LHR whistlers and lhr spherics in the outer ionosphere

Special types of VLF signals, which follow whistlers and spherics and have an anomalous dispersion near the lower hybrid resonance (LHR) frequency, have been observed on the low-altitude Intercosmos satellites. These signals have been named LHR whistlers and LHR spherics, respectively. A mechanism is suggested for the formation of their spectra, based on the peculiarities of quasi-resonance wave propagation at frequencies near the LHR frequencies. It is shown that the large dispersion observed may be accounted for by a significant increase in the propagation time of the wave as its frequency approaches the maximum in the LHR frequency profile.     

Very unusual low latitude whistlers with additional traces of the Earth-ionosphere waveguide propagation effect

The present paper reports very unusual whistlers strongly influenced by the Earth-ionosphere waveguide propagation after emerging from the ionosphere, as observed simultaneosly at our two stations, Sakushima (geomag. lat. 24°) and Kagoshima (20°). These unsual whistlers are characterized by clearly exhibiting additional dispersion effects near the cut-off frequencies of the 1st and 2nd order modes of waveguide propagation and, to our knowledge, they are a new finding. All the subionospheric dispersion is deduced to occur between the ionospheric exit point and the receiver. Detailed spectral analysis, after extracting the small waveguide dispersion effect from the overall spectrum by taking the beat with the appropriate pseudo-whistler, has enabled us to determine the propagation distance of the ionospheric exit region from each station. These distances have then been used to locate the ionospheric exit region, which is found to be about 3000 km east of the stations and in the local sunrise time sector. The generation mechanism of such unusual whistlers is discussed in terms of the joint influences of the ionospheric transmission mechanism (longitudinal gradient of the ionosphere, wave scattering by density irreglarities) and magnetospheric propagation and characteristics of ducts.     

The polarisation of whistlers received on the ground near L = 4

The observed polarisation of the horizontal magnetic components of whistler mode signals received at Halley, Antarctica (L≈ 4.3), is in many cases that expected from a simple model of the transionospheric and sub-ionospheric propagation in the southern hemisphere; i.e. right-hand elliptical (field vectors rotate clockwise, looking towards the source) for ionospheric exit points close to the receiver, tending towards linear for more distant exit points. This suggests it may be possible to use the observed polarisation to estimate the propagation distance. However, in other cases, in certain frequency ranges, left-hand elliptically polarised signals have been observed. More realistic models do predict polarisation reversals at certain frequencies and exit point to receiver distances, but not over such a wide frequency range as has sometimes been observed. Also, in some cases, signals with nearly right-hand circular polarisation have been observed for exit points at large distances where linear polarisation would be expected.     

Propagation characteristics of night-time whistlers in the region of equatorial anomaly

In this paper results of simultaneous multi-station observations of night-time whistlers obtained at very low latitudes for the last three years are presented. The propagation mechanism of these whistlers is also discussed. Some records can be shown to have the characteristics of ducted propagation by calculating the dispersion of the whistlers along a ducted path and by noticing the feature of strong intensity, as well as the existence of three-hop echoes. Whistlers in some other records, however, can be shown to be propagating along a non-ducted path by numerical ray-tracing, in which a non-dipole field (IGRF) is used and a negative horizontal gradient of ionization in the equatorial ionosphere is taken into account. The agreement of the results of calculation with observed facts seems to confirm the existence of a definite whistler path at very low latitudes. Finally, based on analysis of typical events, the effects of magnetic storms on the parameters of low latitude whistlers due to variations in the equatorial ionosphere are also discussed.     

A neural network approach to the classification of electron and proton whistlers

Fractional whistlers, whistlers, and proton whistlers are automatically identified and characterized by means of a neural network. A feed-forward neural network with Time Delay Neural Network (TDNN) architecture is used. It has the ability to represent structures in frequency time diagrams; a set of 50 spectrogram elements (5 Fourier components × 10 time intervals) serves as input to the network. Applications to date have used ELF data recorded on board the low-altitude AUREOL-3 satellite. A first neural network was designed to identify and characterize fractional whistlers and whistlers. A set of 997 vector data is used for the training phase and 1088 other vector data are used for evaluating performance. It is observed that fractional whistlers and whistlers can be distinguished from noise with an accuracy of 90%. A second neural network, with the same architecture, was used for studying proton whistlers. Although the training database contains less examples, the accuracy of the classification is 89%. Neural networks of this type could be used in satellites for real-time classification and characterization of electron and proton whistlers.     

An asymmetry in the direction of arrival of whistlers at Sanae,Antarctica

The directions of arrival of over 1300 whistlers have been measured at Sanae, Antarctica and it is shown that whistlers arriving from lower latitudes than the station predominantly come from the west. In this paper we report on the observations and discuss the possible reasons for this asymmetric distribution of arrival bearings.     

Current and velocity of the return stroke lightning

An expression for the current flowing through the return stroke channel is derived from the actual flow of charge across the tip of the channel. From the current model a double exponential velocity expression is obtained. The consequence of this double exponential velocity expression for the spectrum of atmospherics is discussed. The variation of current and velocity with increasing length of channel is also discussed and appropriate expressions for the same are obtained.     

地球皇冠

青藏高原因其地势高起,气候寒冷,被人们拿来与冰天雪地的南北两极并列,称之为地球的"第三极"。如果我们从太空中俯视这个地球第三极,就会发现在青藏高原上的雪域高山之间,竟然有一大块四周被群山包围、内部相对平坦的草原地区,这就是羌塘。这一圈山脉中,羌塘的南部边界是冈底斯山,这座近东西走向的山脉把羌塘与藏南的雅鲁藏布江、喜马拉雅山分割开来;沿着羌塘的边界顺     

Average electron density profiles in the plasmasphere between L = 1.4 and 3.2 deduced from whistlers

985 whistlers recorded at Tihany, Hungary (L = 1.9) between December 1970 and May 1975 have been processed for equatorial crossing radius L, equatorial electron density n_eq and tube electron content N_T. The obtained L values lie in the range L = 1.4-3.2. The median values of n_eq and N_T as a function of L fit well to the density profiles published by Park et al. The results also indicate that at lower L values the whistlers are ducted by stronger density enhancements.     

Wave form and spectral distribution of the electromagnetic field of lightning currents

In a resonant wave guide model of lightning currents, two impulse type standing waves can exist: aperiodic waves of the Bruce-Golde form (type 1), and damped oscillations (type 2). The electromagnetic waves generated by these two types of lightning currents are calculated for various distances and compared with observations. It is shown that the measured wave forms of sferics at distances smaller than about 300 km of return strokes (R strokes) as well as of intracloud strokes (K strokes) are generated mainly by type 2 lightning currents. The channel parameters like channel length and channel diameter derived from the observed sferics are 19 km and 4.6 cm, respectively, for the average R stroke, and 4 km and 1.6 cm for typical K strokes. The large values of the lengths probably correspond to the real lengths of oblique and tortuous channels, rather than to their vertical elevation. The finite electric conductivity of the earth modifies the high frequency component of the wave forms. With decreasing conductivity and/or increasing distance, the rise times of the radiation component to its first maximum increases and the maximum amplitude decreases.Typical rise times for R-strokes are about 3 μs consistent with the observations if the electric conductivity of the earth is of the order of 10⁻³ S/m. The spectral functions of the wave forms are also calculated. The spectral amplitude of the average type 2 R-stroke has its maximum near 4 kHz, and that of the type 2 K-stroke maximizes near 35 kHz. Within the high frequency region at frequencies greater than about 300 kHz. the spectral amplitudes decay proportional to the reciprocal third power of the frequency. The radiation component in the far field contains 7% (16%) of the total electromagnetic energy of type 2 R (K) strokes.     

秦陇社火--黄土地上的狂欢节

秦陇一带的农家,从古运至今,一直崇尚珍重传统的春节和元宵节.     

The Earth of the Modern

One of the central questions in comparative studies of colonialism is what makes more recent variants of imperial extension so culturally distinctive, aside from the more obvious political-economic dimensions? This set of papers focuses on how European and Euro-American promulgated variants of colonialism can be viewed as embodying central tenets of modernism, such as progressivism, technocentrism, and hybridity. Moreover, the authors demonstrate how colonial practices in the era of the modern were not merely the result of policies emanating from imperial capitals, but were an outgrowth of conflict, mediation, and accommodation between colonizer and colonized. Thus, archaeological research is important for stressing that the past five centuries have seen a time of contested modernities, rather than the growth of ‘a’ modernist sensibility.     

中国中暹协会史料

1939年11月,中国中暹协会向社会部呈送该会工作计划纲要及职员名单,社会部则依据抗战爆发后中暹关系现状指示该会今后工作改进及实施要点.     

塔尔寺古建筑的雷电环境分析与防护措施

青海塔尔寺具有很高的佛教历史和文物价值,但在2011年8月30日由于雷电波侵入,造成了塔尔寺的时轮坛城和大吉哇殿内的消防、安防及低压配电系统部分设备遭雷击损坏,也严重威胁到僧侣、游客的安全。因此,对塔尔寺古建筑实施雷电防护已是非常必要和十分紧迫。为此,在分析塔尔寺所在的地理环境、气候特点、雷暴特征、雷击风险评估结果等基础上,提出了对塔尔寺古建筑采取内部防护和外部防护相结合的综合防护措施:外部防护采用通过在塔尔寺雷暴路径上安装一定高度的避雷针来提前接闪拦截,再由建筑物天面安装的避雷带进行二次接闪,从而有效预防和减少塔尔寺建筑物遭受直接雷击。内部防雷采用屏蔽、合理布线、等电位连接、电源和其他进出建筑物的线路上安装电涌保护器等方法,预防和减少感应雷、雷电波侵入造成的危害。事实表明,避雷措施是可行的,能预防建筑物、人员免受雷击。对于与塔尔寺有类似环境的古建筑的防雷电有参考价值。     

Temporal variations of the global lightning activity deduced from the Schumann resonance data

Temporal variations of the global lightning activity were deduced from long-term Schumann resonance (SR) continuous records. The intensities of the horizontal magnetic field component in the vicinity of the first, second, and third SR modes were monitored at Tottori observatory (35.5°N, 134.33°E) from 1968. Variations of the effective source-observer distance were estimated using the ratios of the intensities of individual modes. This allowed us to obtain average diurnal variations of the global lightning activity for each month over a one-year period. The results show that the distances estimated between the field-site and the effective source are very stable, while the temporal changes of the fields and the global lightning intensity derived demonstrate substantial variability.     

基于事故树的布达拉宫雷击火灾风险分析与保护

布达拉宫自兴建以来曾遭受多次不同程度雷击,一旦雷击引发火灾会造成不可挽回的损失,因此需要进行科学合理的雷击火灾分析以有效指导布达拉宫减灾工作。对于布达拉宫雷电可能引起火灾的风险,建立布达拉宫雷击火灾事故树,综合考虑布达拉宫因雷电引发火灾事件发生的可能过程、可能途径。最后对雷击火灾事故树最小割集、最小径集、基本事件的结果重要度进行比较,同时分析布达拉宫地区雷电活动规律。分析结果表明:布达拉宫雷击火灾事故树一共有22个基本事件,有308种可能导致布达拉宫因雷击引起火灾事件发生的途径。布达拉宫雷击火灾防护是一项复杂工程。研究表明,最便于采取的防护措施是加强其雷电防御能力,如清除引雷隐患、安装电涌保护器、进行等电位连接等。     

The Limits of Super-Rationality: A New Look at the Conception of Jupiter in Prometheus Unbound

In Prometheus Unbound, the empire of Jupiter is a mythic figuration of monotheism and its corresponding hegemonies, broadly conceived in both instances as the domain of supreme oppressive governance. The ties of governance are reified by paternalism—hence the use of Jupiter (Gk. Zeu + pater) as the master embodiment of the Father, combining the role of God-the-Father in Judeo-Christianity, of the Trinity, of pope or monarch, and that of paterfamilias, such that, in Shelley's unifying vision, one becomes indistinguishable from the other: all emanations of the Law of the Father, the symbolic order of “rationality” which represses primordial desire, associated with Prometheus and Asia. The overthrow of Jupiter in Prometheus Unbound is an implicit rejection of European rationalist hegemony, embodied in the conception of a manic, autocratic sky God, uniting sacred and secular aspects, and a reinstatement of an extra, or at least more profound and enduring identity that is consistent with re-ascendant primeval forces, paradoxically embodied in the shadowy figure of Demogorgon, but repressed as long as Jupiter reigns.