Analysis of the Bugatti data for turbulent parameters

The high frequency measurements of N₂ and Ar concentrations by rocket borne mass spectrometers in the region 95 to ∼ 120 km are analysed for turbulence coefficients. The data, measured every 2m, are averaged over 20 m, and spectrally analysed. The spectra in the lower altitude region (Z < 108 km) are representative of lower atmospheric turbulence wherein the spectrum displays the “inertial” behavior. Thus we may determine turbulent parameters such as: viscous dissipation (ϵ), Reynolds stress (<u‘w’>), density flux (<w‘n’), diffusivity (K_ϱ), the flux Richardson number, mean wind shear and an estimate of local temperature.Also determined at the upper region (108<z<120 km) is a non-“turbulent” noise-like fluctuation that diffusively transfers mass, but demonstrates random statistics. Density, spectral distributions, analytic processes and statistical characteristics of the two atmospheric mechanisms will be given.     

北京地区大气温度及重力波活动的季节变化

利用瑞利激光雷达观测数据,分析了北京地区35~70km高度范围内大气温度和重力波活动的季节变化.发现北京地区30~70km高度范围内的大气温度有明显的年周期变化:平流层顶最高温度出现在6,7月份,大约为270K;中间层70km高度最低温度也出现在6,7月份,大约为200K.以2014年10月14日晚数据为例,分析重力波势能密度,发现50km以下重力波势能存在耗散,而在50km以上重力波近乎无耗散地向上传播.通过对比35~50km高度范围内的平均势能密度,对北京地区重力波活动强弱的季节变化进行了研究.研究结果表明,北京上空重力波活动强度具有明显的年周期变化,冬季平均势能密度为18J·kg-1,夏季为8J·kg-1,且冬季重力波活动强度约为夏季的两倍.此外,还分析了春夏秋冬四个季节重力波势能密度随高度的变化.结果表明,不同季节和不同高度的重力波势能密度不同.      

Modelled ionospheric Te profiles at mid-latitudes for possible IRI application

The electron temperature (T_e) variation in the mid-latitude ionosphere at altitudes between 120 – 800 km has been modelled for various seasonal and solar-cycle conditions. The calculated electron temperatures are consistent with plasma densities and ion temperatures computed from a time-dependent ionospheric model. The T_e distribution can be represented by a subset of standard T_e profiles. T_e above 200 km is controlled by the magnetospheric heat flux into the ionosphere. For realistic values of the magnetospheric heat flux, the maximum electron temperature ranges from 3000 to 10,000 K at 800 km. The effect of increasing the heat flux is to increase the topside temperature but retain the profile shape. Hence, given a topside T_e observation and selection of an appropriate profile shape, the entire T_e distribution can be computed.     

Characterization of the semi-annual-oscillation in mesospheric temperatures at low-latitudes

Novel measurements of the seasonal variability in mesospheric temperature at low-latitudes have been obtained from Maui, Hawaii (20.8°N, 156.2°W) during a 25-month period from October 2001 to January 2004. Independent observations of the OH (6, 2) Meinel band (peak height ∼87 km) and the O₂ (0–1) atmospheric band emission (∼94 km) were made using the CEDAR Mesospheric Temperature Mapper. The data revealed a coherent oscillation in emission intensity and rotational temperature with a well-defined periodicity of 181 ± 7 days. The amplitude of this oscillation was determined to be ∼5–6 K in temperature and ∼8–9% in intensity for both the OH and O₂ data sets. In addition, a strong asymmetry in the shape of the oscillation was also observed with the spring maximum significantly larger than the fall peak. These data provide new evidence in support of a semi-annual-oscillation in mesospheric temperature (and airglow emission intensities) and help quantify its seasonal characteristics.     

The influence of radiative cooling and turbulence on the heat budget of the thermosphere

Numerical models of the thermal budget of the Earth's upper atmosphere in the height range of 90–500km are developed. The main sources and sinks of energy including infra-red radiative cooling by vibrational-rotational bands of NO, CO₂, OH and O₃ as well as heating and cooling arising from dissipation of turbulent energy and eddy heat transport are taken into account. The calculated temperature and density height profiles are in good agreement with the respective profiles from CIRA 72 and Jacchia 1977 models. It is shown for the models considered that IR-radiative cooling by CO₂ and NO in the 15μ and 5.3μ bands, not eddy turbulence provides the major loss of heat from 90 to 180km.     

Thermospheric model calculations based on turbulence data

Thermospheric model calculations are presented which explain the seasonal compositional changes of helium and argon by the combined effect of seasonal-latitudinal variations of turbulence and global seasonal winds. The observational base of the model calculations is given by empirical data of upper thermospheric densities and by estimates of the turbopause height derived from composition measurements and incoherent scatter temperatures in the lower thermosphere. The results are compared with observations of the seasonal variability of atomic oxygen in the turbopause region.     

北纬30°中层顶区域钠与铁原子层的结构和年际变化

基于武汉大学Na和Fe激光雷达在2004年1月至2011年12月期间的观测数据，得到武汉上空中层顶区域Na和Fe原子层的平均特性、夜间变化和季节变化特征.Na层平均质心高度为91.36km，平均RMS（均方根）宽度为4.64km.Fe层平均质心高度为88.99km，平均RMS宽度为4.57km.在充分考虑金属层夜间变化和季节变化对数据样本影响的基础上，获取了Na层和Fe层结构在此期间的年际变化特征.对Na层和Fe层质心高度及RMS宽度的年际变化进行线性拟合，发现Na层和Fe层在此期间均相对稳定，Na层质心高度在近8年间仅有约58m的下降，变化率为-7.91m·a-1，Na层RMS宽度减小约151m，变化率为-20.60m·a-1.同期，Fe层的质心高度下降了约230m，变化率为-31.36m·a-1，Fe层RMS宽度则有所增大，变化率为21.01m·a-1.      

An empirical model of electron temperature for low and middle latitudes in the 100–200 km height region

An empirical model of electron temperature (T_e) for low and middle latitudes is proposed in view of IRI. It is constructed on the basis of experimental data obtained at 100 to 200 km by probe and incoherent scatter methods. Below 150 km the model gives two T_e values: one from incoherent scatter data and another from probe measurements. The model can be used for all seasons for quiet geomagnetic conditions (Kp not greater 3) and at almost all levels of solar activity (F_10.7 between 70 and 200). It is presented in an analytical form that allows one to calculate T_e profiles for different latitudes, longitudes and at any season (day). Depending on geomagnetic latitude and solar zenith angle, electron temperature distributions are presented for two heights along with T_e profile variations during the day (at middle latitudes).     

An empirical model of electron density for low and middle latitudes below 200 km

Our empirical model of electron density (n_e) for quiet and weakly disturbed geomagnetic conditions (Kp not greater 4) takes account of comparative analysis of existing models and of experimental data obtained by rockets and incoherent scatter radar. The model describes the n_e distribution in the 80 to 200 km height range at low and middle latitudes, and to some extent, in the subauroral region. It is presented in analytical form thus allowing one to calculate electron density profiles for any time. The electron density distribution at 140 km depends on the season (day of the year) and on the solar zenith angle. Profile variations during the day are for one season shown. Different from other models, ours specifies the variations during sunrise and sunset and reflects the particular profile shape at night admitting the occurrence of an intermediate layer.     

Latitudinal variation of the topside electron temperature at different levels of solar activity

A database of electron temperature (T_e) measurements comprising of most of the available satellite measurements in the topside ionosphere is used for studying the solar activity variations of the electron temperature T_e at different latitudes, altitudes, local times and seasons. The T_e data are grouped into three levels of solar activity (low, medium, high) at four altitude ranges, for day and night, and for equinox and solstices. We find that in general T_e changes with solar activity are small and comparable in magnitude with seasonal changes but much smaller than the changes with altitude, latitude, and from day to night. In all cases, except at low altitude during daytime, T_e increases with increasing solar activity. But this increase is not linear as assumed in most empirical T_e models but requires at least a parabolic approximation. At 550 km during daytime negative as well as positive correlation is found with solar activity. Our global data base allows to quantify the latitude range and seasonal conditions for which these correlations occur. A negative correlation with solar activity is found in the invdip latitude range from 20 to 55 degrees during equinox and from 20 degrees onward during winter. In the low latitude (20 to −20 degrees invdip) F-region there is almost no change with solar activity during solstice and a positive correlation during equinox. A positive correlation is also observed during summer from 30 degrees onward.     

Atmospheric sampling

Four important sampling techniques are briefly reviewed: Selective sampling on impregnated filters for measuring acidic gases, the matrix isolation technique for measuring radicals, whole air grabsampling and whole air cryogenic sampling for measuring stable source gases.Vertical profiles of H₂, CH₄, CO, N₂O, CFCl₃ and CF₂Cl₂ resulting from gas chromatographic analysis of whole air samples collected with a cryogenic sampler are presented. Year-to-year variations are observed for H₂, CH₄ and N₂O above 25 km, while CFCl₃ and CF₂Cl₂ mixing ratios show a noticeable increase between 1977 and 1979 at almost every height level.The CO₂ mixing ratio is not constant with height but rather decreases from 332 ppmV at 10 km to 325 ppmV at 30 km.The vertical distribution of methyl chloride is characterized by a rapid decrease from 600 pptV in the troposphere to less than 10 pptV at 32 km in agreement with model results.     

Turbulence in the region 80–120 km

Measurements of turbulent energy dissipation rates and eddy diffusion coefficients have been collated, and mean height profiles of fundamental turbulence parameters in the region 80–120 km are presented.     

Ion composition behaviour in low and mid-latitudes during high solar activity

In the present analysis, the mass spectrometer data from the ISS-b satellite, available in the form of contour plots at an average height of 1100 km for every alternate hour, is used. This analysis showed some interesting results in terms of the diurnal variation of the transition heights; at times dominance of He⁺ over the other ions, and the seasonal variations of different constituents. In the development of ion composition models, it is suggested that this type of result should be taken into consideration.     

Connection between winter mesopause region temperatures and diurnal LF reflection height variations measured at Collm

Scale height, H, estimates are calculated from the decrease/increase of ionospheric virtual reflection heights of low-frequency (LF) radio waves at oblique incidence in suitably defined morning intervals around sunrise during winter months. The day-to-day variations of H qualitatively agree with daily mean temperature variations around 90 km from meteor radar measurements. Since mesospheric long-period temperature variations are generally accepted to be the signature of atmospheric planetary waves, this shows that LF reflection height measurements can be used for monitoring the dynamics of the upper middle atmosphere. The long-term variations of monthly mean H estimates have also been analysed. There is no significant trend, which is in agreement with other measurements of mesopause region temperature trends.     

高超声速飞行器在中间大气层内的飞行速度研究

基于FLUENT软件, 采用Sp-A湍流模型并运用AUSM计算格式,通过对球头模型在高超声速来流下的外流场模拟,得到了该模型在30km,45km,53km,60km和75km高度处,满足氧化铝陶瓷最大使用温度的极限飞行马赫数。结果表明：在53km以下时,极限马赫数随高度增加而减小,之后再增大,变化趋势符合气温变化规律,静温对驻点处的最高温影响巨大。     

On the role of tidal winds in the descending of the high type of sporadic layer (Esh)

As the prevailing tidal winds in the E region are generated by heating mechanisms, the dynamics of Es layers impacted by solar tides is a relevant theme in the space weather studies. This paper aims to identify the tidal wind component involved in the mechanism of formation and descending of the high type of sporadic layer (Es_h). The Es_h layers observed at altitudes between around 120 and 150 km in the Brazilian low latitude stations of Jataí and São José dos Campos during the months of April, June, September and December of 2016 are used in this analysis. The height variability and altitude descent of the Es_h layers are analyzed from the h′Es parameter obtained by ionosonde data. In this study, the observational data are compared with the simulations generated by an extended version of the Ionospheric E-Region Model (MIRE). At higher altitudes in the E region, the results show that the prevailing tidal pattern and wind direction controlling the Es_h layer formation and descent are different depending on month: (a) in April and June the zonal wind component and the associated semidiurnal tidal oscillations prevail, with some differences in terms of time of occurrence and descending speeds, and (b) in September and December the diurnal tidal periodicities become dominant, and both the meridional and zonal wind components seem to control the descending of the Es_h layers. Since the role of the tidal periodicities and wind directions changed depending on the month, the results suggest a possible seasonal tidal wind pattern, which is not well understood from the present study but requires further investigation. Other relevant aspects of the observations and the modeling are highlighted and discussed.     

An empirical model of electron density in low latitude at 600 km obtained by Hinotori satellite

An empirical model of electron density (Ne) was constructed by using the data obtained with an impedance probe on board Japanese Hinotori satellite. The satellite was in circular orbit of the height of 600 km with the inclination of 31 degrees from February 1981 to June 1982. The constructed model gives Ne at any local time with the time resolution of 90 min and between −25 and 25 degrees in magnetic latitude with its resolution of 5 degrees in the range of F_10.7 from 150 to 250 under the condition of K_p < 4. Spline interpolations are applied to the functions of day of year, geomagnetic latitude and solar local time, and linear interpolation is applied to the function of F_10.7. Longitude dependence of Ne is not taken into account. Our density model can reproduce solar local time variation of electron density at 600 km altitude better than current International Reference Ionosphere (IRI2001) model which overestimates Ne in night time and underestimates Ne in day time. Our density model together with electron temperature model which has been constructed before will enable more understanding of upper ionospheric phenomenon in the equatorial region.     

Turbulence in the region 80–120 km

Measurements of turbulent energy dissipation rates and eddy diffusion coefficients have been collated, and mean height profiles of fundamental turbulence parameters in the region 80–120 km are presented.