V/m for NGF, and 1200 V/m for PGF. The sensor responds to about 90 per cent of all flashes at 8 km, about 40 per cent at 11 km, and approaching zero above 16 km.

Long-range correlations in [formula omitted] investigated by DFT calculations and electron holography

The system In 2 O 3 ( ZnO ) 7 exhibits a strained ZnO-like domain structure intersected by indium containing, parallely arranged defect planes with a regular spacing of about 2.4 nm. We propose that the strain within the domains originates from long-range electric fields due to charge localization at the defects inducing ionic displacements. The origin of the electric fields has been investigated theoretically by means of density functional theory (DFT). Calculated electric fields were incorporated as scattering potentials in holographic imaging simulations. Since the exact structure of the system is unknown, a novel structure model was derived for In 2 O 3 ( ZnO ) 7 from known members of the homologous series of In 2 O 3 ( ZnO ) m with m = 3 , 5 and refined by structure optimization at DFT level. The theoretical results are compared to experimental findings in high-resolution phase images obtained by means of electron holography, which suggest residual intrinsic electric fields. A careful consideration of noise levels and the influence of the microscope, however, show that the electric field signal is at the detection limit of state-of-the-art high-resolution electron holography.

다이폴 모델링 기법을 이용한 수중 전기장 신호 특성 예측 기법 연구

본 논문에서는 함정 선체의 갈바닉 부식 전류에 의해 발생되는 수중 전기장 신호를 경계요소 해석 도구인 FNREMUS 소프트웨어를 이용하여 예측하고, 예측된 신호로부터 함정 전기장 신호 특성을 특이치 분해(singular value decomposition) 방법을 이용하여 등가적으로 다이폴 모델링하는 방법에 대해 기술하고 있다. 제안...

Modulational instability of electromagnetic electron-cyclotron wave packets in the magnetosphere with non-Maxwellian electron distribution

The satellite observations of the magnetosphere in the low-frequency ion dynamics revealed several facts: (1) localized structures for electric field signal parallel to the magnetic field; (2) anisotropy for the electron velocity distribution such that T⊥⪡T∥; and (3) non-Maxwellian distribution function for the electrons. Based on these evidences, a nonlinear model is presented to develop the electromagnetic electron-cyclotron (EMEC) theory to the non-Maxwellian plasmas. Then, the modulational instability analysis of EMEC waves is investigated.