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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Observations of large magnetospheric electric fields during the onset phase of a substorm

An auroral substorm is a highly transient process which is triggered on auroral L shells and leads to an abrupt change of state in the nightside magnetosphere. Direct measurements of electric fields in the outer magnetosphere are of critical importance to understand the processes involved in sudden substorm enhancements. Shepard et al. (1980) reported direct measurements of electric fields from the GEOS 2 satellite at equatorial latitudes which showed 15 mV/m westward inductive electric fields in association with tail collapses. Similar direct electric field measurements of the westward inductive electric field at low latitudes from the ISEE 1 satellite during the onset phase of an auroral substorm are reported in the present investigation. The observations show a rapid inward magnetic field (westward electric field) motion near midnight at low or equatorial latitudes simultaneous with the sudden onset of auroral substorm enhancements near the foot of the satellite field line.

Aggson, T. L.↗
NASA NTRS2002

Bubble Detachment in Variable Gravity Under the Influence of Electric Fields

The objective of the research is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Situations were considered with both uniform and nonuniform electric fields. Bubble formation and detachment were visualized in terrestrial gravity as well as for several levels of reduced gravity (lunar, martian and microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angles at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment in an initially uniform electric field was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. The results of the study indicate that the level of gravity and the electric field magnitude significantly affect bubble behavior as well as shape, volume and dimensions.

Herman, Cila↗
NASA NTRS1991

Conductivity and electric field variations with altitude in the stratosphere

Data regarding electric field, derived current density, and conductivity are presented for two balloons from the Electrodynamics of the Middle Atmosphere experiment which underwent the longest period of daily altitude variation. The magnetic L values range from 4.3 to 9.5 for the 18 days of Southern Hemisphere statistics, and the average conductivity and vertical electric fields are given. Simultaneous measurements of the average conductivity scale height and the vertical electric-field scale height indicate that vertical current density does not vary with altitude in the 10-28-km range. The measured conductivity varies significantly at a given altitude on a particular day, and some conductivity data sets are similar to other measurements between 10 and 30 km. Comparisons of the measured data to predictions from models of stratospheric conductivity demonstrate significant discrepancies.

Holzworth, Robert H.↗
NASA NTRS1976

A model for polar cap electric fields

A model is proposed relating polar cap ionospheric electric fields to the parameters of the solar wind near the orbit of the earth. The model ignores the notion of field line merging. An essential feature is the role played by velocity shear instabilities in regions of the outer magnetosphere, in which mapping of the magnetosheath electric field would produce sunward convection. The anomalous resistivity which arises from velocity shear turbulence, suffices to essentially disconnect the magnetosphere from the magnetosheath, at any place where that resistivity is large enough. The magnetosheath-magnetosphere system, as a consequence, acts as a kind of diode or rectifier for the magnetosheath electric fields. Predictions of the model are compared with several observations related to polar cap convection.

Dangelo, N.↗
NASA NTRS1979

Motions of charged particles in the Magnetosphere under the influence of a time-varying large scale convection electric field

The motions of charged particles under the influence of the geomagnetic and electric fields were quite complex in the region of the inner magnetosphere. The Volland-Stern type large scale convection electric field was used successfully to predict both the plasmapause location and particle enhancements determined from Explorer 45 measurements. A time dependence in this electric field was introduced based on the variation in Kp for actual magnetic storm conditions. The particle trajectories were computed as they change in this time-varying electric field. Several storm fronts of particles of different magnetic moments were allowed to be injected into the inner magnetosphere from L = 10 in the equatorial plane. The motions of these fronts are presented in a movie format.

Smith, P. H.↗
NASA NTRS2006

Analyzing Electric Field Morphology Through Data-Model Comparisons of the GEM IM/S Assessment Challenge Events

The storm-time inner magnetospheric electric field morphology and dynamics are assessed by comparing numerical modeling results of the plasmasphere and ring current with many in situ and remote sensing data sets. Two magnetic storms are analyzed, April 22,2001 and October 21-23,2001, which are the events selected for the Geospace Environment Modeling (GEM) Inner Magnetosphere/Storms (IM/S) Assessment Challenge (IMSAC). The IMSAC seeks to quantify the accuracy of inner magnetospheric models as well as synthesize our understanding of this region. For each storm, the ring current-atmosphere interaction model (RAM) and the dynamic global core plasma model (DGCPM) were run together with various settings for the large-scale convection electric field and the nightside ionospheric conductance. DGCPM plasmaspheric parameters were compared with IMAGE-EUV plasmapause extractions and LANL-MPA plume locations and velocities. RAM parameters were compared with Dst*, LANL-MPA fluxes and moments, IMAGE-MENA images, and IMAGE-HENA images. Both qualitative and quantitative comparisons were made to determine the electric field morphology that allows the model results to best fit the plasma data at various times during these events. The simulations with self-consistent electric fields were, in general, better than those with prescribed field choices. This indicates that the time-dependent modulation of the inner magnetospheric electric fields by the nightside ionosphere is quite significant for accurate determination of these fields (and their effects). It was determined that a shielded Volland-Stern field description driven by the 3-hour Kp index yields accurate results much of the time, but can be quite inconsistent. The modified Mcllwain field description clearly lagged in overall accuracy compared to the other fields, but matched some data sets (like Dst*) quite well. The rankings between the simulations varied depending on the storm and the individual data sets, indicating that each field description did well for some place, time, and energy range during the events, as well as doing less well in other places, times, and energies. Several unresolved issues regarding the storm-time inner magnetospheric electric field are discussed.

Liemohn, Michael W.↗
DOE OSTI2025

Elucidating the Role of Electric Fields in Fe Oxidation via an Environmental Atom Probe

Abstract We quantify the effects of intensely applied electric fields on the Fe oxidation mechanism. The specimen are pristine Fe single crystals exposing a variety of surface structures identified by field ion microscopy. These crystals are simultaneously exposed to low pressures of pure oxygen gas, on the order of 10 −7 mbar, while applying intense electric fields on their surface of several tens of volts per nanometer. The local composition of the different surface structures is probed directly and in real time using an Environmental Atom Probe and successfully compared with first principles‐based models. We found that rough Fe{244} and Fe{112} facets are more reactive toward oxygen than compact Fe{024} and Fe{011} facets. Results demonstrate that the influence of an electric field on the oxidation kinetics depends on the timescales that are involved as the system evolves toward equilibrium. The initial oxidation kinetics show that strong increases in electric fields facilitate the formation of an oxide. However, as one approaches equilibrium, high field values mitigate this formation. Ultimately, this study elucidates how high externally applied electric fields can be used to dynamically exploit reaction dynamics at the nanoscale towards desired products in a catalytic reaction at mild reaction conditions.

Lambeets, Sten V. [Physical and Computational Scie↗
DOE OSTI2026

Pulsed Electric Field Processing of Apples

Pulsed electric field (PEF) processing is a nonthermal technology that has the potential to improve the efficiency of apple processing, particularly for firm cultivars that are growing in popularity. This study evaluated the effects of PEF pretreatment on the processability and product quality of Cosmic Crisp apples, a modern cultivar known for its firmness. Apples were treated with PEF and assessed for tissue softening, mechanical energy requirements, particle size reduction, browning tendencies, and juice yield. PEF treatment significantly softened the apple tissue, as demonstrated by reduced compression forces in Instron testing, and this softening translated to decreased grinding energy during applesauce production. There were no changes to the particle size distribution of the resulting applesauce. PEF treatment also altered browning behavior and produced higher juice yields following mechanical disruption, suggesting enhanced membrane permeability and mass transfer. Together, these results show that PEF pretreatment can reduce mechanical energy demands and increase extractability without reducing product quality in firm apple varieties. These outcomes highlight the potential of PEF to increase the value recovered from processing-grade apples and to support more efficient and sustainable apple processing operations.

32 - ENERGY CONSERVATION, CONSUMPTION, AND UTILIZA↗
NASA NTRS1989

A new source of horizontal electric fields in the mid-latitude stratosphere

Superpressure balloon-borne instruments that measure the vector stratospheric electric field at latitudes near 45 + or - 10 deg S reveal several features in fair weather that cannot be attributed to ionospheric, thunderstorm, or other known sources. Over 180 days of electric field, conductivity, and current density data have been taken at the constant altitude of 26 km, using long-duration balloon flights in the Southern Hemisphere. Throughout these data the fair-weather horizontal electric field has a magnitude (10-50 mV/m) that cannot be due to mid-latitude ionospheric dynamo action. Furthermore, the fields are highly variable in amplitude, almost turbulent in appearance, while the vector direction steadily rotates in a counterclockwise manner. The period of this rotation is close to the quasi-inertial wave period for the latitude of the balloon. For these flights, the electric field rotation period varies between 14 and 21 hours. Some possible causes that might explain the electric field and current measurements reported herein are discussed.

Holzworth, R. H.↗
NASA NTRS1985

Electric Field Containerless Processing Technology

The objective of this task is to develop the science and technology base required to design and construct a high temperature electric field positioning module that could be used by materials scientists to conduct containerless science experiments in a low gravity environment. Containerless science modules that employ electric fields to position and manipulate samples offer several advantages over acoustic or electromagnetic systems. The electric field system will operate not only at atmospheric pressures but also in a vacuum, in contrast to the acoustic modules which can only operate in atmosphere where the acoustic forces are sufficient. The electric field technique puts minimum energy into the sample, whereas the electromagnetic system can deposit energy into the sample through eddy current heat as well as physical mixing in the sample. Two types of electric field modules have been constructed and tested to date. One employs a charged sample and uses electrostatic forces to position and control the sample. The second type of module induces electrical polarization of the sample and electric field gradients to position and control the sample.

Elleman, D. D.↗
NASA NTRS1985

Electrostatic ion-cyclotron instability caused by a nonuniform electric field perpendicular to the external magnetic field

A new mechanism that can destablize kinetic ion-cyclotron waves in the presence of a nonuniform electric field perpendicular to the uniform ambient magnetic field is given. In the absence of the electric field, the mode energy is positive, while in the presence of a uniform electric field the mode energy could be negative. However, when the electric field is nonuniform, it is possible for a finite region to be of negative wave energy surrounded by regions of positive wave energy. A nonlocal wave packet couples the two regions so that a flow of energy from the region of negative wave energy to the region of positive wave energy will cause the mode to grow. This gives rise to the instability.

Ganguli, G.↗
NASA NTRS1988

A model study of how electric field structures affect the polar cap F region

The ionospheric polar F region's response to a series of electric field structures is studied theoretically, modeling individual electric field structures as elongated two-cell Volland patterns. A semiempirical model of a single electric field structure is developed, and specific structure polar cap electric field models are described. The results of using these models as an input to the Utah State University time-dependent ionospheric model (TDIM) are presented. The implications of the results for present-day 'smooth' input simulations are considered.

Sojka, J. J.↗
NASA NTRS2002

Bubble Formation and Detachment in Reduced Gravity Under the Influence of Electric Fields

The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Both uniform and nonuniform electric field configurations were considered. Bubble formation and detachment were recorded and visualized in reduced gravity (corresponding to gravity levels on Mars, on the Moon as well as microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

Herman, Cila↗
NASA NTRS1972

Lightning criteria relative to space shuttles: Currents and electric field intensity in Florida lightning

The measured electric field intensities of 161 lightning strokes in 39 flashes which occurred between 1 and 35 km from an observation point at Kennedy Space Center, Florida during June and July of 1971 have been analyzed to determine the lightning channel currents which produced the fields. In addition, typical channel currents are derived and from these typical electric fields at distances between 0.5 and 100 km are computed and presented. On the basis of the results recommendations are made for changes in the specification of lightning properties relative to space vehicle design as given in NASA TMX-64589 (Daniels, 1971). The small sample of lightning analyzed yielded several peak currents in the 100 kA range. Several current rise-times from zero to peak of 0.5 microsec or faster were found; and the fastest observed current rate-of-rise was near 200 kA/microsec. The various sources of error are discussed.

Uman, M. A.↗
NASA NTRS1994

Geotail observations of spiky electric fields and low-frequency waves in the plasma sheet and plasma sheet boundary

Electric field data from the Geotail spacecraft provide an opportunity to extend the observations of spiky fields made by International Sun Earth Explorer-1 (ISEE-1) to a region of the magnetosphere where quasistatic electric field measurements have not previously been msde, to examine their possible importance in the dynamics of the middle and distant tail, and to test some hypotheses about their formation. In this paper, examples of large fields in the plasma sheet and its boundary at radial distances up to approximately 90 R(sub E) are presented. It is shown that three different types of large electric fields can occur: (1) spiky fields; (2) 'DC' fields; and (3) waves at frequencies comparable to the lower hybrid frequency. There is usually a gradation between (1) and (3), and often large electric field spikes are embedded in regions of lower amplitude waves. The waves tend to occur in short (few to 10's of seconds) packets whose start and stop times are not always correlated with changes in the magnetic field and/or density (as indicated by the spacecraft potential). The peak frequency is often less than but comparable to the lower hybrid frequency in agreement with theories of lower hybrid drift waves in the magnetotail. The largest spikes are not always associated with the largest changes in the spacecraft potential and/or magnetic field. It is suggested that the spiky fields may represent the nonlinear development of the waves.

Cattell, C.↗
NASA NTRS1993

The cone structure and focusing of the electric field of VLF and LF waves at high altitudes of the ionosphere

This paper presents a short review of the frequency and angle dependencies of the electric field radiated by an electric dipole E = E(sub 0)cos(omega)t in a magnetoplasma and detailed results of numerical calculations of (E) in the VLF and LF frequency bands 0.02f(sub b) is less than or equal to F is less than or equal to 0.5f(sub b) in the ionosphere and magnetosphere in the altitude region Z = (800 - 6000) km (F is approximately (4 - 500) kHz and f(sub b) is approximately equal to (1.1 to 0.2) MHz is the electron gyro-frequency). The amplitudes of the electric field have large maxima in four regions: close to the direction of the Earth magnetic field line B(sub 0) (it is the so called Axis field E(sub 0); in the Storey E(sub St); Reversed Storey E(sub RevSt); and Resonance E(sub Res) Cones. The maximal values of E(sub 0), E(sub Res), and E(sub Rev ST) are the most pronounced close to the low hybrid frequency, F is approximately F(sub L). The flux of the electric field is concentrated in very narrow regions, with the apexes angles of the cones delta(beta) is approximately (0.1 - 1) degree. The enhancement and focusing of the electric field increases with altitude starting at Z is greater than 800 km. At Z is greater than or equal to 1000 up to 6000 km, the relative value of E, in comparison with its value at Z equals 800 km is about (10(exp 2) to 10(exp 10)) times larger. Thus, the flux of VLF and LF electromagnetic waves in the Earth magnetoplasma produces and is guided by very narrow pencil beams, similar, let us say, to laser beams.

Alpert, Y. L.↗
NASA NTRS1988

Comparison of fast electric field changes from subsequent return strokes of natural and triggered lightning

Fast electric field changes from subsequent return strokes of natural and triggered lightning with propagation paths almost entirely over water are compared. Data were collected at the Kennedy Space Center, Florida. Comparisons have been made of the average shape, the rise time and the spectrum of the electric field changes. The electric field changes from the triggered flashes tend to rise to peak faster and decay faster than do their counterparts in natural cloud-to-ground flashes.

Le Vine, D. M.↗