Ionospheric effetcs of an intense geomagnetic storm

An investigation of the response of the mid-high, mid and low latitude critical frequency foF2 to the geomagnetic storm of 15 July 2000 is made. Ground-based hourly foF2 values (proportional to square root of peak electron density of F2-layer) from four chains of ionospheric stations located in the geographic longitude ranges 10°W–35°E, 60°E–120°E, 130°E–170°E, 250°E–295°E are used. Relative deviations of foF2 are considered. The main ionospheric effects for the considered storm are: long-duration negative disturbances at mid-high latitudes in summer hemisphere in sectors where the storm onset occurred in the afternoon/night-time hours; short-duration positive disturbances in the summer hemisphere at mid-high latitudes in the pre-sunset hours during the end of main phase-first stage of the recovery; small and irregular negative disturbances in the low latitude winter hemisphere which predominate during the main phase and first part of the recovery, and positive disturbances in both hemispheres at mid-high and mid latitudes prior to the storm onset irrespective of the local time. In addition, the validity of some physical mechanisms proposed to explain the F2 region behaviour during disturbed conditions is considered. gus-mansilla@hotmail.com     

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.     

Large-scale impacts of bottom trawling on shelf primary productivity

Disturbance of the seabed resulting from bottom trawling affects ecosystem processes, such as the rate and magnitude of nutrient regeneration. The potential responses of the plankton community arising from such effects can be modelled, provided that reliable data on the effects on nutrient fluxes are available. In a north Cretan outer continental shelf and upper slope fishing ground (Heraklion Bay, Crete, Eastern Mediterranean) we applied a new field instrument which can simulate the passage of trawl groundropes across the sea floor and made direct seasonal measurements of the rate of dissolved and particulate nutrient releases resulting from seabed disturbance. These observational data were then integrated in a 3D ecosystem model. Results revealed that bottom trawling may trigger off considerable productivity pulses, in addition to pulses from the natural seasonal cycle.     

THE DEVELOPMENT OF SYMMETRIC DISTURBANCE SUPERPOSED ON BAROCLINIC FRONTAL ZONE UNDER THE ACTION OF DEFORMATION FIELD*

The development of symmetric disturbance superposed on the background field of Hoskins-Bretherton (1972) frontogenesis model is investigated by means of WKBJ approach,It is found that the forcing of large-scale deformation,the frontal circulation and the spatial-temporal variations of stability parameters (F²,N²,M²) can bring about the development of symmetric disturbance,even though the frontal baroclinic flow is symmetric stable (F²N²-M²>0),The frontogenetical process of deformation confluence zone and the ascending branch of frontal circulation are in favor of the development of symmetric disturbance,The actions of ageostrophic shear in frontal zone and the variation of stability parameters are dependent on the structure of disturbance.     

夏季西风带定常扰动对东北亚阻塞高压的影响

利用ECMWF 1980～1988年9年的格点资料，分析了定常扰动与东北亚阻塞高压之间的关系。分析结果表明:定常扰动的分布对阻塞高压维持日数有着重要的影响，定常扰动的季节变化可以很好地说明阻塞高压冬季多在太平洋和大西洋上发生和维持，而夏季多在东北亚地区发生和维持的特征。此外，从定常扰动的分布可以看到，不仅中高纬地区上空的正距平强度可以影响着阻塞高压的发生和维持，其南侧的负距平强度也同样重要地影响着阻塞高压。分析结果还表明:不仅定常扰动的水平结构对阻高有着重要影响，其垂直结构亦有着重要影响。最后，对夏季定常扰动进行了波数域分析，表明在夏季定常扰动的作用主要通过其中所包含的行星波、特别是行星波1波来实现，定常扰动中行星波部分的振幅变化是影响阻塞高压发生和维持的重要物理机制。     

梅雨期长江流域两类气旋性扰动和暴雨

文章通过分析长江中游大暴雨和特大暴雨个例，研究了两类梅雨涡的产生、演变及与之联系的暴雨发展过程。一类是移到长江中游的典型西南涡，其斜压结构出现在副热带暖环境中，是在这个系统本身发生、发展的动力-热力过程中产生的；另一类是串行于梅雨切变线上的小型正涡度扰动，其演变过程更复杂一些。文章结合这两次个例对作者过去的一些结果作了验证、充实和归纳。并论及复杂暴雨发展过程的一些预报难点。     

电离层诸参量对大气重力波的响应与重力波参数反演

本文利用欧洲非相干散射雷达数据,分析研究了电离层不同等离子体参量对大气重力波的响应之间的关系.应用这种关系,发展了一种在垂直于地磁场的电场可以忽略等简化假设下,由电子密度和离子沿场速度的同时测量数据,反演求解较高（约250km以上）F区中引起TID的重力波传播参数的方法.用此法对一典型TID事件进行分析计算,所得结果与全波解数值研究结果很好符合.     

S_q发电机电流的逐日变化和S_q指数

用中国地磁台站的资料,研究了S_q逐日变化的形态学特征,用理论模型计算了磁层环电流、部分环电流、场向电流、磁尾电流、Chapman-Ferraro电流的地磁效应.在消除了这些磁层电流体系的影响之后,得到了电离层潮汐风发电机电流产生的磁场S_q变化.对1973年的资料研究表明,S_q发电机电流的逐日变化主要表现在强度上,即使在磁扰期间,也可以分离出形态稳定的S_q变化.由此提出了一种新的地磁指数——S_q指数,用来描述S_q发电机电流强度的逐日变化.     

辽东湾丛式钻井陀螺侧钻及导向钻井防碰技术

本文介绍渤海辽东湾实验区AI平台丛式定向井最后钻完的3口侧钻绕障井。在有邻井和本井套管磁干扰情况下,特别是与邻井间距最小仅为0.6m,采用陀螺定向侧钻以及导向钻井技术相结合,安全顺利的钻完了这3口井。总结和介绍了侧钻、防碰的工艺特声,以及安全措施。研究和分析了使用陀螺定向侧钻,钻速与造斜率,井眼轨迹合理控制等问题。     

中低纬过渡地区潜热影响下中尺度扰动的对称发展

本文引入第二科里奥利参数讨论了中低纬过渡地区含非绝热(潜热)作用的对称扰动波包发展问题。结果表明:这一地区扰动波包的发展不仅包含了中高纬度波包发展条件［1］，而且与潜热和基本风场梯度经向切变及波包传播的非垂直性有关。过渡地区基本风场的作用是通过第一和第二科里奥利参数完成的。