Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “LIGHTNING”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Functional test and calibration plan for the Lightning Imaging Sensor

The Lightning Imaging Sensor (LIS) wide field-of-view solid-state camera can measure the global distribution of lightning from LEO, through the use of a narrowband interference filter to detect the neutral O band at 777.4 nm. Prelaunch testing and calibration of the LIS has required three separate laboratory systems; absolute radiometric calibration of the sensor will be furnished over the whole spectral range by a high resolution monochromator and motorized gimbals.

Bergstrom, James W.↗
NASA NTRS1991

Radar characteristics of cloud-to-ground lightning producing storms in Florida

The interrelation between cloud-to-ground lightning, convective rainfall, and the environment in Central Florida storms is examined. The rain flux, storm area, and ground discharge rates are computed within the outlined area. Time-height cross sections of maximum dBZ values at each level for two storms are shown. The multicellular nature of these storms is readily apparent. The cloud-to-ground lightning activity occurs mainly where high reflectivity values (30-40 dBZ) extend above 7 km.

Buechler, D. E.↗
NASA NTRS1993

Interaction with the lower ionosphere of electromagnetic pulses from lightning - Heating, attachment, and ionization

A Boltzmann formulation of the electron distribution function and Maxwell's equations for the EM fields are used to simulate the interaction of lightning radiated EM pulses with the lower ionosphere. Ionization and dissociative attachment induced by the heated electrons cause significant changes in the local electron density, N(e). Due to 'slow' field changes of typical lightning EM pulses over time scales of tens of microsec, the distribution function follows the quasi-equilibrium solution of the Boltzmann equation in the altitude range of interest (70 to 100 km). The EM pulse is simulated as a planar 100 microsec long single period oscillation of a 10 kHz wave injected at 70 km. Under nighttime conditions, individual pulses of intensity 10-20 V/m (normalized to 100 km horizontal distance) produce changes in N(e) of 1-30 percent while a sequence of pulses leads to strong modification of N(e) at altitudes less than 95 km. The N(e) changes produce a 'sharpening' of the lower ionospheric boundary by causing a reduction in electron density at 75-85 km (due to attachment) and a substantial increase at 85-95 km (due to ionization) (e.g., the scale height decreases by a factor of about 2 at about 85 km for a single 20 V/m EM pulse). No substantial N(e) changes occur during daytime.

Taranenko, Y. N.↗
NASA NTRS1993

FNAS lightning detection

A review of past and future investigations into lightning detection from space was incorporated into a brochure. Following the collection of background information, a meeting was held to discuss the format and contents of the proposed documentation. An initial outline was produced and decided upon. Photographs to be included in the brochure were selected. Quotations with respect to printing the document were requested. In the period between 28 March and June 1993, work continued on compiling the text. Towards the end of this contract, a review of the brochure was undertaken by the technical monitor. Photographs were being revised and additional areas of lightning research were being considered for inclusion into the brochure. Included is a copy of the draft (and photographs) which is still being edited by the technical monitor at the time of this report.

Miller, George P.↗
NASA NTRS1994

Chondrule formation in lightning discharges

Chondrules represent a significant mass fraction of primitive meteorites. These millimeter-sized glassy droplets appear to be the products of intensive transient heating events. Their size distribution, chemical and mineral composition, texture, isotope composition suggest that chondrules were produced as a result of short-duration melting followed by rapid cooling of solid precursor particles. Gas-dynamics heating, magnetic reconnection, and electrostatic discharges are thought to be the leading candidates to explain chondrule formation. In this paper we summarize our recent theoretical progress on the effects of 'lightning' in the early solar system and also report on preliminary results from our laboratory experiments. Differential settling of various sized dust particles toward the midplane of the nebula is suspected to build large-scale charge separations that episodically relax via the electric breakdown of the nebular gas. The electrostatic discharge os analogous to lightning in the Earth's atmosphere.

Horanyi, M.↗
NASA NTRS1994

Effect of surface conductivity on the peak magnetic field radiated by first return strokes in cloud-to-ground lightning

The effect of surface conductivity on the peak magnetic field radiated by the first return stroke in cloud-to-ground lightning was investigated by comparing the peak magnetic fields from return strokes that struck water with those that struck land. The data were obtained from a network of three gated, wideband magnetic direction finders (DFs) at the NASA Kennedy Space Center during the summer of 1985. Two geographical areas that were equidistant from two of the direction finders were compared where the flash distances ranged from approximately 40 to 60 km. An unbiased data set was obtained by correcting site errors, equalizing differences in sensor gain, eliminating directional biases in DF triggering, and keeping differences in signal attenuation over the two surfaces to a minimum. When a statistical analysis was performed on the frequency distributions of the signal amplitudes, there was no statistically significant difference in the peak amplitudes of first return strokes over land (lambda = 8.2 x 10(exp -3) mho/m) and over water (lambda = 4 mho/m). Therefore we infer that the conductivity of the underlying surface does not significantly affect the magnitude of the peak magnetic field, and hence the peak current, in the first return stroke of a cloud-to-ground lightning flash.

Tyahla, Lori J.↗
NASA NTRS1993

The interaction with the lower ionosphere of electromagnetic pulses from lightning: Excitation of optical emissions

A self consistent and fully kinetic simulation of the interaction of lightning radiated electromagnetic (EM) pulses with the nighttime lower ionosphere indicates that optical emissions observable with conventional instruments would be excited. For example, emissions of the 1st and 2nd positive bands of N2 occur at rates reaching 7 x 10(exp 7) and 10(exp 7) cu cm/s respectively at 92 km altitude for a lightning discharge with an electric field E(sub 100) = 20 V/m (normalized to a 100 km distance). The maximum height integrated intensities of these emissions are 4 x 10(exp 7) and 6 x 10(exp 6) R respectively, lasting for approx. 50 micrometers.

Taranenko, Y. N.↗
NASA NTRS1995

An assessment of plasma instabilities or planetary lightning as a source for the VLF bursts detected at Venus

Very low frequency (VLF) signals detected in the nightside ionosphere of Venus have generally been attributed to atmospheric lightning. However it has recently been suggested that these bursts could be generated by either whistler-mode or lower hybrid drift instabilities. It has previously been shown that the growth rate for whistler-mode instabilities in the nightside ionosphere is too small for appreciable growth at altitudes less than 200 km, where the VLF burst rate is highest. We show that the bursts are usually observed in regions of low electron beta, where whistler-mode attenuation is small. We further show that many of the bursts are detected in regions of high collision frequency, which stabilizes the lower hybrid drift instability. Lastly, the waves are also detected in regions where the wavelength required for Doppler-shift of lower hybrid waves to 100 Hz is shorter than the electron Larmor radius, which also argues against a lower hybrid drift instability. Planetary lightning is consequently a more likely source for the VLF bursts.

Strangeway, R. J.↗
NASA NTRS1995

Venus planetary lightning rate as deduced from VLF bursts

Statistical studies of the VLF bursts detected in the nightside ionosphere of Venus show that the bursts fall into two classes. The first consists of signals detected when vertical propagation within the whistler-mode resonance cone is allowed. The second consists of signals whose burst rate decreases rapidly as a function of increasing altitude, with a scale height of about 20 km. These non-whistler-mode signals also display a strong dependence on local time, with the burst rates being largest in the post-dusk local time sector. Since these signals are not propagating we assume that they correspond to a 'near-field' or prompt response to a lightning stroke. As such we can use these signals to estimate the planetary lightning rate, and we find that the rate at Venus is comparable to or greater than the terrestrial planetary rate of 100 flashes/sec.

Ho, C.-M.↗
NASA NTRS1995

Plasma wave evidence for lightning on Venus

Plasma wave data from the Pioneer Venus Orbiter provide the largest body of data cited as evidence for lightning on Venus. These data are also the most controversial, mainly because of the ambiguity in mode identification due to limited spectral information. We review some of the more recent studies of the plasma wave data at Venus, and we demonstrate that the characteristics of the 100 Hz waves are consistent with whistler-mode waves propagating vertically from below the ionosphere. We further show that in situ instabilities are too weak to generate whistler-mode waves, mainly because the thermal pressure is comparable with the magnetic field pressure in the ionosphere of Venus. The lower hybrid drift instability has also been suggested as an alternative source for the 100 Hz waves. However, the wave properties are more consistent with whistler-mode propagation; the lower hybrid dirft instability requires very short gradient scale lengths to overcome damping due to collisions. We also note that an apparent association between Langmuir probe anomalies and 100 Hz waves is much lower than previously reported, once we apply a consistent intensity threshold for identifying wave bursts. The lightning hyposthesis remains the most probable explanation of the plasma waves detected at low altitudes in the nightside ionosphere of Venus.

Strangeway, Robert J.↗
NASA NTRS1995

Low-pressure electrical discharge experiment to simulate high-altitude lightning above thunderclouds

Recently, extremely interesting high-altitude cloud-ionosphere electrical discharges, like lightning above thunderstorms, have been observed from NASA's space shuttle missions and during airborne and ground-based experiments. To understand these discharges, a new experiment was conceived to simulate a thundercloud in a vacuum chamber using a dielectric in particulate form into which electrodes were inserted to create charge centers analogous to those in an electrified cloud. To represent the ionosphere, a conducting medium (metallic plate) was introduced at the top of the chamber. It was found that for different pressures between approximately 1 and 300 mb, corresponding to various upper atmospheric altitudes, different discharges occurred above the simulated thundercloud, and these bore a remarkable similarity to the observed atmospheric phenomena. At pressures greater than 300 mb, these discharges were rare and only discharges within the simulated thundercloud were observed. Use of a particulate dielectric was critical for the successful simulation of the high-altitude lightning.

Jarzembski, M. A.↗
NASA NTRS1995

Lightning electromagnetics

This project involved the determination of the effective radiated power of lightning sources and the polarization of the radiating source. This requires the computation of the antenna patterns at all the LDAR site receiving antennas. The known radiation patterns and RF signal levels measured at the antennas will be used to determine the effective radiated power of the lightning source. The azimuth and elevation patterns of the antennas in the LDAR system were computed using flight test data that was gathered specifically for this purpose. The results presented in this report deal with the azimuth patterns for all the antennas and the elevation patterns for three of the seven sites.

Wahid, Parveen↗
NASA NTRS1997

Development of Design Standards and Guidelines for Electromagnetic Compatibility and Lightning Protection for Spacecraft Utilizing Composite Materials

This final report presents information concerning technical accomplishments by Tec-Masters, Inc. (TMI) for this contract effort. This effort included the accomplishment and/or submission by TMI of the following items: (1) Literature Survey Report, Electrical Properties of Non-Metallic Composites by Mr. Hugh W. Denny; (2) Interim Report, Composite Materials - Conductivity, Shielding Effectiveness, and Current Carrying Capability by Mr. Ross W. Evans; (3) Fault Current Test Plan by Mr. Ross W. Evans (4) Fault Current Test Procedure by Mr. Ross W. Evans (5) Test Report, Fault Current Through Graphite Filament Reinforced Plastic, NASA CR-4774, Marshall Space Flight Center, Alabama, September 1996, by Mr. Ross W. Evans; (6) Test Plan, Lightning Effects on Composite Materials by Mr. Ross W. Evans; (7) Test Report, Lightning Effects on Composite Materials, NASA CR-4783, Marshall Space Flight Center, Alabama, February 1997, by Mr. Ross W. Evans; (8) Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials, NASA CR-4784, Marshall Space Flight Center, Alabama, September 1996, by Mr. Ross W. Evans. These items are not attached but are considered to be a part of this final report. Efforts on two additional items were accomplished at no increase in cost to NASA/MSFC. These items consisted of updating the 'MSFC EMC Design and Interference Control Handbook,' and revising the 'Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials.'

Camp, Dennis W.↗
NASA NTRS1996

Lightning Generated Gamma Ray Bursts

The prime focus of this effort is to advance the state of understanding of correlation between lightning strokes and gamma-ray flashes. key issue addressed was the revision of the existing models of runaway breakdown in the stratosphere due to low altitude lightning, which are related to the source of gamma-ray flashes. The revision includes the assessment of the effect due to geomagnetic field on the development of runaway discharge.

Milikh, Gennady↗
NASA NTRS1999

A Multipole Expansion Method for Analyzing Lightning Field Changes

Changes in the surface electric field are frequently used to infer the locations and magnitudes of lightning-caused changes in thundercloud charge distributions. The traditional procedure is to assume that the charges that are effectively deposited by the flash can be modeled either as a single point charge (the Q model) or a point dipole (the P model). The Q model has four unknown parameters and provides a good description of many cloud-to-ground (CG) flashes. The P model has six unknown parameters and describes many intracloud (IC) discharges. In this paper we introduce a new analysis method that assumes that the change in the cloud charge can be described by a truncated multipole expansion, i.e., there are both monopole and dipole terms in the unknown source distribution, and both terms are applied simultaneously. This method can be used to analyze CG flashes that are accompanied by large changes in the cloud dipole moment and complex IC discharges. If there is enough information content in the measurements, the model can also be generalized to include quadrupole and higher order terms. The parameters of the charge moments are determined using a dme-dimensional grid search in combination with a linear inversion, and because of this, local minima in the error function and the associated solution ambiguities are avoided. The multipole method has been tested on computer-simulated sources and on natural lightning at the NASA Kennedy Space Center and U.S. Air Force Eastern Range.

Koshak, William J.↗
NASA NTRS1998

A Multipole Expansion Method for Analyzing Lightning Field Changes

Changes in the surface electric field are frequently used to infer the locations and magnitudes of lightning-caused changes in thundercloud charge distributions. The traditional procedure is to assume that the charges that are effectively deposited by the flash can be modeled either as a single point charge (the Q-model) or a point dipole (the P-model). The Q-model has 4 unknown parameters and provides a good description of many cloud-to-ground (CG) flashes. The P-model has 6 unknown parameters and describes many intracloud (IC) discharges. In this paper, we introduce a new analysis method that assumes that the change in the cloud charge can be described by a truncated multipole expansion, i.e., there are both monopole and dipole terms in the unknown source distribution, and both terms are applied simultaneously. This method can be used to analyze CG flashes that are accompanied by large changes in the cloud dipole moment and complex IC discharges. If there is enough information content in the measurements, the model can also be generalized to include quadrupole and higher order terms. The parameters of the charge moments are determined using a 3-dimensional grid search in combination with a linear inversion, and because of this, local minima in the error function and the associated solution ambiguities are avoided. The multipole method has been tested on computer simulated sources and on natural lightning at the NASA Kennedy Space Center and USAF Eastern Range.

Koshak, William J.↗
NASA NTRS1999

Diurnal Lightning Distribution as Observed by the Optical Transient Detector (OTD)

Since April 1995, lightning activity around the globe has been monitored with the Optical Transient Detector (OTD). The OTD observations acquired during the one year period from September 1995 through August 1996 have been used to statistically determine the number of flashes that occur over the Earth during each hour of the diurnal cycle, expressed both as a function of local time and universal time. The globally averaged local [il,htnina activity displays a peak in late afternoon (1500-1800 local time) and a minimum in the morning hours (0600- 1000 local time) consistent with convection associated with diurnal heating. No diurnal variation is found for oceanic storms. The diurnal lightning distribution (universal time) for the globe displays a variation of about 35% about its mean as compared to the Carnegie curve which has a variation of only 15% above and below the mean.

Blakeslee, Richard J.↗
NASA NTRS1999

Model Calculations of the Impact of NO(x) from Air Traffic, Lightning and Surface Emissions, Compared with Measurements

The impact of NO(x) from aircraft emissions, lightning and surface contributions on atmospheric nitrogen oxides and ozone has been investigated with the three-dimensional global chemistry transport model TM3 by partitioning the nitrogen oxides and ozone according to source category. The results have been compared with POLINAT II and SONEX airborne measurements in the North Atlantic flight corridor in 1997. Various cases have been investigated: measurements during a stagnant anti-cyclone and an almost cut-off low, both with expected high aircraft contributions, a southward bound flight with an expected strong flight corridor gradient and lightning contributions in the South, and a transatlantic flight with expected boundary layer pollution near the U.S. coast. The agreement between modeled results and measurements is reasonably good for NO and ozone. Also, the calculated impact of the three defined sources were consistent with the estimated exposure of the sampled air to these sources, obtained by specialized back-trajectory model products.

Meijer, E. W.↗