共查询到20条相似文献，搜索用时 31 毫秒
1.
M. Yu. Andreev D. V. Blagoveshchensky V. M. Vystavnoi V. S. Mingalev G. I. Mingaleva 《Geomagnetism and Aeronomy》2007,47(4):502-509
The experimental ionograms of the oblique-incidence sounding of the ionosphere, obtained on the St. Petersburg-Spitsbergen high-latitude HF radio path during the magnetically quiet period December 14–15, 2001, are compared with the model calculations of radiowave trajectories. For this purpose, the corresponding oblique-incidence ionograms are numerically synthesized using the technique based on the shooting method and the computer program for constructing HF radiowave trajectories. The three-dimensional electron density distribution, calculated using the mathematical model of the high-latitude ionosphere previously developed at the Polar Geophysical Institute (PGI), is used to model radio propagation. The numerical calculations make it possible mainly to explain the specific features of the experimental data on the oblique-incidence sounding of the ionosphere. 相似文献
2.
V.I. Kurkin O.M. Pirog N.M. Polekh A.V. Mikhalev I.N. Poddelsky A.E. Stepanov 《Journal of Atmospheric and Solar》2008,70(18):2346-2357
We present the results of studies of the subauroral and mid-latitude ionosphere variations in the north-eastern region of Asia. We used the data from network of vertical and oblique-incidence sounding ionosondes and optical measurements. Long-term experiments on the radio paths Magadan–Irkutsk and Norilsk–Irkutsk were carried out within the period 2005–2007. Vertical sounding stations operated in standard regime. Observation of airglow near Irkutsk was provided by the zenith photometer that measured intensities of 557.7 and 630.0 nm atomic oxygen emissions. The results may be summarized as follows. (1) Large daytime negative disturbances are observed during the main and recovery phases mainly at high latitudes, whereas the positive disturbances observed during the main phase at mid latitudes. The disturbances changed their sign between Yakutsk and Irkutsk. (2) During the main and recovery storm phases the fall of foF2 associated with the equatorward wall of the main ionospheric trough is observed in the afternoon and evening. (3) Fluctuations of the electron density more intensive at mid latitudes during the storm main phase are observed during all considered periods. They are classed as traveling ionospheric disturbances (TID). Such sharp gradients of electron density are responsible for the strong changes in the characteristics of the radio wave propagation, particularity MOF. (4) A large-scale ionospheric disturbance is noted at the meridional chain of ionosonds in December 2006 as the sharp increase of foF2. It appears in the evening in the minimum of Dst at high latitude and propagate to equator. (5) A maximum of 630 nm emission above Irkutsk corresponds to the foF2 increase. (6) The obtained experimental data on the net of vertical and oblique-incidence sounding with high time resolution show that such net is the effective facility to study the conditions of the radio wave propagation and can be used for the diagnostic of the ionosphere. 相似文献
3.
The series of ionograms of the satellite radio sounding from altitudes below the ionospheric maximum, which were called a delayed lower track, is considered. The method for analyzing ionograms in such a series has been described. The appearance of the delayed lower track on ionograms is explained by the presence of a large ionospheric inhomogeneity which turns radiowaves of many frequencies toward a satellite. It has been assumed that the series of ionograms diagnoses the same inhomogeneity, the structural parameters of which can be determined. The electron density profiles in individual vertical sections of inhomogeneity and the inhomogeneity plasma frequency gradient have been presented, and an attempt to construct the spatial model of inhomogeneity has been made. 相似文献
4.
5.
Complex ionograms from the Intercosmos-19 satellite with strongly delayed and sometimes multiple reflections from the Earth are considered. An analysis shows that these reflections are usually associated with sharp horizontal gradients of the ionospheric plasma. Such gradients are formed on the walls of the main ionospheric trough, at peaks of electron density, and on the inner and, especially frequently, on the outer slope of the crest of the equatorial anomaly. In one case, distant reflections from the Earth (DREs) formed near the equator, when the satellite in perigee was lower than the F2-layer maximum height. A quantitative interpretation of the most typical cases of DREs is given based on ray tracing. For this purpose, the model of the ionosphere under the satellite is developed, ray paths are calculated, and model ionograms are formed. The good agreement between experimental and model ionograms allows us to conclude that the task of interpreting complicated ionograms obtained by Intercosmos-19 with DRE has been solved successfully. 相似文献
6.
The height-latitude distributions of the electron density in the European Arctic sector of the subauroral and high-latitude ionosphere have been reconstructed based on the data of satellite radio tomography. The reconstructions have been compared with the results of the numerical modeling obtained using the UAM global numerical model and the IRI-2001 empirical ionospheric model. The goal of the paper was to find the degree of adequacy of these models to the observational data during geomagnetic disturbances. The UAM theoretical model adequately reproduces the dynamics of the main ionospheric trough, in particular, the position of its equatorward wall, and to a certain degree better describes the behavior of the high-latitude ion-osphere than the IRI empirical model. The discrepancies are observed in the regions of increased electron density poleward of the trough. To eliminate such disagreements, it was proposed to correct the model input distributions of precipitating high-energy electron fluxes with an energy of about 0.5 keV; i.e., the inverse problem of determining these distributions has been solved for extremely strong geomagnetic disturbances. 相似文献
7.
N. A. Barkhatov S. E. Revunov G. G. Vertogradov V. G. Vertogradov V. A. Valov V. P. Uryadov 《Geomagnetism and Aeronomy》2006,46(1):84-93
The algorithm for predicting one of the main parameters of the ionospheric HF radio channel—maximum observed frequency (MOF)—for the interval 0.5–3 h has been synthesized based on the technology of artificial neural networks (ANNs). The data of oblique-incidence LFM sounding obtained on the Inskip (England)-Rostov-on-Don path have been used for this purpose. The studies have been performed under different geophysical conditions. The relation of MOF to the variations in the key parameters of the solar wind and IMF, responsible for the succession of development of magnetospheric-ionospheric disturbances leading to a change in the HF radiocommunication conditions, has been established. The time scales of the ionospheric response have been determined. The practical value of the performed work consists in that the obtained results are used to increase the reliability of ionospheric HF radiocommunication. 相似文献
8.
D. V. Blagoveshchensky 《Geomagnetism and Aeronomy》2016,56(1):19-29
Two high-latitude high-frequency (HF) paths of oblique-incidence ionospheric sounding were selected: Gor’kovskaya (GRK)–Dixon Island (DIK) and GRK–Lovozero (LOZ).The following propagation parameters were studied: F2MOF and F2MUF for the main signal, F2MOFl for lateral signals, EsMOF for a signal reflected from the sporadic ionospheric layer, and MOFm for the propagation modes of the M (or N) type. Here MOF and MUF are the maximum observed and usable frequencies, respectively. It was found that the reciprocal theorem is satisfied on two radio paths depending on the studied propagation parameter: the path length and location, time of day, and degree of magnetospheric disturbance. It was found that the reciprocal theorem is satisfied in 78, 50, and 30% of cases on the first path for the F2MUF values in the daytime under moderately disturbed conditions, in the morning, and at night, respectively. For the MOFm and moderately disturbed conditions on this path, the reciprocal theorem is satisfied in 40, 35, and 20% of cases in the daytime, morning, and at night, respectively. For the F2MUF values on the second path, reciprocity is satisfied in 73% of cases in the daytime and under moderately disturbed conditions and in 30% of cases at night during a quiet period. On this path, reciprocity is satisfied in 33% of all cases at night under strongly disturbed conditions. An unusual fact was also detected when ionograms of oblique-incidence ionospheric sounding were analyzed: the F2MUF values in the LOZ–GRK direction are almost always slightly (by 1–4%) larger than in the GRK–LOZ direction. A similar difference in the F2MUF values in the forward and backward directions can apparently be explained by the steep horizontal gradient in the electron density distribution from north to south in the reflection region of this path. Such a situation is not observed on the DIK–GRK line. 相似文献
9.
O. A. Laryunin 《Geomagnetism and Aeronomy》2018,58(2):245-251
The characteristic U-shaped traces (cusps) in ionograms are associated with the passage of traveling ionospheric disturbances (TIDs), which lead to horizontal electron density gradients in the ionosphere and, therefore, to off-angle reflections in radio sounding. A new form of representation is considered for daily ionospheric sounding data. A compound parabolic layer model is proposed, which allows analytical calculation of ray paths to speed up the “homing-in” of the rays. Changes in the shape of the trace in the ionogram due to varying the TID characteristics are examined. A discussion is given of the possibilities for estimating TID characteristics from digitized vertical sounding ionograms. 相似文献
10.
P. Šauli Z. Mošna J. Boška D. Kouba J. Laštovička D. Altadill 《Studia Geophysica et Geodaetica》2007,51(3):449-459
The changing state of the ionosphere is generally monitored by networks of vertical ionosondes that provide us with regular
ionospheric sounding. Many ionospheric applications require determination of the true-height electron density profiles. Therefore,
ionograms must be further inverted into real-height electron density profiles. The paper presents the comparison study of
the true-height electron density profiles inverted from ionograms using two different methods POLAN (Titheridge, 1985) and
NHPC (Huang and Reinish, 1996; Reinish et al., 2005), widely used by the ionospheric research community. Our results show
significant systematic differences between electron density profiles calculated by these two inversion methods.
pkn@ufa.cas.cz 相似文献
11.
高频天波返回散射探测作为重要的电离层探测手段,能够实现遥远区域电离层空间上的连续监测,探测获取的返回散射扫频电离图显示了探测频率-群路径-回波能量三者之间的关系.由于电离图包含了探测路径上的电离层状态信息,通过对其反演可以实时获取大面积范围的电离层参数.本文提出了一种基于解空间约束的返回散射前沿反演算法,能够重构电离层水平不均匀结构.针对反演非线性问题,采用Newton-Kontorovich方法进行求解,同时又引入了求解不适定问题的Tikhonov正则化方法,有益于解的稳定性和唯一性.利用模拟数据和实测数据分别对本文建立的算法进行了验证,并与Fridman和Fridman于1994年提出的反演方法进行了对比.结果表明,本文算法反演结果稳定,对返回散射前沿判读误差不敏感,与Fridman和Fridman 1994年方法相比,本文方法对电离层局部精细结构反演更加准确,具有较高的反演精度.本文提出的算法不但能够反演白天和夜间这种电离层较平稳时期的电离层状态,而且对于日出/日落时段等电子浓度分布变化较快情形下的电离层,也有很好的反演效果,表明了该算法在处理复杂多变的实际探测的返回散射电离图中的应用价值. 相似文献
12.
N. M. Polekh N. A. Zolotukhina E. B. Romanova S. N. Ponomarchuk V. I. Kurkin A. V. Podlesnyi 《Geomagnetism and Aeronomy》2016,56(5):557-571
Using vertical and oblique radio-sounding data, we analyze the ionospheric and thermospheric disturbances during the magnetic storm that occurred in northeastern Russia on March 17–19, 2015. We consider the heliospheric sources that induced the magnetic storm. During the main and early recovery phases, the midlatitude stations are characterized by extremely low values of electron density at the F2 layer maximum. Using oblique sounding data, we recorded signals that propagated outside the great circle arc. In evening and night hours, no radio signals were found to pass along the Norilsk–Irkutsk and Magadan–Irkutsk paths. The observed ionospheric effects are shown to be caused by a sharp shift of the boundaries of the main ionospheric trough to the invariant latitude 46° N during the main phase of the magnetic storm. The negative ionospheric disturbance during the recovery phase of the storm, which was associated with significant variations in the composition of the neutral atmosphere, led to a change in the mode composition of received radio signals and a decline in observed maximal frequencies in daytime hours of March 18, 2015 by more than 2 times. 相似文献
13.
《Journal of Atmospheric and Solar》1999,61(8):619-628
This paper presents results of an experimental verification of our earlier suggested spectral-polarization method of measuring the interference pattern velocity by analyzing three mutually orthogonal projections of the radio signal field vector using a single receiving antenna. The measurements were made on an HF radio path about 100 km in length, with a simultaneous monitoring of the ionospheric situation using an oblique-incidence sounding chirp–ionosonde. In an effort to eliminate multipath effects, in the analysis we used nighttime intervals, for which a stable one-mode reflected radio signal was observed. It is shown that the proposed method gives the mean values of the azimuth and zenith angle which differ by no more than 2 to 5° from calculated values. Mean values of the velocity of travelling ionospheric disturbances (of order 50 m/s) and propagation directions (north-westward changing to northward by the morning hours) obtained for these time intervals are consistent with existing published data. 相似文献
14.
A mathematical model of the convecting high-latitude ionosphere is described which produces three-dimensional distributions of electron density, positive-ion velocity and electron and ion temperatures at the F-layer altitudes. The results of simulation of the behaviour of the high-latitude ionosphere, in particular, the heat regime of the F-layer, are presented and analysed. From our study, it was found that electron-temperature hot spots in the main ionospheric trough can arise owing to internal ionospheric processes, and not due to effects of any external causes. Three conditions, to be satisfied simultaneously, are necessary for the formation of the considered electron-temperature hot spots: first, low values of electron density; second, solar illumination of the upper F region and darkness of the lower F region; third, low values of neutral-component densities. These conditions are valid in the main ionospheric trough near the terminator on the nightside when the density of the neutral atmosphere is not high. The physical processes which lead to the formation of the electron-temperature hot spots are the heat transfer from the upper into the lower F region, the reduced heat capacity of electron gas and the weakened cooling of electron gas due to inelastic collisions with neutral atoms and molecules. Also investigated is the influence of seasonal and solar-activity variations on the efficiency of the identified mechanism responsible for the formation of the electron temperature peaks in the main ionospheric trough by the internal processes. 相似文献
15.
电离层垂直探测方法获得的频高图是电离层观测中历史最为悠久的资料,利用现代微电子和计算机技术对大量历史胶片频高图的数字化转换、分析和保存,已成为拯救保护和利用这些珍贵历史资料的十分紧迫和重要的工作.本文采用数字和图像处理等技术对胶片频高图像进行数字化、校正、修复和格式转换,并开发出胶片频高图分析与转换程序,结合常用的SAO Explorer软件对武汉地区的胶片频高图进行了实例的分析.结果表明,该方法具有较好的可靠性和通用性,对大量历史频高图的数字化转换和分析具有实用性. 相似文献
16.
The results of a comparison of the critical frequency values measured by an ionosonde of the Mir manned station (MS) and ground-based automatic ionospheric stations in various regions of the globe are presented in the paper. A comparison with European stations showed a coincidence of the results with a high significance level. The distributions of the critical frequencies in the regions of the equator in South America and in Southeast Asia obtained on the basis of the Mir results are qualitatively compared with the data of the International GPS Service (IGS) for the determination of the total electron content. The picture of the electron density distribution coincides qualitatively with the IGS data. The intervals of the strongest changes in the electron density in these regions were accompanied by the appearance of extra traces with large group delays in ionograms. 相似文献
17.
Joseph M. Grebowsky Robert F. Benson Phillip A. Webb Vladimir Truhlik Dieter Bilitza 《Journal of Atmospheric and Solar》2009,71(16):1669-1676
The projection of the plasmapause magnetic-field lines to low altitudes, where the light-ion chemistry is dominated by O+, tends to occur near the minimum electron density in the main (midlatitude) electron density trough at night. With increasing altitude in the trough, where H+ emerges as the dominant ion on the low-latitude boundary, we have found cases where the plasmapause field lines are located on the sharp low-latitude side of the trough as expected if this topside ionosphere H+ distribution varies in step with the plasmapause gradient in the distant plasmasphere. These conclusions are based on near-equatorial crossings of the plasmapause (corresponding to the steep gradient in the dominant species H+) by the Explorer-45 satellite as determined from electric-field measurements by Maynard and Cauffman in the early 1970s and ISIS-2 ionospheric topside-sounder measurements. The former data have now been converted to digital form and made available at http://nssdcftp.gsfc.nasa.gov. The latter provide samples of nearly coincident observations of ionospheric main trough crossings near the same magnetic-field lines of the Explorer 45-determined equatorial plasmapause. The ISIS-2 vertical electron density profiles are used to infer where the F-region transitions from an O+ to a H+ dominated plasma through the main trough boundaries. 相似文献
18.
Specific features of the variations and structure of the ionosphere above northern Europe during the known magnetospheric storm of January 10, 1997, have been analyzed using the oblique-incidence backscatter (OIB) methods. The OIB equipment installed near St. Petersburg, Gor’kovskaya (AANII), represent a BIZON small radar, the data of which were compared with the CUTLASS radar data, GPS observations of TEC, and geophysical data of the Sweden, Finnish, and Russian high-latitude observatories. A local substorm that occurred from 1451 to 1655 UT has been studied in detail, and 52 OIB ionograms have been obtained. The types of reflections from the MIT polar wall and the narrow ionization trough have been identified. 相似文献
19.
20.
This paper considers the results of an experiment conducted in May 2002 on the radio path St. Petersburg-Spitsbergen with
a length of D = 2150 km and equipped with instrumentation for oblique ionospheric sounding (OIS). The features of OIS ionograms at various
degrees of magnetic activity are revealed, and a comparison of these ionograms with the vertical sounding (VS) data at the
Sodankyla observatory (Finland) is performed. This observatory is located near the reflection point of the path in question.
In order to estimate the auroral absorption, riometer data from the Sodankyla observatory were included in the analysis of
the OIS and VS ionograms. The merits of the OIS method as a diagnostic tool of ionospheroic plasma in comparison with VS at
high latitudes are demonstrated. These merits are mainly formulated for magnetically disturbed periods: in the presence of
B events (black-outs), anomalous sporadic Es formations, and a series of other events. 相似文献