摘要:

Data from the Shuttle Potential and Return Electron Experiment (SPREE) flown as part of the Tethered Satellite System (TSS 1) are used to determine the detailed characteristics of beam arc distributions of pickup ions due to molecules outgassed or ejected from the shuttle. These ion distributions are only detected near the plane perpendicular to the magnetic field direction in an angular range of ±45° about the minimum angle to ram. Their flux is largest when the angle between this plane and the shuttle ram direction is smallest. Generally, ion spectra peak in the range 19 to 25 eV at the minimum angle between the perpendicular plane and the ram direction. The peak energy decreases smoothly as this angle increases. Weak fluxes are measured above the peak, to energies as high as 150 eV. Within the SPREE energy range, two‐dimensional distribution functions of beam arc ions in the perpendicular plane have teardrop shapes, symmetric about the minimum angle to shuttle ram with deep minima in the centers. Variations in the peak energies of differential number fluxes agree with collisionless trajectory analysis, assuming that the ions are H2O+and allowing for different initial velocities before charge exchange. The lowest densities for beam arc ions occur during periods of purely residual outgassing from the shuttle. Ion densities increase by a factor of 5 during waste water dumps. The highest densities occur during operation of the flash evaporator system when the pickup ion densities in daylight can exceed 105ions cm−3, about 30% of the estimated ambient plasma density. We also present a nonlinear numerical analysis to study the stability of beam arc generated plasma waves and explain electrostatic spectra measured during previous shuttle fl

ISSN:0148-0227    

DOI:10.1029/96JA00190

年代:1996

数据来源: WILEY

摘要:

A unified theory has been developed to explain the formation of a quasi‐dc electric pulse (ω ≤ Ωi) induced by an ionizing neutral barium beam across an ionospheric plasma. We obtained a generalized form for the dc electric field in the plane perpendicular to the magnetic field within a simplified slab barium cloud moving perpendicular to the geomagnetic fields. A current system associated with the quasi‐dc electric field was also proposed to provide a way to transfer the momentum between the streaming barium cloud and the ambient plasma. The characteristic time derived by using this model for momentum coupling between the streaming barium cloud and the ambient plasma is found to be in agreement with the previous result. The quasi‐dc electric field predicted by this model is reasonably consistent with the “CRIT II” critical ionization velocity measurements. On the basis of the constrains of the conservation of energy and momentum, we found that Alfvén's critical ionization velocity (CIV) effect is a self‐limiting ionization process in a finite extent neutral cloud. It may be the reason why the CIV effect took place in CRIT II but lasted only for a very short period, and it may have resulted in low ionization yields in most of space

ISSN:0148-0227    

DOI:10.1029/96JA00393

年代:1996

数据来源: WILEY

摘要:

At the interface between the upper atmosphere and the radiation belt region there exists a secondary radiation belt consisting mainly of energetic ions that have become neutralized in the ring current and in the main radiation belt and then re‐ionized by collisions in the inner exosphere. The time history of the proton fluxes in the 0.64–35 MeV energy range was traced in the equatorial region beneath the main radiation belts during the 3‐year period from February 21, 1984, to March 26, 1987, using data obtained with the High‐Energy Particle experiment on board the Japanese OHZORA satellite. During most of this period a fairly small proton flux of ∼1.2 cm−2s−1sr−1was detected on geomagnetic field lines in the range 1.05

ISSN:0148-0227    

DOI:10.1029/96JA01518

年代:1996

数据来源: WILEY

摘要:

A radio‐interferometer array illuminated by 136‐MHz beacons of several geosynchronous satellites has been used to study small (≥ 1013m−2) transient disturbances in the total electron content along the lines of sight to the satellites. High‐frequency (ƒ>3 mHz) electron content oscillations are persistently observed, particularly during night and particularly during geomagnetically disturbed periods. The oscillations move across the array plane at speeds in the range 200–2000 m/s, with propagation azimuths that are strongly peaked in lobes toward the western half‐plane. Detailed analysis of this azimuth behavior, involving comparison between observations on various satellite positions, indicates compellingly that the phase oscillations originate in radio refraction due to geomagnetically aligned plasma density perturbations in the inner plasmasphere. The motion of the phase perturbations across the array plane is caused byE×Bdrift of the plasma medium in which the irregularities are embedded. We review the statistics of 2.5 years of around‐the‐clock data on the local time, magnetic disturbance, seasonal, and line‐of‐sight variations of these observed irregularities. We compare the irregularities' inferred electrodynamic drifts to what is known about midlatitude plasma drift from incoherent scatter. Finally, we show in detail how the observation of these irregularities provides a unique and complementary monitor of inner plasmasphere irregularity in

ISSN:0148-0227    

DOI:10.1029/96JA01253

年代:1996

数据来源: WILEY

摘要:

The Release Experiments to Derive Airglow Inducing Reactions (RED AIR) conducted on April 3, 1989, and December 6, 1991, offer a unique set of observations for studying the specific processes associated with the production of the O(3P–1D) emission at 6300 Å. In these experiments, sounding rockets were used to place equal quantities of CO2above and belowhmaxof the nocturnalFregion. CO2leads to 6300 Å emission by a three‐step process: (1) CO2+ O+→ O2++ CO, (2) O2++ e−→ O*+ O, (3) O*→ O +hv6300. Direct measurements of plasma parameters and indirect measurements of the neutral atmosphere densities were used in conjunction with the Fluid Element Simulation (FES) computer code to model the temporal and spatial evolution of the observed 6300 Å airglow enhancement and accompanying plasma depletion. Using the currently accepted set of reaction rates relevant toFregion chemistry, the quantum yield of O(1D) from reaction (2) was found to have a mild altitude dependence, decreasing by 16% from 275 to 350 km. Since the initial vibrational distribution of the nascent O2+was the same for the two releases, this result implies an altitude dependence in the quenching of O2+vibrational states. Building on previous evidence that O2+is vibrationally excited in the nighttime thermosphere, we further conclude that this vibrational distribution is altitude dependent. In terms of 6300 Å airglow production, the effect is manifested in an altitude dependence of f(1D). Additionally, quenching by O(3P) was found to contribute very little to the depopulation of the nascent O(1D), with QO= 0 giving the best fit to the RED A

ISSN:0148-0227    

DOI:10.1029/96JA01485

年代:1996

数据来源: WILEY

摘要:

A study of sporadic sodium (Ns) layers observed at São José dos Campos (23°S, 46°W) shows that during their occurrence the form of the background sodium layer is different from that which it normally takes when Ns layers are absent. During Ns events, peak sodium in the background layer typically occurs below 90 km, whereas the peak of the average layer observed at our location is around 93 km. The observed change could be caused either by a loss of sodium on the topside of the layer or by a displacement of sodium to lower heights. The consistency of these two mechanisms with our observations, and with the known properties of Ns layers, is examined, but we are unable to determine which of the mechanisms is responsible for the observed phenome

ISSN:0148-0227    

DOI:10.1029/96JA00824

年代:1996

数据来源: WILEY

摘要:

A quantitative interpretation is given of the observed quiescent nighttime radiance of nitric oxide in the fundamental vibration‐rotation band near 5.3 μm. The radiance measured in the space shuttle experiment Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS‐1A) is known to have two components, one characterized by a thermal population of rotational levels and the other by a highly excited rotational population. The analysis presented here confirms that the thermal population is due to impact excitation of NO by atomic oxygen and attributes the highly excited distribution to the reaction of N(4S) atoms with O2. The measured nighttime emission profile is compared with predictions for several model atmospheres. Both sources of excited NO depend upon the latitude, longitude, local time, and geomagnetic indices. The fraction of vibrationally excited NO produced by the reaction of N(4S) with O2increases rapidly with altitude from 130 to 200 km and its contribution to cooling, though much less than that from inelastic excitation of NO(v=0) is, at higher altitudes, comparable to cooling produced by the atomic oxygen fine‐structure line at

ISSN:0148-0227    

DOI:10.1029/96JA01004

年代:1996

数据来源: WILEY

摘要:

Daytime line‐of‐sight rates of production of vibrationally excited CO, CO2(v3) and NO+and their rotational temperatures are derived for the lower terrestrial thermosphere from the CIRRIS 1A database and compared with those calculated by models assuming rotational local thermodynamic equilibrium (LTE). It is found that vibrationally excited CO is in rotational LTE, although the calculated rate of its production is about 3 times too small. The observed radiance in the 4.3 μm band of CO2is found to be in good agreement with the predictions of the rotational LTE model SHARC (strategic high altitude radiance code). The line‐of‐sight rotational temperature of this emission is, however, less than that calculated by SHARC, in agreement with earlier non‐LTE model calculations. The reaction of N2+with O is shown to be the dominant mechanism for producing NO+above 140 km; the experimental data are consistent with the production of N(2D) and rotationally and vibrationally non‐LTE NO+as the main reac

ISSN:0148-0227    

DOI:10.1029/96JA01495

年代:1996

数据来源: WILEY

摘要:

The cross‐section for production of the N2+B2Σu+state by electron impact on N2is one of the most important cross‐sections for aeronomy because of the prominence of the N2+first negative (0,0) band (B2Σu+←X2Σg+, λ3914 Å) in the day glow and aurora. Recently developed electron‐electron coincidence experiments have made possible the measurement of the branching ratios for ionization‐excitation of N2by electron impact at the 100‐eV maximum of the cross‐section. The N2total ionization cross‐section, measured in other experiments, can then be used to calculate the cross‐section for production of the N2+B2Σu+state at 100‐eV. Photoionization partial cross‐sections and branching ratios from high‐energy electron impact experiments are used to calculate the N2+B2Σu+cross‐section at 2000‐eV. The 100‐ and 2000‐eV results are compared with cross‐sections from electron impact optical emission experiments at the same incident energies. The cross‐sections from electron impact and photoionization experiments are 30% smaller than the optical emission cross‐section of Borst and Zipf at both 100‐eV and 2000‐eV incident energies but within 20% of the results of the most recent optical measurement at 100‐eV. A value of 14.8 × 10−18cm2for the N2+B2Σu+first negative (0,0) band cross‐section maximum at 100‐eV is within the e

ISSN:0148-0227    

DOI:10.1029/96JA01493

年代:1996

数据来源: WILEY

摘要:

The full electric and magnetic field data set from the subpayload of the CRIT II sounding rocket experiment is presented for the first time. CRIT II was an ionospheric injection experiment aimed at studying the critical ionization velocity (CIV) effect. It consisted of two payloads located on nearly the same magnetic field line. By using the data from both payloads, we are able to reach a good understanding of the momentum transfer between the injected ions and the ambient ionosphere. The data also make it possible to resolve the conflict between the two competing models for the energy transfer from the newly created ions to hot electrons in the CIV process. The results give a natural coupling between the energy and momentum transfer processes in CIV experiments.

ISSN:0148-0227    

DOI:10.1029/96JA01284

年代:1996

数据来源: WILEY