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1.
Vertical profiles of nitric oxide in the altitude range 90 to 105 km are derived from 553 nm nightglow continuum measurements made with the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS). The profiles are derived under the assumption that the continuum emission is due entirely to the NO+O air afterglow reaction. Vertical profiles of the atomic oxygen density, which are required to determine the nitric oxide concentrations, are derived from coordinated WINDII measurements of the atomic oxygen OI 557.7 nm nightglow emission. Data coverage for local solar times ranging from 20 h to 04 h, and latitudes ranging from 42°S to 42°N, is achieved by zonally averaging and binning data obtained on 18 nights during a two-month period extending from mid-November 1992 until mid-January 1993. The derived nitric oxide concentrations are significantly smaller than those obtained from rocket measurements of the airglow continuum but they do compare well with model expectations and nitric oxide densities measured using the resonance fluorescence technique on the Solar Mesosphere Explorer satellite. The near-global coverage of the WINDII observations and the similarities to the nitric oxide global morphology established from other satellite measurements strongly suggests that the NO+O reaction is the major source of the continuum near 553 nm and that there is no compelling reason to invoke additional sources of continuum emission in this immediate spectral region.  相似文献   

2.
In December 1995, a campaign was carried out to study the day-to-day variability in precursor signatures to large-scale ionospheric F-region plasma irregularities, using optical diagnostic techniques, near the magnetic equator in the Brazilian sector. Three instruments were operated simultaneously: (a) an all-sky (180° field of view) imaging system for observing the OI 630 nm nightglow emission at Alcântara (2.5°S, 44.4°W); (b) a digisonde (256-Lowell) at São Luis (2.6°S, 44.2°W); and (c) a multi-channel tilting filter-type zenith photometer for observing the OI 630 nm and mesospheric nightglow emissions at Fortaleza (3.9°S, 38.4°W). During the period December 14–18, 1995 (summer in the southern hemisphere), a good sequence of the OI 630 nm imaging observations on five consecutive nights were obtained, which are presented and discussed in this study. The observing period was geomagnetically quiet to moderate (Kp = 0+ to 5+ Dst = 18 nT to −37 nT). On four nights, out of the five observation nights, the OI 630 nm imaging pictures showed formations of transequatorial north-south aligned intensity depletions, which are the optical signatures of large-scale ionospheric F-region plasma bubbles. However, considerable day-to-day variability in the onset and development of the plasma depleted bands was observed. On one of the nights it appears that the rapid uplifting of the F-layer in the post-sunset period, in conjunction with gravity wave activity at mesospheric heights, resulted in generation of very strong plasma bubble irregularities. One of the nights showed an unusual formation of north-south depleted band in the western sector of the imaging system field of view, but the structure did not show any eastward movement, which is a normal characteristic of plasma bubbles. This type of irregularity structure, which probably can be observed only by wide-angle imaging system, needs more investigations for a better understanding of its behaviour.  相似文献   

3.
The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S) green-line emission in the Earths mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.  相似文献   

4.
A new retrieval method for satellite remote sensing of global sodium during nighttime is proposed. This method uses satellite limb observations of ozone density, neutral temperature, and Na D nightglow volume emission rate to retrieve sodium density. Our calculations show that, in the ideal condition in which there is no measurement noise, the retrieval error in the main region of sodium layer is very small (less than 1%). The retrieval error is mainly determined by the uncertainties in the observations of ozone, temperature and the Na D-line nightglow emission.  相似文献   

5.
Volume emission rate profiles of the O(1D-1S) 5577 Å dayglow measured by the WIND imaging interferometer on the Upper Atmosphere Research Satellite are analyzed to examine the O(1S) excitation mechanisms in the sunlit lower thermosphere and upper mesosphere. The observed emission profiles are compared with theoretical profiles calculated using a model which takes into account all of the known daytime sources of O(1S). These include photoelectron impact on atomic oxygen, dissociative recombination of O+2, photodissociation of molecular oxygen, energy transfer from metastable N2(A3+u) and three body recombination of atomic oxygen. Throughout most of the thermosphere the measured and modelled emission rates are in reasonably good agreement, given the limitations of the model, but in the region below 100 km, where the oxygen atom recombination source is likely to dominate, the measured emission rates are considerably larger than those modelled using the MSIS-90 oxygen atom densities. This discrepancy is discussed in terms of possible inadequacies in the MSIS-90 model atmosphere and/or additional sources of O(1S) at low altitude.  相似文献   

6.
Intercalibration of HRDI and WINDII wind measurements   总被引：1，自引：0，他引：1  
The High Resolution Doppler Imager (HRDI) and the Wind Imaging Interferometer (WINDII) instruments, which are both on the Upper Atmosphere Research Satellite, measure winds by sensing the Doppler shift in atmospheric emission features. Because the two observation sets are frequently nearly coincident in space and time, each provides a very effective validation test of the other. Discrepancies due to geophysical differences should be much smaller than for comparisons with other techniques (radars, rockets, etc.), and the very large sizes of the coincident data sets provide excellent statistics for the study. Issues that have been examined include relative systematic offsets and the wind magnitudes obtained with the two systems. A significant zero wind position difference of 6 m s–1 is identified for the zonal component, and it appears that this arises from an absolute perturbation in WINDII winds of -4 m s–1 and in HRDI of +2 m s–1. Altitude offsets appear to be relatively small, and do not exceed 1 km. In addition, no evidence is found for the existence of a systematic wind speed bias between HRDI and WINDII. However, considerable day-to-day variability is found in the quality of the agreement, and RMS differences are surprisingly large, typically in the range of 20-30 m s–1.  相似文献   

7.
Basic properties of the mid-latitude traveling ionospheric disturbances (TIDs) during the maximum phase of a major magnetic storm of 6–8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics (51.9°N,103.0°E), and MORTI located at the observatory of the Institute of Ionosphere (43.2°N, 77.0°E). Observations of the O (557.7 and 630.0 nm) emissions originating from atmospheric layers centered at altitudes of 90 and 250 km were carried out at Irkutsk and of the O2(b1∑g+−X3∑g−) (0-1) emission originating from an atmospheric layer centered at altitude of 94 km was carried out at Almaty. Our radio and optical measurement network observed a storm-induced solitary large-scale wave with duration of 1 h and a wave front width of no less than 5000 km, while it traveled equatorward with a velocity of 200 m/s from 62°N to 38°N geographic latitude. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes. A comparison of the auroral oval parameters with dynamic spectra of TEC variations and optical 630 nm emissions in the frequency range 0.4–4 mHz (250–2500 s periods) showed that as the auroral oval expands into mid-latitudes, also does the region with a developed medium-sale and small-scale TEC structure.  相似文献   

8.
We have developed a lidar to study the temperature structure of the nighttime mesopause region over the Arecibo Observatory (18.35°N, 66.75°W) by measuring the lineshape of the fluorescence spectrum of atomic potassium that is deposited in the mesosphere and lower thermosphere (MLT) by meteors. To demonstrate how the potassium lidar can enhance MLT studies at Arecibo, we show recent results for: (1) comparisons with airglow temperature measurements; (2) simultaneous operations with stratospheric and mesospheric temperature profiling by Rayleigh lidar; (3) simultaneous observations of K, Ca+, and E-region electron density profiles; and (4) occurrences of sporadic K layers, and relationships to sporadic E layers.  相似文献   

9.
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   

10.
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11.
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12.
Measurements of visible and diffuse gas emission were conducted in 2006 at the summit of Sierra Negra volcano, Galapagos, with the aim to better characterize degassing after the 2005 eruption. A total SO2 emission of 11?±?2?t day?1 was derived from miniature differential optical absorption spectrometer (mini-DOAS) ground-based measurements of the plume emanating from the Mini Azufral fumarolic area, the most important site of visible degassing at Sierra Negra volcano. Using a portable multigas system, the H2S/SO2, CO2/SO2, and H2O/SO2 molar ratios in the Mina Azufral plume emissions were found to be 0.41, 52.2, and 867.9, respectively. The corresponding H2O, CO2, and H2S emission rates were 562, 394, and 3?t day?1, respectively. The total output of diffuse CO2 emissions from the summit of Sierra Negra volcano was 990?±?85?t day?1, with 605?t day?1 being released by a deep source. The diffuse-to-plume CO2 emission ratio was about 1.5. Mina Azufral fumaroles released gasses containing 73.6?mol% of H2O; the main noncondensable components amounted to 97.4?mol% CO2, 1.5?mol% SO2, 0.6?mol% H2S, and 0.35?mol%?N2. The higher H2S/SO2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions. 3He/4He ratios measured at Mina Azufral fumarolic discharges showed values of 17.88?±?0.25?R A , indicating a mid-ocean ridge basalts (MORB) and a Galapagos plume contribution of 53 and 47?%, respectively.  相似文献   

13.
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   

14.
A meridional scanning OI 630.0-nm dayglow photometer was operated from Ahmedabad (17.2°N dip lat.) scanning a region towards the south in the upper atmosphere extending over \sim5° in latitude from 10.2°N to 15.2°N dip latitude. From the spatial and temporal variabilities of the dayglow intensity in the scanning region we show for the first time, evidence for the passage of the crest of the equatorial ionization anomaly (EIA) in the daytime by means of a ground-based optical technique. The relationship between the daytime eastward electric field over the dip equator in the same longitude zone as inferred from the equatorial electrojet strength and the evolutionary pattern of EIA is clearly demonstrated. The latter as inferred from the dayglow measurements is shown to be consistent with our present understanding of the electrodynamical processes in the equatorial region. The present results reveal the potential of this ground-based optical technique for the investigation of ionospheric/thermospheric phenomena with unprecedented spatial and temporal resolution.  相似文献   

15.
A model of auroral precipitation (AP) developed on the basis of statistical processing of DMSP F6 and F7 satellite data (Vorobjev and Yagodkina, 2005, 2007) was used for the calculation of the global distribution of the auroral luminosity in different spectral ranges. The algorithm for the calculation of the integral intensity in bands N2 LBH (170.0 nm), ING N 2 + (391.4 nm), 1PG N2 (669.0 nm), and (OI) 557.7-nm emission is shown in detail. The processes of formation of electronically excited atoms O(1S) as a result of the transport of excitation energy from metastable state N2(A3Σ u + ), excitation of O(3P) by primary and secondary electrons, and dissociative recombination were taken into account to calculate the intensity of emission at 557.7 nm. A high correlation between the model distribution of the auroral luminosity in the UV spectral range and the observations of the Polar satellite is demonstrated.  相似文献   

16.
The nightglow OH(9,4) and O2 atmospheric (0,1) band emission intensities and their rotational temperatures T(OH) and T(O2), respectively, observed at Cachoeira Paulista (23° S, 45°W), Brazil, during the period from October 1989 to December 1990, have been analyzed to study the nighttime mesospheric energy loss rates through the radiations from the vibrationally excited OH* and electronically excited O*2 bands. The total emission rates of the OH Meinel bands, O2 atmospheric (0,0) and O2 infrared atmospheric (1g) bands were calculated using reported data for the relative band intensities and . It was found that there is a minimum in equivalent energy loss rate by the OH* Meinel bands during December/January (equivalent energy loss rate of 0.39 K/day*, where day* means averaged over the night) and maximum in equivalent energy loss rate during September (equivalent energy loss rate of 0.98 K/day*). Energy loss rate by the O*2 radiation, on the other hand, is weaker than that by the OH* Meinel bands, showing equivalent energy loss rates of 0.12 K/day* and 0.22 K/day* during January and September, respectively.  相似文献   

17.
Since the auroral ionosphere provides an important energy sink for the magnetosphere, ionosphere-thermosphere coupling must be investigated when considering the energy budget of the ionosphere-magnetosphere coupling. We present the first Scandinavian ground-based study of high-latitude F-region ion-neutral frictional heating where ion velocity and temperature are measured by the EISCAT incoherent scatter radar as well as neutral wind and temperature being measured simultaneously by a Fabry-Perot interferometer. A geomagnetically active period (Kp = 7- - 5-) and quiet period (Kp = 0+ - 0) were studied. Neglecting the neutral wind can result in errors of frictonal heating estimates of 60% or more in the F-layer. About 96% of the local ion temperature enhancement over the neutral temperature is accounted for by ion-neutral frictional heating.  相似文献   

18.
Over two campaigns in 1998 and 1999, multiple sporadic sodium events were observed by the Arecibo Observatory sodium density lidar while simultaneously monitoring the plasma density using the incoherent scatter radar. In this paper, we test the theoretical explanation proposed by Cox and Plane (1998) where Na+ in a plasma layer is neutralized via an ion–molecule mechanism to form a sporadic sodium layer. A particular challenge is to interpret observations made in a Eulerian frame of observation where the spatial and temporal characteristics of events cannot easily be separated. The reaction scheme in the original mechanism is modified to include the reactions NaO++N2→Na+·N2+O and NaO++O2→Na++O3, following the results of theoretical quantum calculations. Six unique case studies of sporadic sodium layers are presented here, and excellent agreement between simulation and observations was obtained for five of them.  相似文献   

19.
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20.
A common feature of evening near-range ionospheric backscatter in the CUTLASS Iceland radar field of view is two parallel, approximately L-shell-aligned regions of westward flow which are attributed to irregularities in the auroral eastward electrojet region of the ionosphere. These backscatter channels are separated by approximately 100–200 km in range. The orientation of the CUTLASS Iceland radar beams and the zonally aligned nature of the flow allows an approximate determination of flow angle to be made without the necessity of bistatic measurements. The two flow channels have different azimuthal variations in flow velocity and spectral width. The nearer of the two regions has two distinct spectral signatures. The eastern beams detect spectra with velocities which saturate at or near the ion-acoustic speed, and have low spectral widths (less than 100ms–1), while the western beams detect lower velocities and higher spectral widths (above 200ms–1). The more distant of the two channels has only one spectral signature with velocities above the ionacoustic speed and high spectral widths. The spectral characteristics of the backscatter are consistent with E-region scatter in the nearer channel and upper-E-region or F-region scatter in the further channel. Temporal variations in the characteristics of both channels support current theories of E-region turbulent heating and previous observations of velocity-dependent backscatter cross-section. In future, observations of this nature will provide a powerful tool for the investigation of simultaneous E- and F-region irregularity generation under similar (nearly co-located or magnetically conjugate) electric field conditions.  相似文献   

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