bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photometry and Polarimetry of the Lunar Regolith as Measured by Surveyor
Authors: Holt Henry E. 
Published: February 2008

Photometric and polarimetric properties of lunar soil and rock fragments were determined from Surveyor pictures. High resolution measurements (centimeter scale) revealed differences in the photometric functions of various materials concomitant with probable different fine‐scale surface textures. The photometric function of the light, undisturbed fine‐grained lunar soil is similar to the function measured through an earth‐based telescope (kilometer resolution), whereas the darker, disturbed soil has a more peaked backscatter function, and smooth compressed soil has more Lambertian‐like reflectivity. Most rock fragments seem to have essentially dust‐free surfaces and a Lambertian‐like photometric function; their normal albedos are estimated to range from 9 to 22%.The polarimetric function of lunar soil is similar to that of basalt and gabbro powdered to a grain size of 30 to 75 μ. Lunar rocks reflecting strongly polarized light (up to 34% polarized) have the highest albedos. The observed polarimetric function of lunar rocks is more similar to that of basalt and gabbro than any other common rock type.
The Behavior of Antennas in Plasma as a Function of the Frequency of Excitation: Summary Report
Authors: Bachynski M. P. 
Published: February 2008

A feature of the session on the behavior of antennas in a plasma as a function of frequency of excitation was the variety of antenna configurations which was being investigated by various research groups.The emphasis by the Groupe de Recherches Ionosphériques du Centre National d'Etudes de Télécommunications (France) was on quadrupole probes. L. R. O. Storey and J.‐M. Chasseriaux reported on theoretical studies of plasma probes based on the mutual electrical coupling between pairs of dipole antennas. Two types of antennas were analysed, Hertzian dipoles which are short compared with the Debye‐length and double‐sphere dipoles which are long compared with the Debye‐length. In both cases the complete probe is formed by two such antennas separated by a distance much larger than a Debye‐length. The mode of operation of these quadrupole probes can be either active (by driving a current in one dipole and measuring the open circuit potential difference induced on the other) or passive (by measuring the cross‐spectrum of the fluctuating potential differences induced on the two dipoles by the plasma microfield). The quadrupole probes can be applied to the measurement of plasma resonant frequencies, collision frequencies, and the velocity of motion with respect to the probes.
Laboratory Plasmas: Summary Report
Authors: Watanabe Tomiya 
Published: February 2008

Three papers were presented in this session, two on plasma resonances and one about Bernstein‐mode electrostatic waves.M. P. Bachynski and B. W. Gibbs (RCA Laboratories, Montreal, Canada) gave the results of their experiment which concerns electrostatic resonances excited in a layer of isotropic plasma by means of plane transverse electromagnetic waves incident from free space. The angle of incidence was small, i.e., θ = 0° ∼ 12°. Incident waves are polarized, circularly and linearly, and have a fixed frequency, 9.2 GHz. The incident power density was of the order of 0.1 mw cm−2. The thickness of the plasma slab was 1.56 free‐space wave lengths. Two electric dipoles were used as receiving antennas, one totally immersed in the plasma and the other placed outside the plasma. The immersed dipole was oriented normal to the plasma‐slab boundary and consequently nearly longitudinal to the incident wave. Strong electric fields were observed in the regions under conditions in which the frequency of the incident wave equaled the plasma frequency, and the electric vector of the incident field was in the plane of incidence. These strong fields seem to be longitudinal electrostatic fields, since only weak electric fields of longitudinal direction were observed if the incident electric field was perpendicular to the plane of incidence.
An extreme UV photometer for solar observations from Atmosphere Explorer
Authors: Heath Donald F. , Osantowski John F. 
Published: February 2008

A broadband photometer experiment is being prepared for the Atmosphere Explorer‐C, ‐D, and ‐E missions to record the solar irradiance in seven wavelength bands in the range from 40 to 1250 Å. The experiment contains four spiral electron multipliers located behind a moving eight‐position filter wheel. Six of the eight sections of this wheel contain metallic filters used to spectrally isolate the solar irradiance. In addition, three Al2O3 diodes, two with filters, are being used to record the solar irradiance over the full range of orbital altitudes including those at which operation of multipliers with high voltages on open structures would be unsafe. A principal goal of the experiment will be to measure time dependence of the solar irradiance.Photometric calibration will be based on preflight exposure to a storage‐ring synchrotron light source which has been calibrated by combining synchrotron theory with the absolute values of irradiance at 4000 Å obtained from comparison with the best available standard of irradiance.
Skywave polarization rotation in swept‐frequency sea backscatter
Authors: Barnum James R. 
Published: February 2008

A 2.5‐km long slewable broadside receiving‐antenna array was used to study ionospherically propagated backscatter from the Pacific Ocean. Swept‐frequency continuous‐wave recordings revealed a new type of amplitude variation, periodic in both time delay and radio frequency, which caused recordings of time delay versus frequency to resemble large thumbprints. This new phenomenon was seen frequently during the fall and winter and also during spring and summer evenings. It is shown that magnetoionic splitting in the ionosphere (polarization rotation) was responsible for a modulation on the received backscatter signals. This concept was verified experimentally by switching the polarization of the transmitting antenna between vertical and horizontal. Computer ray tracing was used to contruct a synthetic backscatter record displaying lines of signal enhancement due to polarization rotation.When the receiving antenna beamwidth is broadened from 1/2 to 4° the amplitude variation due to polarization rotation is undetectable, which probably explains why the effect was not positively identified in backscatter using F‐layer propagation taken prior to the availability of the 2.5‐km array. This result is also explained by the use of computer ray tracing. The modulation lines have not been seen to date by the author in recordings of backscatter from the land, probably because of the irregularities of backscattering from land surfaces.
Pattern recognition for VLF studies
Authors: Jones Dyfrig 
Published: February 2008

The pattern‐recognition technique to be described requires the simultaneous recording of a signal on two antennas, for example, orthogonal magnetic or electric sensors; after these signals are cross‐correlated, a fast Fourier transform yields the complex cross‐spectrogram. Provided that the polarization of the waves does not vary rapidly with time, it is possible to reject unwanted noise and to recognize the signal by utilizing the phase information in the cross‐spectrum.This technique has been tested using computer‐simulated signals, and it has been found that variable frequency signals, for example, whistlers, which are more than 12 db below an incoherent‐noise background and more than 18 db below a coherent‐noise background, are still recognized and are recorded to the exclusion of noise.The technique is applicable to plasma waves recorded on spacecraft as well as to electro‐magnetic waves. Although the polarizations of ground‐recorded VLF signals are usually more complicated than those in the magnetosphere, the method is still relevant.
Magnetospheric current sheets
Authors: Speiser T. W. 
Published: February 2008

A review is presented of theories and observations of current sheets in the magnetosphere, emphasizing the magnetopause and tail current sheets.Theoretical models of the magnetopause current sheet can be divided into two types: specular reflection and fluid models containing no external magnetic field, and models with an interplanetary/magnetosheath magnetic field. Our understanding of the first type is much better than of the second, although magnetospheric observations indicate that the external magnetic field plays an important role.Most of the theoretical models of the tail current sheet attempt to arrive at an understanding of the reconnection process or start with the assumption that reconnection is important. Observations are reviewed and implications for the models are discussed.
Selective fading and the propagation of radio waves in the magnetoplasma (ionosphere)
Authors: Cutolo M. 
Published: February 2008

The technique called “modulated pulse” (the emission of HF pulses of suitable length modulated with high or low audiofrequencies) allows an exhaustive study of the propagation of modulated radio waves in the ionosphere. Using this system it is possible to establish that the diminution or the gain, in regard to that emitted by the transmitting antenna, of the percentage of modulation of the received modulated waves is not due in any way, as some researchers have declared, to the interference in the receiving antenna of rays that have travelled different paths in the ionosphere or to multiple echoes, but should be attributed to other reasons.The experiments were made with carrier frequencies varying around the cyclotronic frequency and with different modulation frequencies. It was possible to obtain either a resonance curve of demodulation or a resonance curve of overmodulation and it was shown that the selective fading could be obtained with low frequencies as well as with high frequencies of modulation. The most important contribution herein is the determination that the interference does not alter in any way the depth of modulation of a modulated wave provided that the envelopes remain undistorted. If the amplitude of the echo is less than the minimum B, as generally happens, the interference never alters the sinusoidal form of the envelope. If the amplitude is greater the envelope always becomes distorted.
F‐layer irregularities as determined by backscatter studies at 19 MHz over half of a solar cycle
Authors: Basu Sunanda , Vesprini Robert L. , Aarons Jules 
Published: February 2008

A continuous series of backscatter observations at 19 MHz made at Plum Island, Massachusetts, 56°N invariant latitude, over nearly half a solar cycle is utilized to derive occurrence characteristics of ground backscatter propagated by means of F‐layer reflection, 1F, as well as those of aspect‐sensitive field‐aligned echoes from the F layer, FAE(F). Neither field‐aligned E‐layer echoes nor ground backscatter propagated by means of sporadic E were found to produce any noticeable blanketing of the radar signal for this frequency and radar location. The 1F propagation showed marked sunspot cycle and azimuthal dependence and was strongest in winter and weakest in summer.Under quiet magnetic conditions FAE(F) was primarily a sunset phenomenon, occurring usually at delays of 7 to 10 msec, with a marked sunspot cycle dependence. Some daytime activity was observed at longer delays of 20 to 22 msec which could be explained in terms of F‐layer field alignment after one intermediate ground reflection. The occurrence of FAE(F) during magnetic storms showed a seasonal variation in agreement with the well‐known storm behavior of f0F2 at these latitudes. In general, however, the occurrence of FAE(F) increased monotonically with increasing magnetic activity until the threshold of KFr = 4 was reached, beyond which the depletion in the F‐layer background ionization caused it to decrease, with complete cut‐off occurring irrespective of season during very disturbed conditions, KFr ≥ 7.With the aid of ray traces, the occurrence statistics of both 1F and FAE(F) are interpreted and discussed in terms of the geometry of the probing radar, the various factors controlling F‐layer propagation, and the extent of the F‐layer irregularity region.
Dispersive motions in the equatorial ionosphere
Authors: Misra R. K. 
Published: February 2008

The results of the dispersion analysis of the spaced receiver records of fading for an equatorial station in the Indian zone are discussed. It is shown that the apparent drift speed increases almost linearly with the frequency of fading in all the cases studied for both the E and F regions. The dispersion of drift speed is larger for the F region than for the E region in general. Furthermore, the F region shows a larger dispersion during the daytime whereas it is of the same order in the day and nighttimes for the E region. The drift speed corresponding to the highest Fourier frequency present in a particular record is found to be close to the apparent drift speed Va as determined from the shift of the peak of cross correllograms while the total frequency spread of the speed is linearly related to the random drift speed Vc derived by the full correlation analysis.Several possible causes of dispersion in the ionosphere such as gravity waves, independently moving reflecting screens, height gradient of the horizontal drift and size of irregularities, the dispersive nature of the vertical drift velocity, and the variability of the drift during the course of record are discussed. Interference of the signals reflected from two or more highly aspect‐sensitive areas in the ionosphere is suggested as a possible mechanism resulting in the positive and linear dispersion observed on the ground at an equatorial station.
Concluding remarks, session 3: Neutral and ion chemistry
Authors: Monro P. E. 
Published: February 2008

When one begins to summarize the conference proceedings dealing with the neutral and ion chemistry of the E region, one becomes forcefully aware of the spectacular advances that have been made in this area during the past decade. This conference has well demonstrated that these advances are continuing, and that there is yet a wide range of problems to be overcome. Both these aspects will be discussed briefly below.Some consideration will, first of all, be given to the neutral chemistry at E‐region heights although it cannot be separated realistically from the ion chemistry. Most of the proceedings in this area were devoted to the chemistry of odd nitrogen and it now seems clear that the major problems are associated with uncertainties related to the production and loss of N(2D).
Concluding remarks, session 5: Models, electric fields; session 6: Electric currents, late contributions
Authors: Holzer T. E. 
Published: February 2008

These two sessions, which cover the topics of E‐region models, electric fields, and electric currents, underscore a major difficulty necessarily encountered in studies of the E region. This difficulty arises from the fact that the E region of the ionosphere is just one part of a very large system, all of whose component parts are strongly coupled electrodynamically and hydrodynamically. Before describing a general approach to overcome this difficulty, let me briefly discuss some of the important coupling processes in the overall system.As the solar wind flows past the earth, it exerts a tangential stress at the magnetopause boundary. Information of this stress is propagated by hydromagnetic waves to the polar cap ionosphere, where an electric potential distribution is established that is consistent with the plasma motions required by the applied tangential stress. The resultant electric field pattern covers not only the polar cap region, but extends to the auroral zone and, to some extent, to middle and low latitudes. The electric fields imposed on the ionosphere equatorward of the polar cap are mapped into the closed field line regions of the magnetosphere, thus establishing a plasma convection pattern in the magnetosphere. The actual electric field pattern established is strongly affected by the magnetospheric plasma population, ionospheric conductivity, and neutral thermospheric winds. In fact, due to magnetospheric plasma effects, the electric field is largely shielded (on time scales of several hours or more) from the middle and low latitude regions. Nevertheless, relatively steady solar‐wind‐generated electric fields of a few mv m−1, along with much larger transient fields, probably are imposed at middle and low latitudes.
Theory of low‐frequency conductivity probing of roof structures in coal mines
Authors: Ralston Margarete A. , Wait James R. 
Published: February 2008

Determining electrical ground constants of the earth is an important problem in geophysical probing [Keller, 1971; Wait, 1979] and underground communication system design [Aldredge, 1973]. Several different methods are used to determine the relative permittivity εr and resistivity p or conductivity ó of a stratified earth. As noted in the Institute of Electrical and Electronics Engineers (IEEE) [1974] Standard 356, techniques for determining the electrical constants of the earth are roughly divided into two categories: (1) methods where drill hole access into the earth does not exist or is not required, (2) techniques requiring drill hole access into the earth. Methods using drill holes are primarily for determining electrical ground constants in a local area.This article contains supplementary material.
Scattering by Pruppacher‐Pitter raindrops at 30 GHz
Authors: Yeh C. , Woo R. , Armstrong J. W. , Ishimaru A. 
Published: February 2008

Optimum design of modern ground‐satellite communication systems requires the knowledge of rain‐induced differential attenuation, differential phase shift, and cross‐polarization factors. After a comprehensive assessment of different available analytical techniques, an efficient technique is chosen to yield the desired scattering results. Tabulation of the scattered fields for Pruppacher‐Pitter raindrops with sizes ranging from 0.25 mm to 3.5 mm at 20°C and at 30 GHz for several incidence angles is given.Table 1 is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N. W., Washington, D. C. 20009. Document S82‐001; $5.00. Payment must accompany order.
North American apparent polar wander, plate motion, and left‐oblique convergence: Late Jurassic‐Early Cretaceous orogenic consequences
Authors: May Steven R. , Beck Myrl E. , Butler Robert F. 
Published: February 2008

The North American apparent polar wander (APW) path indicates an episode of unusually rapid absolute northward motion of western North America between 150 and 135 Ma. During this time the northward component of absolute motion of points along the Washington‐Oregon‐California coast was in excess of 150 km/m.y. and perhaps as high as 230 km/m.y. We believe that such high absolute northward velocity for North America probably ensures that relative motions of oceanic plates and terranes influenced by them were to the south at this time.The inception of rapid northward motion and left‐oblique convergence was abrupt and should be recorded in the geology of the western Cordillera. It is tempting to correlate this period of unusual Pacific basin‐North American interaction with the “Nevadan orogeny” in the Klamath Mountains as well as with left‐lateral strike‐slip structures such as the Pine Nut fault and Bear Mountains fault zone. Significant differences exist between North American plate motion recorded by the Late Jurassic‐Cretaceous APW path and that predicted by a fixed hotspot model. We believe that this discrepancy reflects uncertainty associated with pre‐Late Cretaceous hotspot tracks and poorly constrained relative plate motions during the Cretaceous normal polarity superchron.
Origin of igneous rocks associated with Mélanges of the Pacific Rim Complex, western Vancouver Island, Canada
Authors: Brandon Mark T. 
Published: February 2008

The Pacific Rim Complex (PRC) has previously been interpreted as a late Mesozoic subduction complex that formed along the western margin of Vancouver Island. This paper examines a specific aspect of this interpretation: that igneous rocks within the PRC are fault slices derived from the footwall or hanging wall of a subduction thrust. The footwall would have been an oceanic plate, and the hanging wall, Wrangellia, a large coherent terrane that underlies most of Vancouver Island. New mapping has shown that the PRC comprises a lower Mesozoic volcanic unit, herein named the Ucluth Formation, and a superjacent sequence, more than 2 km thick, of Lower Cretaceous sediment‐rich mélanges. Within the mélanges are large blocks of volcanic and plutonic rocks, most of which were derived from the underlying Ucluth Formation. A minor fraction of these blocks cannot be assigned to Ucluth; they consist of Upper Jurassic pillow basalt and rare ultramafite. Fossil ages and chemical data indicate that the bulk of the igneous rocks in the PRC, as represented by the Ucluth Formation and blocks derived from the Ucluth, could not have come from Wrangellia nor from a subducting oceanic plate. The blocks of Upper Jurassic pillow basalt do represent fragments of oceanic crust, but field relations indicate that they are not fault slices. The mudstone matrix surrounding the blocks contains interbeds of “green tuff” which are shown to be scree deposits derived from the Ucluth and the Upper Jurassic pillow basalts. My interpretation is that the PRC mélanges formed by surficial mass wasting, and not by faulting along a subduction thrust. Furthermore, regional geologic relations indicate that the present location of the PRC, outboard of Wrangellia, is a result of strike slip faulting during the latest Cretaceous or early Tertiary. This event postdates the formational age of the mélanges by at least 45 m.y.An appendix of chemical analyses, locality descriptions, sample petrography, analytical methods, and estimated accuracy is available with the entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document T89‐004; $2.50. Payment must accompany order.
Aimantation induite par le champ terrestre sur les aimants
Authors: Mascart Par M. E. 
Published: February 2008

Dans la méthode de Gauss, généralement employée pour évaluer la composante horizontale H du champ terrestre, on détermine d'abord le produit P = M H du moment magnétique M d'un barreau par cette composante, à l'aide des oscillations, puis le quotient
au moyen des déviations que le barreau produit sur un déclinomètre.Dans ces expériences, le moment magnétique du barreau est modifié par l'aimantation induite que produit le champ terrestre; on est d'ailleurs autorisé à admettre que cette aimantation est uniquement temporaire, réversible sans hystérésis, et proportionnelle au champ.