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1.
In this paper we present the results of a study of the electron cooling rate, the production rates of vibrationally excited N2(v), and the production frequency of the N2 vibrational quanta arising from the collisions of electrons with unexcited N2(0) and vibrationally excited N2(1) molecules as functions of the electron temperature. The electron energy transfer rates for vibrational excitation of N2 have been calculated and fit to analytical expressions by use of the revised vibrationally excited N2 cross sections. These new analytical expressions are available to the researcher for quick reference and accurate computer modeling with a minimum of calculations.  相似文献   

2.
The paper presents the results of numerical photochemical simulations of the impact of the most powerful solar proton flares during the 23rd solar cycle on the ozonosphere in the polar regions of the Earth. A global 3D photochemical model, CHARM, developed at Central Aerological Observatory (CAO) was used in the simulations. The model introduces an additional source of nitrogen atoms and OH radicals. These components are formed due to the ionization effect of solar protons in the Earth’s atmosphere. The ionization rate was determined from data on proton fluxes measured by GOES satellites. The production rate of additional NO x and HО x molecules per ion pair was based on published theoretical studies. It is shown that the most intense flares in the 23rd solar cycle (2000, 2001, and 2003) destroyed ozone in the mesosphere to a great extent (sometimes completely, for example, during the July 14, 2000, event). It is found that the response of ozone to solar proton events follows a seasonal pattern. For the first time, the long-term effect of solar proton events is identified; it is approximately one year.  相似文献   

3.
This study compares the Isis II satellite measurements of the electron density and temperature, the integral airglow intensity and volume emission rate at 630 nm in the SAR arc region, observed at dusk on 4 August, 1972, in the Southern Hemisphere, during the main phase of the geomagnetic storm. The model results were obtained using the time dependent one-dimensional mathematical model of the Earth’s ionosphere and plasmasphere (the IZMIRAN model). The major enhancement to the IZMIRAN model developed in this study to explain the two component 630 nm emission observed is the analytical yield spectrum approach to calculate the fluxes of precipitating electrons and the additional production rates of N+2, O+2, O+(4S), O+(2D), O−(2P), and O+(2P) ions, and O(1D) in the SAR arc regions in the Northern and Southern Hemispheres. In order to bring the measured and modelled electron temperatures into agreement, the additional heating electron rate of 1.05 eV cm−3 s−1 was added in the energy balance equation of electrons at altitudes above 5000 km during the main phase of the geomagnetic storm. This additional heating electron rate determines the thermally excited 630 nm emission observed. The IZMIRAN model calculates a 630 nm integral intensity above 350 km of 4.1 kR and a total 630 nm integral intensity of 8.1 kR, values which are slightly lower compared to the observed 4.7 kR and 10.6 kR. We conclude that the 630 nm emission observed can be explained considering both the soft energy electron excited component and the thermally excited component. It is found that the inclusion of N2(v > 0) and O2(v > 0) in the calculations of the O+(4S) loss rate improves the agreement between the calculated Ne and the data on 4 August, 1972. The N2(v > 0) and O2(v > 0) effects are enough to explain the electron density depression in the SAR arc F-region and above F2 peak altitude. Our calculations show that the increase in the O+ + N2 rate factor due to the vibrationally excited nitrogen produces the 5–19% reductions in the calculated quiet daytime peak density and the 16–24% decrease in NmF2 in the SAR arc region. The increase in the O+ + N2 loss rate due to vibrationally excited O2 produces the 7–26% decrease in the calculated quiet daytime peak density and the 12–26% decrease in NmF2 in the SAR arc region. We evaluated the role of the electron cooling rates by low-lying electronic excitation of O2(a1δg) and O2(b1σg+), and rotational excitation of O2, and found that the effect of these cooling rates on Te can be considered negligible during the quiet and geomagnetic storm period 3–4 August, 1972. The energy exchange between electron and ion gases, the cooling rate in collisions of O(3P) with thermal electrons with excitation of O(1D), and the electron cooling rates by vibrational excitation of O2 and N2 are the largest cooling rates above 200 km in the SAR arc region on 4 August, 1972. The enhanced IZMIRAN model calculates also number densities of N2(B3πg+), N2(C3πu), and N2(A3σu+) at several vibrational levels, O(1S), and the volume emission rate and integral intensity at 557.7 nm in the region between 120 and 1000 km. We found from the model that the integral integral intensity at 557.7 nm is much less than the integral intensity at 630 nm.  相似文献   

4.
Freezing can increase the emissions of carbon dioxide(CO_2) and nitrous oxide(N_2O) and the release of labile carbon(C) and nitrogen(N) pools into the soil. However, there is limited knowledge about how both emissions respond differently to soil freezing and their relationships to soil properties. We evaluated the effect of intensity and duration of freezing on the emissions of CO_2 and N_2 O, net N mineralization, microbial biomass, and extractable C and N pools in soils from a mature broadleaf and Korean pine mixed forest and an adjacent secondary white birch forest in northeastern China. These soils had different contents of microbial biomass and bulk density. Intact soil cores of 0–5 cm and 5–10 cm depth sampled from the two temperate forest floors were subjected to -8, -18, and -80°C freezing treatments for a short(10 d) and long(145 d) duration, and then respectively incubated at 10°C for 21 d. Soil cores, incubated at 10°C for 21 d without a pretreatment of freezing, served as control. Emissions of N_2 O and CO_2 after thaw varied with forest type, soil depth, and freezing treatment. The difference could be induced by the soil water-filled pore space(WFPS) during incubation and availability of substrates for N_2 O and CO_2 production, which are released by freezing. A maximum N_2 O emission following thawing of frozen soils was observed at approximately 80% WFPS, whereas CO_2 emission from soils after thaw significantly increased with increasing WFPS. The soil dissolved organic C just after freezing treatment and CO_2 emission increased with increase of freezing duration, which paralleled with a decrease in soil microbial biomass C. The cumulative net N mineralization and net ammonification after freezing treatment as well as N_2 O emission were significantly affected by freezing temperature. The N_2 O emission was negatively correlated to soil p H and bulk density, but positively correlated to soil K_2SO_4-extractable NO_3~--N content and net ammonification. The CO_2 emission was positively correlated to the cumulative net N mineralization and net ammonification. From the above results, it can be reasonably concluded that for a wide range of freezing temperature and freezing duration, N_2 O and CO_2 emissions after thaw were associated mainly with the changes in soil net N mineralization and the availability of substrate liberated by freezing as well as other soil properties that influence porosity.  相似文献   

5.
Anomalous changes in the diffuse emission of carbon dioxide within the Masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site. Their epicenters are located, respectively, south of Managua in Las Colinas (4.3 magnitude) and the Xiloa caldera (3.6 magnitude), in 2002 and 2003, recorded by the geochemical station located at El Comalito, Masaya volcano (Nicaragua). Anomalous increases were observed, which occurred around 50 and 8 days before the main seismic event that took place in Las Colinas, and 4 days before the seismic swarm at the Xiloa caldera, with a maximum CO2 efflux of 9.3 and 10.7 kg m?2 day?1, respectively. The anomalous CO2 efflux increases remained after filtering with multiple regression analysis was applied to the CO2 efflux time series, which indicated that atmospheric variables, during the first 4 months, explained 23 % CO2 variability, whereas, during the rest of the time series, CO2 efflux values are poorly controlled with only 6 %. The observed anomalies of the diffuse CO2 emission rate might be related to pressure changes within the volcanic–hydrothermal system and/or to geostructural changes in the crust due to stress/strain changes caused before and during the earthquakes’ formation, and seem not to be related to the activity of the main crater of Masaya volcano.  相似文献   

6.
The first-order perturbation approximation is applied to calculate the rate coefficients of vibrational energy transfer in collisions involving vibrationally excited molecules in the absence of non-adiabatic transitions. The factors of molecular attraction, oscillator frequency change, anharmonicity, 3-dimensionality and quasiclassical motion have been taken into account in the approximation. The analytical expressions presented have been normalized on experimental data of VT-relaxation times in N2 and O2 to obtain the steric factors and the extent of repulsive exchange potentials in collisions N2–N2 and O2–O2. The approach was applied to calculate the rate coefficients of vibrational-vibrational energy transfer in the collisions N2–N2, O2–O2 and N2–O2. It is shown that there is good agreement between our calculations and experimental data for all cases of energy transfer considered.  相似文献   

7.
This paper discusses the formation mechanisms of infrared radiation in the mesosphere and lower thermosphere (MLT), the energetic effects of the radiative absorption/emission processes, and the retrieval of atmospheric parameters from infrared radiation measurements. In the MLT and above, the vibrational levels of the molecules involved in radiative transitions are not in local thermodynamic equilibrium (LTE) with the surrounding medium, and this then requires specific theoretical treatment. The non-LTE models for CO2, O3, and H2O molecules are presented, and the radiative cooling/heating rates estimated for five typical atmospheric scenarios, from polar winter to polar summer, are shown. An optimization strategy for calculating the cooling/heating rates in general circulation models is proposed, and its accuracy is estimated for CO2. The sensitivity of the atmospheric quantities retrieved from infrared observations made from satellites to the non-LTE model parameters is shown.  相似文献   

8.
Solar geoengineering has been proposed as a potential mechanism to counteract global warming. Here we use the University of Victoria Earth System Model (UVic) to simulate the effect of idealized sunshade geoengineering on the global carbon cycle. We conduct two simulations. The first is the A2 simulation, where the model is driven by prescribed emission scenario based on the SRES A2 CO2 emission pathway. The second is the solar geoengineering simulation in which the model is driven by the A2 CO2 emission scenario combined with sunshade solar geoengineering. In the model, solar geoengineering is represented by a spatially uniform reduction in solar insolation that is implemented at year 2020 to offset CO2-induced global mean surface temperature change. Our results show that solar geoengineering increases global carbon uptake relative to A2, in particular CO2 uptake by the terrestrial biosphere. The increase in land carbon uptake is mainly associated with increased net primary production (NPP) in the tropics in the geoengineering simulation, which prevents excess warming in tropics. By year 2100, solar geoengineering decreases A2-simulated atmospheric CO2 by 110 ppm (12%) and causes a 60% (251 Pg C) increase in land carbon accumulation compared to A2. Solar geoengineering also prevents the reduction in ocean oxygen concentration caused by increased ocean temperatures and decreased ocean ventilation, but reduces global ocean NPP. Our results suggest that to fully access the climate effect of solar geoengineering, the response of the global carbon cycle should be taken into account.  相似文献   

9.
In this work I present the results of a study of the electron cooling rate, the production rates of vibrationally excited O2, and the production frequency of the O2 vibrational quanta arising from the collisions of electrons with O2 molecules as functions of the electron temperature. The electron energy transfer and cooling rates by vibrational excitation of O2 have been calculated and fitted to analytical expressions by use of the revised vibrationally excited O2 cross sections. These new analytical expressions are available to the researcher for quick reference and accurate computer modeling with a minimum of calculations. It is also shown that the currently accepted rate of electron energy loss associated with rotational transitions in O2 must be decreased by a factor of 13.  相似文献   

10.
Theoretical and experimental aspects of the production, transformation, diffusion and loss of N2 in the upper atmosphere are considered. The N2-CO2 near-resonant system in theD andE regions is taken into account. We describe our understanding of the methods necessary to find the vibrational populations of N2 and CO2 (asymmetric mode of CO2). The calculations of the vibrational temperatures in theD, E, andF regions for the mid-latitude ionosphere and an aurora are presented. The connection between the excited species and the 4.26-m radiation intensities is considered. The models for the rate coefficient of the reaction of O+ with N2 and the electron density decrease resulting from N2 in the F region are discussed.  相似文献   

11.
The influence of atmospheric solar radiation absorption on the photodetachment, dissociative photodetachment, and photodissociation rate coefficients (photodestruction rate coefficients) of O?, Cl?, O2 ?, O3 ?, OH?, NO2 ?, NO3 ?, O4 ?, OH?(H2O), CO3 ?, CO4 ?, ONOO?, HCO3 ?, CO3 ?(H2O), NO3 ?(H2O), O2 +(H2O), O4 +, N4 +, NO+(H2O), NO+(H2O)2, H+(H2O) n for n = 2–4, NO+(N2), and NO+(CO2) at D-region altitudes of the ionosphere is studied. A numerical one-dimensional time-dependent neutral atmospheric composition model has been developed to estimate this influence. The model simulations are carried out for the geomagnetically quiet time period of 15 October 1998 at moderate solar activity over the Boulder ozonesonde. If the solar zenith angle is not more than 90° then the strongest influence of atmospheric solar radiation absorption on photodestruction of ions is found for photodissociation of CO4 ? ions when CO3 ? ions are formed. It follows from the calculations that decreases in the photodestruction rate coefficients of ions under consideration caused by this influence are less than 2 % at 70 km altitude and above this altitude if the solar zenith angle does not exceed 90°.  相似文献   

12.
On January 16, 2002, short-term unrest occurred at San Miguel volcano. A gas-and-steamash plume rose a few hundred meters above the summit crater. An anomalous microseismicity pattern, about 75 events between 7:30 and 10:30 hours, was also observed. Continuous monitoring of CO2 efflux on the volcano started on November 24, 2001, in the attempt to provide a multidisciplinary approach for its volcanic surveillance. The background mean of the diffuse CO2 emission is about 16 g m-2 d-1, but a 17- fold increase, up to 270 g m-2 d-1, was detected on January 7, nine days before the January 2002 short-term unrest at San Miguel volcano. These observed anomalous changes on diffuse CO2 degassing could be related to either a sharp increase of CO2 pressure within the volcanic-hydrothermal system or degassing from an uprising fresh gas-rich magma within the shallow plumbing system of the volcano since meteorological fluctuations cannot explain this observed increase of diffuse CO2 emission.  相似文献   

13.
A fully time-dependent mathematical model, SUPIM, of the Earth’s plasmasphere is used in this investigation. The model solves coupled time-dependent equations of continuity, momentum and energy balance for the O+, H+, He+, N+2, O+2, NO+ ions and electrons; in the present study, the geomagnetic field is represented by an axial-centred dipole. Calculation of vibrationally excited nitrogen molecules, which has been incorporated into the model, is presented here. The enhanced model is then used to investigate the behaviour of vibrationally excited nitrogen molecules with F10.7 and solar EUV flux, during summer, winter and equinox conditions. The presence of vibrational nitrogen causes a reduction in the electron content. The diurnal peak in electron content increases linearly up to a certain value of F10.7, and above this value increases at a lesser rate, in agreement with previous observations and modelling work. The value of F10.7 at which this change in gradient occurs is reduced by the presence of vibrational nitrogen. Vibrational nitrogen is most effective at F-region altitudes during summer daytime conditions when a reduction in the electron density is seen. A lesser effect is seen at equinox, and in winter the effect is negligible. The summer reduction in electron density due to vibrational nitrogen therefore reinforces the seasonal anomaly.  相似文献   

14.
This study compares the OV1-10 satellite measurements of the integral airglow intensities at 630 nm in the SAR arc regions observed in the northern and southern hemisphere as a conjugate phenomenon, with the model results obtained using the time-dependent one-dimensional mathematical model of the Earth ionosphere and plasmasphere (the IZMIRAN model) during the geomagnetic storm of the period 15–17 February 1967. The major enhancements to the IZMIRAN model developed in this study are the inclusion of He+ ions (three major ions: O+ H+ and He+ and three ion temperatures), the updated photochemistry and energy balance equations for ions and electrons, the diffusion of NO+ and O+2 ions and O(1D) and the revised electron cooling rates arising from their collisions with unexcited N2, O2 molecules and N2 molecules at the first vibrational level. The updated model includes the option to use the models of the Boltzmann or non-Boltzmann distributions of vibrationally excited molecular nitrogen. Deviations from the Boltzmann distribution for the first five vibrational levels of N2 were calculated. The calculated distribution is highly non-Boltzmann at vibrational levels v > 2 and leads to a decrease in the calculated electron density and integral intensity at 630 nm in the northern and southern hemispheres in comparison with the electron density and integral intensity calculated using the Boltzmann vibrational distribution of N2. It is found that the intensity at 630 nm is very sensitive to the oxygen number densities. Good agreement between the modeled and measured intensities is obtained provided that at all altitudes of the southern hemisphere a reduction of about factor 1.35 in MSIS-86 atomic oxygen densities is included in the IZMIRAN model with the non-Boltzm-ann vibrational distribution of N2. The effect of using of the O(1D) diffusion results in the decrease of 4–6% in the calculated integral intensity of the northern hemisphere and 7–13% in the calculated integral intensity of the southern hemisphere. It is found that the modeled intensities of the southern hemisphere are more sensitive to the assumed values of the rate coefficients of O+(4S) ions with vibrationally excited nitrogen molecules and quenching of O+(2D) by atomic oxygen than the modeled intensities of the northern hemisphere.  相似文献   

15.
Based on the DMSP F6 and F7 satellite observations, the characteristics of precipitating particles in different auroral precipitation regions of the dayside sector have been studied depending on the solar wind plasma density. Under quiet geomagnetic conditions (|AL| < 100 nT and B z > 0), a considerable increase in the fluxes of precipitating ions is observed in the zones of structured auroral oval precipitation (AOP) and soft diffuse precipitation (SDP). A decrease in the mean energy of precipitating ions is observed simultaneously with the flux growth in these regions. The global pattern of variations in the fluxes of precipitating ions, which shows the regions of effective penetration of solar wind particles into the magnetosphere at a change in the solar wind density from 2 to 20 cm?3, has been constructed. The maximal flux variation (ΔJ i = 1.8 · 107 cm?2 s?1, i.e., 3.5% of an increase in the solar wind particle flux) is observed in the SDP region on the dayside of the Earth. The dependence of precipitating ion fluxes in the low-latitude boundary layer (LLBL), dayside polar cusp, and mantle on the solar wind density at positive and negative values of the IMF B z component has been studied. In the cusp region, an increase in the precipitating ion flux is approximately 17% of an increase in the solar wind density. The IMF southward turning does not result in an appreciable increase in the ion precipitation fluxes either in the cusp or in the mantle. This fact can indicate that the reconnection of the geomagnetic field with southward IMF is not the most effective mechanism for penetration of solar wind particles into these regions.  相似文献   

16.
Solar, sky, and aureole radiance data from Kensington, Australia, and Lagos, Nigeria, are analysed. The values of the aerosol optical thickness at Lagos are comparable to measured values elsewhere in the subregion (Abidjan) under light haze. The values at Kensington are close to those of the “background aerosol.” Identical and anomalous values of aerosol optical thickness occurred at 1.67 μm at both stations as less than 15% of the values can be accounted for by aerosols. The high optical depths are therefore explained in terms of absorption, possibly mainly by CO2 (59–65%) and, to a lesser extent, by H2O (20–26%). Following correction for molecular multiple scattering, the aerosol scattering phase function increases substantially at 0.5 μm in Kensington and decreases considerably at 0.76 μm in Lagos when compared to the uncorrected function, confirming the relative fineness of the Kensington aerosol. The Lagos aerosol size distribution for moderately dusty air is reasonably bimodally log-normal with modal radiusr m=0.49 μm (1.36 μm) for the moder≤1 μm (r>1 μm). The Kensington aerosol resembles one withr m=0.05 μm forr<1 μm. There the Born approximation appears appropriate, and the weighted mean square radiusp 2=0.13 μm2. In the near forward direction the aerosol scattering phase funciton for Lagos resembles Deirmendjian’s simulations for a silicate-L haze and, for Kensington, a silicate-H haze.  相似文献   

17.
A model of auroral electron deposition processes has been developed using Monte Carlo techniques to simulate electron transport and energy loss. The computed differential electron flux and pitch angle were compared with in situ auroral observations to provide a check on the accuracy of the model. As part of the energy loss process, a tally was kept of electronic excitation and ionization of the important atomic and molecular states. The optical emission rates from these excited states were computed and compared with auroral observations of (3914 Å), (5577 Å), (7620 Å) and (N2VK). In particular, the roles played by energy transfer from N2(A3+u) and by other processes in the excitation of O(1S) and O2(b1+g) were investigated in detail. It is concluded that the N2(A3+u) mechanism is dominant for the production of OI(5577 Å) in the peak emission region of normal aurora, although the production efficiency is much smaller than the measured laboratory value; above 150 km electron impact on atomic oxygen is dominant. Atomic oxygen densities in the range of 0.75±0.25 MSIS-86 [O] were derived from the optical comparisons for auroral latitudes in mid-winter for various levels of solar and magnetic activity.  相似文献   

18.
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19.
The lidar measurements at Verhnetulomski observatory (68.6°N, 31.8°E) at Kola peninsula detected a considerable increase of stratospheric aerosol concentration after the solar proton event of GLE (ground level event) type on the 16/02/84. This increase was located at precisely the same altitude range where the energetic solar protons lost their energy in the atmosphere. The aerosol layer formed precipitated quickly (1–2 km per day) during 18, 19, and 20 February 1984, and the increase of R(H) (backscattering ratio) at 17 km altitude reached 40% on 20/02/84. We present the model calculation of CN (condensation nuclei) altitude distribution on the basis of an ion-nucleation mechanism, taking into account the experimental energy distribution of incident solar protons. The meteorological situation during the event was also investigated.deceased  相似文献   

20.
The results of rocket and satellite measurements of carbon dioxide emissions at a wavelength of 15 μm in the upper atmosphere have been systematized and analyzed. Analytical expressions describing the dependence of the altitude distribution of 15-μm CO2 emission intensity and its variation in the altitude range from 100 to 130 km on the season, latitude, and solar activity have been obtained.  相似文献   

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