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Wind observations by Meteor radars from the year of 2009 to 2018 are utilized to knowledge the climatological characteristics at Mohe (53.1N), Beijing (40.3N), Wuhan (30.5N), Kunming (25.6N) and Sanya (18N). The tidal components with the period of 24h (diurnal), 12h (semidiurnal) are derived by the decomposition of observations using harmonic fitting method. The results show that the magnitude of diurnal tidal amplitude in the zonal and meridional winds increases with decreasing latitude, especially for the meridional wind. Annual and semi-annual changes dominate the main features. However, large difference of annual and semi-annual changes between the zonal and meridional could be seen clearly. Moreover, the diurnal tidal amplitude in the zonal wind at Mohe shows opposite changes above 90km and below 88 km, which is that the amplitude displays large value below 88km during February and March, while small value is prevailing above 90km during this time. When the diurnal amplitude above 90km is large accompanying with small value below 88 km. For the semidiurnal tide, the annual variation is clearly found for the zonal and meridional winds in their amplitudes at all stations. Meanwhile, the magnitude of semidiurnal tidal amplitude decreases with decreasing latitude, and that of meridional amplitude is larger than that of zonal amplitude. At all stations, the zonal diurnal tidal amplitude at Wuhan is largest above 88km in Spring and 94 km in Summer, that at Kunming is largest below 92 km in autumn and winter. The meridional diurnal amplitude at Sanya is biggest above 88 km in four seasons, and that at Kunming is biggest below 86 km in four seasons. For all seasons, the amplitudes in the zonal and meridional winds at Mohe are smallest. For the zonal wind, semidiurnal tidal amplitude at Beijing is largest at 82 – 94 km in Spring, 82 – 96 km in Summer, above 92 km in Autumn. Meantime, the semidiurnal tidal amplitude at Mohe is larger above 94 km and below 82 in Spring, above 96 km and 82 km in Summer, below 90 km in Autumn and at all heights in Winter. Simultaneously, the semidiurnal tidal amplitude at Sanya is smallest in Spring, Summer, Autumn and above 98 km in Winter. However, the variation of meridional semidiurnal tidal amplitude becomes complicated.

The spread-F echo of ionograms and scintillation of satellite signal propagation along the Earth-space path are two typical phenomena induced by ionospheric irregularities. In this study, we obtained spread-F data from HF (high frequency) digital ionosonde and scintillation index (S4) data from L-band and UHF receivers at low- and mid-latitudes in China during the 24th solar cycle. These four sites were located at Haikou (HK) (20°N, 110.34°E), Kunming (KM) (25.64°N, 103.72°E), Qingdao (QD) (36.24°N, 120.42°E), and Manzhouli (MZL) (49.56°N, 117.52°E). We used these data to investigate spread-F and scintillation occurrence percentages and variations with local time, season, latitude and solar activity. A comparative study of spread-F and scintillation occurrence rates has been made. The main conclusions are as follows: (a) FSF occurred mostly during post-midnight, while RSF and scintillation appeared mainly during pre-midnight at HK and KM; (b) FSF occurrence rates were larger at QD and MZL than expected; (c) the FSF occurrence percentages were anti-correlated with solar activity at HK and KM; meanwhile RSF and scintillation occurrence rates increased with the increase of solar activity at this two sites; (d) the highest FSF occurrence rates mostly appeared during the summer months, while RSF and scintillation occurred mostly in the equinoctial months at HK and KM; (e) the scintillation occurrence was usually associated with the appearance of RSF, probably due to a different physical mechanism comparing with FSF. Some of these results verified the conclusions of previous papers, whereas some show slight difference. These results are important in understanding ionospheric irregularities variations characteristic at low- and mid-latitudes in China.

Real-time and accurate modeling of three-dimensional (3D) electron density in the ionosphere is important for space navigation and communication technology as well as space weather. This paper investigates ionospheric tomography based on compressive sensing (CS) to achieve high resolution with sparse observation. This methodology includes the slant electron density (STEC) extraction by the un-difference and un-combined precise point positioning algorithm (UPPP), VTEC mapping based on basis function and compressive sensing reconstruction. The validation of the sparse sensing methods have been tested in both simulation and real navigation data in Yunnan from Beidou Ground Based Augmentation System (GBAS) by Qianxun Spatial Intelligence Inc. The constructed electron density by compressive sensing based on real GBAS navigation data agrees well with incoherent scatter radar (ISR) and ionosonde data in Qujing, Yunnan. The sparse sensing method shows 50% accuracy improvement in comparison to traditional ART method. In conclusion, the CS method can effectively reconstruct the three-dimensional electron density of the regional ionosphere by only relying on sparse observation, which can be used for real-time ionospheric tomography.

Ionospheric irregularities are an important phenomenon in scientific studies and applications of radio-wave propagation. Spread-F echoes in ionograms are a type of high-frequency band irregularities that include frequency spread-F (FSF), range spread-F (RSF), and mixed spread-F (MSF) events. In this study, we obtained spread-F data from four ionosondes at low- and mid-latitudes near the 120°E chain in China during the 23rd solar cycle. We used these data to investigate spread-F occurrence percentages and variations with local time, season, latitude, and solar activity. The four ionosondes were located at Haikou (HK) (20°N, 110.34°E), Guangzhou (GZ) (23.14°N, 113.36°E), Beijing (BJ) (40.11°N, 116.28°E), and Changchun (CC) (43.84°N, 125.28°E). We also present possible correlations between spread-Fs and other ionospheric parameters, such as the critical frequency of the F2-layer (foF2) and the virtual height of the bottom-side F-layer (h′F). In particular, we investigated the possible threshold of the foF2 affecting the FSF and the relationship between the h′F and the RSF. The main conclusions are as follows: (a) the FSF occurrence percentages were anti-correlated with solar activity at all four sites; meanwhile, RSF occurrence rates increased with the increase in solar activity at HK, but not at the other three sites; (b) FSF occurrence rates were larger at the mid-latitudes than expected, while FSFs occurred more often after midnight; (c) the highest FSF occurrence rates mostly appeared during the summer months, while RSFs occurred mostly in the equinoctial months of 2000–2002 at HK and GZ; (d) a lower foF2 was suitable for FSF events; nevertheless, h′F and RSF occurrences satisfied the parabolic relationship; (e) the foF2 thresholds for FSFs were 15, 14, 7.6, and 7.8 MHz at HK, GZ, BJ, and CC, respectively. The h′Fs occurring between 240 and 290 km were more favorable for RSF occurrences. These results are important for understanding ionospheric irregularity variations in eastern Asia and for improving space weather modeling and forecasting capabilities .

The Fabry–Pérot interferometer (FPI) and meteor radar are two important techniques for measuring the horizontal wind field in mesopause region, the observations of which still lack comprehensive comparison. Kunming Observatory (25.6°N,103.8°E) has deployed both instruments in recent years and provides collocated meteor radar and FPI observations. The meteor radar measures the horizontal wind fields over 24 hours every day continuously, whereas the FPI can only work during the night with clear air condition. FPI horizontal wind data from the 892.0-nm airglow emission (with a peak height at ~87 km) from 26 January to 8 February 2019 were comparatively analyzed with simultaneous meteor radar observations, which cover the range between 80 and 90 km with a vertical resolution of 1.8 km. It was found that the temporal variations in the horizontal wind fields observed by the FPI and meteor radar were generally consistent with one another, with the highest 2-D correlation coefficients of 0.91 (0.88) at 88 (87) km for the meridional (zonal) wind, which agreed with the peak height of OH airglow emission observed by the TIMED/SABER instrument. In addition, the correlation coefficient for the weighted meteor radar horizontal wind by OH concentration between 86 and 88 km and 85 and 89 km increased slightly from 0.91 (0.89) to 0.92 (0.89) for the meridional (zonal) wind, which indicated the contribution of OH concentration beyond the peak height to the FPI wind observations. We also found that the absolute horizontal wind values detected by two instruments were linearly correlated with a slope of ~1.3 for both wind components, and meteor radar wind observations were usually larger than the FPI observations.

Spread-F is known as the electron density inhomogeneous structures in F layer of ionosphere and can usually be classified as frequency spread-F (FSF) and range spread-F (RSF). Few studies have reported on the statistical characteristics of spread-F occurrences at midlatitudes in Eastern Asia, particularly the comparison of spread-F occurrences between China and Japan. In this paper, we used spread-F data recorded by ten ionosondes located between 25°N and 45°N from 1997 to 2016, to investigate the longitudinal differences in the statistical characteristics of spread-F occurrence and the probable mechanism for its occurrence at midlatitudes in Eastern Asia. Variations in the spread-F occurrences with the solar and geomagnetic activities, season and local time are presented. The main conclusions are as follows: (a) the occurrence percentage of FSF is higher than that of RSF, of which the former is anti-correlated with the solar or geomagnetic activities; (b) higher FSF occurrence percentages mostly appeared during summer, while RSF occurred more frequently in winter near 45°N latitude such as Urumqi, Changchun and Wakkanai; (c) the maximum of the FSF occurrence percentages mostly appeared between 01:00 and 02:00 LT approximately, whereas that of RSF appeared near 00:00 LT; (d) the spread-F occurrence percentages in the coastal or marine areas are higher than those in the inland region between 35°N and 45°N latitudes; however, this phenomenon is not obvious at lower latitudes; and (e) both the mean occurrences of FSF and RSF reach the minimum around 31°N latitude. These above results are helpful for understanding variations in spread-F occurrence at midlatitudes in Eastern Asia.

In the post-sunset ionosphere, plasma depleted bubbles with associated irregularity structures of scale sizes varying from centimeters to kilometers are generated due to plasma instability processes which causes the ionospheric irregularities. Ionospheric spread-F was discovered some decades ago. The variation in spread-F occurrence percentages continues to be an active area for scientific investigations at the present time. The spread-F presents a large dependence on the solar flux, the local time, the season, the latitude and longitude and the magnetic disturbances. In this paper, we present simultaneous ionosonde observations carried out at Chongqing (29.51°N, 106.42°E), which is located at the middle latitude in China, to study the characteristics of spread-F occurrence percentages and variations with local time, season and solar activity during 1997 to 2016. The results show that the onset time of spread-F seems to start at around 20 LT and continue till 05 LT at middle latitude. The spread-F occurs during summer most frequently at Chongqing. The spread-F occurrences decrease with the increase of solar and geomagnetic activity at middle latitude. These observations may improve our understanding of the factors responsible for the generation, growth and dynamics of the middle latitude spread-F events.

The ever-increasing space debris circling over geospace can be hard to detect by use of ground-based radar due to its small size and high-order radial motion, which can easily lead to considerable integration loss. In this paper, we propose an efficient method that can achieve good integration performance for moving targets like space debris, of up to second-order dynamics, meaning only velocity and acceleration be taken into account. Overall, range migration can be resolved by limiting the integration number so that all echoes of different pulses are within the same range unit. As for doppler migration problem, we use the combination of Fast Fourier Transform (FFT) and Inverse Fourier Transform (IFFT) to compute and compensate for velocity and acceleration terms, respectively.

The ionospheric plasma temperatures in March and June measured by the Qujing incoherent scatter radar have been used to study the diurnal variation of electron and ion temperatures with altitude (193-513km). It is found that there exist the morning and sunset enhancement and the daytime constant valley in electron temperature in March. The features like morning overshoot, day time valley (about 1000K) and sunset enhancement (with the maximum 3500K) show larger values at higher altitudes. The electron temperature above 1000K decreases with an increase in density. The sunset peak occurs earlier at higher altitudes. These above characteristic isn't prominent for electron temperature in June and ion temperature in all seasons. Both the electron and ion temperature reach a peak at about 200km and then decreases. The possible mechanism is also presented.

Incoherent scatter radar (ISR) detects the Thomson scatter echo of free electrons to inverse ionosphere parameters and is thought as the most powerful instrument to observe the ionosphere on the ground. In fact there are usually severe ground clutters around altitude 100km in the echo data. This paper introduces pulse subtraction to deal with ground clutter by using the Qujing incoherent scatter radar data. The results show that this pulse subtraction suppresses ground clutter well.

Incoherent scatter radar (ISR) is the most comprehensive ground-based technique for studying the ionosphere, which can also be used to observe and investigate the space objects (such as space debris, etc.). Compared with the space debris, the ionosphere is a typical soft target, and the echoes from ionosphere are extremely week. The ionosphere scattering signal will be hidden under the strong echoes of ISR of space debris. In this paper, we propose the integrated processing of ionosphere and space debris simultaneously. First, the order statistics filter is proposed to detect the space debris. Then if the debris exists, the matched filtering method is used to estimate some important parameters of debris, such as range, Doppler frequency, radial velocity. Based on these parameters, we remove the space debris from the incoherent scatter results. Experiments on simulation signal and real echoes from Qujing ISR demonstrate the validity and efficiency of the proposed method.

We have investigated the variation of mean wind almost continuously monitored by the Kunming (25.6°N, 103.8°E) MF radar over the period from August 2008 to August 2010. The mean circulation in zonal winds presents a obvious annual variation above 90 km and semiannual variation below 85 km, but has different direction up 90 km and down 85 km. An eastward flow is prevailing in spring and autumn below 85 km and in spring and summer up 90 km with amplitudes as large as 24 m/s and 21 m/s, respectively. But a westward flow dominates in summer and winter below 85 km and in autumn and winter up 90 km with amplitudes as large as −12 m/s and −10 m/s, respectively. Meanwhile the eastward wind dominates for all months at 85–90 km. The annual variation also appears in meridional wind below 90 km, which means a poleward flow occurs from September to April with amplitude maximum of 11 m/s, while the equatorward wind dominates almost for two years with maximum of −26 m/s above 90 km. Comparison of the wind vertical profile along with standard errors with the HWM07 model winds shows that the zonal wind agrees well with model in winter, autumn and summer, but the meridional wind in spring, winter and summer.

Lower Core Support Plate (LCSP) and Core Barrel (CB) are key components of reactor vessel internals. Especially, since the fuel assemblies are installed on the LCSP, its flatness is critical for the safe operation of fuel assemblies. However, for SM1 and HY1 nuclear power plant (NPP), after heat treatment of the weld between LCSP and CB, the LCSP deforms seriously and its flatness exceeds the limitation, which results in a time-consuming and costly reprocessing. A numerical model of heat treatment process between LCSP and CB was developed first. The general rules of temperature and deformation distribution of LCSP and CB were obtained. Also, an experiment was conducted to validate the model. With the validated model, the deformation mechanism of LCSP due to heat treatment is studied. At last, the heat treatment process between LCSP and CB was optimized to avoid similar issues for the following NPPs.

15th MST Radar WorkshopSession M3: Ionospheric irregularities and IS experimentsMay 27 (Sat), NIPR Auditorium

One year's data of an MF (medium frequency) radar installed at Kunming (25.6°N, 103.8°E) station, China, are used to study the tidal structure over Kunming. The tidal parameters including amplitudes and phases are analyzed, which show a strong diurnal tide and weak semidiurnal tide for both zonal and meridional components. The maxima diurnal and semidiurnal amplitudes are approximately 40 and 20 m/s, respectively. The diurnal phases and amplitudes show strong seasonal variability. Maximum amplitudes occur in March, and subsidiary maxima are attained in August and October, while the phase indicates an annual cycle. Semidiurnal amplitudes vary not so evidently. The vertical structures of the tidal parameters are compared with the Global Scale Wave Model (GSWM-09) values. The observed amplitudes of diurnal tide are smaller than the model values, but reversed for the semidiurnal tide. The observed phases of the diurnal tide show similar variations to GSWM-09 values. The agreement between the observed semidiurnal phase and model values is not so good.

Incoherent scattering radar (ISR) provides an efficient tool for measuring ionosphere parameters, such as electron and ion temperature, electron density and ion drift of the ionospheric plasma, etc. The modulation types and signal processing of incoherent scattering radar are totally different from the common radars. In this paper, the conventional modulation types for ISR and some of their actual experimental results are presented first. Then some new modulation types are proposed which are the combinations of different radar codes. And finally the comparison among various modulation types is demonstrated by some simulation experiments.

The real-time automatic acquisition and analysis of the ionospheric parameters play important roles in monitoring and forecasting of the ionospheric space weather. For the automatic scaling and analysis of the ionospheric parameters, a method based on the empirical orthogonal function (EOF) analysis of the ionospheric electron density profiles is proposed in this paper. This method is applied to the measured ionograms of CADI (Canadian Advanced Digital Ionosonde), which is set up at Beijing Space Environment Observation Station (40.3 degrees N, 116.2 degrees E). The results show that the method owns good reliability and universality and can show some variations of ionosphere. So it is feasible to use this method to monitor and analyze the ionospheric space weather in real time.

In this paper we apply a method based on empirical orthogonal function (EOF) analysis to automatically scale the F2-layer parameters obtained from ionograms. For a given location, the F layer’s height profiles of ionospheric electron density are represented as an EOF series with adjustable coefficients derived from the EOF analysis of electron density profiles obtained from the International Reference Ionosphere (IRI-2001) model or measured ionograms. By adjusting the coefficients of the series and combining image matching technique, we were able to construct a calculated trace that approximates as close as possible the observed ionogram F2 trace. The corresponding parameters are then known, including the critical frequency (foF2), peak height (hmF2) and maximum usable frequency [MUF(3000)F2] of the F2 layer. Polarization information is unnecessary; only an amplitude array is essential. Consequently, this method is universal and can be applied to many kinds of ionograms (even the film ionograms after an appropriate conversion of the information to the digital form from the film ionogram). To evaluate the acceptability of the obtained parameters, large numbers of foF2, hmF2 and MUF(3000)F2 values from the manually scaled ionograms at Wuhan (114.4°E, 30.5°N), China are compared with those from automatically scaled ionograms by the Automatic Real Time Ionogram Scaler with True height (ARTIST) and our method. The results indicate that the scaled parameters are acceptable and stable.

We presented in this paper the ionosphere variation characteristics during solar flares with location, season and solar activity level at Kunming site (25.6°N, 103.8°E), using the data measured by MF radar and ionosonde. Results showed: (1) the maximum amplitudes both D region and f min during solar flares appeared near at noon; there was no the strict corresponding relationship during solar flares between F layer critical frequency (foF2) and location time. (2) seasonal variation of increasing amplitude of electron density in D layer during solar flares reached the maximum in summer; that of f min was maximal in autumn, second in spring; that of foF2 reached the maximum in winter, second in autumn and least in spring. (3) the variation of ionosphere showed the positive correlation with the level of solar flare. (4) the ionosphere of D region had different characteristics with F layer ionosphere during solar flare on November 4, 2008.

We investigated disturbance propagation characteristics of ionosphere at three stations near 120° meridian chain using data by Vertical sounder during geomagnetic storms form April 12, 1981 to April 16, 1981. The result showed that there have significant perturbation of foF2 and h'F in the ionosphere at three stations during Magnetic storm, at the same time seven traveling ionospheric disturbance (TID) events occurred from higher latitude to lower latitude. Most events of TID happened at night, and the phase velocity increase gradually directing to low latitude.

By using the ionosonde data at Haikou, China over the time period of 1996-2006, this paper analyses the diurnal and seasonal behaviour of the ionospheric MUF variability at low latitude. Data used in this study are the critical frequency foF2 and the propagation factor M(3000)F2 with hourly interval resolution. Four parameters including upper quartile(Qup), lower quartile(Qlo), monthly inter-quartile(DeltaMUF) and their percentage ratio(DeltaMUF(%)) to the monthly medians are used as quantitative measurement of the MUF variability in diurnal and seasonal study, where in the latter the seasonal averages of these quantities are calculated for winter, equinox and summer, separately. Our study shows: (1)MUF values and their variability are greatly affected by foF2 values and their variability. (2)Instead of falling off after sunset, in high solar active years MUF values remain large until the next early morning. (3)Both MUF Qup and Qlo have the similar trends as those of their corresponding monthly medians. However, the departure of Qup and Qlo from the monthly medians is not symmetric. (4)For the DeltaMUF(%) parameter, the variability is much lower during daytime than nighttime, and the maximum variability appear in the pre-sunrise generally. (5)The seasonal averages of DeltaMUF(%) from 1996 to 2006 are of difference in magnitude in different season. The variation range fluctuates from 18.1% to 49.0% in winter, from 18.4% to 46.2% in equinox and from 17.6% to 39.7% in summer respectively. It is also shown that the seasonal averages of the DeltaMUF(%) is usually smaller in equinox than in winter and summer, except that in pre-sunrise time when they are larger in summer.

A fuzzy decoupling strategy with a compensator and a design method for the decoupling compensator are put forward based on the research on the decoupling control theory for a multivariable coupling nuclear power system. The designing method for the compensator is discussed. The fuzzy decoupling and compensating table is designed in detail for the double inputs and double outputs control system. The fuzzy decoupling technology is applied to design of the decoupling compensator for the basic class of coordinated control system of a nuclear power system, and a control system structure is present in the paper also. Under the typical load disturbance, the simulation result shows that the coordinated control system with the fuzzy decoupling strategies is better than the coordinated control system without decoupling strategies, especially good for the steam pressure of steam generator.