Radiation fields of energetic electrons in helical orbits within a magnetoactive plasma
Radiation fields produced by energetic electrons in helical orbit within magnetoactive plasma derived by solving Maxwell equations
Ogawa, T.↗
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Radiation fields of energetic electrons in helical orbits within a magnetoactive plasma.
Radiation fields from energetic electron moving in helical orbit in magnetoactive plasma, using Maxwell equations
Ogawa, T.↗
Regular and Chaotic Quantum Dynamics of Two-Level Atoms in a Selfconsistent Radiation Field
Dynamics of two-level atoms interacting with their own radiation field in a single-mode high-quality resonator is considered. The dynamical system consists of two second-order differential equations, one for the atomic SU(2) dynamical-group parameter and another for the field strength. With the help of the maximal Lyapunov exponent for this set, we numerically investigate transitions from regularity to deterministic quantum chaos in such a simple model. Increasing the collective coupling constant b is identical with 8(pi)N(sub 0)(d(exp 2))/hw, we observed for initially unexcited atoms a usual sharp transition to chaos at b(sub c) approx. equal to 1. If we take the dimensionless individual Rabi frequency a = Omega/2w as a control parameter, then a sequence of order-to-chaos transitions has been observed starting with the critical value a(sub c) approx. equal to 0.25 at the same initial conditions.
Konkov, L. E.↗
Thermal radiation fields and antenna parameters in magnetoplasma.
Spectral densities of electromagnetic fields of thermal radiation in magnetoplasma as related to radiation resistance of immersed antenna
ANTENNA FIELD↗
The radiation field wave forms produced by intracloud lightning discharge processes
The large-amplitude radiation field pulses produced by intracloud lightning discharge processes have been recorded with submicrosecond time resolution. The wave forms are distinctly different from those produced by return strokes in cloud-to-ground lightning, yet they are surprisingly alike within a discharge and in different discharges. The shapes tend to be bipolar, with two or three narrow, fast-rising pulses superimposed on the initial half cycle. Pulses with a positive initial polarity are usually produced in the several tens of milliseconds prior to the first return stroke in a cloud-to-ground discharge. Positive pulses tend to occur at regular intervals and have a mean full width of about 40 + or - 13 microsec. Negative pulses are usually produced during isolated cloud discharges at more random intervals and have shapes similar to the positive pulses but with more variability. The implications of the field shapes and polarities for the physics of intracloud discharge processes are discussed.
Weidman, C. D.↗
Far-field radiation patterns of Y and T shaped arrays with Chebyshev loading
The far-field radiation patterns for Chebyshev loaded Y- and T-shaped array antennas are given for a number of cases. Included are full- and half-length loaded array arms. The goal of the investigation is to determine the effect of different Chebyshev loading arrangements on this type of array. It is found that in both the Y- and T-shaped arrays, the main lobes are defined by the shape of the array and that the level of the side-lobes is mainly dependent on the Chebyshev loading (that is, complete or partial).
Gabriel, A. K.↗
Radiation field from an in-cloud lightning process with arbitrary orientation
The expression for the radiation electric field from a current pulse propagating along a channel of arbitrary orientation is derived. Representative radiation fields indicate that approximately 1-msec duration pulses occur at rates of up to 1/msec in intracloud flashes, thereby furnishing a valuable tool for the tracking of streamer development. Attention is given to the errors which arise when radiation pulse measurements are inverted, in order to determine the pulse's current-waveshape, channel-orientation, and current-speed product properties.
Thomson, E. M.↗
Electrical properties of xenon-filled thermionic diodes in radiation field of a nuclear reactor
Electrical properties of xenon filled thermionic diodes in nuclear reactor radiation field
Forman, R.↗
Study of interaction of low dose power source radiation fields with selected space scientific instruments Quarterly progress report
Interaction of low dose power source radiation fields with selected space scientific instruments
Endres, G. W. R.↗
Calculating far-field radiated sound pressure levels from NASTRAN output
FAFRAP is a computer program which calculates far field radiated sound pressure levels from quantities computed by a NASTRAN direct frequency response analysis of an arbitrarily shaped structure. Fluid loading on the structure can be computed directly by NASTRAN or an added-mass approximation to fluid loading on the structure can be used. Output from FAFRAP includes tables of radiated sound pressure levels and several types of graphic output. FAFRAP results for monopole and dipole sources compare closely with an explicit calculation of the radiated sound pressure level for those sources.
Lipman, R. R.↗
Assessing High-Intensity Radiated Fields (HIRF) from High-Power Antennas for Air Vehicle Safety
Advanced Air Mobility (AAM), including Urban Air Mobility (UAM), vehicles may be required to meet stringent High-Intensity Radiated Fields (HIRF) certification requirements. HIRF can cause interference and even damage to vehicle systems. A recently proposed map-based avoidance approach can help reduce HIRF protection costs compared to the standard approach. However, it necessitates knowing the locations, frequencies, and transmit powers of high-power antennas within the operating area. This study aims to provide the necessary transmitter data by utilizing regulatory license databases. Using New York City as a representative urban area, fixed transmitter data are presented for AM, FM, TV, satellite uplink, land-mobile radio, microwave link, weather radars, and others. The maximum effective isotropic radiated powers of the antenna are reported. The associated electric field envelopes at 100 feet (30.48 m) distance are compared against the current rotorcraft HIRF standard. The results show that the current standards for protecting vehicles are inadequate. Maps of regions with high HIRF are illustrated. Data for several other cities are also being considered.
HIRF↗
Assessing High-Intensity Radiated Fields (HIRF) from High-Power Antennas for Air Vehicle Safety
Advanced Air Mobility (AAM), including Urban Air Mobility (UAM), vehicles may be required to meet stringent High-Intensity Radiated Fields (HIRF) certification requirements. HIRF can cause interference and even damage to vehicle systems. A recently proposed map-based avoidance approach can help reduce HIRF protection costs compared to the standard approach. However, it necessitates knowing the locations, frequencies, and transmit powers of high-power antennas within the operating area. This study aims to provide the necessary transmitter data by utilizing regulatory license databases. Using New York City as a representative urban area, fixed transmitter data are presented for AM, FM, TV, satellite uplink, land-mobile radio, microwave link, weather radars, and others. The maximum effective isotropic radiated powers of the antenna are reported. The associated electric field envelopes at 100 feet (30.48 m) distance are compared against the current rotorcraft HIRF standard. The results show that the current standards for protecting vehicles are inadequate. Maps of regions with high HIRF are illustrated. Data for several other cities are also being considered.
HIRF↗
Observations of the diffuse interstellar EUV radiation field
Results are reported for observations and a preliminary theoretical analysis of the diffuse interstellar EUV radiation field exhibiting positive measurable fluxes in the wavelength range from 912 to 1150 A. The observations were made with the UV spectrometers on the two Voyager spacecraft, and a spectral half-width of 30 A was obtained. The procedures used in the analysis are described in detail, particularly those relating to the elimination of thermal and cosmic-ray noise, internal instrumental scattering from bright lines, and possible contributions from direct starlight. Measurements in several directions reveal diffuse intensities at 975 A ranging from a maximum of about 10 to the -7th erg/sq cm per (sec sr A) near the galactic plane to an upper limit of 10 to the -8th erg/sq cm per (sec sr A). A comparison of the present measurements with various theoretical predictions and previous measurements indicates reasonable agreement with some theoretical predictions of the interstellar EUV intensity.
Sandel, B. R.↗
High-Intensity Radiated Field (HIRF) Map - An Avoidance Approach for UAM, AAM, and UAS Vehicles
Advanced Air Mobility (AAM), Urban Air Mobility (UAM), and Unmanned Aerial Systems (UAS) vehicles will fly in similar airspace to Transport Category Rotorcraft, thereby requiring them to meet the most severe requirements for HighIntensity Radiated Fields (HIRF) certification. The environment is severe for rotorcraft, much more so than for fixed-wing aircraft, due to lower altitude operations, potentially exposing the vehicles to close and direct view of high-power transmitters on the ground. High-level HIRF exposure potentially leads to avionic system upsets, interference, and undesirable effects. Shielding and circuit protection against HIRF will be a significant barrier to size, weight, and cost, especially for emerging electric vertical take-off and landing (eVTOL) and electric short take-off and landing (eSTOL) vehicles. This paper proposes a novel approach to HIRF protection, which reduces costs by testing and certifying vehicles to a “vehicle tolerance level” that is lower than required for Transport Category Rotorcraft. The remaining protection is achieved by maintaining a safe distance from known HIRF sources, calculated based on the vehicle's tolerance level and transmitter characteristics such as transmit power, antenna beamwidth, and direction. Tailored maps are developed, identifying transmitters and avoidance zones within an operating area or along a flight path, allowing for restricted vehicle operations. The HIRF avoidance zones could be smaller for vehicles with higher tolerance levels, enabling them to operate closer to transmitters. Transmitter data can be extracted from regulatory databases like the FCC and NOAA. A map tool is developed in Matlab to calculate and plot HIRF avoidance zones from transmitters in FCC and NOAA databases as proof of concept. Illustrations are presented for AM/FM/TV transmitters, communication satellite dishes, and weather radars. Also illustrated are HIRF zones for smaller transmitters, including land-mobile radios, pagers, microwave links, and cellular towers. An example of flight planning around the transmitters is presented. This method is a substantial deviation from the standard approach and involves slightly higher flight-planning complexity, but the potential cost savings are significant. Future AAM/UAM/UAS aeronautical charts could include these new HIRF avoidance zones.
HIRF↗
High-Intensity Radiated Field (HIRF) Map - An Avoidance Approach for UAM, AAM, and UAS Vehicles
Advanced Air Mobility (AAM), Urban Air Mobility (UAM), and Unmanned Aerial Systems (UAS) vehicles will fly in similar airspace to Transport Category Rotorcraft, thereby requiring them to meet the most severe requirements for High Intensity Radiated Fields (HIRF) certification. The environment is severe for rotorcraft, much more so than for fixed-wing aircraft, due to lower altitude operations, potentially exposing the vehicles to close and direct view of high-power transmitters on the ground. High-level HIRF exposure potentially leads to avionic system upsets, interference, and undesirable effects. Shielding and circuit protection against HIRF will be a significant barrier to size, weight, and cost, especially for emerging electric vertical take-off and landing (eVTOL) and electric short take-off and landing (eSTOL) vehicles. This paper proposes a novel approach to HIRF protection, which reduces costs by testing and certifying vehicles to a “vehicle tolerance level” that is lower than required for Transport Category Rotorcraft. The remaining protection is achieved by maintaining a safe distance from known HIRF sources, calculated based on the vehicle's tolerance level and transmitter characteristics such as transmit power, antenna beamwidth, and direction. Tailored maps are developed, identifying transmitters and avoidance zones within an operating area or along a flight path, allowing for restricted vehicle operations. The HIRF avoidance zones could be smaller for vehicles with higher tolerance levels, enabling them to operate closer to transmitters. Transmitter data can be extracted from regulatory databases like the FCC and NOAA. A map tool is developed in Matlab to calculate and plot HIRF avoidance zones from transmitters in FCC and NOAA databases as proof of concept. Illustrations are presented for AM/FM/TV transmitters, communication satellite dishes, and weather radars. Also illustrated are HIRF zones for smaller transmitters, including land-mobile radios, pagers, microwave links, and cellular towers. An example of flight planning around the transmitters is presented. This method is a substantial deviation from the standard approach and involves slightly higher flight-planning complexity, but the potential cost savings are significant. Future AAM/UAM/UAS aeronautical charts could include these new HIRF avoidance zones.
HIRF↗
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.↗
Radiation field of spiral antennas employing multimode slow wave techniques
Multimode slow wave planar spiral antenna design and radiation field characteristics
Cubley, H. D.↗
Analysis of the Radiated Field in an Electromagnetic Reverberation Chamber as an Upset-Inducing Stimulus for Digital Systems
Preliminary data analysis for a physical fault injection experiment of a digital system exposed to High Intensity Radiated Fields (HIRF) in an electromagnetic reverberation chamber suggests a direct causal relation between the time profile of the field strength amplitude in the chamber and the severity of observed effects at the outputs of the radiated system. This report presents an analysis of the field strength modulation induced by the movement of the field stirrers in the reverberation chamber. The analysis is framed as a characterization of the discrete features of the field strength waveform responsible for the faults experienced by a radiated digital system. The results presented here will serve as a basis to refine the approach for a detailed analysis of HIRF-induced upsets observed during the radiation experiment. This work offers a novel perspective into the use of an electromagnetic reverberation chamber to generate upset-inducing stimuli for the study of fault effects in digital systems.
Torres-Pomales, Wilfredo↗