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1.
The observations of the state of the midlatitude ionospheric D region during the March 29, 2006, solar eclipse, based on the measurements of the characteristics of partially reflected HF signals and radio noise at a frequency of f = 2.31 MHz, are considered. It has been established that the characteristic processes continued for 2–4 h and were caused mainly by atmospheric gas cooling, decrease in the ionization rate, and the following decrease in the electron density. An increase in the electron density on average by 200–250% approximately 70–80 min after the eclipse beginning at altitudes of 90–93 km and approximately 240 min after the end of the solar eclipse at altitudes of 81–84 km, which lasted about 3–4 h, has been detected experimentally. This behavior of N is apparently caused by electron precipitation from the magnetosphere into the atmosphere during and after the solar eclipse. Based on this hypothesis, the fluxes of precipitating electrons (about 107–108 m?2s?1) have been estimated using the experimental data.  相似文献   

2.
We present 9 bottom222Rn profiles measured from the western and southern Indian Ocean during the 1977–1978 GEOSECS expedition. These profiles can be grouped into three cypes: one-layer, two-layer, and irregular types. The one-layer profiles with quasi-exponential distributions allow one to estimate the apparent vertical eddy diffusivity,Kv, with a simple model. The two-layer profiles show that there is a benthic boundary layer of the order of 50–100 m in which the excess222Rn distribution shows a vertical gradient much smaller than that of the layer immediately above. Within the boundary layer, the STD potential temperature (θ) and density(σ4) profiles are practically constant, and theKv values are of the order of 1000 cm2/s. The STD profiles for the water column above the boundary layer show gradients of increasing stability, and theKv values are of the order of 100 cm2/s. Modeling of the Rn data in the water column above the boundary layer indicates that there is a transition layer which effectively reduces the penetration of excess Rn from the benthic boundary layer into the upper layer.Sarmiento et al. [10] have shown that the buoyancy gradient or stability is inversely correlated with the apparent vertical eddy diffusivity, and the resulting buoyancy flux is fairly uniform, ranging from 1 to 14 × 10?6 cm2/s3 in the Atlantic and Pacific Oceans. However, Sarmiento et al. [11] show that a much higher buoyancy flux is associated with an intensified flow of the bottom water through a passage. In the Indian Ocean basins, we have found that the buoyancy flux has a comparable range (3–14 × 10?6 cm2/s3), except for a couple of stations where both stability and apparent vertical diffusivity are higher, resulting in a much higher buoyancy flux, probably indicative of rapid bottom water flow.  相似文献   

3.
Vertical eddy diffusivities (Kv's) have been estimated at fourteen widely separated locations from fourteen222Rn profiles and two228Ra profiles measured near the ocean floor as part of the Atlantic and Pacific GEOSECS programs. They show an inverse proportionality to the local buoyancy gradient [(g/?)(??pot/?z)] calculated from hydrographic measurements. The negative of the constant of proportionality is the buoyancy flux [?Kv(g/?)(??pot/?z)] which has a mean of ?4 × 10?6 cm2/sec3. Our results suggest that the buoyancy flux varies very little near the ocean floor. Kv's for the interior of the deep Pacific calculated from the relationship Kv = (4 × 10?6cm2/sec3)/[(g/?)(??pot/?z)] agree well with published estimates. Kv's calculated for the pycnocline are one to two orders of magnitude smaller than upper limits estimated from tritium and7Be distributions.Heat fluxes calculated with the model Kv's obtained from the222Rn profiles average 31 μcal cm?2 sec?1 in the Atlantic Ocean and 8 μcal cm?2 sec?1 in the Pacific Ocean.  相似文献   

4.
The dislocation density and the subgrain size of olivine in peridotite xenoliths in southwest Japan were investigated in order to draw out the lateral variation of the differential stress in the upper mantle of the island arc. Alkali basaltic and andesitic dykes including peridotite xenoliths of Dogo, Kikuma, and Shingu are situated about 200 km behind the Nankai Trough, and those of Oki-Dogo and Takashima located at the portions 400–500 km apart from the trough. The mean dislocation densities of olivine are 2 × 106 cm?2 for Oki-Dogo, 8 × 106 cm?2 for Takashima, 1 × 107 cm?2 for Hamada, 5 × 107 cm?2 for Aratoyama, 4 × 107 cm?2 for Kikuma, 3 × 107 cm?2 for Dogo, and 5 × 106 cm?2 for Shingu peridotites.It is concluded that the differential stress is high in the uppermost mantle beneath the island arc and low in the back-arc and the mantle wedge behind the plate boundary. The lateral variation of stress may be due to the diapiric upwelling of upper mantle materials under the island arc. The size of the diapir is suggested to be 200 km in width and 60–150 km in depth.  相似文献   

5.
We present the distribution of226Ra in eight vertical profiles from the eastern Pacific. The profiles are located along a meridional trend near 125°W, from 43°S to 29°N. Surface226Ra concentrations are about 7 dpm/100 kg, except for the two stations south of 30°S where the higher values are due to the Antarctic influence. Deep waters show a distinctive south-to-north increase in the226Ra content, from about 26 to 41 dpm/100 kg near the bottom. Unlike in the Atlantic and Antarctic Oceans, the effect of226Ra injection from bottom sediments is clearly discernible in the area. The presence of this primary226Ra can be traced up to at least 1–1.5 km above the ocean floor, making this part of the sea bed among the strongest source regions for the oceanic226Ra. Numerical solutions of a two-dimensional vertical advection-diffusion model applied to the deep (1.2–4 km)226Ra data give the following set of best fits: upwelling velocity(Vz) = 3.5m/yr, vertical eddy diffusivity(Kz) = 0.6cm2/s, horizontal (north-south) eddy diffusivity(Ky) = 1 × 107cm2/s, and water-column regeneration flux of226Ra(J) = 3.3 × 10?5dpmkg?1yr?1 as an upper limit. These parametric values are in general agreement with one-dimensional (vertical) model fits for the Ra-Ba system. However, consideration of226Ra balance leads us to suspect the appropriateness of describing the vertical exchange processes in the eastern Pacific with constantVz and Kz. If future modeling is attempted, it may be preferable to treat the area as a diffusion-dominant mixing regime with depth-dependent diffusivities.  相似文献   

6.
This study examined the UV/H2O2 decolorization efficiency under high UV photon flux (intensity normalized by photon energy) irradiation; the incident UV was ranging from 3.13 × 10?8 to 3.13 × 10?6 einstein cm?2 s?1. The experimental results showed that complete decolorization of 20 mg L?1 methylene blue (MB) can be achieved within 5 s and 99% decolorization of 1000 mg L?1 MB can be achieved in 180 s under the best condition of high UV intensity UV/H2O2 process. To the best of our knowledge, UV/H2O2 decolorization process in such a short time has not been reported. The electrical energy per order of the process was 16.21 kWh m?3 order?1 and it is relatively economical compared with other advanced oxidation processes. The kinetics of decolorization follows pseudo‐first order. There is a linear relationship between rate constant and UV intensity, which indicates that increasing UV intensity does not cause decline in light utilization efficiency. The experiment related to initial substrate concentration shows decolorization rate of different substrate concentration (20–1000 mg L?1) are closed to each other. Besides, optimal H2O2 concentration, comparative study with low photon flux light, decolorization of other types of dyes and TOC removal were also studied.  相似文献   

7.
Seven vertical profiles of226Ra have been measured along an east-west traverse at about 30°N from San Diego to northwest of Hawaii. These profiles show that there is a distinct core of Ra maximum spreading westward as a tongue in the northeast Pacific deep water. This core starts in the east with 21.1 Ra units (1Ra unit= 10?14g/kg) at 3.9 km depth at about 130°W, and deepens westward to 4.1 km with its Ra reduced to 18.3 units at 150°W. A similar core with some uncertainty due to possible sampling errors extends westward near the bottom at 5.2 km depth from 19.4 Ra units at 150°W to 15.9 units at about 180° longitude. In addition, these profiles appear to be correlated with each other in structure above the cores of Ra maximum. These cores indicate that the Ra input depends locally on the type and composition of sediments and so the flux varies over the ocean bottom. On the basis of a one-dimensional diffusion-decay model, a horizontal diffusion coefficient of 106 cm2/sec has been computed along these cores. Although this value appears to be slightly lower, it is not inconsistent with those derived from other physical methods.  相似文献   

8.
The relative rate constants of O2(b1Σ g + , v= 1–4) production at an inelastic interaction between electronically excited N(2D) atoms and O2(X3Σ g ? , v = 0) oxygen molecules have been calculated. It was shown that an increase in equilibrium distances between oxygen atoms in NO2 quasi-molecule, produced during the interaction, substantially increases the calculated relative production rates of O2(b1Σ g + , v > 1). The obtained coefficients are used to calculate the O2(b1Σ g + , v= 1–4) relative populations at 110 km (T = 250 K) and 150 km (T = 500 K) altitudes of the polar ionosphere. The calculated populations have been compared with the results of the published measurements of the Atmospheric system band luminosity intensities, and satisfactory agreement has been obtained for low altitudes.  相似文献   

9.
Unique measurements by a solar submillimeter radio telescope (SST) have been carried out in the sub-THz radiation at 212 and 405 THz over the past decade. The spectrum of RF radiation in this region increased with frequency for the three flares of November 2 and 4, 2003, and December 6, 2006, and the flux value reached 5 × 103?2 × 104 sfu at 405 GHz (Kaufman et al., 2009). In this work, we consider a set of nonlinear equations for an accelerated electrons beam and the Langmuir wave energy density. The distribution functions of the accelerated electron beam and wave energy density are calculated taking into account Coulomb collisions, electron scattering by waves, and wave scattering by plasma ions. In addition, the source of accelerated particles and the heat level of the Langmuir turbulence are specified. The beam and plasma parameters are chosen based on the aims of a problem. The plasma concentration varies from n = 1013 to 1015 cm?3, the electron plasma frequency f p = (3 × 1010?3 × 1011) Hz in this case. The ratio of plasma and beam concentrations, sufficient to explain the value of the radio flux at a frequency of 300 GHz, is n b/n = 10?3. The Langmuir turbulence is excited due to the instability of the accelerated electron beam with an initial distribution function of the ??bump-in-tail?? type. Then, the parameters of radiowaves are calculated in the sub-THz range under the assumption of coalescence of two plasma waves. The calculation results show that a sub-THz radio flux can be obtained under the condition of injection of accelerated electrons. The fine time structure of radio flux observed is easily simulated based on this statement by the pulsed time structure of electron beams and their dynamics in overdense plasma. X-ray and gamma radiation was recorded during the events under study. Hard X-ray radiation is bremsstrahlung radiation from accelerated electron beams.  相似文献   

10.
Quasi-periodic variations in the power of incoherent scattered signals, caused by wave disturbances of the electron concentration in the ionosphere, are analyzed for the day of a partial solar eclipse and for a background day. The windowed and adaptive Fourier transforms and the wavelet transform are used for spectral analysis. The spectral parameters of the wave disturbances at altitudes of 100–500 km in the 10–120 min period range differed significantly on the day of the solar eclipse and on the background day. Variations in the spectrum began near the onset of the phase of maximum disk occultation and continued no less than 2 h. The amplitude of time variations N was 2 × 109–4 × 1010 m?3, and the relative amplitude was 0.10–0.15. Wave disturbances have been compared for five solar eclipses; the comparison shows a noticeable variation in the spectrum of the wave disturbances during these events.  相似文献   

11.
The fundamental mode Love and Rayleigh waves generated by ten earthquakes and recorded across the Tibet Plateau, at QUE, LAH, NDI, NIL, KBL, SHL, CHG, SNG and HKG are analysed. Love- and Rayleigh-wave attenuation coefficients are obtained at time periods of 5–120 s using the spectral amplitudes of these waves for 23 different paths. Love wave attenuation coefficient varies from 0.0021 km?1, at a period of 10 s, to 0.0002 km?1 at a period of 90 s, attaining two maxima at time periods of 10 and 115 s, and two minima at time periods of 25 and 90 s. The Rayleigh-wave attenuation coefficient also shows a similar trend. The very low value for the dissipation factor, Qβ, obtained in this study suggests high dissipation across the Tibetan paths. Backus-Gilbert inversion theory is applied to these surface wave attenuation data to obtain average Qβ?1 models for the crust and uppermost mantle beneath the Tibetan Plateau. Independent inversion of Love- and Rayleigh-wave attenuation data shows very high attenuation at a depth of ～50–120 km (Qβ ? 10). The simultaneous inversion of the Love and Rayleigh wave data yields a model which includes alternating regions of high and low Qβ?1 values. This model also shows a zone of high attenuating material at a depth of ～40–120 km. The very high inferred attenuation at a depth of ～40–120 km supports the hypothesis that the Tibetan Plateau was formed by horizontal compression, and that thickening occurred after the collision of the Indian and Eurasian plates.  相似文献   

12.
Abundant fluid inclusions in olivine of dunite xenoliths (～1–3 cm) in basalt dredged from the young Loihi Seamount, 30 km southeast of Hawaii, are evidence for three coexisting immiscible fluid phases—silicate melt (now glass), sulfide melt (now solid), and dense supercritical CO2 (now liquid + gas)—during growth and later fracturing of some of these olivine crystals. Some olivine xenocrysts, probably from disaggregation of xenoliths, contain similar inclusions.Most of the inclusions (2–10 μm) are on secondary planes, trapped during healing of fractures after the original crystal growth. Some such planes end abruptly within single crystals and are termed pseudosecondary, because they formed during the growth of the host olivine crystals. The “vapor” bubble in a few large (20–60 μm), isolated, and hence primary, silicate melt inclusions is too large to be the result of simple differential shrinkage. Under correct viewing conditions, these bubbles are seen to consist of CO2 liquid and gas, with an aggregate ? = ～ 0.5–0.75 g cm?3, and represent trapped globules of dense supercritical CO2 (i.e., incipient “vesiculation” at depth). Some spinel crystals enclosed within olivine have attached CO2 blebs. Spherical sulfide blebs having widely variable volume ratios to CO2 and silicate glass are found in both primary and pseudosecondary inclusions, demonstrating that an immiscible sulfide melt was also present.Assuming olivine growth at ～ 1200°C and hydrostatic pressure from a liquid lava column, extrapolation of CO2P-V-T data indicates that the primary inclusions were trapped at ～ 220–470 MPa (2200–4700 bars), or ～ 8–17 km depth in basalt magma of ? = 2.7 g cm?3. Because the temperature cannot change much during the rise to eruption, the range of CO2 densities reveals the change in pressure from that during original olivine growth to later deformation and rise to eruption on the sea floor. The presence of numerous decrepitated inclusions indicates that the inclusion sample studied is biased by the loss of higher-density inclusions and suggests that some part of these olivine xenoliths formed at greater depths.  相似文献   

13.
We analyzed meteor decay times measured by a VHF radar at King Sejong Station by classifying strong and weak meteors according to their estimated electron line densities. The height profiles of monthly averaged decay times show a peak whose altitude varies with season at altitudes of 80?85 km. The higher peak during summer is consistent with colder temperatures that cause faster chemical reactions of electron removal. By adopting temperature dependent empirical recombination rates from rocket experiments and meteor electron densities of 2×105?2×106 cm?3 in a decay time model, we are able to account for decreasing decay times below the peak for all seasons without invoking meteor electron removal by hypothetical icy particles.  相似文献   

14.
Average shear-velocity models for the upper mantle have been derived by controlled Monte Carlo inversion of global average Rayleigh wave group velocity (GAGV) data for periods between 50 and 300 seconds. GAGV data have been corrected for attenuative dispersion using a method based on the theory of Liu, Anderson and Kanamori. Two types of model bounds have been used with one- or two-layer low-velocity zones beginning at depths of 70 and 100 km. All models fitting GAGV data within one standard deviation have low-velocity zones in the 100–200 km depth range. Models with low-velocity zones beginning at 70 km, as well as 100 km, fit GAGV data within one standard deviation, so the average thickness of the lithosphere (taken as the depth to the top of the low-velocity zone) cannot be determined with precision.Global average models for shear-wave attenuation (Q?1β) have been derived from global average Rayleigh wave attenuation coefficients for periods between 50 and 300 s and average shear-velocity models. Zones of high Q?1β coincide with the low-velocity zones of all shear-velocity models, however, models with low-velocity zones beginning at a depth of 70 km have the highest-attenuation layer in the lower half of the low-velocity zone. Resolution kernels for these attenuation models show that parameters for layers shallower than the lower part of the low-velocity-high-attenuation zone are strongly coupled but are distinct from the lower part of this zone. This suggests that the deeper part of the low-velocity-high-attenuation zone is the most mobile part of the zone or that on the average, the top of the zone is deeper than 70 km.The average Qβ of the lithosphere, low-velocity zone, and sub-low-velocity layer (asthenosphere) are approximately 200, 85–110 and 170–200, respectively.  相似文献   

15.
An improved resonant fluorescence instrument for measuring atomic oxygen concentration was developed to avoid the Doppler effect and the aerodynamic shock effect due to the supersonic motion of a rocket. The shock effect is reduced by adopting a sharp wedge-shaped housing and by scanning of the detector field of view to change the distance between the scattering volume and the surface of the housing. The scanning enables us to determine absolute values of atomic oxygen concentration from relative variation of the scattered light signal due to the self-absorption. The instrument was calibrated in the laboratory, and the numerical simulation reproduced the calibration result. Using the instrument, the altitude profile of atomic oxygen concentration was observed by a rocket experiment at Uchinoura (31°N) on 28 January 1992. The data obtained from the rocket experiment were not perfectly free from the shock effect, but errors due to the effect were reduced by the data analysis procedure. The observed maximum concentration was 3.8× 1011 cm−3 at altitudes around 94 km. The systematic error is estimated to be less than ±0.7×1011 cm−3 and the relative random error is less than±0.07× 1011 cm−3at the same altitudes. The altitude profile of the OI 557.7-nm airglow was also observed in the same rocket experiment. The maximum volume emission rate was found to be 150 photons cm−3 s−1 at 94 km. The observed altitude profiles are compared with the MSIS model and other in situ observations.  相似文献   

16.
It has been tried to develop the method for estimating the ratio of the densities of oxygen atoms (n 1) and nitrogen molecules (n 3) as well as n 1/n 2 and n 2/n 3 (where n 2 is the density of oxygen molecules) at the reference level of the upper thermosphere (120 km), using the data on electron density at altitudes of 120–200 km. This approach is based on an analysis of the semiempirical model (SEM) equation describing the dependence of electron density (N) on the characteristics of the thermospheric neutral gas. The series of the SEM versions [Shchepkin et al., 1997, 2004] was previously developed by the authors of this work. The estimates were performed based on the regular N measurements with the help of a digital ionosonde at ISZF SO RAN, Irkutsk, in 2003–2005.  相似文献   

17.
We apply a measurement technique that utilizes thermal video of vapor-dominated volcanic plumes to estimate the H2O gas flux at three degassing volcanoes. Results are compared with H2O flux measurements obtained using other methods to verify the thermal camera-derived values. Our estimation of the H2O emission rate is based on the mass and energy conservation equations. H2O flux is quantified by extracting the temperature and width of the gas plume from the thermal images, calculating the transit velocity of the gas plume from the thermal video, and combining these results with atmospheric parameters measured on-site. These data are then input into the equations for conservation of mass and energy. Selected volcanoes for this study were Villarrica in Chile, Stromboli in Italy, and Santa Ana in El Salvador. H2O fluxes estimated from the thermal imagery were 38–250?kg?s?1 at Villarrica, 4.5–14?kg?s?1 for Stromboli’s Central Crater, and 168–219?kg?s?1 at Santa Ana. These compare with H2O flux values estimated by other methods of 73–220, 3–70 and 266?kg?s?1, at the three volcanoes, respectively. The good agreement between thermal image-derived results and those estimated by other methods seem to validate this method.  相似文献   

18.
We report observations of seasonal and local time variation of the averaged electron and iron concentrations, as well as simultaneous measurements of the two species, above the Arecibo Observatory (18.35°N, 66.75°N), Puerto Rico. The average Fe profile between 21:00 and 24:00 LT has a single peak at about 85 km with the exception of the summer when an additional peak exists at about 95 km. The higher Fe peak in the summer is correlated with higher electron concentrations in this season. The three nights of simultaneous measurements of electron and iron concentrations show that narrow layers of Fe and electrons are well correlated. Comparison of the climatological and simultaneous Fe and electron data suggests that recombination of Fe+ plays an important role in determining the Fe profile in the upper part of the Fe layer. Above 93 km, the Fe concentration appears to increase after sunset if the electron concentration exceeds about 4000 electrons cm−3. The average rate of Fe production is about 0.1 atom cm−3 s−1 for all seasons at 100 km in the early evening hours. A chemical model reveals that the concentration of Fe+ must be 50–80% of the total ionization over Arecibo for typical equinox conditions to explain the observed rate of Fe production. These high relative Fe+ concentrations are consistent with in situ observations that Fe+ is usually the dominant ion in sporadic E layers in the nighttime lower E region. This suggests that the source of Fe+ is provided by sporadic E layers descending over Arecibo after sunset. The Fe density between 80 and 85 km decreases during the night, for all seasons. This is attributed to the formation of stable molecular Fe species, such as FeOH, due to the increase in O3 and decrease in atomic O and H during the night at these altitudes.  相似文献   

19.
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   

20.
It is convenient to use the semi-empirical model (SEM), developed by the authors earlier and describing the relation of the electron density at heights of the middle ionosphere (120–200 km) to the parameters of the thermosphere and the integral flux of the ionizing solar radiation, to estimate the gas composition characteristics using the data of ionospheric measurements [Shchepkin et al., 2008]. The ratios of the concentrations of oxygen atoms and nitrogen molecules to those of oxygen molecules and atoms at a height of 120 km are compared using two SEM versions. The first version is based on the usage of the coefficients obtained from the measurements of N(h) profiles at Moscow observatory. The electron densities at heights of 120–200 km, obtained at the Institute of Solar-Terrestrial Physics in 2003–2006 using the digisonde, were the experimental data for the second version.  相似文献   

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