摘要:

Radio tracking data associated with the February 1977 encounters between the Martian satellite Phobos and the Viking Orbiter I spacecraft have been analyzed to determine the gravitational constant (GM) of Phobos. A linear error analysis was conducted to determine the selection of data and the parameter solution set which would yield the best estimate of GM. This error analysis indicated that the optimal data set was a data arc beginning just prior to the closest encounter and spanning three consecutive spacecraft orbits; data near periapsis were deleted. The most feasible parameter solution set consisted of the Phobos GM and the spacecraft initial conditions. The result of the data analysis was an estimate of (7.3 ± 0.7) × 10−4km³/sec² for GM of P

ISSN:0094-8276    

DOI:10.1029/GL004i012p00551

年代:1977

数据来源: WILEY

摘要:

The mass of the Martian satellite Phobos has been determined by processing radiometric tracking data obtained from the Viking‐1 spacecraft during a series of 14 near encounters which occurred in February 1977. Distances of closest approach ranged from 89 to 213 km from the center of mass of the satellite. Our best estimate for the gravitational constant, GM, of Phobos is (6.6 ± 0.8) × 10−4km³/s². The corresponding density of Phobos based on a volume estimate of 4800 ± 960 km³ from Mariner 9 imaging is 2.0 ±

ISSN:0094-8276    

DOI:10.1029/GL004i012p00555

年代:1977

数据来源: WILEY

摘要:

The nonlinear behavior of the collisional Rayleigh‐Taylor instability is studied in equatorial Spread F by including a dominant two‐dimensional nonlinearity. It is found that on account of this nonlinearity the instability saturates by generating damped higher spatial harmonics. The saturated power spectrum for the density fluctuations is discussed. A comparison between experimental observations and theory is presen

ISSN:0094-8276    

DOI:10.1029/GL004i012p00558

年代:1977

数据来源: WILEY

摘要:

Using the Ion Composition Experiment (ICE) on board ESA'S GEOS satellite we have observed He2+and O2+ions of terrestrial origin in the outer magnetosphere predominantly in the energy range ∼ 1 ‐ 100 eV. Data were obtained near the equatorial plane at geocentric distances of 3 to 7 earth radii in the local time sector 1500 ‐ 2100 hours. During periods when doubly charged ions are observed typical abundances are O2+/O+∼ 30% and He2+/He+∼ 0.5% ‐ 10%. The proportions of the major constituents H+, He+, and O+are highly variable with He+occasionally the dominant species at highe

ISSN:0094-8276    

DOI:10.1029/GL004i012p00561

年代:1977

数据来源: WILEY

摘要:

Spectra of plasma wave intensities (kTp) in the ionosphere over Arecibo are calculated and compared with those from observations of the plasma line intensity. This approach involving directly observed quantities avoids the uncertainties that have plagued past comparisons with photoelectron theory. In addition, careful comparisons in physically relevant segments of the spectra show that any significant increase in the magnitude of the solar EUV flux would lead to a contradiction of the observed plasma wave intensities. Further, the comparisons indicate that resolution of the thermal electron‐gas heat balance problem must be sought through better heat transfer rates (e.g., heating and cooling rates, etc.), rather than in the solar EUV. This approach utilizes more fully the potential of the plasma line experiment as a diagnostic tool for aeronomical studies, (e.g., photoelectrons, auroral secondaries, ionosphere‐modification experiments, et

ISSN:0094-8276    

DOI:10.1029/GL004i012p00565

年代:1977

数据来源: WILEY

摘要:

Analysis of electron observations in the drift and bounce loss cones of the slot region of the magnetosphere indicates that the predominant mode in which electrons in the 100 to 400 keV energy range arrive in the drift loss cone is via discrete events. These events are usually traceable back to the vicinity of a high‐power‐level VLF transmitter. No gradual buildup of electron flux, proceeding eastward from the South Atlantic Anomaly, is observed. Estimates of the loss rate due to the discrete events show that this process can result in a depletion of 50% per day of the electron flux in the slot region. The wave‐particle interaction probably occurs relatively low on the field line ( ≈ 30° to 50°) because of the relationship of particle energies and wave frequencies involved. Additional scattering of the particles near the equator, either by power‐line harmonic emissions or naturally occuring ELF hiss, may be required to transport the particles to the lower interac

ISSN:0094-8276    

DOI:10.1029/GL004i012p00569

年代:1977

数据来源: WILEY

摘要:

Coordinated optical and incoherent‐scatter radar observations were made during an aluminum vapor trail rocket experiment conducted at the Poker Flat Research Range. Altitude profiles of E‐region neutral winds, deduced from optical tracking of the aluminum vapor trail, were compared with profiles derived from the Chatanika radar data. The radar was operated in a multipulse mode that provided an altitude resolution of about 8 km over an altitude region of 80 to 200 km. The radar data show more than a 360‐degree rotation of the neutral‐wind direction over a 30‐km altitude interval. Good agreement was found between the radar‐derived and optically‐derived neutral‐wind profiles over most of the altitude region (105 to 129 km) of the aluminum trail release. This close agreement verifies the ability of the radar to monitor E‐region neutral winds, with a resolution approximately equal to the lo

ISSN:0094-8276    

DOI:10.1029/GL004i012p00573

年代:1977

数据来源: WILEY

摘要:

Several reported NO2measurements are based on the inversion of absorption curves as measured from balloon platforms during sunrise or sunset. This measurement method takes advantage of the long pathlengths which result when the suns' rays pass tangentially through the atmospheric layers below the balloon. The tangent ray measurement technique may be affected by variations of NO2concentrations at twilight since NO is being converted to NO2during sunset and NO2is being photolyzed to NO during sunrise. The effect of NO2changes during twilight on tangent ray NO2measurements has been quantitatively analyzed. The correction factors were found to be small.

ISSN:0094-8276    

DOI:10.1029/GL004i012p00577

年代:1977

数据来源: WILEY

摘要:

The ultraviolet absorption cross sections of hydrogen peroxide vapor have been determined over the wavelength range 210 to 350 nm at 296°K. At the longer wavelengths, the gas phase absorptivities are significantly larger than the corresponding values in condensed phase. The atmospheric H2O2photodissociation rate for overhead sun at the earth's surface is estimated to be about 1.3 × 10−5se

ISSN:0094-8276    

DOI:10.1029/GL004i012p00580

年代:1977

数据来源: WILEY

摘要:

Gulf Stream meanders and the associated vertical motions present water of varying densities at the shelf break along the southeast United States continental shelf. Under certain conditions of wind and Gulf Stream motion the vertically advected, deeper, Gulf Stream waters will intrude into these shelf waters. Depending on the ambient shelf water density the intruding water willoverride,interleaveor form abottom intrusion. Analysis of available hydrographic data indicates 20°C Gulf Stream water could form a bottom intrusion anywhere along the coast except in January when shelf water densities are relatively higher. 24°C Gulf Stream water could only form bottom intrusions in April through November. The remainder of the year 24°C waters would interleave or overri

ISSN:0094-8276    

DOI:10.1029/GL004i012p00583

年代:1977

数据来源: WILEY