Response of the magnetic field and plasmas at the geosynchronous orbit to interplanetary shock

Interplanetary shock can greatly disturb the Earth＇s magnetosphere and ionosphere, causing the temporal and spatial changes of the magnetic field and plasmas at the geosynchronous orbit. In this paper, we use the magnetic field data of GOES satellites from 1997 to 2007 and the plasma data of MPA on the LANL satellites from 1997 to 2004 to study the properties of magnetic field and plasma （0.03-45 keV） at the geosynchronous orbit （6.6 RE） within 3 hours before and after the arrival of shock front at the geosynchronous orbit through both case study and superposed epoch analysis. It is found that following the arrival of shock front at the geosynchronous orbit, the magnetic field magnitude, as well as GSM Bzcomponent increases significantly on the dayside （8-16 LT）, while the By component has almost no change before and after shock impacts. In response to the interplanetary shock, the proton becomes much denser with a peak number density of 1.2 cm^-3, compared to the typical number density of 0.7 cm^-3. The proton temperature increases sharply, predominantly on the dusk and night side. The electron, density increases dramatically on the night side with a peak number density of 2.0 cm^-3. The inferred ionospheric O^＋ density after the interplanetary shock impact reaches the maximum value of 1.2 cm^-3 on the dusk side and exhibits the clear dawn-dusk asymmetry. The peak of the anisotropy of proton＇s temperature is located at the noon sector, and the anisotropy decreases towards the dawn and dusk side. The minimum of temperature anisotropy is on the night side. It is suggested that the electromagnetic ion cyclotron （EMIC） wave and whistler wave can be stimulated by the proton and electron temperature anisotropy respectively. The computed electromagnetic ion cyclotron wave （EMIC） intense on the day side （8--16 LT） with a frequency value of 0.8 Hz, and the wave intensity decreases towards the dawn and dusk side, the minimum value can be found on the night side. The computed electron whistler wave locates on the day side （8--16 LT） with a value of 2 kHz.     

Responses of properties in the plasma sheet and at the geosynchronous orbit to interplanetary shock

On July 22, 2004, the WIND spacecraft detected a typical interplanetary shock. There was sustaining weak southward magnetic field in the preshock region and the southward field was suddenly enhanced across the shock front （i.e., southward turning）. When the shock impinged on the magnetosphere, the magnetospheric plasma convection was abruptly enhanced in the central plasma sheet, which was directly observed by both the TC-1 and Cluster spacecraft located in different regions. Simultaneously, the Cluster spacecraft observed that the dawn-to-dusk electric field was abruptly enhanced. The variations of the magnetic field observed by TC-1, Cluster, GOES-10 and GOES-12 that were distributed in different regions in the plasma sheet and at the geosynchronous orbit are obviously distinct. TC-1 observations showed that the magnetic intensity kept almost unchanged and the elevation angle decreased, but the Cluster spacecraft, which was also in the plasma sheet and was further from the equator, observed that the magnetic field was obviously enhanced. Simultaneously, GOES-12 located near the midnight observed that the magnetic intensity sharply increased and the elevation angle decreased, but GOES-10 located in the dawn side observed that the magnetic field was merely compressed with its three components all sharply increasing. Furthermore, the energetic proton and electron fluxes at nearly all channels observed by five LANL satellites located at different magnetic local times （MLTs） all showed impulsive enhancements due to the compression of the shock. The responses of the energetic particles were much evident on the dayside than those on the nightside. Especially the responses near the midnight were rather weak. In this paper, the possible reasonable physical explanation to above observations is also discussed. All the shock-induced responses are the joint effects of the solar wind dynamic pressure pulse and the magnetic field southward turning.     

从隋唐到明清时期孙思邈思想的发掘研究

孙思邈为中国古代名医之一,他在中医史上做出了承前启后的贡献,使中医继后汉之后的唐代又登上一个新高峰.他的<千金要方>、<千金翼方>两部著作留下的宝贵遗产,对后世中医学甚至在国际上影响都很大.但是孙思邈及其著作的思想发掘却是一个漫长过程.     

对孙中山宇宙观几个问题的探讨

孙中山不仅是我国近代史上著名的革命家,而且是我国近代资产阶级唯物主义哲学的主要代表者。他继承了我国古代唯物论的传统,吸取西方近代自然科学知识,用进化论的观点,论述了宇宙的起源、人类的起源等根本问题。但是孙中山的唯物主义哲学也有很大的历史局限性。     

An early extrasolar planetary system revealed by planetesimal belts in beta Pictoris

beta Pictoris (beta Pic) is a main-sequence star with an edge-on dust disk that might represent a state of the early Solar System. The dust does not seem to be a remnant from the original protoplanetary disk, but rather is thought to have been generated from large bodies like planetesimals and/or comets. The history and composition of the parent bodies can therefore be revealed by determining the spatial distribution, grain size, composition and crystallinity of the dust through high-resolution mid-infrared observations. Here we report that the sub-micrometre amorphous silicate grains around beta Pic have peaks in their distribution around 6, 16 and 30 au (1 au is the Sun-Earth distance), whereas the crystalline and micrometre-sized amorphous silicate grains are concentrated in the disk centre. As sub-micrometre grains are blown quickly out from the system by radiation pressure from the central star, the peaks indicate the locations of ongoing dust replenishment, which originates from ring-like distributions of planetesimals or 'planetesimal belts'.     

唐代孙过庭《书谱》所蕴含的哲理探析

唐代孙过庭的《书谱》是一部专门教导书法学习者的经典论著,它不但有专业的书法语言和很深刻的教育意义,还蕴含着丰富的哲理,对学习者有极大的益处。     

论孙诒让的《墨子间诂》在墨学复活与勃兴中的作用

孙诒让的《墨子间诂》被王焕镳誉之为“墨学研究中的旷代之作”，又被罗检秋称为“墨学发展史上的一个重要里程碑”。它继承吸取了20世纪以前墨学研究的成果，基本恢复了《墨子》文本的真实面目，为墨学思想的研究和现代价值的挖掘铺平了道路，扫清了障碍，促进五四时期墨学科学价值的被发现和平民学说、逻辑价值的确立，以至引来20世纪30至60年代墨学研究的全面丰收，最终促成墨学的伟大复兴。     

Depth of a strong jovian jet from a planetary-scale disturbance driven by storms

The atmospheres of the gas giant planets (Jupiter and Saturn) contain jets that dominate the circulation at visible levels. The power source for these jets (solar radiation, internal heat, or both) and their vertical structure below the upper cloud are major open questions in the atmospheric circulation and meteorology of giant planets. Several observations and in situ measurements found intense winds at a depth of 24 bar, and have been interpreted as supporting an internal heat source. This issue remains controversial, in part because of effects from the local meteorology. Here we report observations and modelling of two plumes in Jupiter's atmosphere that erupted at the same latitude as the strongest jet (23 degrees N). The plumes reached a height of 30 km above the surrounding clouds, moved faster than any other feature (169 m s(-1)), and left in their wake a turbulent planetary-scale disturbance containing red aerosols. On the basis of dynamical modelling, we conclude that the data are consistent only with a wind that extends well below the level where solar radiation is deposited.     

从孙梨的散文探析其现实主义主张

孙犁源于现实生活的现实主义观念,以真实性、现实性、积极向上的倾向性、真实生动的细节描写和充分发挥作家的主观能动性为其基本内涵,在历史的发展中以其坚定不移的个性参与着文坛现实主义文学创作多元化的建构。     

Pumping of nutrients to ocean surface waters by the action of propagating planetary waves

Primary productivity in the oceans is limited by the lack of nutrients in surface waters. These nutrients are mostly supplied from nutrient-rich subsurface waters through upwelling and vertical mixing, but in the ocean gyres these mechanisms do not fully account for the observed productivity. Recently, the upward pumping of nutrients, through the action of eddies, has been shown to account for the remainder of the primary productivity; however, these were regional studies which focused on mesoscale (100-km-scale) eddies. Here we analyse remotely sensed chlorophyll and sea-surface-height data collected over two years and show that 1,000-km-scale planetary waves, which propagate in a westward direction in the oceans, are associated with about 5 to 20% of the observed variability in chlorophyll concentration (after low-frequency and large-scale variations are removed from the data). Enhanced primary production is the likely explanation for this observation, and if that is the case, propagating disturbances introduce nutrients to surface waters on a global scale--similar to the nutrient pumping that occurs within distinct eddies.     

Scattering by chorus waves as the dominant cause of diffuse auroral precipitation

Earth's diffuse aurora occurs over a broad latitude range and is primarily caused by the precipitation of low-energy (0.1-30-keV) electrons originating in the central plasma sheet, which is the source region for hot electrons in the nightside outer magnetosphere. Although generally not visible, the diffuse auroral precipitation provides the main source of energy for the high-latitude nightside upper atmosphere, leading to enhanced ionization and chemical changes. Previous theoretical studies have indicated that two distinct classes of magnetospheric plasma wave, electrostatic electron cyclotron harmonic waves and whistler-mode chorus waves, could be responsible for the electron scattering that leads to diffuse auroral precipitation, but it has hitherto not been possible to determine which is the more important. Here we report an analysis of satellite wave data and Fokker-Planck diffusion calculations which reveals that scattering by chorus is the dominant cause of the most intense diffuse auroral precipitation. This resolves a long-standing controversy. Furthermore, scattering by chorus can remove most electrons as they drift around Earth's magnetosphere, leading to the development of observed pancake distributions, and can account for the global morphology of the diffuse aurora.     

A magnetic torsional wave near the Galactic Centre traced by a 'double helix' nebula

The magnetic field in the central few hundred parsecs of the Milky Way has a dipolar geometry and is substantially stronger than elsewhere in the Galaxy, with estimates ranging up to a milligauss (refs 1-6). Characterization of the magnetic field at the Galactic Centre is important because it can affect the orbits of molecular clouds by exerting a drag on them, inhibit star formation, and could guide a wind of hot gas or cosmic rays away from the central region. Here we report observations of an infrared nebula having the morphology of an intertwined double helix about 100 parsecs from the Galaxy's dynamical centre, with its axis oriented perpendicular to the Galactic plane. The observed segment is about 25 parsecs in length, and contains about 1.25 full turns of each of the two continuous, helically wound strands. We interpret this feature as a torsional Alfvén wave propagating vertically away from the Galactic disk, driven by rotation of the magnetized circumnuclear gas disk. The direct connection between the circumnuclear disk and the double helix is ambiguous, but the images show a possible meandering channel that warrants further investigation.     

Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere.

The bright night-time aurorae that are visible to the unaided eye are caused by electrons accelerated towards Earth by an upward-pointing electric field. On adjacent geomagnetic field lines the reverse process occurs: a downward-pointing electric field accelerates electrons away from Earth. Such magnetic-field-aligned electric fields in the collisionless plasma above the auroral ionosphere have been predicted, but how they could be maintained is still a matter for debate. The spatial and temporal behaviour of the electric fields-a knowledge of which is crucial to an understanding of their nature-cannot be resolved uniquely by single satellite measurements. Here we report on the first observations by a formation of identically instrumented satellites crossing a beam of upward-accelerated electrons. The structure of the electric potential accelerating the beam grew in magnitude and width for about 200 s, accompanied by a widening of the downward-current sheet, with the total current remaining constant. The 200-s timescale suggests that the evacuation of the electrons from the ionosphere contributes to the formation of the downward-pointing magnetic-field-aligned electric fields. This evolution implies a growing load in the downward leg of the current circuit, which may affect the visible discrete aurorae.     

沙尘暴过程观测数据与实测数据的综合分析

不断加深沙尘暴起沙、传输、沉降机制及其辐射强迫机理认识,提高沙尘暴的预测预警以及防治水平,已成为科研界和政府部门共同关注的问题.我们充分利用已观测的数据进行了深入的综合研究和方法探索,在数据处理本身和多元数据分析方面均取得一些新进展.本文充分利用遥感观测和地面实测手段,对亚洲沙尘暴进行监测.通过对多元数据进行分析和综合,建立了遥感监测结果与地面观测结果之间的关联关系,这些监测结果能够为综合风侵蚀模型系统和GCM(全球尺度沙尘模拟模型)模型系统提供参数和验证数据,同时为沙尘暴的预警预报提供基础数据和客观依据.     

试析《太阳照常升起》的存在主义主题

海明威的长篇小说《太阳照常升起》围绕一群从一战战场归来的年轻人放浪形骸的生活展开,反映了一战后迷惘一代的生存困境和精神苦闷。通过对作品主人公杰克·巴恩斯经历的分析,可知此小说是以存在主义主题揭示杰克在困境中运用自由意志支撑个人尊严、勇敢面对伤痛面对明天的。     

Filamentary structure on the Sun from the magnetic Rayleigh-Taylor instability

Magnetic flux emerges from the solar surface as dark filaments connecting small sunspots with opposite polarities. The regions around the dark filaments are often bright in X-rays and are associated with jets. This implies plasma heating and acceleration, which are important for coronal heating. Previous two-dimensional simulations of such regions showed that magnetic reconnection between the coronal magnetic field and the emerging flux produced X-ray jets and flares, but left unresolved the origin of filamentary structure and the intermittent nature of the heating. Here we report three-dimensional simulations of emerging flux showing that the filamentary structure arises spontaneously from the magnetic Rayleigh-Taylor instability, contrary to the previous view that the dark filaments are isolated bundles of magnetic field that rise from the photosphere carrying the dense gas. As a result of the magnetic Rayleigh-Taylor instability, thin current sheets are formed in the emerging flux, and magnetic reconnection occurs between emerging flux and the pre-existing coronal field in a spatially intermittent way. This explains naturally the intermittent nature of coronal heating and the patchy brightenings in solar flares.