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1.
Height distribution of the stratospheric aerosol extinction coefficient was measured in the altitude range 10 to 20 km by a balloon-borne multi-color sunphotometer in May 1978. It is demonstrated that detailed structures of the distribution of stratospheric aerosol can be remotely measured by the solar occultation method as well as by lidar andin situ particle counter observations. In the aerosol layer appearing at 18 km altitude the extinction coefficient at 800–1000 nm wavelength reached to 3×10–7 m–1, which was reasonable compared with lidar observations. Wavelength dependence of the aerosol optical depth was crudely estimated to be proportional to
–1.5. 相似文献
2.
《Journal of Atmospheric and Solar》1999,61(10):775-788
Measurements of electron temperature made by the thermal electron energy distribution (TED) instrument on board the EXOS-D (Akebono) satellite have been analysed. From the data taken between 1989 and 1995, averaged daytime and nighttime temperature profiles for different geophysical conditions have been produced. These profiles represent the averaged thermal electron temperature between 1000 and 8000 km altitude for conditions of high (F10.7>150) and low (F10.7<120) solar activity. Results indicate that increased solar activity has a marked effect on the electron temperature. At 8000 km altitude, the typical low-latitude daytime electron temperature is around 8000 K. The nighttime electron temperature at 8000 km is around 4000 K. The averaged daytime difference between high and low solar activity conditions is around 1000 K at altitudes above 2500 km. Between 1000 and 2000 km altitude this situation is reversed, and the electron temperature is comparatively higher during periods of low solar activity during both day and night. Composition changes in the region are proposed as a mechanism for this reversal. In addition, there is evidence of an asymmetry in thermal electron temperature between the northern and southern hemispheres. The averaged electron temperature is found to be comparatively higher in the northern hemisphere during the daytime and comparatively higher in the southern hemisphere during the nighttime. This difference between hemispheres is particularly evident during the nighttime, and during the rapid heating and cooling periods around sunrise and sunset. Possible reasons for the asymmetry are discussed. Profiles are also presented for conditions of high (Ap>30) and low (Ap<20) magnetic activity. Analysis has confirmed that geomagnetic activity has little effect on electron temperature below L=2.2. 相似文献
3.
The HOBr molecule is a potential reservoir of Br compounds in the atmosphere. In this work, the UV-visible spectrum of HOBr was measured over the range 242–400 nm. Its absorption consists of two maxima at 280 nm (max=2.7±0.4×10-19 cm2 molecules−1) and 355 nm (max=7.0±1.1×10-20 cm2 molecules−1), respectively, where the error is ±1. Atmospheric photolysis lifetime calculations for HOBr in the lower stratosphere have been made using the PHOTOGT model. The results show a strong dependence on the solar zenith angle (SZA) implying a longer lifetime at high latitudes and a relatively short lifetime at low latitudes for example 714 s (albedo of 25%, SZA of 20° and an altitude of 17 km), and 3226 s (albedo of 25%, SZA of 88° and an altitude of 17 km). The UV-visible absorption spectrum of Br2O, which is an intermediate in the preparation, used in this study and is together with H2O in equilibrium with HOBr, was measured from 205 to 450 nm. The spectrum shows a maximum at 315 nm (max=2.3±0.3×10-18 cm2 molecules−1) with a shoulder at 355 nm. From the results of the atmospheric lifetime calculations for Br2O, it is clear that this molecule has a short stratospheric lifetime and is not likely to have a large daytime concentration, for example, 20 s (albedo of 25%, SZA of 20° and an altitude of 17 km), and 83 s (albedo and 25%, SZA of 88° and an altitude of 17 km). 相似文献
4.
An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR) (14°N, 80°E, dip latitude 5.5°N) to study electron density and electric field irregularities during spread F. The rocket was launched at 2130 local time (LT) and it attained an apogee of 348 km. Results of electron density fluctuations are presented here. Two extremely sharp layers of very high electron density were observed at 105 and 130 km. The electron density increase in these layers was by a factor of 50 in a vertical extent of 10 km. Large depletions in electron density were observed around 175 and 238 km. Both sharp layers as well as depletions were observed also during the descent. The presence of sharp layers and depletions during the ascent and the descent of the rocket as well as an order of magnitude less electron density, in 150/300 km region during the descent, indicate the presence of strong large-scale horizontal gradients in the electron density. Some of the valley region irregularities (165/178 km), in the intermediate scale size range, observed during this flight, show spectral peaks at 2 km and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of new type. The growth rate of intermediate scale size irregularities, produced through generalized Rayleigh Taylor instability, was calculated for the 200/330 km altitude, using observed values of electron density gradients and an assumed vertically downward wind of 20 ms–1. These growth rate calculations suggest that the observed irregularities could be produced by the gradient drift instability. 相似文献
5.
The earthquake was modeled using regional broad-band stations in Greece (epicentral distances up to 340 km). Inversion of the amplitude spectra of complete waveforms (0.05–0.08 Hz), later confirmed by the forward waveform modeling, provided strike = 150°, dip = 70°, rake = 10°, scalar moment M
o = 4.1e18 Nm, and depth of 8 km. As the aftershock distribution had the same strike, the earthquake was interpreted as a left-lateral strike slip. The fault length was estimated by combining observed mainshock spectra and synthetic spectra of a weak event, representing impulse response of the medium. This gave the fault length estimate of 16 to 24 km. Similar results were obtained by means of a true M
w = 5 aftershock. The waveform modeling (0.05–0.20 Hz) was performed for the 20 × 10 km finite-extent fault, with a homogenous slip of 0.63 m. It showed that the rupture propagation along the 150° strike was predominantly unilateral, from NW to SE. 相似文献
6.
An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR) (14°N, 80°E, dip 14°N) along with other experiments, as a part of equatorial spread F (ESF) campaign, to study the nature of irregularities in electric field and electron density. The rocket was launched at 2130 local time (LT) and it attained an apogee of 348 km. Results of vertical and horizontal electric field fluctuations are presented here. Scale sizes of electric field fluctuations were measured in the vertical direction only. Strong ESF irregularities were observed in three regions, viz., 160/190 km, 210/257 km and 290/330 km. Some of the valley region vertical electric field irregularities (at 165 km and 168 km), in the intermediate-scale size range, observed during this flight, show spectral peak at kilometer scales and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of a new type. Scale sizes of vertical electric field fluctuations showed a decrease with increasing altitude. The most prominent scales were of the order of a few kilometers around 170 km and a few hundred meters around 310 km. Spectra of intermediate-scale vertical electric field fluctuations below the base of the F region (210/257 km) showed a tendency to become slightly flatter (spectral index n = –2.1 ± 0.7) as compared to the valley region (n = –3.6 ± 0.8) and the region below the F peak (n = –2.8 ± 0.5). Correlation analysis of the electron density and vertical electric field fluctuations suggests the presence of a sheared flow of current in 160/330 km region. 相似文献
7.
The relative contributions of quasi-periodic oscillations from 2 to 35 days to the variability of foF2 at middle northern latitudes between 42°N and 60°N are investigated. The foF2 hourly data for the whole solar cycle 21 (1976–1986) for four European ionospheric stations Rome (41.9°N, 12.5°E), Poitiers (46.5°N, 0.3°E), Kaliningrad (54.7°N, 20.6°E) and Uppsala (59.8°N, 17.6°E) are used for analysis. The relative contributions of different periodic bands due to planetary wave activity and solar flux variations are evaluated by integrated percent contributions of spectral energy for these bands. The observations suggest that a clearly expressed seasonal variation of percent contributions exists with maximum at summer solstice and minimum at winter solstice for all periodic bands. The contributions for summer increase when the latitude increases. The contributions are modulated by the solar cycle and simultaneously influenced by the long-term geomagnetic activity variations. The greater percentage of spectral energy between 2 to 35 days is contributed by the periodic bands related to the middle atmosphere planetary wave activity. 相似文献
8.
A decrease of the direct solar radiation at the Earths surface and associated variations of the altitudinal temperature profile observed during Solar Proton Events (SPE) discussed by Pudovkin and Babushkina, 1992b, Pudovkin and Veretenenko, 1994 are believed to be caused by the appearance of a layer which partially reflects solar radiation (by up to 10%) at an altitude of about 9 km. This layer is associated with the cirrus cloud that can be nucleated by Solar Cosmic Ray (SCR) particles (see Tinsley and Deen, 1991; Tinsley and Heelis, 1993). The calculated variations of the altitudinal profile of the air temperature in the high latitude atmosphere (Sodankyla, Finland, φ ≈ 67° N) after the SPE, caused by the appearance of this layer, are in good agreement with experimental data.The variations of the temperature profile (|ΔT| ? 2–3 K at z < 10 km) in the high latitude atmosphere during the SPE may produce a time variation of the meridional pressure profile, which in turn might cause a change of the zonal circulation. The expected changes of pressure at the Earths surface, the heights of constant pressure levels and the zonal circulation are shown to be similar to those observed, but which are smaller in magnitude. These quantitative differences can be associated with the oversimplification of the atmospheric model that we used. 相似文献
9.
Previous work has shown the importance of the diffuse solar field in the photochemistry of atmospheric active species, the solar zenith angle being an effective parameter. In view of the diurnal and seasonal variability of this single quantity, in this paper estimates are presented of the daily-integrated values of the photodissociation coefficient of ozone throughout the year, for a purely molecular atmosphere in the absence of scattering and when the effects of molecular scattering are included, and for an absorbing-scattering turbid atmosphere characterized by two different aerosol loads. Also, different values of the ground albedo have been taken into account.Results are shown for a latitude of 45oN. The seasonal dependence is strong at altitudes below 20 km and less marked above 20 km. For an albedoA=0.3, the inclusion of molecular scattering increases the daily-integrated photodissociation coefficients approximately by 20% and 40% at 15 km and by 15% and 22% at 30 km, at the winter and summer solstice respectively. The presence of a heavy aerosol load modifies these results by a further factor which is approximately –5% and 10% at 15 km at the winter and summer solstice respectively, and is approximately constant at 8% throughout the year at 30 km. 相似文献
10.
Rocket-borne ultraviolet photometers operating at =0.31 m have been used at Thumba (8°33N, 76°52E) to make measurements of atmospheric scattering at tropospheric and lower stratospheric altitudes. Measurements could be made of the amplitude of the scattered fluxes and the angular distribution up to an altitude of about 24 km on three rocket flights conducted as part of the 16 February 1980 solar eclipse campaign. These measurements have been used to study the size distribution as well as the number densities of aerosols in the troposphere and lower stratosphere over Thumba. 相似文献
11.
The seasonal variation of gravity wave activity at altitudes around 95 km is investigated using digital measurements of low-frequency nighttime radiowave absorption at Prhonice (50°N, 15°E) between 1989 and 1993. The analysis of 5 years of data allows two conclusions to be drawn: (1) under high solar activity conditions, there is no clearly detectable seasonal variation of gravity wave activity; (2) under medium solar activity conditions (1992, 1993), there is a tendency to a pronounced summer maximum. 相似文献
12.
《Journal of Atmospheric and Solar》2007,69(13):1587-1598
In this paper, we investigate the solar flare effects of the ionosphere at middle latitude with a one-dimensional ionosphere theoretical model. The measurements of solar irradiance from the SOHO/Solar EUV Monitor (SEM) and GOES satellites have been used to construct a simple time-dependent solar flare spectrum model, which serves as the irradiance spectrum during solar flares. The model calculations show that the ionospheric responses to solar flares are largely related to the solar zenith angle. During the daytime most of the relative increases in electron density occur at an altitude lower than 300 km, with a peak at about 115 km, whereas around sunrise and sunset the strongest ionospheric responses occur at much higher altitudes (e.g. 210 km for a summer flare). The ionospheric responses to flares in equinox and winter show an obvious asymmetry to local midday with a relative increase in total electron content (TEC) in the morning larger than that in the afternoon. The flare-induced TEC enhancement increases slowly around sunrise and reaches a peak at about 60 min after the flare onset. 相似文献
13.
E. V. Vashenyuk Yu. V. Balabin B. B. Gvozdevsky L. I. Shchur 《Geomagnetism and Aeronomy》2008,48(2):149-153
The characteristics of relativistic solar protons have been obtained using the methods of optimization based on the data of ground detectors of cosmic rays during the event of December 13, 2006, which occurred under the conditions of solar activity minimum. The dynamics of relativistic solar protons during the event has been studied. It has been indicated that two populations (components) of particles exist: prompt and delayed (slow). The prompt component with a hard energy spectrum and strong anisotropy manifested itself as a pulse-shaped enhancement at Apatity and Oulu stations, which received particles with small pitch-angles. The delayed component had a wider pitch-angle distribution, as a result of which an enhancement was moderate at Barentsburg station and at most neutron monitors of the worldwide network. The energy spectra obtained from the ground-based observations are in good agreement with the direct measurements of solar protons on balloons and spacecraft. 相似文献
14.
J. Zahradník M. Antonini G. Grünthal J. Janský D. Procházková E. Schmedes A. Špičak J. Zedník 《Pure and Applied Geophysics》1990,133(1):53-71
The main shock of the West-Bohemian earthquake swarm, Czechoslovakia, (magnitudem=4.5, depthh=10 km) exhibits an irregular areal distribution of macroseismic intensities 6° to 7° MSK-64. Four lobes of the 6° isoseismal are found and the maximum observed intensity is located at a distance of 8 km from the instrumentally determined epicentre. This distribution can be explained by the energy flux of the directS wave generated by a circular source, the hypocentral location and focal mechanism of which are taken from independent instrumental studies. The theoretical intensity, which is assumed to be logarithmically proportional to the integrated squared ground-motion velocity (i.e.,I=const+log v
2
(t)dt), fits the observed intensity with an overall root-mean-square error less than 0.5°. It is important that the present intensity data can also be equally well explained by the isotropic source. The fit was attained by means of a horizontally layered model though large fault zones and an extended sedimentary basin suggest a significant lateral heterogeneity of the epicentral region. The results encourage a broader application of the simple modelling technique used. 相似文献
15.
A. I. Efimov N. A. Armand L. A. Lukanina L. N. Samoznaev I. V. Chashei M. K. Bird 《Geomagnetism and Aeronomy》2009,49(8):1165-1169
The two-position radio sounding of the solar wind by the Galileo and Cassini spacecraft has been first performed. These spacecraft
followed the Sun from east to west from May 12 to 24, 2000 and sounded the regions spaced in radial directions by several
millions of kilometers. Stable correlation has been revealed between fluctuation effects detected in spatially spaced radio-sounding
paths of disturbed plasma structures of the coronal mass ejection (CME) type. The radio effects have been found to correlate
also with the data on the solar wind density near the Earth orbit. It has been shown that the two-position radio-sounding
method together with the data on solar radiation in the X-ray and optic ranges and with the results of local plasma measurements
provides information on the structure and velocity of the propagation of CMEs from the photosphere to the Earth orbit. In
the most powerful event recorded on May 13, 2000, the CME velocity at the heliocentric distances of about 15R
⊙ (R
⊙ is the solar radius) reached 1200 km/s. At (15–25) R
⊙, the velocity was about 1300 km/s. At distances larger than 25R
⊙, disturbance was decelerated from 1300 to 450 km/s near the Earth orbit. 相似文献
16.
17.
E. V. Vashenyuk Yu. V. Balabin B. B. Gvozdevskii S. N. Karpov 《Geomagnetism and Aeronomy》2006,46(4):424-429
Using the optimization methods, the characteristics of relativistic solar protons (RSPs) have been obtained from the data of ground-based cosmic ray detectors in the event of January 20, 2005, which was the largest event in the last 50 years since the event of February 23, 1956. The RSP dynamics during the event has been studied. The existence of two populations (components) of particles, fast and delayed (slow) has been shown. The fast component with a hard exponential energy spectrum and strong anisotropy was shown as a giant pulselike enhancement at several southern polar stations. The delayed component had a power-law energy spectrum and a wider pitch-angle distribution, which caused the enhancement effect at the majority of stations at the global network. 相似文献
18.
L. V. Tverskaya S. V. Balashov N. N. Vedenkin V. V. Ivanov T. A. Ivanova D. S. Karpenko S. G. Kochura I. A. Maksimov N. N. Pavlov I. A. Rubinstein M. V. Tel’tsov D. A. Trofimchuk V. I. Tulupov V. V. Khartov 《Geomagnetism and Aeronomy》2008,48(6):719-726
Increases in solar protons and variations in the electron and proton fluxes from the outer radiation belt are studied based on the GLONASS satellite measurements (the circular orbit at an altitude of ～20000 km with an inclination of ～65°) performed in December 2006. Indications in the channels, registered protons with energies of Ep = 3–70 MeV and electrons with energies of Ee > 0.04 and >0.8 MeV, are analyzed. The data on electrons with Ee = 0.8–1.2 MeV, measured on the Express-A3 geostationary satellite, are also presented. Before the strong magnetic storm of December 14 (|Dst|max = 146 nT), the maximum of the outer belt electrons with the energy >0.7 MeV was observed at L ～ 4.5. After the storm, the fluxes of these electrons increased by more than an order of magnitude as compared to the prestorm level, and the maximum of a “new” belt shifted to L < 4 (minimal L reached by the GLONASS orbit). Under quiet geomagnetic conditions, solar protons with the energies >3 MeV fill only high-latitude legs of the GLONASS orbit. During the strong magnetic storm of December 15, the boundary of proton penetration into the magnetosphere almost merged with the orbital maximum of the proton radiation belt. 相似文献
19.
Observations of mesospheric winds over a period of four years with the partial reflection radar at Tirunelveli (8.7°N, 77.8°E), India, are presented in this study. The emphasis is on describing seasonal variabilities in mean zonal and meridional winds in the altitude region 70–98 km. The meridional winds exhibit overall transequatorial flow associated with differential heating in the Northern and Southern Hemispheres. At lower altitudes (70–80 km) the mean zonal winds reveal easterly flow during summer and westerly flow during winter, as expected from a circulation driven by solar forcing. In the higher altitude regime (80–98 km) and at all altitudes during equinox periods, the mean zonal flow is subjected to the semi-annual oscillation (SAO). The interannual variability detected in the occurrence of SAO over Tirunelveli has also been observed in the data sets obtained from the recent UARS satellite mission. Harmonic analysis results over a period of two years indicate the presence of long-period oscillations in the mean zonal wind at specific harmonic periods near 240, 150 and 120 days. Results presented in this study are discussed in the context of current understanding of equatorial wave propagation. 相似文献
20.
A statistical analysis of F-region and topside auroral ion upflow events is presented. The study is based on observations from EISCAT Common Programmes (CP) 1 and 2 made between 1984 and 1996, and Common Programme 7 observations taken between 1990 and 1995. The occurrence frequency of ion upflow events (IUEs) is examined over the altitude range 200 to 500 km, using field-aligned observations from CP-1 and CP-2. The study is extended in altitude with vertical measurements from CP-7. Ion upflow events were identified by consideration of both velocity and flux, with threshold values of 100 m s–1 and 1013 m–2 s–1, respectively. The frequency of occurrence of IUEs is seen to increase with increasing altitude. Further analysis of the field-aligned observations reveals that the number and nature of ion upflow events vary diurnally and with season and solar activity. In particular, the diurnal distribution of upflows is strongly dependent on solar cycle. Furthermore, events identified by the velocity selection criterion dominate at solar minimum, whilst events identified by the upward field-aligned flux criterion dominated at solar maximum. The study also provides a quantitative estimate of the proportion of upflows that are associated with enhanced plasma temperature. Between 50 and 60% of upflows are simultaneous with enhanced ion temperature, and approximately 80% of events are associated with either increased F-region ion or electron temperatures. 相似文献