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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

High-latitude day side electric field and particle measurements

Two rockets carrying electric field and low-energy particle instrumentation were launched near noon at 80 deg magnetic latitude. One flight encountered polar cap conditions only, whereas the other traversed part of the polar cusp. Although weak particle precipitation was measured on both flights, bursts of intense magnetosheath-type electron fluxes were detected on the latter. Strong electric fields such as would result from antisunward convection were observed during both flights. The measurements are compared with results obtained by other types of spacecraft and are interpreted in the light of those data. It is concluded that direct access of magnetosheath electrons is very variable and occurs in small regions within a larger overall region.-

Maynard, N. C.↗
NASA NTRS1982

A thundercloud electric field sounding - Charge distribution and lightning

An instrumented free balloon measured electric fields and field changes as it rose through a thundercloud above Langmuir Laboratory, New Mexico. The variation of the electric field with altitude implied that the cloud contained negative space charge of density -0.6 to -4 nC/cu m between 5.5 and 8.0 km MSL. The environmental temperature at these levels ranged from -5 to -20 C. The measurements imply that the areal extent of this negative charge center was significantly greater than that of the cloud's intense precipitation shafts. At altitudes greater than 8 km, the instrument ascended past net positive charge. In addition, positive space charge adjacent to the earth's surface (concentration 0.6 nC/cu m and in the lowest portion of the cloud (1.0 nC/cu m) is inferred from the measurements. Electric field changes from intracloud lightning were interpreted by using a simple model for the developing streamer of the initial phase. Thunder source reconstructions provided estimates for the orientation of lightning channels. Seven 'streamers' so analyzed propagated on the average, at 50,000 m/s and carried a current of 390 A. The mean charge dissipated during a flash was 30 C.

Weber, M. E.↗
NASA NTRS2007

Inner Magnetospheric Electric Fields Derived from IMAGE EUV

The local and global patterns of plasmaspheric plasma transport reflect the influence of electric fields imposed by all sources in the inner magnetosphere. Image sequences of thermal plasma G:istribution obtained from the IMAGE Mission Extreme Ultraviolet Imager can be used to derive plasma motions and, using a magnetic field model, the corresponding electric fields. These motions and fields directly reflect the dynamic coupling of injected plasmasheet plasma and the ionosphere, in addition to solar wind and atmospheric drivers. What is being learned about the morphology of inner magnetospheric electric fields during storm and quite conditions from this new empirical tool will be presented and discussed.

Gallagher, D. L.↗
NASA NTRS2006

Retrieving Storm Electric Fields from Aircrfaft Field Mill Data: Part II: Applications

The Lagrange multiplier theory developed in Part I of this study is applied to complete a relative calibration of a Citation aircraft that is instrumented with six field mill sensors. When side constraints related to average fields are used, the Lagrange multiplier method performs well in computer simulations. For mill measurement errors of 1 V m(sup -1) and a 5 V m(sup -1) error in the mean fair-weather field function, the 3D storm electric field is retrieved to within an error of about 12%. A side constraint that involves estimating the detailed structure of the fair-weather field was also tested using computer simulations. For mill measurement errors of 1 V m(sup -l), the method retrieves the 3D storm field to within an error of about 8% if the fair-weather field estimate is typically within 1 V m(sup -1) of the true fair-weather field. Using this type of side constraint and data from fair-weather field maneuvers taken on 29 June 2001, the Citation aircraft was calibrated. Absolute calibration was completed using the pitch down method developed in Part I, and conventional analyses. The resulting calibration matrices were then used to retrieve storm electric fields during a Citation flight on 2 June 2001. The storm field results are encouraging and agree favorably in many respects with results derived from earlier (iterative) techniques of calibration.

Koshak, William↗
NASA NTRS1998

Effects of Convection Electric Fields on Modeled Plasmaspheric Densities and ccc Temperatures

This paper examines the effects of convection electric fields on plasmaspheric H+, O+, He+, and N+ densities and electron and ion temperatures. These effects are studied with the aid of the Field Line Interhemispheric Plasma (FLIP) model, which has recently been extended to include the effects of ExB drifts. The FLIP model solves the continuity and momentum equations for the major ion species as well as the energy equations for ions and electrons along entire drifting flux tubes from 100 km altitude in the northern hemisphere to 100 km altitude in the southern hemisphere. Electron heating in the ionosphere and plasmasphere is provided by the solution of two-stream equations for photoelectrons. The dawn-dusk electric field imposed by the solar wind causes changes in plasmaspheric density and temperature as the plasma drifts onto flux tubes having different volumes. In an idealized convection model, outward drifts in the afternoon cause decreases in the plasmasphere density and temperature while inward drifts in the evening cause increases in plasmasphere density and temperature. In this paper we examine the effects of convection electric fields on the rate of refilling of flux tubes and investigate the hypothesis that convection electric fields are responsible for the unusually high evening electron temperatures and the post-midnight density maxima often observed in the winter ionosphere above Millstone Hill.

Comfort, Richard H.↗
NASA NTRS1986

dc electric field meter with fiber-optic readout

The design of a dc electric field meter capable of measuring the magnitude and direction of the electric field at an arbitrary location above the ground plane is described. The meter is based on measuring induced charge on a split cylindrical electrode pair which is rotated around its axis of symmetry. Data readout is by fiber-optic cable using pulse frequency encoding. The sensing head is electrically isolated. Initial results are reported from a series of tests at General Electric's High Voltage Transmission Research Facility, Pittsfield, MA. The electric field was measured in a large test cage and under a dc test line. Measurement of field magnitude and direction around a human subject standing under the conductor was demonstrated.

Johnston, Alan R.↗
NASA NTRS1972

Recent probe measurements of dc electric fields from IMP 1

The measurement of dc electric fields in the magnetosphere by IMP 1 are presented. Electric fields on the order of 1 mV/m in the solar wind, with about a 40% jump at the bow shock were observed. Observational results are graphed.

Aggson, T. L.↗
NASA NTRS1986

On the influence of an external electric field on magnetotail reconnection

Magnetotail reconnection is studied under the influence of a dawn to dusk electric field applied at the high-latitude tail boundary using a two-dimensional resistive MHD code. It is found that the basic unstable sequence of tearing and plasmoid formation and ejection was not changed if the external electric field was fairly uniform. The externally forced compression, however, could shorten the onset time and the growth time of the evolution. The faster growth can be understood by the fact that the forced compression gradually alters the lobe field strength and the plasma sheet width and reduces thereby the relevant Alfven time. In fact, if the evolution of the cases with imposed electric field is rescaled on the basis of these characteristic parameters, a good quantitative agreement with the case without external electric field is found.

Birn, J.↗
NASA NTRS1973

Electric field observations by incoherent scatter radar in the auroral zone.

Analysis of ion drift velocity measurements, made for a 24-hour period in February 1972 by the incoherent scatter radar at Chatanika, Alaska (L = 5.7), provides a detailed view of electric fields and currents in the auroral zone. Large northward electric fields were seen in the evening sector, and an abrupt change to southward occurred at the start of a midnight sector substorm. The westward electric field was generally much smaller than the north-south electric field but showed a rapid increase at the time of a westward auroral surge. Study of global magnetograms and all-sky camera photographs has led to the identification of five substorms during the 24-hour observation period. These substorms were sufficiently separated in time to allow identification of the electric field and current variations in late afternoon, evening, and morning local time sectors.

Banks, P. M.↗
NASA NTRS1985

Electric fields in the plasma sheet and plasma sheet boundary layer

Results obtained by Forbes et al. (1981) on the basis of time delay measurements between ISEE 1 and ISEE 2 imply that the plasma flow and the boundary contracting velocity were nearly the same, whereas the expanding boundary velocity was not accompanied by any significant plasma sheet plasma motion. In the present study, this observation is discussed in conjunction with electric field data. The study is based on electric field data from the spherical double probe experiment on ISEE 1. Electric field data from GEOS 2 are used to some extent to monitor the electric fields near the geostationary orbit during the considered eve nts. Electric field data during CDAW 6 events are discussed, taking into account positions of ISEE 1/ISEE 2 and GEOS 2; March 22, 0600-1300 UT; and March 22, UT; and March 31, 1400-2400 UT.

Pedersen, A.↗
NASA NTRS1984

Fourier analysis of polar cap electric field and current distributions

A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

Barbosa, D. D.↗
NASA NTRS1979

Direct observation of a tangential electric field component at the magnetopause

Results are presented for direct, in situ measurements of the quasi-static electric field at and near the magnetopause, in the magnetosheath, bow shock, and solar wind, obtained by the ISEE-1 satellite. Both the large-scale average electric field and the fine-scale field observed during a magnetopause crossing show the existence of significant tangential electric field components on both sides of the magnetopause. The data in the satellite frame also show significant normal electric field components that point toward the magnetopause on both sides. The observed local level of power dissipation would correspond to a total power of 1 TW, if it existed over the entire front of the magnetopause.

Mozer, F. S.↗
NASA NTRS1972

Electric field variations during substorms - OGO-6 measurements.

The general pattern of high electric fields in magnetic time-invariant latitude coordinates is reviewed in the light of OGO-6 electric field measurements. This pattern is found to show little variability and, when unusual variations or field distributions occur, they are relatively isolated in time and space. Significant indications of direct correlation between electric field behavior and stages of magnetic bay development have not been found.

Heppner, J. P.↗
NASA NTRS1996

The Dynamics of Ultrasonically Levitated Drops in an Electric Field

Ultrasonic and electrostatic levitation techniques have allowed the experimental investigation of the nonlinear oscillatory dynamics of free droplets with diameter between 0.1 and 0.4 cm. The measurement of the resonance frequencies of the first three normal modes of large amplitude shape oscillations in an electric field of varying magnitude has been carried out with and without surface charges for weakly conducting liquids in air. These oscillations of nonspherical levitated drops have been driven by either modulating the ultrasonic field or by using a time-varying electric field, and the free decay from the oscillatory state has been recorded. A decrease in the resonance frequency of the driven fundamental quadrupole mode has been measured for increasing oblate deformation in the absence of an electric field. Similarly, a decrease in this frequency has also been found for increasing DC electric field magnitude. A soft nonlinearity exists in the amplitude dependence of the resonant mode frequencies for freely decaying as well as ultrasonically and electrically driven uncharged drops. This decrease in resonance frequency is accentuated by the presence of free surface charge on the drop. Subharmonic resonance excitation has been observed for drops in a time-varying electric field, and hysteresis exists for resonant modes driven to large amplitude. Mode coupling from lower-order resonances to higher-order modes has been found to be very weak, even for fairly large amplitude shape oscillations. Most of these results are in general agreement with predictions from recent analytical and numerical investigations.

Trinh, E. H.↗
NASA NTRS1995

The Dynamics of Ultrasonically Levitated Drops in an Electric Field

Ultrasonic and electrostatic leviation techniques have allowed the experimental investigation of the nonlinear oscillatory dynamics of free droplets with diameter between 0.1 and 0.4 cm. The measurement of the resonance frequencies of the first three normal modes of large amplitude shape oscillations in an electric field of varying magnitude has been carried out with and without surface charges for weakly conducting liquids in air. These oscillations of nonspherical levitated drops have been driven by either modulating the ultrasonic field or by using a time-varying electric field, and the free decay from the oscillatory state has been recorded. A decrease in the resonance frequency of the driven fundamental quadrupole mode has been measured for increasing oblate deformation in the absence of an electric field. Similarly, a decrease in this frequency has also been found for increasing DC electric field magnitude. A soft nonlinearity exists in the amplitude dependence of the resonant mode frequencies for freely decaying as well as ultrasonically and electrically driven uncharged drops. This decrease in resonance frequency is accentuated by the presence of free surface charge on the drop. Subharmonic resonance excitation has been observed for drops in a time-varying electric field, and hysteresis exists for resonant modes driven to large amplitude. Mode coupling from lower-order resonances to higher-order modes has been found to be very weak, even for fairly large amplitude shape oscillations. Most of these results are in general agreement with predictions from recent analytical and numerical investigations.

Ultrasonically↗
NASA NTRS1982

A one-dimensional model of the atmospheric electric field near the Venusian surface

A one-dimensional model is developed for the development of an electric field below the Venus cloud layer, assuming an absence of cloud-to-ground lightning. The ion-bearing medium is considered as a collision dominated, partially ionized gas. Ion production by cosmic rays is accompanied by a sink of recombining positive and negative ions. The net diffusion of ions to the surface was examined, and modeled as resulting from differences between the ion diffusivities and electrical activity within the clouds. Calculations were made of the conduction and diffusion currents profiles, positive and negative ion densities, and the net space charge. Higher positive ion diffusivity was found to enhance the surface positive charge, producing an electric field which depended on the boundary layer mixing. Charge separation in the clouds also produces an electric field. Assuming a fair weather conduction current similar to earth leads to an electric field of 5 kV/sq m at the surface, with continuity to a few kilometers altitude.

Tzur, I.↗
NASA NTRS2014

Interplanetary and Interstellar Dust Observed by the Wind/WAVES Electric Field Instrument

Observations of hypervelocity dust particles impacting the Wind spacecraft are reported here for the first time using data from the WindWAVES electric field instrument. A unique combination of rotating spacecraft, amplitude-triggered high-cadence waveform collection, and electric field antenna configuration allow the first direct determination of dust impact direction by any spacecraft using electric field data. Dust flux and impact direction data indicate that the observed dust is approximately micron-sized with both interplanetary and interstellar populations. Nanometer radius dust is not detected by Wind during times when nanometer dust is observed on the STEREO spacecraft and both spacecraft are in close proximity. Determined impact directions suggest that interplanetary dust detected by electric field instruments at 1 AU is dominated by particles on bound trajectories crossing Earths orbit, rather than dust with hyperbolic orbits.

Wind spacecraft↗