Solar wind—magnetosphere coupling: A review of recent results

This paper reviews some aspects of solar wind–magnetosphere–ionosphere interaction. It is shown that in addition to the interplanetary electric field, the solar wind dynamic pressure also has a significant role in determining the state, dynamics, and energetics of the system. It is demonstrated how the state of the magnetosphere and the prior driving affect the amount of energy input to the system, which highlights the capability of the magnetosphere to control the energy flow. The active role of the magnetosphere in determining the dynamics is illustrated by statistical results of the flux balance in the magnetotail and the various dynamic cycles the system can enter. The inner magnetosphere processes during storms are shown to be a result of a complex interplay of processes at the magnetopause and in the magnetotail in response to the solar wind driving. The conclusions are drawn from statistical observational results, empirical models, and global MHD simulations.     

Emergence and evolution of active and ephemeral regions: Comparison between observations and models

This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following legs of the flux tubes. These results are briefly discussed in the light of most recent models.     

Sea-level rise: A review of recent past and near-future trends

Global mean sea level is a potentially sensitive indicator of climate change. Global warming will contribute to worldwide sea-level rise (SLR) from thermal expansion of ocean water, melting of mountain glaciers and polar ice sheets. A number of studies, mostly using tide-gauge data from the Permanent Service for Mean Sea Level, Bidston Observatory, England, have obtained rates of global SLR within the last 100 years that range between 0·3 and 3 mm yr^?1, with most values concentrated between 1 and 2 mm yr^?1. However, the reliability of these results has been questioned because of problems with data quality and physical processes that introduce a high level of spatial and temporal variability. Sources of uncertainty in the sea-level data include variations in winds, ocean currents, river runoff, vertical earth movements, and geographically uneven distribution of long-term records. Crustal motions introduce a major source of error. To a large extent, these can be filtered by employing palaeo-sea-level proxies, and geophysical modelling to remove glacio-isostatic changes. Ultimately, satellite geodesy will help resolve the inherent ambiguity between the land and ocean level changes recorded by tide gauges. Future sea level is expected to rise by ～ 1 m, with a ‘best-guess’ value of 48 cm by the year 2100. Such rates represent an acceleration of four to seven times over present rates. Local land subsidence could substantially increase the apparent SLR. For example, Louisiana is currently experiencing SLR trends nearly 10 times the global mean rate. These recently reduced SLR estimates are based on climate models that predict a zero to negative contribution to SLR from Antarctica. Most global climate models (GCMs) indicate an ice accumulation over Antarctica, because in a warmer world, precipitation will exceed ablation/snow-melt. However, the impacts of attritional processes, such as thinning of the ice shelves, have been downplayed according to some experts. Furthermore, not all climate models are in agreement. Opposite conclusions may be drawn from the results of other GCMs. In addition, the West Antarctic Ice Sheet is potentially subject to dynamic and volcanic instabilities that are difficult to predict. Because of the great uncertainty in SLR projections, careful monitoring of future sea-level trends by upgraded tide-gauge networks and satellite geodesy will become essential. Finally, because of the high spatial variability in crustal subsidence rates, wave climates and tidal regimes, it will be the set of local conditions (especially the relative sea-level rise), rather than a single global mean sea-level trend, that will determine each locality's vulnerability to future SLR.     

Some aspects of the secular variation of the geomagnetic elements H,Z and F between 1958–1974 in Romania

The paper presents some results concerning the secular variation of H, Z and F in Romania between 1958–1974. Curves of the variation of , Z and F at 31 repeat stations are given. The effect of solar activity on the horizontal component is separated and its characteristics discussed. For the interval 1969.5–1974.5 maps of the smoothed secular variation of H, Z and F are given, with isopores described by curves of second degree with respect to the geographical coordinates.     

基于GNSS观测的全球赤道等离子体泡对太阳和地磁活动及季节依赖特征

赤道等离子体泡是在磁赤道和低纬地区一种通常发生在夜间的大尺度电离层不规则结构.本文利用2010—2021年全球低纬地区GNSS TEC监测仪长期观测数据,分析了赤道等离子体泡对太阳和地磁活动及季节的依赖特征.结果表明,全球每个经度区赤道等离子体泡发生率与太阳活动都显著正相关,赤道等离子体泡的日发生率与F₁₀₇指数相关系数接近0.70.经度-60°~-30°在赤道等离子体泡高发月份的日落后发生率与F₁₀₇的相关关系有明显的饱和效应.在季节变化方面,经度-60°~-30°赤道等离子体泡主要发生在1—3月和10—12月,其他经度主要发生在分季.不同经度区赤道等离子体泡日落后发生率季节不对称性存在显著区别,在太阳活动上升期,经度-60°~-30°的10—12月发生率明显高于1—3月;在太阳活动下降期,0°~180°经度区3月分季高于9月分季.此外,地磁扰动对产生赤道等离子体泡主要是抑制作用,特别是在太阳活动高年、分季.

     

基于中国地震台网观测报告的M_L与M_S经验关系

根据1990～2000年《中国地震年报》和2001～2008年《中国数字地震台网观测报告》的大量数据,研究了测定面波震级MS与近震震级ML的不确定性;采用双随机变量的回归方法,用3种不同的数据组,获得二者之间的3组新的转换关系。结果表明,自20世纪70年代使用至今的公式MS=1.13ML-1.08严重偏离数据组,已不适用于新的数据。考虑到测定震级的不确定性及数据的离散性较大等因素,认为采用关系式MS=0.03+0.98ML作为新的经验关系更合理适用。     

Tsunami hazard assessment in the South China Sea: A review of recent progress and research gaps

Science China Earth Sciences - The South China Sea region is potentially threatened by tsunami hazards originated from multiple sources: the Manila subduction zone in the east, the Littoral Fault...     

Evaporation from boreal reservoirs: A comparison between eddy covariance observations and estimates relying on limited data

Hydrological models used for reservoir management typically lack an accurate representation of open-water evaporation and must be run in a scarce data context. This study aims to identify an accurate means to estimate reservoir evaporation with simple meteorological inputs during the open-water season, using long-term eddy covariance observations from two boreal hydropower reservoirs with contrasting morphometry as reference. Unlike the temperate water bodies on which the majority of other studies have focused, northern reservoirs are governed by three distinct periods: ice cover in the cold season, warming in the summer and energy release in the fall. The reservoirs of interest are Eastmain-1 (52°N, mean depth of 11 m) and Romaine-2 (51°N, mean depth of 42 m), both located in eastern Canada. Four approaches are analysed herein: a combination approach, a radiation-based approach, a mass-transfer approach, and empirical methods. Of all the approaches, the bulk transfer equation with a constant Dalton number of 1.2 x 10⁻³ gave the most accurate estimation of evaporation at hourly time steps, compared with the eddy covariance observations (RMSE of 0.06 mm h⁻¹ at Eastmain-1 and RMSE of 0.04 mm h⁻¹ at Romaine-2). The daily series also showed good accuracy (RMSE of 1.38 mm day⁻¹ at Eastmain-1 and RMSE of 0.62 mm day⁻¹ at Romaine-2) both in the warming and energy release phases of the open-water season. The bulk transfer equation, on the other hand, was incapable of reproducing condensation episodes that occurred soon after ice breakup. Basic and variance-based sensitivity analyses were conducted, in particular to measure the variation in performance when the bulk transfer equation was applied with meteorological observations collected at a certain distance (~10–30 km) from the reservoir. This exercise illustrated that accurate estimates of open water evaporation require representative measurements of wind speed and water surface temperature.     

A review of: “Relation between laboratory and space plasmas”

Abstract

Edited by Hiroshi Kikuchi. D. Reidel Publishing Company, Dordrecht, Holland, 1981. xii + 386 pp. + index (Dfl. 110, U.S. $58.00) (ISBN 90277 1248 4)     

基于成像射线的偏移剖面和速度时深转换评述

深度域地震波速度模型是地震勘探中最重要的参数之一,是获得精确深度域偏移剖面的基础.本文基于成像射线的概念,阐述了时间偏移域和深度域之间的关系,明确了时间偏移后的像点是通过成像射线与深度域的散射点联系起来的.在有横向变速的情况下,时间偏移剖面需要经过时深转换才能真实反映深度域层位,同样,从时间偏移剖面上提取的速度也需要经过时深转换才能得到深度域的速度.与前者不同的是,在速度的时深转换中,不仅速度的位置需要改变,且其数值也需要进行校正.该校正因子有几种等价的描述形式：度规量、速度扩散因子和几何扩散因子.     

Altitude of the upper boundary of AAR based on observations of ion beams in inverted-V structures: A case study

Outflowing ion beams forming four successive inverted-V structures in the energy-time spectrograms of H+, He+, and O+ were observed at an altitude of 3.4 RE by Cluster satellites travelling above the auroral acceleration region (AAR) in the southern hemisphere on February 14, 2001. Energization by negative U-shaped potential structures in the AAR is believed to be responsible for the formation of these outflowing ion inverted-V structures. Thus, utilizing the different motion properties of the three ion species, the altitude of the upper boundary of the AAR is estimated to be ~11100 km. Moreover, based on multi-satellite observations, each of these U-shaped potential structures involved in this event crosses the latitudinal direction at ~0.4°–1° invariantlatitude (ILAT), moving poleward at an average speed of ~0.2° ILAT per minute, before disappearing at ~71.5° ILAT.     

Temporal change in scattering and attenuation associated with the earthquake occurrence—A review of recent studies on coda waves

The study of coda waves has recently attracted increasing attention from seismologists. This is due to the fact that it is viewed as a new means by which the stress accumulation stage preceding a large earthquake can be measured, since the scattering paths nearly uniformly cover a fairly large region around the focus and observation stations, compared with the direct ray paths. To date, we have had many reports on the temporal variation of the relation between coda duration and amplitude magnitude, and that of the coda attenuationQ _c ^–1 which is estimated from coda amplitude decay. Some of these have shown a precursor-like behavior; however, others seem to have shown a coseismic change. We have critically reviewed these reports, and discussed what these observational facts tell us about the change in the heterogeneous crust. We found significant temporal variations, not only in the mean but also in the scatter ofQ _c ^–1 , associated with the mainshock occurrence. The formation of new cracks, the reopening and growing of existing cracks, the interaction of these cracks, and the pore water movement through these cracks might correspond to such variations. In addition, we may expect an inhomogeneous distribution of crack clusters in a fairly large region, compared with the aftershock region. The gradual appearance of such crack clusters seems to be the most plausible mechanism by which coda decay gradients are caused to largely scatter in the stress accumulation stage.     

Diagnostics of the magnetosphere based on the outer belt relativistic electrons and penetration of solar protons: A review

The present-day state of the studies of the outer radiation belt relativistic electrons and the boundary of the solar proton penetration into the magnetosphere during magnetic storms is briefly reviewed. The main attention is paid to the results from studying the interrelation between these structural formations and other magnetospheric plasma structures. It has been indicated that the relationship between the position of the maximum of belt of relativistic electrons injected during magnetic storms (L _max) and the magnetic storm amplitude (|Dst|_max = 2.75 × 10⁴/L _max⁴) can be used to predict the extreme latitudinal position of such magnetospheric plasma formations as a trapped radiation region boundary, the nighttime equatorial boundary of the auroral oval, and westward electrojet center during a storm. Using the examples of still rare studies of the solar proton boundary dynamics in the magnetosphere based on the simultaneous measurements on several polar satellites, it has been demonstrated that a change in the geomagnetic field topology during magnetic storms can be diagnosed.     

基于地震和重力观测的深地超宽频带背景噪声初探

深部地下环境的"超静"特点对认识地球内部结构及演变规律具有重要意义.联合淮南深地实验室宽频带地震仪与弹簧重力仪观测资料,利用两种仪器的频率互补优势,初次探究了实验室地表与地下（-848 m）超宽频带（0.0001~50 Hz）的背景噪声水平.研究结果表明,除0.01~0.1 Hz频带内可能由于巷道内的空气流动导致地下噪声高于地表外,其余频带范围地下噪声均低于地表观测,且低频段（0.0001~0.01 Hz）差异较小而高频段（0.1~50 Hz）差异显著.此外,地下地震仪检测到更高信噪比的地球自由振荡简正振型,进一步验证了深部地下环境的"超静"特点.由于淮南深地实验室尚处于基础建设阶段,因此深部地下观测环境的"超静"特点有望随着观测条件的完善更加突显,实验结果可为深地实验室的后续建设和相关地学研究提供重要参考.     

不同模型下地震位错理论的对比 及其应用进展综述

对半空间和球位错理论在理论和应用研究方面的进展进行了综合评述, 讨论了地震位错理论在海啸方面的相关研究进展和位错理论与粒子群算法结合在断层反演方面的研究进展, 对比分析了不同位错模型的优缺点, 总结了位错模型在应用中的影响因素. 本文认为不同位错理论的应用受地球分层的影响最大, 其次是重力、 曲率的影响, 而受地形、 震源深度及断层倾角等因素的影响则较小, 在实际应用中应予以综合考虑.      

A review of the estimation of downward surface shortwave radiation based on satellite data: Methods,progress and problems

The estimation of downward surface shortwave radiation(DSSR) is important for the Earth's energy budget and climate change studies. This review was organised from the perspectives of satellite sensors, algorithms and future trends,retrospects and summaries of the satellite-based retrieval methods of DSSR that have been developed over the past 10 years. The shortwave radiation reaching the Earth's surface is affected by both atmospheric and land surface parameters. In recent years,studies have given detailed considerations to the factors which affect DSSR. It is important to improve the retrieval accuracy of cloud microphysical parameters and aerosols and to reduce the uncertainties caused by complex topographies and high-albedo surfaces(such as snow-covered areas) on DSSR estimation. This review classified DSSR retrieval methods into four categories:empirical, parameterisation, look-up table and machine-learning methods, and evaluated their advantages, disadvantages and accuracy. Further efforts are needed to improve the calculation accuracy of atmospheric parameters such as cloud, haze, water vapor and other land surface parameters such as albedo of complex terrain and bright surface, organically combine machine learning and other methods, use the new-generation geostationary satellite and polar orbit satellite data to produce highresolution DSSR products, and promote the application of radiation products in hydrological and climate models.     

Determination of the photoelectron current density based on comparison between IESP-2 and KM-7 probe measurements of the interball-2 satellite potential relative to plasma

We propose a technique for determining the photoelectron current density based on comparison between simultaneous IESP-2 (electric field meter) and KM-7 (electron temperature sensor) probe measurements of the Interball-2 satellite potential relative to the plasma. We have analyzed the data obtained from ～350 orbital segments in the auroral zone of the magnetosphere at altitudes of 2–3 Earth’s radii from October 1996 to March 1998, i.e., in the period of low solar activity at the beginning of solar cycle 23. The photoelectron current density onboard Inteball-2 has been found to be within the range 1.8–3.6 nA cm^?2.     

A practical review of geostatistical processing applied to geophysical data: methods and applications

Nowadays, geostatistics is commonly applied for numerous gridding or modelling tasks. However, it is still under used and unknown for classical geophysical applications. This paper highlights the main geostatistical methods relevant for geophysical issues, for instance to improve the quality of seismic data such as velocity cubes or interpreted horizons. These methods are then illustrated through four examples. The first example, based on a gravity survey presents how a geostatistical interpolation can be used to filter out a global trend, in order to better define real anomalies. In the second case study, dedicated to refraction surveying, geostatistical filtering is used to filter out acquisition artefacts and identify the main geological structures. The third one is an example of porosity being integrated geostatistically with a seismic acoustic impedance map. The last example deals with geostatistical time to depth conversion; the interest of performing geostatistical simulations is finally discussed.