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At least 1,729 records · Page 96
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NASA NTRS1974

Variations in thermospheric composition - A model based on mass spectrometer and satellite drag data

The seasonal-latitudinal and the diurnal variations of composition observed by mass spectrometers on the Ogo 6 satellite are represented by two simple empirical formulas. The formulas are of a very general nature and predict the behavior of these variations at all heights and for all levels of solar activity; they yield a satisfactory representation of the corresponding variations in total density, as derived from satellite drag. It is suggested that a seasonal variation of hydrogen may explain the abnormally low hydrogen densities at high northern latitudes in July 1964.

Jacchia, L. G.↗
NASA NTRS1974

Empirical solar proton model for orbiting spacecraft applications

An empirical model for energetic solar proton fluxes is presented. With this model the effects of such protons on geocentric space missions, to be flown during the next solar active period (1977-1983), and with orbits involving partial magnetospheric shielding, may be estimated. A synoptic background review is given, followed by a detailed discussion of the model's use, errors, uncertainties, and limitations, including sample calculations which demonstrate the application of specific or general project missions. Finally, for circular trajectories, percentage exposure maps are presented, depicting fractional mission times spent outside particular L shells as functions of orbit altitude and inclination.

Stassinopoulos, E. G.↗
NASA NTRS1974

A representation of Jacchia's thermospheric models in spherical harmonic functions

The Jacchia models are represented in terms of spherical harmonic functions. This representation has the advantage of ease of comparison with other global theoretical and empirical models that use this mathematical form. Furthermore, it is analytic, continuous, and has continuous derivatives all over the globe. The representation of the exospheric temperatures shows clearly the amplitudes of the various periodic terms and uses relatively few constants. An example of a similar representation for the total mass density at a particular height and level of solar activity is given as well.

Blum, P.↗
NASA NTRS1974

Bursts of relativistic electrons from Jupiter observed in interplanetary space with the time variation of the planetary rotation period

Bursts of Jovian electrons in the energy range 3 to 30 Mev have been detected to distances of the order of 1 AU from the planet. The duration of each burst was about two to three days, and the maximum intensity increased with increasing distance from the sun. These events could not be correlated with known solar activity. The conclusion that these electrons originated at Jupiter and were accelerated within the Jovian magnetosphere is based on observations of three of these bursts. The power spectrum of the temporal variations of the 6- to 30-MeV electron flux showed a persistent peak at Jupiter's rotation frequency (corresponding to the ten hour rotation period) out to distances greater than 100,000,000 km from the planet. The slope, or spectral index, of the differential energy spectrum measured as a function of time displayed the ten-hour cyclic variation in the value of the index, which was earlier found to be characteristic of the electrons within the Jovian magnetosphere.

Chenette, D. L.↗
NASA NTRS1974

Long base line interferometry of the sun at centimeter wavelengths

The three-element interferometer of the National Radio Astronomy observatory and the two-element interferometer of the Hat Creek Observatory have been used to observe the fine structure of the sun at 11.1-, 3.7-, and 1.3-cm wavelengths. Solar active regions have been synthesized at 11.1- and 3.7-cm wavelengths with angular resolutions of 9 and 3 arc sec, respectively. Structural components on the scale of a few seconds of arc have also been detected in the quiet-sun and flare regions.

Kundu, M. R.↗
NASA NTRS1974

Our prodigal sun

Characteristics of the sun are reported indicating it as a source of energy. Data from several space missions are discussed, and the solar activity cycle is presented. The corona, flares, prominences, spots, and wind of the sun are also discussed.

Source record↗
NASA NTRS1975

Prognoz reports

Studies conducted outside the effect of the earth's magnetic field during the revolution period by the Prognoz satellite are examined. In particular, the unperturbed solar wind, the flux of charged particles continually given off the sun is studied. Solar activity and its effects on various natural phenomena are discussed.

Narimanov, G.↗
NASA NTRS1975

Determining the parameters of the prognostic operator for undamped fluctuations by the use of the D sub m(kappa; alpha 1,..., alpha sub m)

The prognostic operator is defined as the matrix or integral operation which, when applied to a set of known values of the vector for various earlier moments of time, predicts a value for the vector at a future moment by the amount ahead of time. If the vector represents a function that decays with time, then the predicted values of the function are given as series expansions in terms of the same functions but with unknown coefficients if some change in the process occurs at the moment of prediction. As examples of such changes are considered: (1) the circulation mechanisms of the atmosphere under the influence of solar activity; (2) brightness fields fluctuations; and (3) wave formations or currents in the ocean after a change in wind field.

Dmitriyev, A. A.↗
NASA NTRS1974

The solar corona as seen from Skylab

The white light coronagraph (WLC) experiment of the Skylab/ATM obtained an unprecedented series of observations of the solar corona from 1.5 to 6 solar radii for approximately eight and one-half months. Coronal evolution and disruptions seen by the WLC occur on many different time scales. Some illustrative examples will be shown. The characteristics of mass ejection coronal transients - as we presently know them - will be given. These include: the greater than expected frequency of occurrence; the correlation with solar activity; the quantity of mass and energy contained in a transient; etc.

Hildner, E.↗
NASA NTRS1974

Physical properties of solar chromospheric plages. II - Chromospheric plage models

Chromospheric models of plages are proposed to explain profiles of the Ca II H, K, 8498-A, 8542-A, and 8662-A lines. These models are consistent with boundary conditions imposed by the photosphere and the Lyman continuum. It is found that increasing emission in these lines is consistent with a picture of increasing temperature gradient in the low chromosphere and the resulting increase in pressure and electron density at similar line optical depths. With this picture it is shown how the distribution of chromospheric parameters across the solar disk can be empirically determined directly from Ca II filtergrams. It is also proposed that the high-density aspects of solar activity are produced by steep temperature gradients in the low chromosphere and thus by the enhanced heating mechanisms that steepen these gradients.

Shine, R. A.↗
NASA NTRS1975

Electron density profiles from ionograms - Underlying ionization corrections and their comparison with rocket results

Electron density profiles from nine daytime rocket flights at Wallops Island, Va., conducted at high and low levels of solar activity are compared with profiles calculated by inversion of ionograms obtained at the same times and location. Sources of error and uncertainty in the ionogram inversion are discussed, as are means for their amelioration. In most cases, agreement between the two kinds of measurement within a few percent in electron density and within a few percent of a scale height can be achieved.

Wright, J. W.↗
NASA NTRS1975

Determination of nitric oxide concentrations from sunrise E-region electron density measurements

Midlatitude sunrise electron density profiles have been analyzed in order to determine nitric oxide concentrations in the range 100-160 km. In general, the determinations are restricted to heights for which the ionization of nitric oxide by direct solar Lyman-alpha radiation is the main contribution to the growth of the E region. The concentrations obtained are larger, by factors of approximately 3 to 4, than those obtained from the midlatitude airglow measurements of other workers. Concentrations have been obtained from one sunset measurement and these are significantly lower than the sunrise values. The results also give a clear indication of increasing nitric oxide concentrations above 120 km with increasing solar activity.

Monro, P. E.↗
NASA NTRS1975

Large-scale and solar cycle variations of the solar wind

Space probe observations relevant to the determination of the large-scale, three-dimensional structure of the solar wind and its solar cycle variations are summarized. There is a pronounced decrease in the velocity spread about the average as distance from the sun increases (from 0.6 to 5 AU). A latitude variation is found for several plasma parameters, and a dependence on the phase of the solar activity cycle is demonstrated by some of the data.

Neugebauer, M.↗
NASA NTRS1975

Observations in interplanetary space of relativistic electrons from Jupiter

Evidence for the presence of Jovian electrons in interplanetary space as much as 1 AU inside the orbit of Jupiter is summarized. Electron flux patterns at Pioneer 10 can only rarely be correlated with solar activity. Clear variations in intensity and spectrum with a period of 10 hrs are seen at varying distances from Jupiter, consistent with similar observations inside the magnetosphere. Extrapolated electron flux maxima and minima are in good agreement with the observed phase at distances as large as 80 million km from Jupiter, indicating rapid propagation of electrons from the planet. Anisotropy is greatest during the rising phase of the 10 hr variations and in a direction consistent with the interpretation of electrons traveling toward the sun along interplanetary spiral field lines. The propagation time calculated by Chenette's derivation is much larger than that implied by the data.

Chenette, D. L.↗
NASA NTRS1975

Growth of metric noise continuum storms and its relation to the source of microwave S-emissions

The relationship between metric noise continuum storms and the S-component of solar microwave emissions is examined by considering the properties of a solar active region and its relation to LF radio burst emissions observed by IMP 6. It is noted that the development of radio noise continuum sources in metric frequencies or less is usually preceded by the appearance of an S-emission source, which is formed in complex sunspot groups such as beta-gamma and gamma types. A model for the development of radio noise continuum sources in metric and decametric frequencies is proposed in which the development of relationships between emissions is closely connected to the growth of magnetic-field lines above associated sunspot groups into complex configurations.

Sakurai, K.↗
NASA NTRS1975

A spectral solar/climatic model

A summary is presented of pertinent research on solar activity variations and climate variations, together with the presentation of an empirical solar/climatic model that attempts to clarify the nature of the relationships.

Sleeper, H. P., Jr.↗
NASA NTRS1975

The McDonnell Douglas geophysical observatory program progress report 13 Conjugate point riometer program

This report, the thirteenth and final progress report on the McDonnell Douglas Geophysical Observatory Program, discusses history of the program from 1962 through 1973, and results of the research carried out in 1974. Topic areas covered include: Station operation; Ionospheric work; Solar studies, Magnetospheric studies; Satellite measurements; International participation; and, 1974 research on solar activity, ATS-6 studies, magnetospheric physics, and station operation.

Baker, M. B.↗
NASA NTRS1976

Solar magnetic fields and the corona

Results from a seminar on the role of solar magnetic fields in determining the structure of the corona and interplanetary medium are presented. Some topics considered are: (1) polar regions of the sun which have identical magnetic configurations but display a vastly different appearance in the corona, (2) the influence of latitude on coronal and interplanetary microstructure, and (3) the role of the corona in contributing to the solar wind. It is proposed that an out-of-the-ecliptic solar probe mission would provide needed information on the above topics, and the study of solar activity in general.

Newkirk, G., Jr.↗