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1.
A detailed study is made of the atmospheric attenuation of the dissociation of nitric oxide in the mesosphere and stratosphere. The nitric oxide dissociation profile depends on the absorption of the discrete Schumann-Runge bands of O2. The major contribution to the dissociation rate of NO is the predissociation of the δ(0-0) and δ(1-0) bands which can reach the stratosphere. 相似文献
2.
Marcel Nicolet 《Planetary and Space Science》1981,29(9):951-974
A critical analysis has been made of solar irradiance in the spectral region covering wavelengths from 100 nm upwards; the absorption characteristics of molecules of oxygen and ozone have been taken into account with a view to the direct application of the results to atmospheric photochemistry. The absorption of radiation by these molecules results in the photodissociation of both of them in the homosphere, and it also makes possible the penetration of solar radiation from the thermosphere, through the mesosphere and the stratosphere, down to the troposphere.Special attention has been given to each of the following spectral regions: Lyman-alpha radiation at 121.6 nm, the O2 Schumann-Runge continuum at wavelengths less than 175 nm, the O2 Schumann-Runge band system from 200 to 175 nm, and the O2 Herzberg continuum at 242.4 nm. For absorption by ozone, the solar spectrum has been analysed in the following regions: the Hartley band at wavelengths less than 310 nm, the Huggins bands at wavelengths above 310 nm and the visible Chappuis bands. Finally, for the photodissociation of O3, particular attention has been given to the transition region (300–320 nm) in which there is a change-over from the production of the excited atom O(1D) to that of the atom in its ground state O(3p). 相似文献
3.
Using the SPICAV-UV spectrometer aboard Venus Express in nadir mode, we were able to derive spectral radiance factors in the middle atmosphere of Venus in the 170-320 nm range at a spectral resolution of R ? 200 during 2006 and 2007 in the northern hemisphere. By comparison with a radiative transfer model of the upper atmosphere of Venus, we could derive column abundance above the visible cloud top for SO2 using its spectral absorption bands near 280 and 220 nm. SO2 column densities show large temporal and spatial variations on a horizontal scale of a few hundred kilometers. Typical SO2 column densities at low latitudes (up to 50°N) were found between 5 and 50 μm-atm, whereas in the northern polar region SO2 content was usually below 5 μm-atm. The observed latitudinal variations follow closely the cloud top altitude derived by SPICAV-IR and are thought to be of dynamical origin. Also, a sudden increase of SO2 column density in the whole northern hemisphere has been observed in early 2007, possibly related to a convective episode advecting some deep SO2 into the upper atmosphere. 相似文献
4.
Moderate dispersion (25-35 Å mm–1) spectra were obtained from two carbon stars, V Cyg and WZ Cas, in a wide range of wavelengths (3400-6800 Å) with the echelle-spectrometer, ZEBRA, of the 6 m telescope and two-dimensional photon-counting system. Spectral feature identification was carried out from 3850 to 6200 Å. Most of the bands are due to C2, SiC2, and CN, however, particularly in WZ Cas, moderate atomic lines of the iron peak and s-process elements are also found. WZ Cas is a so-called lithium star, however, we have found no evidence for a strong line of Li. The spectra of V Cyg contain an emission line of H. 相似文献
5.
An area scanning photometer has been used to obtain photometrically calibrated limb-darkening scans of Jupiter at four wavelengths: 6190, 6300, 7250, and 8200 Å. The first and third of these correspond to methane absorptions and the second and fourth to continuum regions near the 4-0 and 3-0 H2 quadrupole bands, respectively. Single-scattering albedos have been calculated for several areas on the planet at all four wavelengths assuming a semi-infinite, homogeneous, isotropically scattering atmosphere. The values obtained at the wavelengths of the quadrupole bands range from 0.98 over the NEB to ? 0.99 over the NTrZ and the bright band in the southern hemisphere. The single-scattering albedo values are used to show that the 5μm-emitting equatorial regions of the planet may be relatively clear and the tropical regions relatively cloudy. 相似文献
6.
Vladimir A. Krasnopolsky 《Planetary and Space Science》2011,59(8):754-766
A scheme of excitation, quenching, and energy transfer processes in the oxygen nightglow on the Earth, Venus, and Mars has been developed based on the observed nightglow intensities and vertical profiles, measured reaction rate coefficients, and photochemical models of the nighttime atmospheres of the Venus and Mars. The scheme involves improved radiative lifetimes of some band systems, calculated yields of the seven electronic states of O2 in termolecular association, and rate coefficients of seven processes of electronic quenching of the Herzberg states of O2, which are evaluated by fitting to the nightglow observations. Electronic quenching of the vibrationally excited Herzberg states by O2 and N2 in the Earth's nightglow is a quarter of total collisional removal of the O2(A, A′) states and a dominant branch for the O2(c) state. The scheme supports the conclusion by Steadman and Thrush (1994) that the green line is excited by energy transfer from the O2(A3Σu+, v≥6) molecules, and the inferred rate coefficient of this transfer is 1.5×10−11 cm3 s−1. The O2 bands at 762 nm and 1.27 μm are excited directly, by quenching of the Herzberg states, and by energy transfer from the O2(5Πg) state. Quenching of the O2 band at 762 nm excites the band at 1.27 μm as well. Effective yield of the O2(a1Δg) state in termolecular association on Venus and Mars is ∼0.7. Quantitative assessments of all these processes have been made. A possible reaction of O2(c1Σu−)+CO is a very minor branch of recombination of CO2 on Venus and Mars. Night airglow on Mars is calculated for typical conditions of the nighttime atmosphere. The calculated vertical intensity of the O2 band at 1.27 μm is 13 kR, far below the recently reported detections. 相似文献
7.
《Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science》2001,26(7):527-532
The nitrogen isotope ratio of middle atmosphere nitrogen oxide is predicted as a function of altitude. Nitrogen oxides originate photochemically either from stratospheric nitrous oxide reacting with O(1D) or in the mesosphere and thermosphere from direct dissociation of N2 and ionization-initiated reactions involving O2 and N2. During its formation process, N2O acquires a nitrogen isotopic composition of N isotopes different than N2. Photodissociation within the stratosphere also modifies the proportion of isotopes. Reaction of stratospheric NO with O3 produces NO2, which when photodissociated yields NO depleted in 15N relative to NO2 in laboratory air. The value of δ15NO in the stratosphere is −100‰. In the altitude region between 50 and 65 km, NO is transformed into NO2 and then returned to NO by reaction of NO2 with O and by NO2 photodissociation. These reactions determine the isotopic makeup of NO. Above 65 km, nitric oxide is produced by local ionization processes and gas phase photochemical reactions involving N2 and excited O2. These processes determine the isotopic composition of NO in the upper mesosphere and thermosphere. Here δ15NO is 0‰. Air transported into the mesosphere above 65 km will reflect the NO isotopic values of the region below, while mesospheric NO transported below 65 km will not be distinguishable from NO originating in the stratosphere. 相似文献
8.
We have obtained spatially resolved spectra of Titan in the near-infrared J, H and K bands at a resolving power of ∼5000 using the near-infrared integral field spectrometer (NIFS) on the Gemini North 8 m telescope. Using recent data from the Cassini/Huygens mission on the atmospheric composition and surface and aerosol properties, we develop a multiple-scattering radiative transfer model for the Titan atmosphere. The Titan spectrum at these wavelengths is dominated by absorption due to methane with a series of strong absorption band systems separated by window regions where the surface of Titan can be seen. We use a line-by-line approach to derive the methane absorption coefficients. The methane spectrum is only accurately represented in standard line lists down to ∼2.1 μm. However, by making use of recent laboratory data and modeling of the methane spectrum we are able to construct a new line list that can be used down to 1.3 μm. The new line list allows us to generate spectra that are a good match to the observations at all wavelengths longer than 1.3 μm and allow us to model regions, such as the 1.55 μm window that could not be studied usefully with previous line lists such as HITRAN 2008. We point out the importance of the far-wing line shape of strong methane lines in determining the shape of the methane windows. Line shapes with Lorentzian, and sub-Lorentzian regions are needed to match the shape of the windows, but different shape parameters are needed for the 1.55 μm and 2 μm windows. After the methane lines are modeled our observations are sensitive to additional absorptions, and we use the data in the 1.55 μm region to determine a D/H ratio of 1.77 ± 0.20 × 10−4, and a CO mixing ratio of 50 ± 11 ppmv. In the 2 μm window we detect absorption features that can be identified with the ν5 + 3ν6 and 2ν3 + 2ν6 bands of CH3D. 相似文献
9.
A model of the atmospheric structure of Uranus is presented which differs from previous types of models in two important respects: (1) The CH4/H2 ratio is sufficiently large that CH4 is saturated to large depths in the Uranian atmosphere. (2) The internal energy flux is small compared with that due to solar heating. Because of the small internal flux, the thermal flux decreases rapidly with depth and the atmosphere is radiative to large optical depths. A CH4 droplet cloud forms where the atmosphere finally becomes convective due to the internal flux. The model is shown to be in reasonable agreement with published observations of the H2 quadrupole 3-0 and 4-0 bands, the visible (4000–6000 Å) CH4 bands, and the infrared emission spectrum. 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.
The 362.156 GHz absorption spectrum of H2O2 in the Mars atmosphere was observed on September 4 of 2003, employing the James Clerk Maxwell Telescope (JCMT) sub-millimeter facility on Mauna Kea, Hawaii. Radiative transfer analysis of this line absorption yields an average volume mixing ratio of 18±0.4 ppbv within the lower (0-30 km) Mars atmosphere, in general accordance with standard photochemical models (e.g., Nair et al., 1994, Icarus 111, 124-150). Our derived H2O2 abundance is roughly three times greater than the upper limit retrieved by Encrenaz et al. (2002, Astron. Astrophys. 396, 1037-1044) from infrared spectroscopy, although part of this discrepancy may result from the different solar longitudes (Ls) of observation. Aphelion-to-perihelion thermal forcing of the global Mars hygropause generates substantial (>200%) increases in HOx abundances above ∼10 km altitudes between the Ls=112° period of the Encrenaz et al. upper limit measurement and the current Ls=250° period of detection (Clancy and Nair, 1996, J. Geophys. Res. 101, 12785-12590). The observed H2O2 line absorption weakens arguments for non-standard homogeneous (Encrenaz et al., 2002, Astron. Astrophys. 396, 1037-1044) or heterogeneous (Krasnopolsky, 2003a, J. Geophys. Res. 108; 2003b, Icarus 165, 315-325) chemistry, which have been advocated partly on the basis of infrared (8 μm) non-detections for Mars H2O2. Observation of Mars H2O2 also represents the first measurement of a key catalytic specie in a planetary atmosphere other than our own. 相似文献
12.
The relations between variations of far UV (FUV) emission in 115–210 nm waveband and L 121.6 nm and F10.7 are studied. The changes of FUV flux are found to lag changes of F10.7 - as a rule for 1 day. It is shown that such a difference may be caused by two factors: 1) differences between the rates of decrease of local sources' (active regions) brightness in FUV and 10.7 cm; 2) differences between limb-darkening curves for different wavelengths. One may expect the fluxes at different wavelengths to exhibit phase shifts of one relative to another. Cross-correlation analysis reveals no time-delay between emission fluxes within the FUV waveband, in spite of different laws for limb-brightening (darkening) for different spectral intervals. The absence of a phase delay can be caused by relatively small contribution of active regions to the flux of the whole Sun at these wavelengths. Thus the Lyman-alpha line intensity variation reflects variations of Solar FUV emission more precisely than F10.7. Therefore, using the L intensity for flux intensity calculations of other FUV wavelengths is preferable to using the F10.7 index. 相似文献
13.
In 1999, observations of the Venus nightglow with the Keck I telescope showed that the 5577 Å oxygen green line was a significant feature, comparable in intensity to the terrestrial green line. Subsequent measurements have been carried out at the Apache Point Observatory (APO) and again at Keck I, confirming the presence of the line with substantially varying intensity. The Herzberg II emission intensity, from the O2(c-X) transition, was found to have an intensity near 3 kR in one APO run, comparable to the value found on all previous measurements. Thus, of the three oxygen features seen at Venus—the green line, the Herzberg II emission system, and the 1.27-μ 0-0 band of the IR atmospheric system—the first is quite variable, the second is relatively constant, while the third also shows large variations. The reaction between O2(, v=0) and CO is considered as a possible mechanism to explain green line production and its variability, as well as the variability of the 1.27-μ emission and the stability of the CO2 atmosphere. This reaction may catalyze CO2 recombination some five orders of magnitude faster than the slow three-body O + CO reaction. 相似文献
14.
More than 500 images of Io in eclipse were acquired by the Cassini spacecraft in late 2000 and early 2001 as it passed through the jovian system en route to Saturn (Porco et al., 2003, Science 299, 1541-1547). Io's bright equatorial glows were detected in Cassini's near-ultraviolet filters, supporting the interpretation that the visible emissions are predominantly due to molecular SO2. Detailed comparisons of laboratory SO2 spectra with the Cassini observations indicate that a mixture of gases contribute to the equatorial emissions. Potassium is suggested by new detections of the equatorial glows at near-infrared wavelengths from 730 to 800 nm. Neutral atomic oxygen and sodium are required to explain the brightness of the glows at visible wavelengths. The molecule S2 is postulated to emit most of the glow intensity in the wavelength interval from 390 to 500 nm. The locations of the visible emissions vary in response to the changing orientation of the external magnetic field, tracking the tangent points of the jovian magnetic field lines. Limb glows distinct from the equatorial emissions were observed at visible to near-infrared wavelengths from 500 to 850 nm, indicating that atomic O, Na, and K are distributed across Io's surface. Stratification of the atmosphere is demonstrated by differences in the altitudes of emissions at various wavelengths: SO2 emissions are confined to a region close to Io's surface, whereas neutral oxygen emissions are seen at altitudes that reach up to 900 km, or half the radius of the satellite. Pre-egress brightening demonstrates that light scattered into Jupiter's shadow by gases or aerosols in the giant planet's upper atmosphere contaminates images of Io taken within 13 minutes of entry into or emergence from Jupiter's umbra. Although partial atmospheric collapse is suggested by the longer timescale for post-ingress dimming than pre-egress brightening, Io's atmosphere must be substantially supported by volcanism to retain auroral emissions throughout the duration of eclipse. 相似文献
15.
An improvement to the volcano-scan algorithm for atmospheric correction of CRISM and OMEGA spectral data 总被引：1，自引：0，他引：1
Patrick C. McGuire Janice L. Bishop Adrian J. Brown Giuseppe A. Marzo Scott L. Murchie Mario Parente Ted L. Roush Michael D. Smith Michael J. Wolff 《Planetary and Space Science》2009,57(7):809-815
The observations of Mars by the CRISM and OMEGA hyperspectral imaging spectrometers require correction for photometric, atmospheric and thermal effects prior to the interpretation of possible mineralogical features in the spectra. Here, we report on a simple, yet non-trivial, adaptation to the commonly-used volcano-scan correction technique for atmospheric CO2, which allows for the improved detection of minerals with intrinsic absorption bands at wavelengths between 1.9 and 2.1 μm. This volcano-scan technique removes the absorption bands of CO2 by ensuring that the Lambert albedo is the same at two wavelengths: 1.890 and 2.011 μm, with the first wavelength outside the CO2 gas bands and the second wavelength deep inside the CO2 gas bands. Our adaptation to the volcano-scan technique moves the first wavelength from 1.890 μm to be instead within the gas bands at 1.980 μm, and for CRISM data, our adaptation shifts the second wavelength slightly, to 2.007 μm. We also report on our efforts to account for a slight ∼0.001 μm shift in wavelengths due to thermal effects in the CRISM instrument. 相似文献
16.
This work presents model calculations of the diurnal airglow emissions from the OH Meinel bands and the O2 IR atmospheric band in the neutral atmosphere of Mars. A time-dependent photochemical model of the lower atmosphere below 80 km has been developed for this purpose. Special emphasis is placed on the nightglow emissions because of their potential to characterize the atomic oxygen profile in the 50-80 km region. Unlike on Earth, the OH Meinel emission rates are very sensitive to the details of the vibrational relaxation pathway. In the sudden death and collisional cascade limits, the maximum OH Meinel column intensities for emissions originating from a fixed upper vibrational level are calculated to be about 300 R, for transitions v′=9→v′?8, and 15,000 R, for transitions v′=1→v′=0, respectively. During the daytime the 1.27 μm emission from O2(), primarily formed from ozone photodissociation, is of the order of MegaRayleighs (MR). Due to the long radiative lifetime of O2(), a luminescent remnant of the dayglow extends to the dark side for about two hours. At night, excited molecular oxygen is expected to be produced through the three body reaction O + O + CO2. The column emission of this nighttime component of the airglow is estimated to amount to 25 kR. Both nightglow emissions, from the OH Meinel bands and the O2 IR atmospheric band, overlap in the 50-80 km region. Photodissociation of CO2 in the upper atmosphere and the subsequent transport of the atomic oxygen produced to the emitting layer are revealed as key factors in the nightglow emissions from these systems. The Mars 5 upper constraint for the product [H][O3] is revised on the basis of more recent values for the emission probabilities and collisional deactivation coefficients. 相似文献
17.
Bruno Bézard Anna Fedorova Jean-Loup Bertaux Alexander Rodin Oleg Korablev 《Icarus》2011,216(1):173-183
Observations of the 1.10- and 1.18-μm nightside windows by the SPICAV-IR instrument aboard Venus Express were analyzed to characterize the various sources of gaseous opacity and determine the H2O mole fraction in the lower atmosphere of Venus. We showed that the line profile model of Afanasenko and Rodin (Afanasenko, T.S., Rodin, A.V. [2007]. Astron. Lett. 33, 203–210) underestimates the CO2 absorption in the high-wavelength wing of the 1.18-μm window and we derived an empirical lineshape that matches this wing well. An additional continuum opacity is required to reproduce the variation of the 1.10- and 1.18-μm radiances with surface elevation as observed by the VIRTIS-M instrument aboard Venus Express. A constant absorption coefficient of 0.7 ± 0.2 × 10−9 cm−1 am−2 best reproduces the observed variation. We compared spectra calculated with different CO2 and H2O line lists. We found that the CDSD line list lacks the 5ν1 + ν3 series of CO2 bands, which provide significant opacity in Venus’ deep atmosphere, and we have constructed a composite line list that best reproduces the observations. We also showed for the first time that HDO brings significant absorption at 1140–1190 nm. Using the best representation of the atmospheric opacity we could reach, we retrieved a water vapor mole fraction of ppmv, pertaining to the altitude range 5–25 km. Combined with previous measurements in the 1.74- and 2.3-μm windows, this result provides strong evidence for a uniform H2O profile below 40 km, in agreement with chemical models. 相似文献
18.
The existence of strong absorption bands of singly deuterated methane (CH3D) at wavelengths where normal methane (CH4) absorbs comparatively weakly could enable remote measurement of D/H ratios in methane ice on outer Solar System bodies. We performed laboratory transmission spectroscopy experiments, recording spectra at wavelengths from 1 to 6 μm to study CH3D bands at 2.47, 2.87, and 4.56 μm, wavelengths where ordinary methane absorption is weak. We report temperature-dependent absorption coefficients of these bands when the CH3D is diluted in CH4 ice and also when it is dissolved in N2 ice, and describe how these absorption coefficients can be combined with data from the literature to simulate arbitrary D/H ratio absorption coefficients for CH4 ice and for CH4 in N2 ice. We anticipate these results motivating new telescopic observations to measure D/H ratios in CH4 ice on Triton, Pluto, Eris, and Makemake. 相似文献
19.
Vladimir A. Krasnopolsky 《Icarus》2010,207(1):17-27
Venus nightglow was observed at NASA IRTF using a high-resolution long-slit spectrograph CSHELL at LT = 21:30 and 4:00 on Venus. Variations of the O2 airglow at 1.27 μm and its rotational temperature are extracted from the observed spectra. The mean O2 nightglow is 0.57 MR at 21:30 at 35°S-35°N, and the temperature increases from 171 K near the equator to ∼200 K at ±35°. We have found a narrow window that covers the OH (1-0) P1(4.5) and (2-1) Q1(1.5) airglow lines. The detected line intensities are converted into the (1-0) and (2-1) band intensities of 7.2 ± 1.8 kR and <1.4 kR at 21:30 and 15.5 ± 2 kR and 4.7 ± 1 kR at 4:00. The f-component of the (1-0) P1(4.5) line has not been detected in either observation, possibly because of resonance quenching in CO2. The observed Earth’s OH (1-0) and (2-1) bands were 400 and 90 kR at 19:30 and 250 and 65 kR at 9:40, respectively. A photochemical model for the nighttime atmosphere at 80-130 km has been made. The model involves 61 reactions of 24 species, including odd hydrogen and chlorine chemistries, with fluxes of O, N, and H at 130 km as input parameters. To fit the OH vibrational distribution observed by VEX, quenching of OH (v > 3) in CO2 only to v ? 2 is assumed. According to the model, the nightside-mean O2 emission of 0.52 MR from the VEX and our observations requires an O flux of 2.9 × 1012 cm−2 s−1 which is 45% of the dayside production above 80 km. This makes questionable the nightside-mean O2 intensities of ∼1 MR from some observations. Bright nightglow patches are not ruled out; however, the mean nightglow is ∼0.5 MR as observed by VEX and supported by the model. The NO nightglow of 425 R needs an N flux of 1.2 × 109 cm−2 s−1, which is close to that from VTGCM at solar minimum. However, the dayside supply of N at solar maximum is half that required to explain the NO nightglow in the PV observations. The limited data on the OH nightglow variations from the VEX and our observations are in reasonable agreement with the model. The calculated intensities and peak altitudes of the O2, NO, and OH nightglow agree with the observations. Relationships for the nightglow intensities as functions of the O, N, and H fluxes are derived. 相似文献
20.
Cyanoacetylene (HC3N) and diacetylene (C4H2) play an important role in the photochemistry of Titan's atmosphere, in part because of their strong absorption between 110 and 180 nm. Accurate photoabsorption cross-sections at temperatures representative of Titan's atmosphere are required to interprete Cassini observations and to calculate photolysis rates used in photochemical models. Using synchrotron radiation as a tunable vacuum ultraviolet (VUV) light source, we have measured absolute photoabsorption cross-sections of C4H2 and HC3N with a spectral resolution of 0.05 nm in the region between 80 and 225 nm and at different temperatures between 173 and 295 K. The measured cross-sections are used to model transmission spectra of Titan atmosphere in the VUV. 相似文献