摘要:

We derive molecular oxygen densities in the atmosphere from 140 to 240 km using measurements of total oxygen atom concentrations made on board the Atmosphere Explorer C satellite by the open source neutral mass spectrometer. A Bates‐Walker profile of atomic oxygen densities was obtained by using a fit to the densities measured at high altitudes. At lower altitudes the difference between the measured total oxygen atom concentration and the value from the diffusive profile is approximately twice the density of molecular oxygen. The predicted O2densities are generally in harmony with values of the O2density derived from ion composition measurement

ISSN:0148-0227    

DOI:10.1029/JA082i025p03503

年代:1977

数据来源: WILEY

摘要:

The 5200‐Å N I (4S‐²D) emission monitored by the visible airglow experiments on Atmosphere Explorer C and D combined with simultaneous measurements of atmospheric composition yields the following results. The metastable ²Dterm of atomic nitrogen must be produced in theFregion at near the maximum rate allowed by currently accepted chemistry. The rate coefficient deduced for the loss of N(²D) by reaction with O2is in good agreement with the laboratory result. The quenching rate of N(²D) by electrons lies in the range 3.6–6.5 × 10−10(Te/300)1/2cm³ s−1if the laboratory rate for N2+recombination is applicable to the thermosphere. The value may be somewhat larger than this if nonthermal effects are important. The quenching rate by atomic oxygen is near 4 × 10−13cm³ s−1, much smaller tha

ISSN:0148-0227    

DOI:10.1029/JA082i025p03509

年代:1977

数据来源: WILEY

摘要:

A Paiute‐Tomahawk sounding rocket containing a 1.5‐ to 5.3‐µm cryogenically cooled spectrometer was flown into a very bright (IBC III+) auroral breakup from Poker Flat, Alaska. The main emission features at 2.8, 4.3, and 5.3 µm were all found to be enhanced owing to the large energy input to the atmosphere associated with the aurora. The most prominent enhancement occurred in the 4.3‐µm feature which is identified as emission from the CO2(ν3) band. The maximum of the peak spectral radiance of this feature was observed at a rocket altitude of 92 km and had a value of about 130 MR/µm, which is nearly 2 orders of magnitude greater than that for an undisturbed atmosphere. By comparing upleg and downleg data, it was ascertained that the time constant for this excitation/radiation process is longer than 5 min. It is concluded that the excitation process involves vibrational excitation of nitrogen followed by collisional radiance ν‐ν transfer to CO2, which then radiates at 4.3 µm. The 5.3‐ and 2.8‐µm features are attributed to radiation from fundamental and f

ISSN:0148-0227    

DOI:10.1029/JA082i025p03518

年代:1977

数据来源: WILEY

摘要:

This paper and two companion papers describe a case study of multiple auroral phenomena in the midnight sector. The duration of the study was 12 hours on December 9, 1971. For 9 of the 12 hours the Air Force Geophysics Laboratory airborne ionospheric observatory flew near local midnight across North America so as to intersect many successive passes of Defense Meteorological Satellite Program (DMSP) and Isis 2 satellites which were also in the midnight sector. The large‐scale DMSP auroral photographs have been combined with the temporally continuous aircraft‐ and ground‐based measurements to provide extensive observations of long duration compared to the lifetimes of the two substorms observed. All the types of observations (satellite pictures, aircraft ionospheric soundings, all‐sky camera photographs, photometer recordings, as well as particle and other satellite‐ and ground‐based measurements) have been combined to describe the temporal histories of a large number of phenomena and of their interrelations. The phenomena are the discrete auroras in the oval and polar cap, the continuous (Elayer) aurora, auroral absorption (nearly absent on this day), and (in the companion papers) theFlayer irregularity zone and 6300‐Å emission, particle precipitation, the electrojet, and interplanetary magnetic field and magnetospheric phenomena. DMSP photographs are found to detect both discrete and continuous auroras; uses and limitations of the data are described. In terms of the overall perspective of this study the phenomena are found to fall into six periods of 1–3 hours each. Two of these periods contain substorms of differing characteristics; the remaining four periods are relatively quiet but also differ from one another. Throughout each of the periods the polar cap, oval, and continuous auroras as a whole retain the same configuration as described, in terms of whether each of the auroras is present or absent and whether adjacent auroras are joined or separated. These configurations are described as phenomenological states of the aurora, and the periods are regarded as the lifetimes of these states. The large‐scale, long‐term features of the auroral states suggest that they reflect individual states

ISSN:0148-0227    

DOI:10.1029/JA082i025p03529

年代:1977

数据来源: WILEY

摘要:

A constant local midnight flight by the Air Force Geophysics Laboratory airborne ionospheric observatory over the North American continent from Goose Bay, Labrador, to Fairbanks, Alaska, stayed under the midnight sector of the auroral oval for 9 hours. Airborne all‐sky cameras, a photometer, and a vertical incidence ionospheric sounder permitted the continuous monitoring, over two periods of auroral disturbance, of the latitudinal extent of discrete auroral forms, auroral emissions, and ionospheric features. These airborne observations were supplemented by auroral photographs from a Defense Meteorological Satellite Program satellite and by particle flux measurements from the Isis 2 satellite. From this data base a band of enhanced red (6300 Å) emission (red band) is identified. This red band extends over 2°–10° in latitude, is oval aligned, and contains within it auroras, both discrete and continuous, as observed from both satellite and aircraft. Thus it differs from the dayside red band, seen in previous measurements, which contains the discrete midday auroras but not the continuous aurora. In the night sector the red band was observed to contract in width near the substorm onset, to expand in width during the substorm expansive phase, to contract during the substorm recovery, and to continue contracting even after recovery was complete. AnFlayer irregularity zone (FLIZ) is associated with the red band, and in the night sector the red band and the FLIZ are most probably produced by low‐energy electrons which have originated in the plasma sheet. Therefore meridional variations of the red band may reflect changes in the configuration of the plas

ISSN:0148-0227    

DOI:10.1029/JA082i025p03547

年代:1977

数据来源: WILEY

摘要:

Airborne observations of auroral activity at midnight were conducted for a period of 9 hours by employing an ionospheric sounder and all‐sky cameras. During the observation period, two substorms occurred. The first substorm was associated with a compression of the magnetosphere (as measured byDst) and with oscillations of the earth's bow shock. At this time, auroral activity was characterized by a series of poleward and equatorward motions and by the absence of a breakup phase. Magnetic disturbances were confined to a small region in the midnight sector. The second auroral substorm displayed many of the features associated with a large‐scale polar magnetic substorm. For selected times the locations of the eastward and westward electrojets were inferred from a number of high‐latitude magnetic records. All‐sky photographs and ionosonde data indicate that the poleward edge of the westward electrojet was bounded by a westward moving auroral surge accompanied by a strong sporadicEionization. The equatorward electrojet boundary was less well defined by visual auroral forms. Soft particle spectrometer measurements from the Isis 2 satellite were made in conjunction with the aircraft measurements and indicate that large fluxes of field‐aligned electrons gave rise to the bright auroral surge, more isotropic fluxes of less energetic electrons contributing to the auro

ISSN:0148-0227    

DOI:10.1029/JA082i025p03557

年代:1977

数据来源: WILEY

摘要:

The infrasonic bow wave from a traveling auroral arc of finite length is calculated, and the results of the infinite length approximation are essentially recovered. The finite length results in a distinct, separate, second trailing pulse that is weaker than, and of the opposite sign from, the main pressure wave. It is shown that the sign‐reversed signatures sometimes observed may be due to arc currents that have strongly defined trailing ends and relatively diffuse frontal structure

ISSN:0148-0227    

DOI:10.1029/JA082i025p03573

年代:1977

数据来源: WILEY

摘要:

Auroral electrojet parameters measured by the Chatanika incoherent scatter radar have been compared with VHF backscatter observed in a comparable spatial area by the 50‐MHz auroral radar located at Anchorage. We find that theDregion absorption, occurring in concert with the morning (westward) electrojet, can significantly decrease the observed scatter amplitude. If the amplitude is corrected for absorption effects, we find that the scatter varies approximately linearly with either eastward or westward current density with the same slope for both periods. A surprising result is that at times, relatively large north‐south current densities do not give rise to detectable backscatter. The Chatanika electric field measurements indicate that during the morning period, substantial backscatter amplitudes occur for southward fields of only 10 mV/m. In contrast, during the evening period the backscatter amplitude is zero or very low until the northward field is at least 25 mV/m. This indicates that most of the auroral backscatter that we observe in the evening period occurs under conditions when the two‐stream plasma instability may be operative. However, in the morning period the backscattering irregularities are strongly generated under conditions associated with either gradient drift or two‐stream instab

ISSN:0148-0227    

DOI:10.1029/JA082i025p03577

年代:1977

数据来源: WILEY

摘要:

We have investigated the possible reactions of chlorine atoms, chlorine monoxide, and hydrogen chloride withDregion negative ions. The mesospheric concentrations of the neutral chlorine gases have been predicted with a diurnally varying one‐dimensional model of the upper atmosphere. Despite the low abundances of chlorine compounds in air their high reactivity leads to the formation of substantial quantities of chlorine negative ions at high altitudes. The concentration of chlorine ions is limited in daylight by rapid reactions with oxygen and hydrogen atoms and at night by the competitive production of other stable ions. The presence of chlorine negative ions in the upper atmosphere is consistent with in situ mass spectrometer observations of charged species. The abundance of chlorinated ions in theDregion may be correlated with mesospheric nitric oxide and water vapor concentration

ISSN:0148-0227    

DOI:10.1029/JA082i025p03585

年代:1977

数据来源: WILEY

摘要:

Angle and energy distributions are reported for gamma rays near the top of the atmosphere for energies of 2–25 MeV and for zenith angles of 0°–50° (downward moving) and 130°–180° (upward moving). These distributions were obtained with the University of California, Riverside (UCR) double Compton scatter gamma ray telescope flown on a balloon to 3.0 g/cm² residual atmosphere from Palestine, Texas, on May 13, 1975 (geomagnetic cutoff: 4.5 GV). Growth curves from 3.4 to 100 g/cm² of residual atmosphere are used to determine the downward‐moving atmospheric fluxes. Results are given for six energy intervals from 2–25 MeV and for five angle intervals from 0°–50°. The downward fluxes are in reasonable agreement with those of Schönfelder and Lichti (1975, 1976) at the lower energies and with those of Kinzer et al. (1974) at the higher energies, where our respective data overlap. The shape of the angular distribution is consistent with that of Lichti et al. (1975) and Thompson (1974) at higher energies. The absolute fluxes of upward moving gamma rays from 130°–170° at 4.2 g/cm² are in agreement with the semiempirical values of Ling (1975) but increase away from the vertical contrary to his predictions. Integrating over zenith angles of 10°–40° and 140°–170°, our ratios of upward moving to downward moving gamma ray fluxes are 12 ± 1 and 9 ± 2 for 3–10 and 10–25 MeV, respectively, in agreement with the theoretical

ISSN:0148-0227    

DOI:10.1029/JA082i025p03593

年代:1977

数据来源: WILEY