On the semiannual variation of the upper atmosphere.
Semiannual density variations in thermosphere and exosphere as function of mixtopause height variations
Harris, I.↗
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Stochastic variations of cosmic rays in the solar system.
Cosmic ray intensity short term stochastic variations in solar system related to turbulent solar wind day-to-day variations
Jokipii, J. R.↗
Variation in the annual general aviation accident rate as it relates to flight training.
Annual general aviation aircraft accident rate variation related to annual variations in pilot flight training activity
Dougherty, J. D.↗
The variational method 2 - Perturbation theory
Variational method to approximate solutions of perturbation equations, perturbation analyses, and use of perturbation theory to infer variational principle
Epstein, S. T.↗
The semiannual variation in the heterosphere - A reappraisal
Representation of heterospheric semiannual variation as density variation with amplitudes as functions of altitude
Jacchia, L. G.↗
A theory of the diurnal variations of the thermosphere
Thermosphere diurnal variations two dimensional model atmosphere characteristic waves, separating density and temperature variations
Mayr, H. G.↗
The multifarious temporal variations of low energy, relativistic cosmic ray electrons
A detailed examination is made of the intensity variations of 3 - 12 MeV interplanetary electrons. The data used are from the cosmic ray experiment flown on the IMP solar minimum through to the onset of the present solar maximum (i.e., from December 1963 through August 1969). A morphology for the intensity changes is tentatively proposed which includes solar flare-associated events, solar co-rotating increases, Forbush decreases, and quiet-time increases, as well as the long term eleven-year variation. It is contended that the electron component observed both during quiescent times and during quiet-time increases are galactic in origin. The quiet-time increases represent a completely new phenomenon that appears to be unique to the low energy electron population. During a quiet-time increase the electron intensity is enhanced by a factor of 3 to 5 over a period of days, and, in general, these periods anti-correlate with low-energy solar particle events. Qualitatively, their amplitude diminishes with increasing solar activity.
Mcdonald, F. B.↗
Variations of cosmic rays associated with chromospheric flares on the sun
Features of the cosmic-ray variations in the geomagnetic pole region and a smooth decrease in the cosmic rays intensity as a result of increased solar activity are reported. A 66-day variation of the cosmic rays was registered, in agreement with the maximum frequency and power of solar chromospheric flares.
Kozin, I. D.↗
Infrared and Raman spectroscopic studies of structural variations in minerals from Apollo 11, 12, 14 and 15 samples, volume 3
Infrared and Raman vibrational spectroscopic data, yielding direct information on molecular structure, were obtained for single grains ( 150 microns) of minerals, basalts, and glasses isolated from Apollo 11, 12, 14, and 15 rock and dust samples, and for grains in Apollo 14 polished butt samples. From the vibrational data, specification substitutions were determined for the predominant silicate minerals of plagioclase, pyroxene, and olivine. Unique spectral variations for grains of K-feldspar, orthopyroxene, pyroxenoid, and ilmenite were observed to exceed the ranges of terrestrial samples, and these variations may be correlatable with formation histories. Alpha-quartz was isolated as pure single grains, in granitic grains composited with sanidine, and in unique grains that were intimately mixed with varying amounts of glass. Accessory minerals of chromite and ulvospinel were isolated as pure grains and structurally characterized from their distinctive infrared spectra. Fundamental vibrations of the SiO4 tetrahedra in silicate minerals were used to classify bulk compositions in dust sieved fractions, basalt grains and glass particles, and to compare modal characteristics for maria, highland and rille samples. No hydrated minerals were found in any of the samples studied, indicating anhydrous formation conditions.
Estep, P. A.↗
Adjoint variational methods in nonconservative stability problems.
A general nonself-adjoint eigenvalue problem is examined and it is shown that the commonly employed approximate methods, such as the Galerkin procedure, the method of weighted residuals and the least square technique lack variational descriptions. When used in their previously known forms they do not yield stationary eigenvalues and eigenfunctions. With the help of an adjoint system, however, several analogous variational descriptions may be developed and it is shown in the present study that by properly restating the method of least squares, stationary eigenvalues may be obtained. Several properties of the adjoint eigenvalue problem, known only for a restricted group, are shown to exist for the more general class selected for study.
Prasad, S. N.↗
Time variations in solar activity.
Long-term variations in the height of solar maxima and in the relative spottedness of the northern and southern solar hemispheres are considered. Mean sunspot numbers in the present solar cycle are found to be similar to those in cycles with maxima in 1937, 1917, 1860, and 1769. Time variations within the 11-year cycle are considered. It is pointed out that all solar latitudes and longitudes do not attain maximum levels of activity at the same time. Furthermore, the course of solar activity as measured by sunspot number and 2800 MHz flux is seldom smooth but appears to advance by series of pulses or episodes. Study of the declining branches of solar cycles 12 through 19 suggests that there will be 5 to 6 primary fluctuations of activity on the declining branch of cycle 20 in the years 1970.5-1975. At least half of these pulses can be expected to include significantly flare-rich centers of activity.
Dodson, H. W.↗
Multifarious temporal variations of low-energy relativistic cosmic-ray electrons.
Detailed examination of the intensity variations of 3- to 12-MeV interplanetary electrons. The data are from the Goddard cosmic-ray experiment on the Imp satellites and cover the period from just before the last solar minimum through the onset of the present solar maximum (i.e., from December 1963 through August 1969). A morphology for the intensity changes is tentatively proposed that includes solar-flare-associated events, solar co-rotating increases, Forbush decreases, quiet-time increases, and the long-term 11-year variation. It is contended that the electron components observed both during quiescent times and during quiet-time increases are galactic in origin. The quiet-time increases represent a completely new phenomenon that appears to be unique to the low-energy electron population. During a quiet-time increase the electron intensity is enhanced by a factor of 3 to 5 over a period of days, and, in general, these periods anticorrelate with low-energy solar particle events. Qualitatively, their amplitude diminishes with increasing solar activity.
Mcdonald, F. B.↗
Space and time variations of the solar Na D line profiles.
Preliminary results are presented of observations of the solar Na D lines obtained with high space and time resolution. The line profiles vary strongly with space and time implying that time averaging over a long period and large area will not produce the 'true' profile. The centre-limb increase in apparent Doppler width in the D lines is intrinsic. It is not due to space or time averaging. The amplitude of the 300-sec oscillation may range up to 1.5 km/sec in the region of formation of the D lines. The variation of the D line profile caused by the 300-sec oscillation may be described as follows: (1) the core is raised and lowered without change of shape, and (2) the wings broaden as the central intensity rises and narrow as it falls. Doppler width values derived from pairs of D line profiles are strongly correlated with the motion of the element observed. Indications of running waves have been found in the time variation of the core line bisectors.
Slaughter, C. D.↗
New evidence for solar cycle variations at great distances
Recent studies of solar planetary relationships are directed toward exploring how far out from the sun one could observe solar cycle variations. A positive solar Jovian relationship is suggested from a Chree superposed epoch study of the intensity of the great red spot of Jupiter over a period of about six solar cycles. The characteristic double maxima observed in the solar cycle variation is common to other observations of solar events in the photosphere, chromosphere, and corona; radio and corpuscular emissions from the sun; cosmic ray intensity and geomagnetic activity. The same method of analysis adopted for the study of luminosity changes of the planets Jupiter, Saturn, Uranus, and Neptune indicates that the fluctuations of luminosity follow the single maximum solar cycle represented by sunspot numbers. In conjunction with changes of upper atmospheric density and temperature, it is suggested that the extreme ultraviolet (EUV) emission from the sun may be connected with luminosity changes. A method of distinguishing between phenomena related to solar wind and those related to solar EUV is presented.
Venkatesan, D.↗
On the determination of the harmonic components of the diurnal variation of the thermosphere from satellite drag data
The accuracy of the diurnal and semidiurnal harmonics of density variation determined from satellite drag data is discussed and compared with data from the Jacchia empirical atmospheric model. The phase discrepancies between densities and temperatures, which are more pronounced in summer, and the extrema of the density data are described. The ratio of the semidiurnal to diurnal component of kinetic temperature, determined from Salah and Evans incoherent scatter radar observations, also indicates a seasonal variation. The radar data are compared with the Jacchia model, and a third harmonic is discussed.
Blum, P. W.↗
Variations in the detectability of major airports in northeastern Kansas and northwestern Missouri
The author has identified the following significant results. Six major airports are located within the ERTS-1 imagery. Runways at four of the airports are readily detectable. Runways at the other two airports are not detectable and the locations must be inferred by other means. This variation is attributed to variation in runway surface composition.
Morain, S. A.↗
Large-scale variations in the obliquity of Mars.
Large-scale variations in the obliquity of the planet Mars are produced by a coupling between the motion of its orbit plane due to the gravitational perturbations of the other planets and the precession of its spin axis which results from the solar torque exerted on the equatorial bulge of the planet. The obliquity oscillates on a time scale of approximately 120,000 years. The amplitude of this oscillation itself varies periodically on a time scale of 1,200,000 years. The present-day obliquity is approximately 25.1 deg. The maximum possible variation is from about 14.9 to 35.5 deg. Significant climatic effects must be associated with the phenomenon.
Ward, W. R.↗
Diurnal and semidiurnal nitrogen density and temperature variations from thermosphere probe measurements.
Amplitudes and phases for the diurnal and semidiurnal variations of thermospheric molecular nitrogen density and temperature are determined from data obtained by six rocket-launched thermosphere probes. The semidiurnal tide is significant for the lower thermosphere variations, where it could dominate in the N2 density at 140 km and in the temperature for altitudes between 170 and 200 km. At exospheric heights, the magnitudes of the semidiurnal modes in density and temperature are significantly smaller than those of the diurnal mode. The temperature phase is height-dependent in both diurnal and semidiurnal components below 200 km, thus contributing to phase differences between N2 density and temperature in both modes. No significant phase differences are apparent between N2 density and thermospheric temperature above 250 km.
Newton, G. P.↗