摘要:

An in situ profile of 5577‐Å night airglow emission in the 100‐km region was obtained over the magnetic equator at Thumba, India. The height of maximum emission was at 102 ± 2 km, and the half thickness of the layer was 11 ± 2 km. Total emission from the rocket and the ground photometer was around 66 R. From the emission the profile of density of atomic oxygen in the 100‐km region was determined and had a maximum value of 3.19 × 1011cm−3at 102 km. Intensity contribution to 5577 Å from theFregion is much smaller than that expected. These results are compared with rocket results obtained at middle and high latitudes and with O

ISSN:0148-0227    

DOI:10.1029/JA081i022p03740

年代:1976

数据来源: WILEY

摘要:

A model developed for the aeronomy of odd nitrogen in the thermosphere is used to analyze rocket measurements of N(4S) and NO densities. Data from Atmosphere Explorer were used to develop a consistent reaction kinetics model for odd nitrogen chemistry. We conclude that most NO+dissociative recombination events must produce N(²D), that N(²D) is quenched by O at a rate of 1 × 10−12cm³ s−1, and that the atmospheric O2quenching rate of N(²D) is consistent with the laboratory rate. The major quenching agent of N(²D) between 140 and 220 km is atomic oxygen, and this reaction is the major source of N(4S). We predict peak N(4S) densities of ≈(2–6) × 107cm−3at 140–150 km, with the variability being indicative of the model sensitivity to a factor of 2 change in the O/O2ratio i

ISSN:0148-0227    

DOI:10.1029/JA081i022p03745

年代:1976

数据来源: WILEY

摘要:

The Triad satellite is maintained in a purely gravitational orbit by the disturbance compensation system (Discos) on the central body of the satellite. Discos consists of a small metal ball (the ‘proof mass’) surrounded by position sensors and an outer shell which holds fuel tanks and cold gas jets. The outer shell shields the proof mass from nongravitational forces. Whenever the outer shell is displaced in relation to the proof mass by 1 mm, the gas jets fire to recenter the outer shell. For 6 days during the period September 14–19, 1972, the position of the proof mass relative to the shell was telemetered to earth and recorded whenever the satellite was visible from the receiving station in Maryland. Local atmospheric densities near 800 km have been measured for the first time by using the ball position data. The observed accelerations have been corrected for the effects of solar radiation pressure. The measured densities reveal a greater dependence on latitude than that indicated by balloon satellites, whose measurements involve more averaging over latitude and longitude. The Triad results also exhibit a dependence on longitude in the limited number of measurements available. However, only a small dependence on the index of geomagnetic activityKpwas observed in the localized region in which the measurements were

ISSN:0148-0227    

DOI:10.1029/JA081i022p03753

年代:1976

数据来源: WILEY

摘要:

We have analyzed daytime composition measurements in the thermosphere from Atmosphere Explorer‐C by use of a theory of the ion chemistry. We compare predicted and measured N2+densities in order to infer global variations of the solar ionizing flux. Our results indicate that the solar flux of Hinteregger measured on Atmosphere Explorer‐C provides an adequate basis for the calculation of solar ultraviolet photo‐ionization rates. The role of metastable species is examined, and theoretical O+(²D) densities are pre

ISSN:0148-0227    

DOI:10.1029/JA081i022p03762

年代:1976

数据来源: WILEY

摘要:

An atomic oxygen beam and mass spectrometer were used to measure the oxygen atom reflection γ16, recombination γ32, general surface reaction γM, and occlusion γ0probabilities on six different engineering surfaces as a function of atomic oxygen exposure. The materials studied include gold, Nichrome V, aluminum, titanium, silver, and platinum. The reflection probability was seen to range from an initial total loss (at time of exposure equal to zero) on aluminum, titanium, and platinum to an observed maximum of 0.65 on titanium after 8.5 h of exposure. Recombination was seen on all surfaces except aluminum and platinum, the maximum recombination probability γ32being 0.27 on gold after 19 h of exposure. The molecules H2O, CO, and CO2were produced in a first‐order reaction of atomic oxygen with surface hydrogen and carbon with varying probabi

ISSN:0148-0227    

DOI:10.1029/JA081i022p03767

年代:1976

数据来源: WILEY

摘要:

An all‐sky imaging system capable of fast monochromatic imaging at very low light levels is described; the system allows real time display of regions of proton precipitation and of soft and hard electron precipitation in the auroral zone. Sample data illustrate various auroral types previously classified from photometric data and/or from particle data from satellites. Time‐lapse film throughout an entire night shows the position and intensity of plasma sheet precipitation, superposition of a harder electron aurora, the relative positions of proton aurora and diffuse aurora, and the changing character of the aurora as a function of local time and substorm activity. These patterns are discussed in terms of the substorm injection boundary model (McIlwain, 19

ISSN:0148-0227    

DOI:10.1029/JA081i022p03771

年代:1976

数据来源: WILEY

摘要:

The time‐dependent latitudinal distribution of the vertical column emission rates of O I 1356 Å and [O I] 6300 Å in the tropical region is theoretically investigated by numerically solving the coupled nonlinear system of time‐dependent continuity equations for the ions O+, O2+, NO+, N2+, and N+in which production and loss of ionization, ambipolar diffusion,E × Bdrifts, and neutral winds are taken into account. Radiative recombination, ion‐ion neutralization, and dissociative recombination are considered as main mechanisms in producing the atomic oxygen tropical nightglow. The specific effects of neutral winds and plasma drifts on the emissions and the time response of the ionosphere and airglow to changes in the wind velocity are investigated. A quantitative relationship is obtained between the neutral wind velocities and the resultant asymmetry about the magnetic equator in the airglow emissions. The method is useful for studying the neutral wind system in the tropical io

ISSN:0148-0227    

DOI:10.1029/JA081i022p03781

年代:1976

数据来源: WILEY

摘要:

The Ogo 4 tropical nightglow data on the O I 1356‐Å and [O I] 6300‐Å emissions during several months in the fall of 1967 are analyzed in conjuction with theoretical models. From the latitudinal asymmetry present in the tropical emissions the neutral wind velocities in the magnetic meridian at the time of the observations are found to reach 150 m/s near 2000 LT in the Pacific sector and 110 m/s in the Indian sector. The longitudinal dependence of the emissions indicates a strong zonal component (referred to geographic coordinates) and allows the resolution of the inferred wind velocities into geographic zonal and meridional wind components. The geographic zonal component reaches a maximum velocity of 260 m/s near 22

ISSN:0148-0227    

DOI:10.1029/JA081i022p03786

年代:1976

数据来源: WILEY

摘要:

In recent years the diffuse radar aurora has been shown to be closely associated with the auroral electrojets. Greenwald et al. (1973, 1975) showed that the range‐integrated amplitude of the diffuse radar aurora is linearly proportional to the horizontal component of the magnetic perturbations found beneath the echoing region. Tsunoda et al. (1974) showed that the evening diffuse radar aurora was characterized by a distinct poleward boundary that was usually aligned along a magneticLshell. They hypothesized that such a boundary could be produced by a latitudinal gradient in either the ionospheric electric field or the conductivity. In either case, field‐aligned currents might be expected to flow in such a region. An initial study was therefore undertaken to examine the spatial relationship of the radar aurora to the field‐aligned currents observed by virtue of the transverse magnetic disturbances detected by the Triad satellite. By utilizing a 398‐MHz phased array radar located at Homer, Alaska, event‐by‐event comparisons were made between the evening radar aurora and the field‐aligned currents in the 1700–2100 MLT sector. The results of this study include the following findings: (1) the downward field‐aligned currents in the evening sector are closely associated with the eastward electrojet; (2) the upward field‐aligned currents in the same time sector are associated with the visual aurora; (3) there is a poleward‐directed electric field across the oppositely directed field‐aligned currents, implying at least partial closure through the ionosphere via a Pedersen current; and (4) the downward field‐aligned currents are associated with the diffuse particle precipitation responsible for the production of the diffuse radar aurora (and hence the eastward electrojet). However, the downward field‐aligned currents must be carried by precipitating protons and/or upward

ISSN:0148-0227    

DOI:10.1029/JA081i022p03791

年代:1976

数据来源: WILEY

摘要:

Nearly simultaneous measurements of energetic particle precipitation and vector ion velocity have been made for the first time on Atmosphere Explorer C. These data have revealed the existence of both shear and rotational reversals in the ion convection velocity within the region of dayside cleft particle precipitation. The ion velocity data have shown that substantial regions of the dayside polar cap boundary are nearly electric equipotentials at which cleft particle precipitation is also observed but which cannot be identified with a merging region producing open field lines. Asymmetries in the polar cap flow, first implied by Heppner, may be determined by the extent and location of the equipotential boundaries.

ISSN:0148-0227    

DOI:10.1029/JA081i022p03803

年代:1976

数据来源: WILEY