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1.
Analysis of observed spectrograms is based on comparison with synthetic spectra. The O2(b1Σ+g?X3Σ?g Atm. (1,1) band in high latitude auroras observed from the ground is found to be the strongest in the Δv = 0 sequence. It is enhanced with altitude relative to the N2 1P(2, 0)and N+2 M(2,0) bands, but the O2 Atm. (2, 2) band has an unexpected low intensity. The range of rotational temperatures of the O2 Atm. bands varies from approx. 200 to above 500 K which indicates that the altitude of the centroid of the emission region varies from about 100 km to the F-region. The highest temperature is found in the midday aurora associated with the magnetospheric cusp. Conspicuous relative variations between the intensities of N2 and O2 spectra are documented, but a satisfactory explanation of the variety is not given. Deviations of the observed O2 Atm. band intensities from the vibrational intensity distribution predicted by Franck-Condor factors indicate that the excitation of the O2 Atm. bands in aurora is not mainly due to particle impact on O2, and the contribution due to energy transfer from hot O(1D) atoms has to be found in future research. 相似文献
2.
The height of the lower red border of type-B aurora has been determined by triangulation using TV cameras at two ground stations. A mean height of 91.4 ± 1.1 km was determined from a set of 12 measurements made under ideal conditions. A TV spectrograph was used simultaneously to seek possible spectral changes between 6400 and 6900 Å which would be indicative of changes in the vibrational distribution in the N2 First Positive bands. No significant difference was found in this distribution between the spectra from 93 and 122 km. The height distribution of contributions to the OI 5577 Å emission relative to the N+2 First Negative emission was modelled from 80 to 160 km. Contributions from electron impact on atomic O, O+2 dissociative recombination and N2(A)O energy transfer were included. Account was taken of recent laboratory data on O(1S) quenching. It was concluded that these processes could explain the excitation of O(1S) in normal aurora and the height distribution of OI 5577 Å in type-B red aurora. It was confirmed that the lifetime ofO(1S) in type-B red auroral rapid time variations is about 0.5 s and it was found from the model that the observed time variation can be reproduced by the mechanisms considered, provided the concentration of NO in the auroral atmosphere is about 1 × 109 at 95 km. Before reasonable certainty can be attained in the correctness of the interpretation it will however be necessary to have reliable simultaneous observations of neutral atmospheric composition particularly for O and NO as well as unchallengeable measurements of the yields of O(1S) for the processes considered and for several other processes which have been suggested recently. 相似文献
3.
The vertical distribution of thermospheric temperature was measured from molecular rotational intensity distributions, in a rocket flight through the aurora at Fort Churchill, Canada. Both the N2+ (1NEG; 0–1) and O2 (ATM ; 0-0) bands were used and a stepping mask photometer was employed to locate each filter passband at seven points on each molecular band. The N2+ temperature follows the appropriate Jacchia (1971) model fairly closely at all altitudes but is higher in temperature by about 60 K. The O2 temperatures follow the model results more closely but one cannot be sure whether the differences between the two sets of measured temperatures are real. 相似文献
4.
It is proposed that energy transfer from excited O2 contributes to the production of O(1S) in aurora. An analysis is presented of the OI5577 Å emission in an IBC II+ aurora between 90 and 130 km. The volume emission rate of the emission at these altitudes is consistent with the production rate of O(1S) by energy transfer to O(3P) from N2 in the A3Σ2+ state and O2 in the A3Σu+, C3Δc1Σu? states, the N2A state being populated by direct electron impact excitation and B → A cascade and the excited O2 states by direct excitation. Above the peak emission altitude (~105 km), energy transfer from N2A is the predominant production mechanism for O(1S). Below it, the contribution from quenching of the O2 states becomes significant. 相似文献
5.
Ion densities and composition are investigated in a time varying model aurora. There is a time lag between turning on the source of ionization and the resulting increase in ion densities that depends on the species and the height level in the ionsophere, so that altitude profiles of auroral electron densities evolve with time. Characteristic buildup times for the ionization are a few seconds at the altitude of maximum energy deposition, increasing to tens of seconds above and below this level. A wide range of composition ratios, n(NO+/n(O2+ and n(NO+/n(O+), can be expected, depending on the time an observation is made during buildup or decay of ionization. The concentrations of atomic nitrogen and nitric oxide increase as a result of auroral ionization, but the associated characteristic times are long compared to the average duration of ‘auroral event’. Thus, intermittent auroral bombardment could result in a gradual buildup of these minor neutral constituents in the auroral atmosphere. Variations in the electron density during pulsating, fluctuating or coruscating aurora lag the source function variations by a few seconds in a typical aurora. 相似文献
6.
Optical spectra of the cleft aurora in the region 5000–8500 Å were measured in December, 1977 at Cape Parry, N.W.T. A Michelson interferometer was used at a resolution of 10 cm?1. The auroral features observed were OI (5577, 6300-64, 7774, 8446 Å), OII (7319-30 Å), NI (5200 Å), Hα, O2 atm (1,1), some weak N21P bands and possibly some Meinel bands of N2+. In addition, nightglow emissions of Na and OH were observed. Theoretical predictions of the OI and NI emission rates using the model of Link et al. (1980) fit the observed rates reasonably well if a 40 eV Maxwellian incident electron spectrum is assumed. The predicted rates for OII exceed the observed value by a factor of 4. It is suggested that the ionization cross-section may be over-estimated. 相似文献
7.
Altitude distributions of electronically excited atoms and molecules of oxygen and nitrogen in the aurora have been obtained by means of rocket-borne wavelength scanning interference filter photometers launched from Fort Churchill, Manitoba (58.4°N, 94.1°W) on January 23, 1974. Atomic oxygen densities derived from mass spectrometer measurements obtained during the flight are used in conjunction with the volume emission rate ratio of the N2(C3Πu?B3Πg) (0-0) second positive and N2(A3Σu+, v = 1?X1Σg+) Vegard-Kaplan bands to derive a rate constant for quenching of the N2(A3Σu+, v = 1) level with O(3P) of 1.7(±0.8) × 10?11 cm3 s?1 These data, together with O den derived from the O2(b1Σg+) state nightglow emission observed during the rocket ascent, suggest that quenching of the N2(A3Σu+, v = 1) level by O2 has a significant positive temperature dependence. The processes involved in the production and loss of the N2(A3Σu+) state are considered and energy transfer from the N2(A3Σu+) state to O(3P) is found to be a significant source of the OI 5577 Å green line in this aurora at altitudes below 130 km. Emission from the NO(A2Σ+?X2Π) gamma bands was not detected, an observation which is consistent with the mass spectrometer data obtained during the flight indicating that the NO density was <108 cm3 at 110 km. On the basis of previous rocket and satellite measurements of the NO gamma bands, energy transfer from the N2(A3Σu+) state to NO(X2Π) is shown to be an insignificant source of the gamma bands in aurora. Altitude profiles of the N2(a1Πg?X1Σg+) Lyman-Birge-Hopfield band system are presented. 相似文献
8.
A theory of the i.r. radiation (2–20 μ) of the upper atmosphere (90–250 km height) has been developed. It includes the calculation of concentrations and temperatures as well as the analysis of atomic and molecular level population kinetics. Various excitation and quenching processes are analysed. Results are given for the following bands: NO (5.3μ), NO+(4.3μ.), CO (4.7 μ), N14N15 (4.4 μ), CO2(4.3 and 15 μ), H2O(2.7 and 6.3 μ), N2O(4.5; 7.8 and 17μ), O3(9.6 and 14.4 μ). The energy aspect of the problem is discussed. It is found that at a height of 120 km intensity in the region of 2 to 20 μ 3 to 10 is that of the 63 μ line of atomic oxygen. The comparison of theory with the experiment was carried out and satisfactory agreement obtained. The correlations of intensities in i.r. bands and emissions in visible and u.v. spectra were considered. 相似文献
9.
A.Vallance Jones 《Planetary and Space Science》1979,27(3):307-312
Height profiles of auroral emissions at 3914 Å, 4861 Å, and 5577 Å were obtained in two rocket flights through medium intensity stable aurora. The 3914 Å N2+ integral intensity data were compared with intensity variations predicted by an auroral model for a range of primary electron energy spectra. The observed profiles for the two flights were well reproduced respectively by a 5.6 keV mono-energtic flux and by a flux with an exponential spectrum cutting off around 12 to 15 keV. The data for 5577 Å (available only above 120 km) bear a constant ratio to that for 3914 Å. The emission profiles derived for 3914 Å, peak at 115 and 107 km respectively. 相似文献
10.
A. C. Balachandra Swamy 《Astrophysics and Space Science》1991,178(1):71-88
Making use of the latest available semi-empirical atmospheric models, solar XUV radiations rates of photoionization and absorbed energy profiles have been graphically presented showing the latitudinal, seasonal and solar cycle variations. The photoionization limits of the major neutral constitutents of the terrestrial atmosphere O2, O, and N2 that occur at wavelengths 102.7, 91.2, and 79.6 nm, respectively have been quantified by showing the photoionization rates of O
2
+
, O+, and N
2
+
for different spectral groups both under quiet and different solar flare conditions. The variability of the photoionization efficiency parameter which is height-dependent, from winter to summer, for solar minimum to solar maximum for four significantly different latitudes under local noon conditions have been investigated during the solar cycle 21. More energy is required to produce an electron-ion pair in a denser atmosphere than in a thinner atmosphere and hence more energy is being deposited in the height range between 100–120 km which itself manifests in raising the electron gas temperatures higher than the neutral gas temperatures. 相似文献
11.
M.H. Rees 《Planetary and Space Science》1984,32(3):373-378
The results of recent laboratory experiments suggest that the reaction N+ + O2 → NO+ + O(1S) is the principal source of O(1S) in aurora. A negligible time delay between auroral ionization and O(1S) production is associated with this indirect process, which is a necessary condition for a viable mechanism. The volume emission rate ratio associated with this production source remains constant with altitude. The problems encountered by the currently accepted source of O(1S), the reaction of N2(A3Σ) molecules with atomic oxygen are explored, and the contributions of this and other reactions to the auroral green line emission are reevaluated. 相似文献
12.
Observations of type-B red and normal aurora were made with a high-speed multichannel photometer and a digital grating spectrometer. The ratio measured in the 5200–5300 Å region with the spectrometer was found to increase by about 16% from normal to type-B aurora. This small change is difficult to reconcile with a height below 90 km for the red border. In the type-B aurora, λ 5577 was weakened by a factor between 1.9 and 3.8 while the ratio was enhanced less than 20%. Rapid intensity variations in the type-B lower border were observed in the λ 5577 and other channels of the photometer. A revised time dependent auroral excitation-ion chemistry model is used in an attempt to reproduce the observations. The observed weakening of λ 5577 could be produced at heights equal to or less than 100 km while the short observed time lag of λ 5577 on the N2+ 1N emission is easier to explain at 100 km than at 80 km. It is concluded that some type-B lower borders may occur near 100 km although it is recognized that there is good evidence rare deep crimson lower borders lie at 80 km or below. The mechanism for the excitation of O(1S) is considered in the light of these results. None of the mechanisms examined is satisfactory on the basis of currently accepted atmospheric models and quenching rate coefficients. 相似文献
13.
A program of observations of Jupiter's H+3auroras was conducted during the first 4 months of 1992, a period that spanned the Ulysses encounter. Daily variations of auroral intensity are small in magnitude (∼20%) and well correlated with variations in the solar wind ram pressure arriving at Jupiter. A much larger (factor of 3) time variation is observed to occur on a time scale of approximately 2 months. During the first 2 months of observation, the inferred total intrinsic intensity of the northern aurora exceeded that of the southern aurora by a factor of 2. Throughout the latter 2 months, characterized by less intense auroral activity, the intensity of the northern aurora was comparable to that of the southern aurora. 相似文献
14.
Fluorescence efficiencies of electrons in a large number of bands of the N2 First Positive and O2+ First Negative groups lying in the 4900–10,500 Å wavelength range have been investigated theoretically. The variation of transition moment with internuclear distance is taken into consideration. For the First Positive group of N2 the calculations are carried out at very low pressure as well as at 600 Torr. In general the present values are higher than the experimental values but in most of the cases fair agreement has been obtained. For the O2+ First Negative group no direct experimental data is available. However, the present ratio of the total efficiency in the O2+ First Negative group to the N2+ First Negative group is found to be in good agreement with the experimental intensity ratio. 相似文献
15.
Laboratory cross-section data on the excitation of the OII(2s 2p44P → 2s2 2p34S; λ834 Å) resonance transition and on the production of O+ and O2+ ions by electron impact on atomic oxygen are used to show that the ratio is nearly constant for incident electron energies > 50 eV. Under auroral conditions, the total electron-ion pair production rate from electron impact on O can be inferred from λ834 Å volume emission rate measurements using the result that . These findings, along with earlier work on the simultaneous ionization-excitation of the 1 Neg (0,0) band of N2+ and the 1 Neg (1, 0) band of O+2, allow the specific ionization rates for the principal atmospheric constituents (O+, O+2, N+2), for the multiply-ionized species (O2+, O2+2, N2+2), and for the dissociatively produced atomic ions to be inferred in aurora from remote satellite observations. 相似文献
16.
The Fabry-Perot interferometer on Dynamics Explorer 2 was used as a low sensitivity photometer to study the O2 Atmospheric A band during the daytime. A study of the brightness of the emission showed that the assumed source of O2(b1Σg+) in the thermosphere, O(1D), can account for the observed intensity up to about 250 km but with a significantly different scale height. This combined with an enhanced brightness above this altitude suggests an additional source for this emission. 相似文献
17.
I.C. McDade E.J. Llewellyn R.G.H. Greer D.P. Murtagh 《Planetary and Space Science》1982,30(11):1133-1136
A simple vibrational relaxation model which reproduces the observed altitude integrated vibrational distribution of the Herzberg I bands in the nightglow is used to derive the altitude profiles of the individual vibrational levels at 1 km intervals in the 85–115 km height range. The possible errors associated with using rocket-borne photometer measurements of a limited number of bands in the O2(A3Σu+?X3Σg?) system to infer the total Herzberg I emission profile are assessed. 相似文献
18.
L. S. Pilyugin 《Kinematics and Physics of Celestial Bodies》2010,26(2):39-50
This paper considers the classical method to determine the electron temperatures t
3,O, t
2,O and t
2,N from forbidden lines of the ions O++, O+, and N+, and investigates the influence of uncertainties in atomic data on the accuracy of the determined electron temperatures.
The uncertainties in atomic data (the Einstein coefficients for spontaneous transitions and electron ionization cross-sections)
are estimated as discrepancies between the values computed by various authors. The error in the electron temperature caused
by uncertainties in the atomic data is found to increase with the growth in the electron temperature. At a temperature 10000
K, the errors in the electron temperatures t
3,O, t
2,N, and t
2,O do not exceed 1, 3, and 7%, respectively. 相似文献
19.
H. Böhringer M. Durup-Ferguson E.E. Ferguson D.W. Fahey 《Planetary and Space Science》1983,31(4):483-487
New experimental techniques have yielded several thermal energy vibrational quenching rate constants for O2+(v). Rates for quenching of O2+(v = 1) by O2, N2, Ar, CO2, H2, and CH4 are 3(?10), 2(?12), 1(?12), 1(?10), 2.5(?12), and 6(?10) cm3s?1 at 300 K. The quenching is somewhat faster for O2+(v = 2). The triatomic ions CO2+, NO2+, N2O+, SO2+, and H2O+ are all vibrationally deexcited with an efficiency greater than 10?3 in Ar or Ne collisions. A theoretical rationalization of the experimental results leads to the prediction that vibrational quenching in planetary atmospheres will generally be efficient, k > 1(?12) cm3s?1 for almost all ion and neutral gas pairs. 相似文献
20.
The ratio of the intensity of the oxygen green line at 5577 A to that of the N2+ First Negative band (0, 0) at 3914 A in morning and evening pulsating aurora has been observed using a ground-based scanning photometer which scans the entire sky in 2.6 sec with 2° resolution.The ratio I(5577)/I(3914), after corrections for scattering and extinction made on the basis of hemispheric averages of the intensities at each wavelength, is up to 50% lower in the pulsations than in the surrounding diffuse aurora and in pre-breakup discrete auroras. In morning pulsations this ratio showed systematic decreases with time and with increasing intensity.We report here what we believe to be the first quantitative intensity measurements made of the rare phenomenon evening pulsations. These also show a reduced ratio and a tendency for the ratio to decrease with time.The range of previously published values of the 5577 A time constant in pulsating auroras would lead to ratio variations of the same magnitude as those reported here, suggesting that quenching effects may be more important than atmospheric composition changes in determining intensity ratios within the altitude range of pulsating auroras. 相似文献