赤道电离层泡短波区密度谱理论分析

本文主要讨论在导致赤道夜间扩展F回波的上升汽泡中,短波区（λ25m）等离子体密度谱分布的物理机制,说明不均匀体内不同的湍动水平将产生不同的谱结构。对于较低湍动水平的汽泡,由于纵向离子声波和具有有限平行波矢漂移波的耦合共振相互作用,导致波模间能量的有效传输,从而控制湍动水平的发展,形成等能多峰谱结构。另一方面,对于湍动充分发展的汽泡,由长波区大幅度扰动维持的短波区强漂移湍动态,在Kr_Li≈2处形成一较宽的极大谱峰,然后谱以K^-2.6的形式减小。理论分析和探测结果符合甚好。     

Measuring magnetic field in the 'diamagnetic' ionosphere

Satellite magnetometers sometimes pass through regions of plasma, such as the terrestrial ionosphere, where the ionization is large enough that some of the original ambient field is excluded from the plasma. This reduction of field inside the plasma region comes from the 'diamagnetic' effect of the charged particles in their helical trajectory around the magnetic field lines. The (container of the) magnetometer will exclude the plasma, and a simple-minded approach, treating the ionosphere in the same way as for a conventional diamagnetic fluid, predicts that the field seen by the magnetometer will be somewhat larger than the (reduced) field in the plasma. However, the 'diamagnetic' properties of the ionosphere are quite different from those of a conventional diamagnetic. In particular, there is a 'reflection' of the ionospheric charged particles at the surface of the magnetometer, and the overall effect is that the magnetometer does actually measure the field present in the plasma before the magnetometer is inserted. Similarly, any leakage fields from the magnetometer have no effect in the magnetosphere.     

Atmosphere–ionosphere vertical electric coupling above thunderstorms of different intensity

The most important features of the quasi-electrostatic fields (QSFs) and currents, generated in the region between a thunderstorm (TS) and the ionosphere between lightning discharges, are theoretically investigated. They depend on different factors having large variability, related to the TS and to the atmospheric conductivity. These features are studied in order to understand better the conditions when QSFs cause modifications of the parameters and chemical balance in the lower ionosphere over TSs due to electron heating, as well as the generation of red sprites. For this purpose, an analytical model based on Maxwell's equations under conditions of curl-free electric fields is presented. The temporal and spatial behaviour of the QSFs is studied as a function of the parameters of lightning discharges and of atmospheric conductivity. The dependence of the QSF, mainly its peak values, on the charge moment change, the discharge time, and the horizontal extent of the discharged region, on the one hand, and of the conductivity profile, on the other, is studied. It is shown that the profile of the QSF time peak changes its scale height at the altitudes where the relaxation time becomes equal to the discharge time, and where the conductivity scale height is diminished; below these altitudes the peak QSFs decrease with time much slower than above them. Also, the QSF peak increases almost linearly with the charge height and depends little on the size of the discharged region. The total Maxwell and conduction currents, which flow from the TS to the ionosphere, are also studied. The peak current is proportional to the charge moment change, and actually does not depend on the frequency of lightning discharges.     

Nonlinear plasma wave processes observed in the polar cusp

We present observations of electric and magnetic field variations from proton (about few Hz) to electron cyclotron frequencies (about few kHz) obtained by STAFF instrument on Cluster satellites during two cusp crossings, at ∼6 R _E altitude, in September 2002. The cusp was identified by the presence of intensive fluxes of counter streaming electrons with low energies and broadband wave activity which is typical for this region. Special attention is given for the interval of measurements when the waveform of the magnetic field fluctuations was taken in this region by CLUSTER satellites. The wave has been processed using the wavelet and bispectral analysis. Results showing the cascade of turbulence and wave-wave interactions are presented in this paper. A three wave process can be responsible for the broadening of the wave spectra in the polar cusp.     

The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations

GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm of November 7–12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004) were created. The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50°N. In the report, features of the response of TEC to the storm for European and North American sectors are analyzed.     

用双频GPS观测值建立小区域电离层延迟模型研究

介绍了用双频GPS伪距观测值建立区域性电离层模型的基本原理和方法。模型的初步结果表明，该电离层模型建立后，可为性病区域的广大单频用户提供在天顶方向优于0．4m精度的电离层延迟改正量，且具有30min以内天顶方向优于0．4m的预报精度。     

Naturally Enhanced Ion-Acoustic Spectra And Their Interpretation

Incoherent scatter radars are designed to detect scatter from thermalfluctuations in the ionosphere. These fluctuations contain, among other things,features associated with ion-acoustic waves driven by random motions within theplasma. The resulting spectra are generally broad and noisy, but neverthelessthe technique can, through a detailed analysis of spectra, be used to measure arange of physical parameters in the Earth's upper atmosphere, and provides apowerful diagnostic in studies of magnetosphere-ionosphere coupling,thermosphere dynamics and the geospace environment in general. In recent yearsthere has been much interest in naturally occurring (as opposed to artificiallystimulated) enhanced ion-acoustic spectra seen in the auroral zone andcusp/cleft region. A study of the plasma instability processes that lead tosuch spectra will help us to better understand auroral particle acceleration,wave-particle and wave-wave interactions in the ionosphere, and theirassociation with magnetospheric processes. There is now a substantial body ofliterature documenting observations of enhanced ion-acoustic spectra, but thereremains controversy over generation mechanisms. We present a review ofliterature documenting observations of naturally enhanced ion-acoustic spectra,observed mainly along the geomagnetic field direction, along with a discussionof the theories put forward to explain such phenomena.     

Evolution of Pangea: paleomagnetic constraints from the Southern Alps, Italy

A new early Late Triassic paleopole for Adria has been obtained from the Val Sabbia Sandstone in the Southern Alps. As Early Permian and Jurassic-Cretaceous paleomagnetic data from para-autochthonous regions of Adria such as the Southern Alps are consistent with ‘African’ APWPs[1–2], paleomagnetic data from this region can be used to bolster the West Gondwana APWP in the poorly known Late Permian-Triassic time interval. The Southern Alpine paleopoles are integrated with the West Gondwana and Laurussia APWPs of Van der Voo [1] and used to generate a tectonic model for the evolution of Pangea. The Early Permian overall mean paleopole for West Gondwana and Adria, in conjunction with the coeval Laurussia paleopole, support Pangea B of Morel and Irving [3]. The Late Permian/Early Triassic and the Middle/Late Triassic paleopoles from Adria and Laurussia support Pangea A-2 of Van der Voo and French [4]. The phase of transcurrent motion between Laurasia and Gondwana[5] that caused the Pangea B to A-2 transition occurred essentially in the Permian (at the end of Variscan orogeny) with an average relative velocity of approximately 10 cm/yr. Finally, the Late Triassic/Early Jurassic paleopoles from West Gondwana and Laurussia agree with Pangea A-1 of Bullard et al. [6], the widely accepted Pangea configuration at the time of the Jurassic breakup.     

Physical mechanisms of man-made influences on the magnetosphere

Since the discovery of the Luxembourg effect in the 1930s, it is clear that man-made activities can perturb the ionosphere and the magnetosphere. The anthropogenic effects are mainly due to different kinds of waves coming from the Earth's surface. Acoustic-gravity waves are generated by large explosions, spacecraft launches, or flight of supersonic planes. Electromagnetic waves are active in different frequency ranges. Power line harmonic radiation which is radiated in the ELF range by electrical power systems can be observed over industrial areas. At VLF and HF, the ground-based transmitters used for communications or radio-navigation heat the ionosphere and change the natural parameters. A large variety of phenomena is observed: wave-particle interaction, precipitation of radiation belt electrons, parametric coupling of EM whistler waves, triggered emissions, frequency shift, and whistler spectrum broadening. This paper will review the different physical mechanisms which are relevant to such perturbations. The possibility of direct chemical pollution in the ionosphere due to gas releases is also discussed.     

南极中山站与北京地磁中心台1991年3月24日磁暴的变化特征

本文分析了１９９１年３月２４日急始型磁暴的变化特征。分析表明，南极极隙区与中低纬区磁暴形态差异很大。中山站地磁台的磁暴急始为ＳＣ＊型，无明显磁暴主相，它是由一组强烈的磁亚暴所组成。北京地磁中心台的磁暴急始为ＳＣ型，磁暴主相持续时间较短，变化较大。这次磁暴是由磁暴前太阳黑子相对数增多、３月２２日２２ｈ４６ｍＵＴ有３ｂ级耀斑爆发等一系列太阳活动所引起的