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1.
On 14 July 1974 the Atmosphere Explorer-C satellite flew through an aurora at F-region altitudes just after local midnight. The effects of the particle influx are clearly evident in the ion densities, the 6300 Å airglow, and the electron and ion temperatures. This event provided an opportunity to study the agreement between the observed ion densities and those calculated from photochemical theory using in situ measurements of such atmospheric parameters as the neutral densities and the differential electron energy spectra obtained along the satellite track. Good agreement is obtained for the ions O2+, NO+ and N2+ using photochemical theory and measured rate constants and electron impact cross sections. Atomic nitrogen densities are calculated from the observed [NO+]/[O2+] ratio. In the region of most intense electron fluxes (20 erg cm−2 sec−1) at 280 km, the N density is found to be between 2 and 7 × 107 cm−3. The resulting N densities are found to account for approx. 60% of the production of N+ through electron impact on N and the resonant charge exchange of O+(2P) with N(4S). This reaction also provides a significant source of O(1S) in the aurora at F-region altitudes. In the region of intense fast electron influx, the reaction with atomic nitrogen is found to be the main loss of O+(2P).  相似文献   

2.
About a year's observations of the N2+ band (3914 Å) at Kitt Peak (latitude 32°) are reported. Morning intensities are the same throughout the year, but there is a strong winter maximum in the evening. It is suggested that the additional ionization is produced by photoelectrons from the magnetic conjugate point. Heights are estimated by the zenith-horizon method, which gives 235 km for the constant component and 350 km during the evening enhancement. The intensity variation through twilight is therefore entirely due to changes of the N2+ concentration; each ion scatters light at a constant rate. The rotational distribution resembles that for a temperature of 1600°K, much higher than the temperature of the atmosphere. It is suggested that part of the ions may be produced by charge transfer from metastable O+(2D). N2+ concentrations resulting from photoionization are calculated; they give a fair account of the observed horizon intensities, but not the zenith. Non-local electrons from higher in the atmosphere are suggested as a possible extra source; alternatively, the zenith measurements may be perturbed by scattered horizon light. The band intensity in the nightglow cannot be measured; the upper limit is 1 R.  相似文献   

3.
A study is made of the intensity distribution among the bands of the Meinel and first negative system of N2+ due to resonance scattering of sunlight. Absolute transition probabilities are used to calculate the relative populations among the ion states under resonance scattering conditions; the mean lifetime for deactivation is the parameter which determines the amount of resonance scattering. Photon scattering rates are calculated for most of the ion bands and it is suggested that an appropriate value for the 3914 Å band would be 0·050 photons/ sec per ion. Observations of the Δυ = −1 sequence of the first negative system in the twilight spectrum are reported. Extended vibrational development is detected which indicates that only about 80 per cent of the emission is resonance scattered. Sunlit auroral spectra of N2+, however, which have been generally considered to be due predominantly to resonance scattering, indicates only about 40 per cent of the emission is due to resonance scattering. Measurable effects resulting from a charge-transfer ion source (O+(2D)) are predicted.  相似文献   

4.
The relative variations between 82 km and 205 km in the emission rates of nightglow radiation features at 5300 Å, 5577 Å, 5893 Å and 6300 Å have been photometrically measured from a Skylark rocket flown from Woomera, S. Australia at 2053 hours CST (1123 hours GMT) on 18 October, 1965.

Emission profiles obtained for the first three features show that these layers have their centre of intensity at, respectively, 94.0 ± 1 km, 94.5 ± 0.5, and 98.0 ± 2 km. The results further indicate that not more than 10% of the 6300 Å radiation was emitted below apogee at 205 km.

By virtue of a rather complicated vehicle motion—almost a slow tumble in the vertical plane—evidence is adduced which suggests that differences between these profiles and those of previous flights could be explained by insufficient or incorrect account being then taken of the contamination from extra-atmospheric sources such as starlight and galactic light.

Regarding the continuum, it is found that, depending on the particular region of sky background, up to 80% of the 5300 Å emission observed from the Earth may be extra-atmospheric in origin. Furthermore, of the extra-atmospheric component, again depending on the viewing direction in the sky, the emission intensity at 5577 Å may be from 10% to 50% greater than that at 5300 Å.

While it is to be expected that, before penetrating the layer, the zenithal emission intensity as registered by the photometers should remain constant, this constancy was not generally observed and the 5300 Å and 5577 Å photometers, both of which were independently duplicated, indicate an initial increasing emission intensity. Marked differences in the variation of each pair of photometers suggest that interpretation by means of aerosol absorption of the radiation in the 80 to 100-km region is incorrect and that the effect is probably instrumental in origin and of a temporary nature.  相似文献   


5.
Absolute values of the emission cross sections for five vibrational bands in the Meinel system of N2+,A2πu to X2Σg+, excited by electron impact are presented. From these, a value was obtained for the total excitation cross section of the A2πu state at 100 eV of 26·5 × 10−18 cm2. The results are compared with those of other workers and with theory. Collisional transfer of the excitation energy from the levels of the A2πu state was also observed with a transfer cross section of approximately 10−14 cm2.  相似文献   

6.
We have constructed a one-dimensional model of the nightside ionosphere of Venus in which it is assumed that the ionization is maintained by day-to-night transport of atomic ions. Downward fluxes of O+, C+ and N+ in the ratios measured on the dayside at high altitudes are imposed at the upper boundary of the model (about 235 km). We discuss the resulting sources and sinks of the molecular ions NO+,CO+,N2+,CO2+ and O2+. As the O+ flux is increased, the peak density of O+ increases proportionally and the altitude of the peak decreases. The O2+ peak density is approximately proportional to the square root of the O+ flux and the peak rises as the O+ flux increases. NO+ densities near the peak are relatively unaffected by changes in the O+ flux. If the ionosphere is maintained mostly by transport, the ratio of the peak densities of O+ and O2+ indicates the downward flux ofO+, independent of the absolute magnitudes of the densities. The densities of mass-28 ions are, however, still considered to be the most sensitive indicator of the importance of electron precipitation. We examine here the inbound and outbound portions of six early nightside orbits with low periapsis and use data from the Pioneer Venus orbiter ion mass spectrometer, the retarding potential analyzer and the electron temperature probe to determine the relative importance of ion transport and electron precipitation. For most of the orbits, precipitation is inferred to be of low to moderate importance. Only for orbit 65, which was the first nightside orbit published by Taylor et al. [J. geophys. Res. 85, 7765 (1980)] and for the inbound portion of orbit 73 does the ionization structure appear to be greatly affected by electron precipitation.  相似文献   

7.
An auroral arc system excited by soft electrons was studied with a combination of in situ rocket measurements and optical tomographic techniques, using data from a photometer on a horizontal, spinning rocket and a line of three meridian scanning photometers. The ground-based scanner data at 4709, 5577, 8446 and 6300 Å were successfully inverted to provide a set of volume emission rate distributions in the plane of the rocket trajectory, with a basic time resolution of 24 s. Volume emission rate profiles, derived from these distributions peaked at about 150 km for 5577 and 4709 Å, while the 8446 Å emission peaked at about 170 km with a more extended height distribution. The rocket photometer gave comparable volume emission rate distributions for the 3914 Å emission as reported in a separate paper by McDade et al. (1991, Planet. Space Sci. 39, 895). Instruments on the rocket measured the primary electron flux during the flight and, in particular, the flux precipitating into the auroral arc overflown at apogee (McEwen et al., 1991; in preparation). The local electron density and temperature were measured by probes on the rocket (Margot and McNamara (1991; Can. J. Phys. 69, 950). The electron density measurements on the downleg were modelled using ion production rate data derived from the optical results. Model calculations of the emission height profile based on the measured electron flux agree with the observed profiles. The height distribution of the N2+ emission in the equatorward band, through which the rocket passed during the descent, was measured by both the rocket and the ground-based tomographic techniques and the results are in good agreement. Comparison of these profiles with model profiles indicates that the exciting primary spectrum may be represented by an accelerated Maxwellian or a Gaussian distribution centered at about 3 keV. This distribution is close to what would be obtained if the electron flux exciting the poleward form were accelerated by a 1–2 kV upward potential drop. The relative height profiles for the volume emission rate of the 5577 Å OI emission and the 4709 Å N2+ emission were almost indistinguishable from each other for both the forms measured, with ratios in the range 38–50; this is equivalent to I(5577)/I(4278) ratios of 8–10. The auroral intensities and intensity ratios measured in the magnetic zenith from the ground during the period before and during the rocket flight are consistent with the primary electron fluxes and height distributions measured from the rocket. Values of I(5577)/I(4278) in the range 8–10 were also measured directly by the zenith ground photometers over which the arc system passed. These values are slightly higher than those reported by Gattinger and Vallance-Jones (1972) and this may possibly indicate an enhancement of the atomic oxygen concentration at the time of the flight. Such an enhancement would be consistent with our result, that the observed values of I(5577) and I(8446) are also significantly higher than those modelled on the basis of the electron flux spectrum measured at apogee.  相似文献   

8.
Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5−3+6) × 10−19 W m−2)(c/s)−1 at 0·700 Mc and (1·8+1.0−0.5 × 10−19 W m−2 (c/s)−1 at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6−3+5) × 10−20 W m−2 (c/s)−1 sr−1b(2·200 Mc) = (1.4+1.0−0.5 × 10−20 W m−2 (c/s)−1 sr−1 The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed.  相似文献   

9.
We discuss the altitude and intensity of the nocturnal green line emission resulting from O2+ recombination. The Doppler profile of this emission is markedly non-thermal, the width being characteristic of the energy at which the O(1S) atoms are produced. A simple theory is formulated which predicts the profile of this line. Experimental evidence on airglow line profiles is reviewed and it is found that the effect predicted here has not yet been observed. However a deliberate search for this effect should yield immediate results.  相似文献   

10.
A detailed analysis of the D-region ion composition measurements performed by Zbinden et al. (1975), during a winter day of high ionospheric absorption, has been carried out. The study examines the interactive mesosphere-D-region processes which occur in such anomalous conditions and their implication for water cluster ion chemistry. Two clustering regimes for NO+ have been observed in the data. Association with N2 is identified as the dominant process below 76 km. Between 76 and 78 km altitude the effective loss rate of NO+ drops by two orders of magnitude. Above 77 km, the three-body reaction NO+ + CO2+M→NO+CO2+M seems to be the main NO+ loss. A mesospheric temperature profile could be derived from the ion composition data. This indicates the presence of a strong inversion above 76 km altitude. The wavelike structure obtained, is shown to be consistent with in situ winter temperature measurements. The sharp suppression of the N2 association reaction could, thus, be explained by an increase in the collisional break-up of the NO+N2 ion because of the enhanced temperature. In conclusion, our study indicates that, besides the increase in the production of NO+ and O2+, due to an enhancement in the minor ionizable constituents, an additional thermal mesosphere-D-region interaction seems necessary to explain this winter anomalous ion composition data.  相似文献   

11.
We report intermediate resolution H spectroscopy of the black hole candidate Nova Muscae 1991 during quiescence. We classify the companion star as a K3-K4V which contributes 85±6 percent to the total flux from the binary. The photospheric absorption lines are broadened by 106±13 kms−1 with respect to template field stars, leading to a system mass ratio of q =M1/M2 = 7.8−2.0+3.4. Doppler imaging of the H line shows strong emission coming from the secondary star (EW=3.1±0.6Å) which we associate with chromospheric activity. However, the hot-spot is not detected and this may indicate a lower mass transfer rate than in other X-ray transients of comparable orbital periods. The surface brightness distribution of the accretion disk in H follows a relation I∝R−1.1, less steep than typically observed in cataclysmic variables. Updated system parameters are also presented.  相似文献   

12.
The absorption of solar ionizing radiation during twilight is investigated. Ion production rates are obtained as a function of altitude and twilight intensities and altitude profiles of emissions arising from the fluorescence of solar ionizing radiation are calculated for various solar depression angles. For an atmosphere with an exospheric temperature of 750°K, the predicted overhead intensity from fluorescence of the O+(2P — 2D) lines at 7319–7330 diminishes from 175 R at dusk to 10 R at a solar depression angle of 10°. The predicted overhead intensities from fluorescence of the N2+ Meinel and first negative systems are respectively about 175 R and 20 R at dusk diminishing to respectively 1.5 R and 0.1 R at a solar depression angle of 10°.

It is suggested that a charge transfer reaction of O+2D in N2 is a significant source of N2+ ions. This reaction offers a possible explanation for the high apparent rotational temperatures in the first negative system observed by Broadfoot and Hunten. Other excitation and ionization mechanisms are briefly discussed.  相似文献   


13.
Recent rocket observations of the N2 V-K (Vegard-Kaplan) system in the aurora have been reinterpreted using an atmospheric model based on mass spectrometer measurements in an aurora of similar intensity at the same time of year. In contrast to the original interpretation, we find that population by cascade from the C3Πu and B3Πg states in the A3Σu+v=0,1 levels, as calculated using recently measured electron excitation cross sections, accurately accounts for the observed relative emission rates (IV-K/12PG0.0). In addition there is no need to change the production rate of A 3 Σ u+ molecules relative to that of C3Πuv=0 as a function of altitude in order to fit the profile of the deactivation probability to the atmospheric model. Quenching of A 3 Σ u+ molecules at high altitudes is dominated by atomic oxygen. The rate constants for the v=0 and v=1 levels are 8 × 10−11 cm3 sec−1 and 1.7 × 10−10 cm3 sec−1 respectively, as determined using the model atmosphere mentioned above. Recent observations with a helium cooled mass spectrometer suggest that conventional mass spectrometer measurements tend to underestimate the atomic oxygen relative concentration. The rate coefficients may therefore be too large by as much as a factor of 3. Below 130 Km we find that it is possible to account for the deactivation in bright auroras by invoking large nitric oxide concentrations, similar to those recently observed mass spectrometrically and using a rate constant of 8 × 10−11 cm3 sec−1 for both the v=1 levels. This rate constant is very nearly the same as that measured in the laboratory (7 × 10−11 cm3 sec−1). Molecular oxygen appears not to play a significant role in deactivating the lower A 3 Σ u+ levels.  相似文献   

14.
We use a 1-D chemical diffusive model, in conjunction with the measured neutral atmospheric structure, to analyze the Voyager RSS electron density, ne, profiles for the ionospheres of Jupiter and Saturn. As with previous studies we find serious difficulties in explaining the ne measurements. The model calculates ionospheres for both Jupiter and Saturn with ne peaks of 10 times the measured peaks at altitudes which are 900–1000 km lower than the altitude of peaks in the RSS electron densities. Based on our knowledge of neutral atmospheric structure, ionization sources, and known recombination mechanisms it seems that, vibrational excitation of H2 must play some role in the conversion of slowly radiatively recombining H+ ions to the relatively more rapidly recombining H2+ and H3+ ions. In addition, vertical ion flow induced by horizontal neutral winds or electric fields probably also play some role in maintaining the plasma peaks observed both for Jupiter and Saturn to be at high altitudes. For the ionosphere of Saturn, the electron densities are affected by a putative influx of H2O molecules, ΦH2O, from the rings. To reproduce the RSS V2 exit ne results model requires an influx of ΦH2O 2 × 107 molecules cm−2 s−1 without invoking H2f vibrational excitation. To maintain the model ne peak at the measured altitude vertical plasma drift maintained by meridional winds or vertical electric fields is required. The amounts of H2O are consistent with earlier estimates of Connerney and Waite (1984) and do not violate any observational constraints.  相似文献   

15.
Measurements of the O2(A3Σ − X3Σ) Herzberg system in the night airglow have been made with the ESRO TD-1 satellite in the wavelength range 2400–3100 A. The slant emission rate varies from 3.5 to 15 kR, indicating an irregular structure of the atomic oxygen near the turbopause. A statistical maximum intensity is found near the tropic in the winter hemisphere. The intensity profile is consistent with excitation by three-body recombination of oxygen atoms. The observed total emission rate can be accounted for by reasonable atomic oxygen densities and an O2(A3Σ) production efficiency of about 20% if quenching by N2 occurs at the rate deduced from laboratory and other airglow measurements.  相似文献   

16.
Auroral luminosities of the main emission lines in the aurora have been calculated for excitation by an isotopic primary electron flux with spectra of the form J(E) = AE exp (−E/E1) + B(E2)E exp (−E/E1). The variation of emissions from O and N2+ with height are shown, as are the variations of column integrated intensities and pertinent intensity ratios with the characteristic energy E2, this leading to a method of estimating the electron spectrum from ground observation.  相似文献   

17.
A sky-mapping filter photometer has been used to determine the 630.0 nm airglow enhancement produced by explosive release of 3 × 1026 CO2 molecules into the F-region at 320 km altitude on 8 September 1982 as part of project BIME. The enhancement is produced when COg molecules engage in atom transfer with the F-region O+ ions to form O2+ ions, which subsequently dissociatively recombine with the ambient electrons to produce O(1D) atoms to yield the 630.0 nm radiation. The morphology of the enhanced airglow region has been traced in a series of 630.0 nm intensity contour maps as a function of time, the enhancement reaching a central brightness of approximately 400 R about 2 min after release and a diameter of 250 km some 3 min after release. The measurements of central intensity and enhanced region radius as a function of time are compared with model calculations by Mendillo and Herniter of diffusive expansion of CO2 molecules from either a point release or from an initial, extended volume. While peak intensities are reasonably reproduced, the measured decay of the 630.0 nm intensity and the growth in size of the enhanced region are rather different from the model predictions. The measured 200 m/s drift southeastward of the enhanced region is consistent with the motion of the neutral thermosphere determined from optical doppler shifts less than an hour earlier.  相似文献   

18.
Band spectra of BaO covering a total wavelength region of 5050 Å-9300 Å were recorded from the ground with a scanning spectrophotometer at 7.1 Å resolution during a series of barium rocket releases at College, Alaska in the Spring of 1969. Rotational and vibrational temperatures, both equal to approximately 850°K at the release altitude of 170 km, were inferred by matching the release spectra with calculated synthetic spectra. This temperature persisted throughout the observing period, from release + 20 sec to 14 min after release.

Analysis of the BaO band spectrum over a large wavelength region reveals that rotational temperatures are best determined at wavelengths below 5500 Å, and that vibrational temperatures should be measured at wavelengths greater than 5500 Å. Comparisons with synthetic spectra show that several broad emission features in the release spectra, located at about 7900 Å 8400 Å and 9000 Å, may be identified as clusters of overlapping BaO bands. A synthetic spectrum of BaO extending from 4700 Å to 15,000 Å is included for general reference and to facilitate future studies in that wavelength region.  相似文献   


19.
During the break-up phase of two strong auroral events, emissions of short duration on the wavelength of He I, 5876 Å have been observed. These records are accurate within 0.5 Å and intensities of up to 120 R have been measured. This high value is not consistent with the theoretical limit suggested by other authors. Simultaneous observations of H, 6563 Å show that the He I and H emissions are not closely related to each other with time, which may be one reason for explaining the discrepancy with the predicted intensity derived from observed ratios of He++/H+ in the solar wind. The emission on 5876 Å has only been detected at the lowest border of very intense ray bundles towards north but not yet in auroral arcs and diffuse glow. It is suggested that two principally different helium events in aurora may be observable, one resulting in a low level He emission lasting for longer time and another in a stronger He emission of short duration. The observational difficulties caused by the presence of OH bands are discussed.  相似文献   

20.
Emission profiles of the 6300Åline are determined from OGO 4 data in the dark ionosphere during conjugate sunrise. From Saint-Santin electron density profile measurements, it is shown that, for the two cases studied in December 1967, the recombination cannot account for the measured O1D emission profiles. However, direct photoelectron-oxygen excitation can reproduce the data: if the photoelectron escape flux in the sunlit ionosphere, computed from standard photoelectron production, is transmitted through the field tube with an additional attenuation of 0.6 due to angular diffusion through photoelectron-electron and photoelectron-ion Coulomb collisions, the Hinteregger (1965) solar flux data must be increased by a factor 2, which agrees with previous results.  相似文献   

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