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No evidence for modulation of the Sco X-1 intensity between 3 and 6 keV at the optical period of 0.787313 day is found during one year of quasi-continuous observation. Any persistent X-ray modulation at this period must be less than one percent.
The paper describes measurements of fluctuations in the total electron content along the propagation path of the radio beam between the ATS-6 geostationary satellite and the ground station. Short-period oscillations of the total electron content of about plus or minus 8 time 10 to the 13th electrons per sq m with a period of about 30 to 50 seconds were detected. These oscillations appear to be well correlated with the appearance of Type PC 4 micropulsations.
Results of broadband photoelectric photometry of 139 Juewa during five consecutive nights in March 1974 are presented. The synodic period found is 20.9 hr. A linear phase coefficient of about 0.080 is determined between phase angles of 0.9 to 1.5 deg. This value is similar to that for the lunar highlands and for three other asteroids (4 Vesta, 20 Massalia, 110 Lydia) at similar phase angles, indicating that these surfaces have comparable porosities. The composite light curve presented covers 80% of the rotational period; short-timescale features in the light curve are seen which correspond to topography a few kilometers in size.
It was previously shown that trapped electron fluxes of energies in the range from 50 keV to 1 MeV observed in the afternoon magnetosphere during substorms frequently undergo periodic variations. High-resolution electron spectrometer data indicate that these electron variations are periodic in the range of about 2-12 min, correlated with magnetic field variations, organized by the local magnetic field, and dependent on pitch angle. The observations suggest that the electron variations are adiabatic. The study derives quantitative adiabatic expressions of particle flux variations in a model geomagnetic field perturbation to show that the observational features are consistent with effects arising from adiabatic modulation of trapped particle fluxes.
Analysis of All-Sky Monitor observations of Cir X-1 (3U 1516-56) over the period from October 1975 to April 1976 has revealed a well-defined modulation of the 3-6-keV flux at a period of 16.585(+ or - 0.01) days. The light-curve is characterized by an abrupt drop in emission occurring on a time scale of no more than about 0.07 day, with epoch JD 2,442,877.181(+ or - 0.07). No clear correspondingly sharp increase in emission is observed during the cycle, so a noneclipse origin for this effect cannot be ruled out.
A reliability analysis of structures subjected to random service loads and periodic proof tests treats gust loads and maneuver loads as random processes. Crack initiation, crack propagation, and strength degradation are treated as the fatigue process. The time to fatigue crack initiation and ultimate strength are random variables. Residual strength decreases during crack propagation, so that failure rate increases with time. When a structure fails under periodic proof testing, a new structure is built and proof-tested. The probability of structural failure in service is derived from treatment of all the random variables, strength degradations, service loads, proof tests, and the renewal of failed structures. Some numerical examples are worked out.
A wind tunnel investigation was conducted to study the flow field in which separation is caused by an expanding plume, with emphasis on effects associated with periodic unsteadiness in the plume. The separation shock was photographed with high speed motion pictures, from which mean shock position and excursion data are reported. Pressure fluctuations were measured beneath the separation shock and statistics of the results are reported. A response of the separation shock to plume periodic unsteadiness was identified, and the magnitude of a corresponding transfer function was defined and is reported.
A four-step mechanism is proposed for the acceleration of energetic protons and relativistic electrons in Jupiter's magnetosphere. According to this mechanism, photoelectrons and ions from the Jovian ionosphere are: (1) ejected along magnetic-field lines toward the equator by the centrifugal force of corotation; (2) accelerated by magnetic-field annihiliation in the magnetotail, which process is modulated at Jupiter's rotational frequency; (3) trapped on closed field lines in the reconnection process, convected inward toward Jupiter from the merging region, and subjected to adiabatic compression; and (4) diffused inward by the conventional radial-diffusion process through a violation of the third adiabatic invariant. It is shown that the proposed mechanism produces magnetic moments much larger than those available from inward diffusion of solar-wind particles or motional emf acceleration at the Galilean satellites, provides a natural explanation for the 10-hr periodicity of the energetic particle fluxes observed inside the magnetosphere by the Pioneer spacecraft, and also produces a 10-hr periodicity in the energetic particle flux from the magnetosphere into interplanetary space in such a way that the phase of interplanetary flux variations is locked to the rotational phase of Jupiter
The paper considers wave propagation in longitudinally periodic media near the first- and higher-order Bragg resonances. An extended coupled-waves (ECW) approach is applied to media with single or multiharmonic periodicities and is numerically compared with the Floquet theory. The ECW approach predicts coupling coefficients that vary as the magnitude of the perturbation raised to the power of the Bragg order. Explicit expressions are also given for the band-gap width and band-gap shift for all Bragg orders. A number of applications are discussed.
The X-ray intensity of the transient source A0620-00 has been measured frequently with the SAS-3 X-ray Observatory from August 8, 1975 to February 13, 1976. This brightest of all known X-ray transients shows intensity variations on a time scale of days superposed on a general decline. Intensity data for the period from January 7 to February 13, 1976, show evidence of an approximate 7.8-day periodicity that may be the result of binary motion.
The first-overtone sequence of vibration-rotation transitions of the free radical silicon monoxide are shown to have extreme phase-dependent variations in the spectra of two M-type long-period variables, Omicron Ceti and R Leonis, and the mild S-type long-period variable, Chi Cygni. At maximum light, the SiO band heads are not detectable. Near minimum light, the band heads of (Si-25)O are detected in the 4-micron spectra of all three stars. The band heads of the terrestrially less abundant isotopic species, (Si-29)O and (Si-30)O, are detected in Chi Cygni. Possible explanations of the phase-dependent behavior are discussed, and the role of the stellar chromosphere is considered.
The generation of satellite coverage patterns is facilitated by three basic strategies: use of a simplified physical model, permitting rapid closed-form calculation; separation of earth rotation and nodal precession from initial geometric analyses; and use of symmetries to construct traces of indefinite length by repetitive transposition of basic one-quadrant elements. The complete coverage patterns generated consist of a basic nadir trace plus a number of associated off-nadir traces, one for each sensor swath edge to be delineated. Each trace is generated by transposing one or two of the basic quadrant elements into a circle on a nonrotating earth model sphere, after which the circle is expanded into the actual 'helical' pattern by adding rotational displacements to the longitude coordinates. The procedure adapts to the important periodic coverage cases by direct insertion of the characteristic integers N and R (days and orbital revolutions, respectively, per coverage period).
Energetic (exceeding 35 MeV) gamma-rays have been observed from the direction of Cygnus X-3 with the SAS-2 gamma-ray telescope. The statistical significance of the excess above the galactic and diffuse radiation is approximately 4.5 sigma. In addition, the gamma-ray flux is modulated at the 4.8-hr period observed in the X-ray and infrared regions, and within the statistical error is in phase with this emission. The flux above 100 MeV has an average value of about 4.4 millionths photon/sq cm per sec. If the distance to Cygnus X-3 is 10 kpc, this flux implies a luminosity of more than 10 to the 37th power erg/s if the radiation is isotropic and about 10 to the 36th power erg/s if the radiation is restricted to a cone of 1 steradian, as it might be in a pulsar. Upper limits are presented for the gamma-ray flux from other known or suspected periodic X-ray sources.
The phase and amplitude of the annual, semiannual, and quasi-biennial oscillations to total ozone data for the Northern Hemisphere in the period 1957-1972 and for Northern Hemisphere ozonesonde data for variable periods from 1962-1974 have been plotted as functions of latitude, longitude, and altitude. The largest annual wave amplitude in total ozone occurs over eastern Siberia. In total ozone, the region of maximum quasi-biennial oscillation (QBO) coincides with that of the annual wave. The major feature of the QBO in the vertical distribution is the maximum amplitude in the arctic just above the tropopause. As for the semiannual wave, the maximum in total ozone lies in the arctic, displaced slightly to the Siberian side. In the vertical, its maximum amplitude is near 18 km. The phase appears to progress poleward, with maxima at high latitudes occurring in March-April.
Observations of GX 304-1 (3U 1258-61) performed with the SAS-3 satellite revealed regular X-ray pulsations with a period of 272 s. Average pulse profiles, derived from 7 days of observation, are presented in four energy intervals covering the range 1-19 keV. The pulses are basically characterized by a single broad peak, and the amount of modulation decreases rapidly with increasing energy. The pulse arrival times are analyzed for effects of possible orbital motion of the X-ray star, and significant constraints are placed on the orbital parameters. For example, if it is established that the companion is an early-type star of at least 5 solar masses, then the orbital period is likely to be greater than about 15 days. Three 100-s flares were observed during which the source intensity rose by a factor of 4 in approximately 10 s.
SAS-3 observations of the X-ray source 3U 1626-67 have revealed the presence of a stable 7.68-sec pulse period. This source was selected for study because of its hard X-ray spectrum. The compilation of source spectra used in the selection process is also presented. Pulse arrival times are analyzed for effects of possible binary orbital motion. Upper limits to the projected orbital radius are obtained which tend to exclude orbital periods in the range from about 0.5 to 35 days. Binary systems with either a very long orbit (at least 175 days) or a very short orbit (no more than about 0.3 day) are most probable
The period of the large coherent structure in a subsonic, compressible, turbulent boundary layer was determined using the autocorrelation of the velocity and pressure fluctuations for Reynolds numbers between 5,000 and 35,000. In low Reynolds number flows the overall correlation period scaled with the outer variables - namely, the free stream velocity and the boundary layer thickness.
A theoretical treatment is presented of the motion of a constant-volume balloon immersed in a three-dimensional spatially nonhomogeneous periodic flow field with a mean translational flow velocity. The governing equations are the equations of conservation of momentum of the balloon, coupled with the equations of conservation of momentum of the fluid. In the mathematical model employed, the flow field is represented by a periodic function. The numerical results are in general agreement with observations. Noteworthy is that the balloon does not move with the same mean velocity as the wind and, thus, when Taylor's hypothesis for the fluid is satisfied, the balloon does not 'lock in' with the wind velocity. When Taylor's hypothesis for the parcel is satisfied, however, the balloon does match the mean wind direction (but not its speed).