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At least 379 records · Page 21
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NASA NTRS1972

Information from Jupiter's decametric radiation

Radiation associated with decametric bursts are observed from about 39.5 MHz downwards, and its occurrence probability depends partly on the central meridian longitude of Jupiter. Three central meridian longitude regions of emission are designated as Sources A, B, and C. Emissions from B and C regions are also dependent on Io's phase. The frequency band of noise storms drifts slowly up or down the spectrum. Pulses with durations of 20 microseconds display drifts at the rate of 1000 MHz/sec. Decametric data are used to estimate Jupiter's surface magnetic field strength to be 10 gauss; however, if the maximum emission, about 10 MHz, is the electron gyrofrequency at Io's orbit, the surface field strength would be about 800 gauss. A model of the emission beam control exercised by Io is summarized. Data are presented which indicate that the width of source A emissions results from the changes in the angle of Jovicentric declination of the earth. One of two recent theories places the plasmapause at least 50 Jupiter radii from the surface on the sunward side, and the other places it within Io's orbit.

Carr, T. D.↗
NASA NTRS1972

POGO observations of the equatorial electrojet

During intervals in 1967 to 1970, the OGO-4 and 6 spacecraft made over 2000 traversals over the equatorial electrojet in the altitude range 400-800 km when local times were between 9 and 15 hours. These spacecraft carried total field magnetometers making measurements to an accuracy of 2 gamma with a sample rate greater than once a second. Delta F values, the deviations from these observations, were formed from an internal reference model. The results were plotted for a 30 deg band about the equator, and the characteristics of the electrojet effect in the data were investigated. This effect was characterized by a sharp negative V-signature of some 16-19 deg in width and a variable amplitude. The position of this minimum was found to lie within 0.5 deg of the dip equator. A slight northward shift was noted at the longitude of Huancayo. The jet amplitudes were normalized to 400 km amplitudes and observed to be highly variable in time. Amplitudes over the longitude range 50 to 90 deg W averaged 60% higher than elsewhere, as expected, due to the weaker main field. However, though the scatter of amplitudes is high, the expected minima in east Asia was not evident. It was speculated that this could be due to a less conducting upper mantle in this area.

Cain, J. C.↗
NASA NTRS1972

Magnetic-field anomalies in the lunar wake.

The interplanetary magnetic field is only slightly perturbed by the presence of the moon in the solar-wind flow. A statistical study of the umbral increases and penumbral decreases and increases was conducted with variation of the solar-wind plasma beta value, the distance from the moon and the selenographic longitude of the limb regions of the lunar surface in the solar-wind flow. All lunar-wake anomalies show a strong positive correlation with the plasma beta value, whereas only penumbral increases show a marked variation with distance from the moon. There is no clear correlation of occurrence of penumbral anomaly with selenographic longitude of the exposed lunar limb in the solar-wind flow.

Whang, Y. C.↗
NASA NTRS1972

Twenty-seven-day recurrences in the solar-wind speed - Mariner 2.

Results of an autocorrelation analysis of the Mariner 2 data concerning solar-wind speed obtained in late 1962. A statistically significant correlation associated with the solar rotation has been found near a lag of 27 days; however, the amplitude of the correlation is only about 0.4, in essential agreement with measurements of Vela 2 and 3 during the period from July 1964 to July 1967. The relatively modest correlation is interpreted to mean that a number of speed structures observed by Mariner 2 did not endure for more than one solar rotation; those structures that did endure evolved significantly in shape, amplitude, and solar longitude from one solar rotation to the next. The analysis also shows that typical solar-wind structures occupied about 30 to 45 deg in solar longitude near 1 AU.

Gosling, J. T.↗
NASA NTRS1972

Atlas/Centaur-29 Intelsat IV (F5) flash flight report

ATLAS/CENTAUR-29 was launched from ETR Complex 36B, June 13, 1972, at a flight azimuth of 101 degrees. The ETR test number was 1240. The launch vehicle consisted of an ATLAS SLV-3C first stage and a CENTAUR second stage. The spacecraft was INTELSAT 4 (F-5). The launch occurred at the opening of the window. Indications are that the spacecraft was injected into the required transfer orbit and has achieved it's final orbit. All orbital parameters were extremely close to nominal. A nominal apogee motor burn took place at 2101 EDT on June 14, 1972 at 124 degrees East longitude and the final duty station of the spacecraft will be at 62 degrees East longitude. A two week communications checkout was started on or about June 15, 1972.

Source record↗
NASA NTRS1972

A computer program for mapping satellite-borne narrow-beam antenna footprints on earth

A computer program has been developed that computes the locus of intersection of a quadric cone and a sphere. The outputs of the program are a list of the longitude and latitude coordinates of the locus of intersection and a plot of the locus. It was written primarily to define the area of the earth covered by a narrow beam antenna carried on a synchronous satellite in circular, near equatorial orbits. The program was written for use with a CalComp 570/563 off-line plotting system and uses the standard CalComp subroutines supplied with the system. The plot is drawn using linear longitude and latitude scales and nonlinear scales such as Mercator scales cannot be used. It should be noted that this program assumes the earth to be spherical rather than oblate is it actually is. However, by assuming a spherical earth, maximum error distances of about 11.5 nautical miles are introduced. For many purposes, this error can be ignored.

Stagl, T. W.↗
NASA NTRS1972

A shock surface geometry: The 15-16 February 1967 event

The flare-associated interplanetary shock observed by Explorer 33 and Pioneer 7 is analyzed to yield an estimation of the ecliptic plane geometry of the shock surface near 1 AU. These spacecraft were separated by 23 deg in the heliocentric longitude and Pioneer 7 was at a distance of 1.12 AU from the sun. Although a data gap occurred at the apparent time of passage of the disturbance at Pioneer 6, which was 85 deg in heliocentric longitude from Pioneer 7 and at 0.83 AU, the recovered data did suggest such a passage. A consistent picture of the shock propagation is given to explain the difference in arrival times at Pioneers 6, 7, and Explorer 33 and the difference of the shock normals observed by Pioneer 7 and Explorer 33. The average shock speed from the sun to each spacecraft and the local speed at Explorer 33 and their relations to the position of the initiating solar flare are obtained and discussed. In the region of space between the earth and Pioneer 7 the shock surface radius of curvature in the ecliptic plane was 0.4 AU or less.

Lepping, R. P.↗
NASA NTRS1973

Propagation pattern of interplanetary shock waves associated with solar proton flares

The two dimensional pattern of interplanetary shock waves is deduced by taking into account the solar longitude dependence of the time intervals between SSC geomagnetic storms and responsible flares. This pattern near the earth's orbit is not symmetric with respect to the meridian plane which crosses the position of the flare, and the highest speed of this wave propagation is observed in the direction about 30 degrees east of this meridian plane. The magnitude of the Forbush decreases of galactic cosmic rays also varies with the longitude positions of those flares. This is used to estimate the distribution of magnetic fields behind the shock waves.

Sakurai, K.↗
NASA NTRS1973

Mariner 9 aerographic coordinate system

Preliminary Mariner 9 map products were based on computed aerocentric coordinates at the point where the optic path intercepts a spherical reference figure for Mars. The intercept point on a reference ellipsoid would in general have slightly different values of radius, latitude, and longitude. For near-vertical viewing used for mapping, these differences are on the order of 0.1 in latitude and longitude, which is negligible compared to the uncertainties of the initial uncontrolled mosaics and maps.

Devaucouleurs, G.↗
NASA NTRS1973

Initial development of the June 1971 south equatorial belt disturbance on Jupiter

Photographs taken with the Catalina 61-inch reflector from June 21 through July 10, 1971 have permitted study and measurement of early developments of a major South Equatorial Belt (SEB) disturbance. High resolution photographs of the disturbance were obtained on seven nights during the 19-day interval. The first photograph at 04:38 UT on June 21 recorded the initial outbreak at 79.5 deg longitude (System 2), and -14 deg Zenographic latitude. From this point, dark spots moved along the SEBs towards increasing longitude. The preceding white spot had an initial period of 9h54m32.5 tor-3.5s, and retrograding dark spots on the SEBs a mean period of 9h58m30s.5 tor- 7s. The feature from which all the spots emerged had a rotation period of 9h55m29s tor- 2.5s, and is close to the System 3 radio period of 9h55m29.73s tor- 0.04s derived by Carr.

Minton, R. B.↗
NASA NTRS1974

A possible correlation between maxima of the far ultraviolet solar irradiance and central meridian passages of solar magnetic sector boundaries

Satellite observations of the sun over almost five years have shown that principally two UV active longitudes have persisted over a significant portion. A comparison between the position of solar magnetic sector boundaries and UV enhancements of the sun indicates that the UV maxima tend to occur near the times when a solar sector boundary is near central meridian. An estimate of the magnitude of the variable UV solar energy input into the atmosphere resulting from the rotation of active solar longitudes is that for wavelengths less than 175 nm and down to H. Lyman-alpha it exceeds the annual variation, whereas at longer wavelengths it is less. The total observed peak-to-peak variation in the UV irradiance from 120 to 300 nm over a solar rotation is typically at least 230 ergs/sq cms.

Heath, D. F.↗
NASA NTRS1973

Test for planetary influences on solar activity

A method due to Schuster is used to test the hypothesis that solar activity is influenced by tides raised in the sun's atmosphere by planets. We calculate the distribution in longitude of over 1000 flares occurring in a 6 1/2 yr segment of solar cycle 19, referring the longitude system in turn to the orbital positions of Jupiter and Venus. The resulting distributions show no evidence for a tidal effect.

Dingle, L. A.↗
NASA NTRS1973

Accuracy analysis of the ephemerides of the Galilean satellites

Known discrepancies between Sampson's Theory and observations of the Galilean satellites produce in plane errors of about 1200 km. Since the mean longitude is responsible for most of the discrepancy a simple time correction may be used to significantly reduce these errors. An analysis of the time corrections derived for Sampson's Theory, concludes that the dominant error in the mean longitudes results from Sampson's definition of time, which was determined by the observations which he used in constructing the theory. Imposition of the libration constraint results in changes to the time corrections which are less than the standard deviation of those quantities. The individual eclipse observational errors are shown to be proportional to the square root of the period. With improved star catalogs, the attainable accuracy of the ephemerides of the Galilean satellites is about 100 km from photographic plates versus about 200 km for eclipse observations.-

Peters, C. F.↗
NASA NTRS1974

Westward equatorial electrojet during daytime hours

The phenomenon of the depression of the geomagnetic horizontal field during the daytime hours of magnetically quiet days at equatorial stations is described. These events are generally seen around 0700 and 1600 LT, being more frequent during the evening than the morning hours. The evening events are more frequent during periods of low solar activity and in the longitude region of weak equatorial electrojet currents. The latitudinal extent of the phenomenon is limited to the normal equatorial electrojet region, and on some occasions the phenomenon is not seen at both stations, separated by only a few hours in longitude. During such an event, the latitudinal profile of the geomagnetic vertical field across the equator is reversed, the ionospheric drift near the equator is reversed toward the east, the q type of sporadic E layer is completely absent, and the height of the peak ionization in the F2 region is decreased. It is suggested that these effects are caused by a narrow band of current flowing westward in the E region of the ionosphere and within the latitude region of the normal equatorial electrojet, due to the reversal of the east-west electrostatic field at low latitudes.

Rastogi, R. G.↗
NASA NTRS1974

A correlation between time-overlapping solar flares and the release of energetic particles

The origin of a large corotating solar particle event in August 1970 is discussed. Proton data from spacecraft at five widely separated heliocentric longitudes are used to identify two distinct release points which are over 100 deg apart in solar longitude. Optical flare data show a high incidence of time-overlapping flares between plage regions close to the two release points, indicating a good connection between them. Unusual X-ray and radio emissions are also observed from these regions. The spectrum of the relativistic electrons in the corotating particle event is represented by a power law with an index gamma equal to approximately -4, considerably steeper than that usually observed from a solar flare. It is concluded that there is a large magnetic loop structure connecting points over 100 deg apart on the sun which is able to trap energetic protons and electrons from an earlier solar flare. Subsequent release of these particles establishes an intense, long-lived corotating event.

Simnett, G. M.↗
NASA NTRS1974

The distribution of cosmic rays in the Galaxy and their dynamics as deduced from recent gamma-ray observations

Recent data from SAS-2 on the galactic gamma-ray line flux as a function of longitude reveal a broad maximum in the gamma-ray intensity in the longitude region less than or equal to 30 deg. These data, when unfolded, imply that the low-energy (1 to 10 GeV) galactic cosmic-ray flux varies with galactocentric distance and is about an order of magnitude higher than the local value in a toroidal region between 4 and 5 kpc from the galactic center. It is further shown that this enhancement can be plausibly accounted for by first-order Fermi acceleration, compression, and trapping of cosmic rays consistent with present ideas of galactic dynamics and galactic structure theory. Calculations indicate that cosmic rays in the 4- to 5-kpc region are trapped and accelerated over a mean time of the order of a few million years or about 2 to 4 times the assumed trapping time in the solar region of the Galaxy.

Puget, J. L.↗
NASA NTRS1975

On the tesseral-harmonics resonance problem in artificial-satellite theory

The longitude-dependent part of the geopotential usually gives rise only to short-period effects in the motion of an artificial satellite. However, when the motion of the satellite is commensurable with that of the earth, the path of the satellite repeats itself relative to the earth and perturbations build up at each passage of the satellite in the same spot, so that there can be important long-period effects. In order to take these effects into account in deriving a theoretical solution to the equations of motion of an artificial satellite, it is necessary to select terms in the longitude-dependent part of the geopotential that will contribute significantly to the perturbations. Attempts made to obtain a selection that is valid in a general case, regardless of the initial eccentricity of the orbit and of the order of the resonance, are reported. The solution to the equations of motion of an artificial satellite, in a geopotential thus determined, is then derived by using Hori's method by Lie series, which, by its properties regarding canonical invariance, has proved advantageous in the classical theory.

Romanowicz, B. A.↗
NASA NTRS1974

SAS-2 observations of gamma rays from the galactic plane

Preliminary data are given for the SAS-2 high energy galactic gamma ray observation. These data include both latitude and longitude distributions. The longitude distribution shows a high density region. The latitude distributions toward the center and the anti-center are markedly different, the former showing a two-component structure of half-widths of approximately 3 and 6 deg. The energy spectrum in the range 35 to 200 MeV is hard, consistent with cosmic ray interactions with interstellar matter, including neutral pions decay and emission from energetic electron interactions. The data is consistent with an interpretation in terms of the confinement of the cosmic rays in the spiral arms.

Thompson, D. J.↗