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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Thermal positive ions in the outer ionosphere and magnetosphere from Ogo 1.

Study of the positive thermal ion densities measured with a spherical electrostatic analyzer aboard OGO 1 between September and October, 1964. A high variability of charged-particle distributions is established within and beyond the plasmapause boundary. The density gradient was in an inverse relation to the plasmapause L position and was consistently about one order of magnitude higher for the afternoon sector orbits than for the nightside orbits. Irregularities of different types were observed in the positive thermal ion densities within the plasmasphere and outside it, showing no correlation with the magnetic activity level. A delay of 3 to 9 hr was observed in the movement of the plasmapause following an increase in the magnetic activity level on the nightside.

Ahmed, M.↗
NASA NTRS1972

Neutral density measurements near 400 kilometers by a microphone density gage on Ogo 6 during July 12-15, 1969.

Analysis of persistent density peaks (maxima) measured near 400 km during daytime (1425 LT) by a microphone density gauge on Ogo 6 during July 12 to 15, 1969. Most of the density peaks occurred between geomagnetic latitudes 50 and 61 N and L values 2.3 and 4.7. The average density change in the peaks was 27%. Most of the peaks appeared in the longitude sector from 150 to 350 E. No density peaks were measured in the 50 to 130 E sector during the 3-1/2 day observation period. A persistent pair of density peaks was present on seven successive orbits during July 13 and July 14 (both geomagnetically disturbed days) near geomagnetic latitudes 53 and 61 N, respectively.

Anderson, A. D.↗
NASA NTRS1972

A global empirical model of thermospheric composition based on OGO-6 mass spectrometer measurements.

A global empirical model for magnetically quiet conditions has been developed to describe longitudinally averaged OGO-6 N2, O, and He densities (in the altitude range 400 to 600 km) by means of an expansion into spherical harmonics. The annual asymmetric component in N2 density corresponds to an increase of about 400 K between winter and summer poles, which is about a factor of three greater than in the Jacchia model. However, the corresponding oxygen component at satellite altitudes reflects an increase between winter and summer comparable to that in the Jacchia model; this implies that at 120 km atomic oxygen increases by more than a factor of two between summer and winter poles. The amplitude of the symmetric semiannual component in N2 is larger at the poles than the equator. At the poles, the N2 variation corresponds to a temperature decrease of about 70 K from mid-April to mid-July. At low latitudes, the daily temperature maximum occurs close to 16 hours local time, nearly in agreement with radar backscatter observations.

Hedin, A. E.↗
NASA NTRS1972

Analysis of Ogo 6 observations of the O I 5577-A tropical nightglow.

Atomic oxygen green line data from the horizon scanning photometer on Ogo 6 have been examined. Unfolding the satellite data from the tropical F region yields altitude and latitude variations of the O(1S) emissions. The spatial variations of the tropical F-region electron density are then calculated by assuming dissociative recombination and using a model atmosphere. Where comparisons to ground based data are possible the results are good. Thus, the satellite observations constitute a form of topside sounding of the ionosphere below the F peak and provide synoptic data about this portion of the ionosphere that are otherwise impractical to obtain.

Thomas, R. J.↗
NASA NTRS1972

Type III solar noise observed below 100 kHz on OGO 3.

Type III solar noise bursts have been observed in the frequency range 25-100 kHz with the VLF detector on OGO 3. The bursts decrease in frequency from 100 kHz (the highest frequency of observation) to as low as 25 kHz in approximately 45 min. The intensity at 100 kHz increases for about 20 min then decays over a period of approximately 1 hr. The variation of the intensity with time becomes less regular at lower frequencies. Bursts are predominantly associated with west-limb flares. Their commencement at 100 kHz tends to follow type III bursts observed at 2-4 MHz by about 10 min. Observed drift rates and decay times correspond roughly to those extrapolated from higher frequency measurements.

Dunckel, N.↗
NASA NTRS1972

Electric field variations during substorms - OGO-6 measurements.

The general pattern of high electric fields in magnetic time-invariant latitude coordinates is reviewed in the light of OGO-6 electric field measurements. This pattern is found to show little variability and, when unusual variations or field distributions occur, they are relatively isolated in time and space. Significant indications of direct correlation between electric field behavior and stages of magnetic bay development have not been found.

Heppner, J. P.↗
NASA NTRS1972

OGO-F-02 data analysis

The OGO-VI satellite, which was launched on June 5, 1969 carried a complement of twenty-six experiments. One of those instruments, the F-02 package, was a cylindrical Langmuir probe experiment whose primary purpose was to measure ionospheric electron temperatures and densities. This report briefly describes the F-02 experiment itself, outlines the computer programs developed to analyze the raw data, and gives a summary of the scientific information obtained, with the aid of this experiment.

Nagy, A. F.↗
NASA NTRS1973

MDAC solar cosmic ray experiment on OGO-6

The instrumentation of the OGO-F solar cosmic ray experiment is described and results of data obtained during the satellite lifetime from launch on June 5, 1969, through September, 1970, and discussed.

Masley, A. J.↗
NASA NTRS1972

Empirical model of global thermospheric temperature and composition based on data from the OGO-6 quadrupole mass spectrometer

An empirical global model for magnetically quiet conditions has been derived from longitudinally averaged N2, O, and He densities by means of an expansion in spherical harmonics. The data were obtained by the OGO-6 neutral mass spectrometer and cover the altitude range 400 to 600 km for the period 27 June 1969 to 13 May 1971. The accuracy of the analytical description is of the order of the experimental error for He and O and about three times experimental error for N2, thus providing a reasonable overall representation of the satellite observations. Two model schemes are used: one representing densities extrapolated to 450 km and one representing densities extrapolated to 120 km with exospheric temperatures inferred from N2 densities. Using the best fit model parameters the global thermospheric structure is presented in the form of a number of contour plots.

Hedin, A. E.↗
NASA NTRS1973

Neutron measurements of the OGO-VI Spacecraft

The neutron measurements with the OGO-6 spacecraft are reported. Topics discussed include: the design and calibration of a neutron monitor for measuring the cosmic ray neutron leakages from the earth's atmosphere, determination of latitude dependence of cosmic ray leakage flux, determination of the angular distribution of neutron leakage flux as deduced by measurements of the altitude dependence, and verification of the solar modulation of the cosmic ray source for the neutron leakage.

Lockwood, J. A.↗
NASA NTRS1973

Role of gas-surface interactions in the reduction of OGO 6 neutral-particle mass spectrometer data

Data obtained with the quadrupole mass spectrometer aboard the OGO 6 satellite show the effects of significant surface interaction processes, including nearly complete recombination of incoming atomic oxygen on the walls of the instrument antechamber plus absorption and desorption of oxygen and carbon monoxide. The observed data are fit by solving the time-dependent continuity equations accounting for production and loss of atomic oxygen, molecular oxygen, and (in the case of mass 28) carbon monoxide. The surface parameters that best fit the data are selected and applied to the determination of ambient densities and their estimated errors.

Hedin, A. E.↗
NASA NTRS1973

The detection of intermediate size magnetic anomalies in Cosmos-49 and OGO-2, 4, and 6 data

Benkova, Dolginov, and Simonenko have recently reported the presence of intermediate size magnetic anomalies in the data from COSMOS-49 and hypothesized a crustal and/or upper mantle origin. The spherical harmonic models of the internal potential function were examined, based on the OGO-2, 4, and 6 data (POGO (10/68) and later models), and verified the locations and amplitudes of those anomalies whose wavelengths approximate 4000 km. The comparison was made by subtracting a field model developed with a truncated series of n* = 9 from one computed with n* = 11 and generating a residual map equivalent to the COSMOS-49 data. The patterns of delta F so computed from POGO were then compared with the IZMIRAN maps and also were analyzed statistically, in both the spatial and frequency domains, using residuals computed from the raw COSMOS-49 data with the n* = 9 COSMOS-49 field model as reference. The two sets of data were thus derived from completely independent sets of observations and field references. The two patterns are shown to agree very well over the whole earth surface up to the 50 deg latitude limit of COSMOS-49.

Regan, R. D.↗
NASA NTRS1972

Banded whistlers observed on OGO-4

Inspection of broadband VLF records from OGO-4 shows that some whistlers exhibit a banded structure in which one or more bands of frequencies are missing from the whistler's spectrum. The phenomenon is commonly observed by satellites on midlatitude field lines at all local times and at various longitudes around the world. The dispersion of banded whistlers (BW) is of several tens of sec to the 1/2 power, indicating that they originated in the opposite hemisphere and are propagating downward at the satellite. BW are generally spread in time (tenths of seconds) rather than sharply defined and tend to occur at random. The frequency spacing of the bands may be either uniform or irregular, and may vary radically between successive events. Several possible explanations for BW are considered. In particular, an analysis of the interaction of plane electromagnetic waves traveling in an anisotropic plasma with a field aligned slab of enhanced ionization is presented with promising results.

Paymar, E. M.↗
NASA NTRS1973

Near earth magnetic disturbance in total field at high latitudes. 2: Interpretation of data from OGO's 2, 4, and 6

Variations in the scalar magnetic field (delta B) from the polar orbiting OGO 2, 4, and 6 spacecraft, with supporting vector magnetic field data from surface observatories, were analyzed at dipole latitudes above 55 deg. Although individual satellite passes, at low altitudes, confirm the existence of electrojet currents, neither individual satellite passes nor contours of average delta B are consistent with latitudinally narrow electrojet currents as the principal source of delta B at the satellite. The ratio of delta B magnitudes in positive and negative regions is variable. The characteristics of the negative delta B region indicate a latitudinally broad ionospheric source. Comparison of the surface magnetic disturbance caused by the equivalent current with the measured average surface disturbance shows good agreement except in localized details. Because delta B decreases very slowly with altitude in the positive delta B region, it is not possible to account for this disturbance in terms of ionospheric currents. The contribution to the satellite delta B due to a model electrojet, which reproduced the measured average surface horizontal disturbance, was computed. Definitive identification of all sources of positive delta B is not possible at this time.

Langel, R. A.↗
NASA NTRS1973

Near earth magnetic disturbance in total field at high latitudes. 1: Summary of data from OGO's 2, 4, and 6

Variations in the total (i.e. scalar) magnetic field data from the polar orbiting OGO-2, 4, and 6 spacecraft (altitudes 400-1510 km) are summarized for invariant latitudes above 55 deg. Data from all degrees of magnetic disturbance are included. The data are presented in terms of the quantity delta B(= measured field magnitude minus the field magnitude from a spherical harmonic model of the quiet field).

Langel, R. A.↗
NASA NTRS1973

OGO 6 ion concentration irregularity studies

Research is reported concerning the ionospheric F-region irregularities. The results are based on in-situ OGO-6 measurements of the total ion concentration N sub i. A proposed mechanism for the generation of equatorial F-region irregularities and the morphological results, and the occurrence of Fe(+) ions in the equatorial F-region are discussed. Related research papers are included.

Mcclure, J. P.↗
NASA NTRS1973

Comparison of Te and Ti from Ogo 6 and from various incoherent scatter radars.

Langmuir probe and retarding potential analyzer (RPA) data on the electron and ion temperatures Te and Ti obtained from Ogo 6 are compared with Te and Ti values obtained from the incoherent scatter network. The satellite to radar temperature ratio TeS/TeR is 1.15 on the average for these comparisons. This discrepancy is larger than the uncertainties usually placed on the probe and radar Te values. The ion temperature ratio TiS/TiR approximately 1.0, independent of the particular radar examined. This comparison serves as an intercalibration of the incoherent scatter network.

Mcclure, J. P.↗