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Theoretical solution for pressure distribution over arbitrarily shaped periodic waves using Fourier series
It has long been known that the periods of Pc 3, 4 pulsations on the ground correlate with the magnitude of the interplanetary magnetic field. This fact has been used to argue for an exogenic source for these pulsations. Particularly attractive candidates for the source of pulsations in this frequency range are the upstream waves of similar frequencies which are associated with populations of ions reflected from the bow shock. However, the dependence of the period of these waves on the strength of the interplanetary magnetic field has never been checked. This paper performs such a check and confirms that the upstream waves have the proper functional relationship.
Systematic perturbation procedures for the analysis of nonlinear problems are reviewed. The cases when the multiplicity of an eigenvalue is finite or infinite are treated for self-sustained and forced oscillations. The possibility of the formation of shock waves is discussed. Applications to acoustic problems are presented.
A search for simultaneous 10- to 45-s waves at the synchronous orbit at the location of ATS 1 and at Tungsten, Northwest Territories, Canada (near the foot of the ATS 1 field line), during 1969 resulted in the identification of only one event. This event occurred near 0900-1000 LT and was identified as a Pc 3 event. By combining 1967 data from College, Alaska (near the same L shell as ATS 1), with ATS 1 data, 90 simultaneous events were identified. Analysis of 60 of these events led to the conclusion that Pi 1 are rarely, if ever, observed on the magnetic equator at synchronous orbit, even when Pi 1 activity is present on the ground near the conjugate point. Pc 3, on the other hand, are common at synchronous orbit. A statistical study of the Pc 3 occurring at ATS 1 during simultaneous College wave activity indicated characteristics similar to those observed at ATS 6.
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Several hundred hours of wind velocity measurements made with the Arecibo 430-MHz radar during the past few years have indicated the presence of persistent wave like structures just above the tropopause. To further investigate these structures, a nearly continuous times series of wind measurements in the upper troposphere and lower stratosphere was made from May 5 to May 12, 1982 at Arecibo. Each of 16 compass points was sampled as the 430-MHz feed was rotated in a velocity azimuth display (VAD) mode at a zenith angle of 15 degrees off-vertical. Using a nonlinear least squares parameter estimation technique line of sight velocities were calculated from Doppler shifts of the received spectra. These velocities were reduced to zonal and meridional components of the wind vector; the vertical component of the wind vector will be available after further reduction.
Lightweight brake rotor design with high heat dissipation using novel surface cooling technology.
An oceanographic-geodetic satellite, designated Geodynamics Experimental Ocean Satellite-C (GEOS-C), an earth-orbiting spacecraft designed to measure precisely the topography of the ocean surface and the sea state (wave height, wave period, wave propagation direction) is described. Launch operations, spacecraft description, and mission objectives are included along with a brief flight history of the NASA satellite geodesy program. Principal investigations to be performed by the GEOS-C mission are discussed.
Impulse-generated waves (tsunamis) may be produced, at varying scales and global recurrence intervals (RI), by several processes. Meteorite-water impacts will produce tsunamis, and asteroid-scale impacts with associated mega-tsunamis may occur. A bolide-water impact would undoubtedly produce a major tsunami, whose sedimentological effects should be recognizable. Even a bolide-land impact might trigger major submarine landslides and thus tsunamis. In all posulated scenarios for the K/T boundary event, then, tsunamis are expected, and where to look for them must be determined, and how to distinguish deposits from different tsunamis. Also, because tsunamis decrease in height as they move away from their source, the proximal effects will differ by perhaps orders of magnitude from distal effects. Data on the characteristics of tsunamis at their origin are scarce. Some observations exist for tsunamis generated by thermonuclear explosions and for seismogenic tsunamis, and experimental work was conducted on impact-generated tsunamis. All tsunamis of interest have wave-lengths of 0(100) km and thus behave as shallow-water waves in all ocean depths. Typical wave periods are 0(10 to 100) minutes. The effect of these tsunamis can be estimated in the marine and coastal realm by calculating boundary shear stresses (expressed as U*, the shear velocity). An event layer at the K/T boundary in Texas occurs in mid-shelf muds. Only a large, long-period wave with a wave height of 0(50) m, is deemed sufficient to have produced this layer. Such wave heights imply a nearby volcanic explosion on the scale of Krakatau or larger, or a nearby submarine landslide also of great size, or a bolide-water impact in the ocean.
Atmospheric tides, shorter period gravity waves and shear waves
Tidal oscillations, shorter period gravity waves and shear waves
The quiet solar chromosphere shows three distinct regions. Ordered according to the strength of the emission from the low and middle chromosphere they are (1) the magnetic elements on the boundary of supergranulation cells, (2) the bright points in the cell interior, and (3) the truly quiet chromosphere, also in the cell interior. The magnetic elements on the cell boundary are associated with intense magnetic fields and are heated by waves with very long periods, ranging from six to twelve minutes; the bright points are associated with magnetic elements of low field strength and are heated by (long-period) waves with periods near the acoustic cutoff period of three minutes; and the quiet cell interior, which is free of magnetic field, may be heated by short-period acoustic waves, with periods below one minute. This paper reviews mainly the heating of the bright points and concludes that the large-amplitude, long-period waves heating the bright points dissipate enough energy to account for their chromospheric temperature structure.
The present investigation has the objective to document examples of anomalous long-period surface wave amplitude behavior and to provide a preliminary appraisal of the effects of global lateral heterogeneity on surface wave propagation from a ray theory perspective. Attention is given to remarkable long-period surface wave anomalies described in literature, an equidistance azimuthal plot centered on the Iranian source region, Rayleigh wave and Love wave spectra for the 256-s period arrivals for the Tabas earthquake, constrained moment tensor and fault model inversion solutions ofr Iranian earthquakes, aspects of surface wave ray tracing, and a table of Rayleigh wave amplitude anomalies for Iranian earthquakes. Surface wave ray-tracing calculations for models of global phase velocity variations proposed by Nakanishi and Anderson (1984) are found to show that large-amplitude anomalies will be observed for Love and Rayleigh waves with periods of 100-250 s.
Long period hydromagnetic waves in magnetosphere and coupling to solar wind studied by Explorer XIV
The chemical-dynamical model of Walterscheid et al. (1987), which describes wave-driven fluctuations in OH nightglow, was modified to include the effects of both eddy thermal conduction and viscosity, as well as the Coriolis force (with the shallow atmosphere approximation). Using the new model, calculations were performed for the same nominal case as used by Walterscheid et al. but with only wave periods considered. For this case, the Coriolis force was found to be unimportant at any wave period. For wave periods greater than 2 or 3 hours, the inclusion of thermal conduction alone greatly modified the results (in terms of a complex ratio 'eta' which expresses the relationship between the intensity oscillation about the time-averaged intensity and the temperature oscillation about the time-averaged temperature); this effect was reduced with the further inclusion of the eddy viscosity.
A new class of ULF waves with periods near 3 s in the earth's upstream region is found by examining the high time resolution magnetic field data from the ISEE spacecraft. These waves are observed in the part of the upstream region which is magnetically connected to the bow shock, but only when the solar wind plasma beta is high (greater than 1). The waves are always right-handed, nearly circularly polarized in the spacecraft frame. The directions of the wave vectors are in the general direction of the average magnetic field, and the waves are convected downstream in the spacecraft frame. This study of these waves has shown that they appear to be intrinsically left-handed ion cyclotron waves in the plasma rest frame.
In order to study the scattering of waves from periodic surfaces, the basic grating equations are reviewed, and a general approach for scattering from impenetrable and penetrable media is formulated. Three analytical methods for scattering on a conducting sinusoidal surface for both TE and TM polarized waves are compared. In The Masel, Merrill, and Miller (MMM) method for quantum scattering of atoms (1975, 1976), the surface field expansions are expressed in terms of Fourier series. The Modified Physical Optics (MPO) method (DeSanto, 1975; Whitman and Schwering, 1977) uses surface field expansions consisting of a leading term proportional to the physical optics approximation multiplied by a Fourier series expansion. The Waterman's Plane Harmonics (WPH) approach (1975) makes use of basis functions which are downward plane harmonics evaluated on the surface. The MMM method proved to be the most efficient one in terms of rate and range of convergence. For dielectric media with periodic rough surfaces, an improved method is developed for calculating the reflected and transmitted powers, and the results are compared with experimental data obtained at optical frequencies.
Stability theory of large amplitude periodic BGK waves in collisionless plasmas using distribution functions