共查询到17条相似文献，搜索用时 78 毫秒
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在用计算机断层成像方法由EUV观测图像重建等离子体层全球密度分布时,地球的遮挡和有限角度都会导致投影数据不完备,从而无法精确重建出等离子体层的密度分布.本文针对该问题,提出一种基于图像总变差极小化的代数迭代算法.通过重建等离子体层投影数据缺失最为严重的中心子午面,证明该算法能够显著提高重建图像的质量. 并且在IMAGE卫星仅能达到90°的有限投影角度下,此算法重建图像的相关系数可达0.760,而代数迭代算法的相关系数仅为0.696. 相似文献
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本文利用IMAGE卫星EUV相机观测的等离子体层图像,并采用最小L算法反演磁赤道面等离子体层顶位置.文中选取了2000-2002年间的3579幅等离子体层图像,并反演得到了时间间隔为1 h的等离子体层顶位置数据库,包含48899个等离子体层顶位置数据.利用该数据库统计研究了等离子体层顶位形随地磁活动的变化特性.统计发现等离子体层顶高度依赖地磁活动,与地磁指数Kp、Dst和AE均呈负相关,且等离子体层顶随地磁指数的变化趋势具有显著的MLT分布特性;亚暴活动对等离子体层顶演化的贡献在不同地磁活动期间有所不同,磁暴期间亚暴活动的贡献小,而地磁平静期亚暴的贡献大.本文研究工作为后续建立等离子体层顶模型和了解等离子体层顶的动态结构提供了重要研究基础. 相似文献
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利用2010~2011年的THEMIS卫星观测的卫星电位数据反演电子密度,并用来确定等离子层顶的位置,研究其与地磁指数的关系.利用观测数据得到了一个THEMIS卫星等离子体层顶位置数据库.利用该数据库建立了新的等离子体层顶位置的磁地方时经验模型,并比较了其与现有的四个等离子体层顶位置经验模型的优劣.发现新建立的等离子体层顶位置模型明显优于其余四个经验模型.在模型的三种输入参数中,Kp指数和Dst指数模型的预测效果相当,并明显优于AE指数的模型,这说明磁层的大尺度对流强度是影响等离子体层顶位置最主要的因素. 相似文献
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利用SOHO/SEM在1996-2008年的太阳EUV观测数据,比较和评估F10.7和Mg II作为EUV代理参数的代表性,不能支持Viereck等关于Mg II是比F10.7更好的代理参数的结论.通过比较对两种参数的多种回归计算结果,确立双因子极大似然估计方法构建EUV计算模式,通过模型计算结果与SEM观测数据比较,表明该模型能够很好地重建EUV数据系列.利用该模式,构建了1978年11月以来的太阳极紫外辐射数据序列. 相似文献
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日本政府已开始对“亚洲及太平洋地球观测卫星应用20年计划”进行研究。这项计划旨在利用围绕地球运行的许多观测卫星,建立用于亚洲及太平洋地区灾害监视和国土开发的基础数据收集网。日本政府是想借用收集了降水量、地形和地表温度等地球环境基础资料的卫星数据,并以此在亚洲为世界做贡献。预定将在7月份召开的主要发达国家首脑会议(东京高级会晤)上,谋求拥有多数观测卫星的欧美 相似文献
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太阳X_EUV成像望远镜用来监测和预报影响空间天气变化的太阳活动,专门服务于空间天气预报研究. 望远镜工作在4～100?的X射线波段和195?极紫外谱段,视场角45′,角度分辨5″,提供全日面、高分辨的成像观测. 文中分析了太阳X、EUV波段的成像观测应用,介绍了X_EUV望远镜的基本设计,分析了望远镜对不同温度日冕等离子体的敏感性、对不同太阳活动现象的响应及反演日冕等离子体参数过滤片的组合利用. 太阳X_EUV成像望远镜集成了掠入射望远镜和正入射望远镜两套系统,扩展了单一X射线望远镜的成像功能,能够观测更多的太阳爆发先兆现象或者伴生现象,是目前国际上同类仪器中最新的太阳成像监测仪器. 相似文献
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M. I. Verigin G. A. Kotova V. V. Bezrukikh O. S. Aken’tieva 《Geomagnetism and Aeronomy》2012,52(6):725-729
Based on experimental data obtained in 1995?C2000 on board the INTERBALL-1 spacecraft using the ALPHA-3 instrument, a semi-empirical two-dimensional model of the Earth plasmasphere is developed, which allows for the plasma distribution in the entire meridional plane to be restored from the temperature and proton density measurements along the satellite orbit. The model has also been tested using the data of the IMAGE spacecraft. The model uses theoretical expressions (Lemaire and Schere, 1974) that describe the plasma distribution in the plasmasphere for the cases of thermal equilibrium and collisionless initial partial filling of plasmaspheric shells; therefore, the parameters of the constructed model have a clear physical meaning and make it possible, in particular, to estimate the degree of plasmasphere filling. 相似文献
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本文介绍了采用一维遗传算法从地球等离子体层极紫外图像反演地球等离子体层He+密度的原理.首先采用通量管近似和磁偶极近似将三维问题转化为一维问题.通过引入权矩阵,将极紫外光强积分离散为求和函数,再采用一维实数编码遗传算法反演得到磁赤道面等离子体层He+密度,最后通过磁力线追迹得到三维密度分布.算法采用动态全球核心等离子体模式模拟的密度和光强分布作为初始输入参数,并通过遗传算法得到相应密度分布.反演结果表明,等离子体层密度相对误差在8%以内,光强相对误差趋于0,算法有效可行.本文研究为中国探月二期工程中月基极紫外图像反演奠定了基础. 相似文献
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《Journal of Atmospheric and Solar》2007,69(3):341-350
The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) Mission extreme ultraviolet (EUV) imager observes He+ plasmaspheric ions throughout the inner magnetosphere. Limited by ionizing radiation and viewing close to the sun, images of the He+ distribution are available every 10 min for many hours as the spacecraft passes through apogee in its highly elliptical orbit. As a consistent constituent at about 15%, He+ is an excellent surrogate for monitoring all of the processes that control the dynamics of plasmaspheric plasma. In particular, the motion of He+ transverse to the ambient magnetic field is a direct indication of convective electric fields. The analysis of boundary motions has already achieved new insights into the electrodynamic coupling processes taking place between energetic magnetospheric plasmas and the ionosphere. Yet to be fulfilled, however, is the original promise that global EUV images of the plasmasphere might yield two-dimensional pictures of mesoscale to macroscale electric fields in the inner magnetosphere. This work details the technique and initial application of an IMAGE EUV analysis that appears capable of following thermal plasma motion on a global basis. 相似文献
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等离子体层已有数十年研究历史,但对其核心等离子体区域却一直没有一个相对准确的界限和模型定义.基于范阿伦辐射带卫星RBSP-A在2012年9月18日至2014年10月13日约两年的观测,我们统计研究了磁宁静期间核心等离子体层电子密度随磁地方时(MLT)及磁壳指数(L-value)的分布特征.发现了核心等离子体层电子密度在不同MLT条件下随L值的变化趋势几乎一致,但与以前的等离子体层经验模式计算的电子密度存在较大的偏差.在不同L值下电子密度随MLT的变化趋势也相差不大,而且随MLT存在明显的逐日和半日变化.最后我们获得了等离子体层电子密度随L值和MLT变化的经验公式.研究结果对空间等离子体层建模及研究具有重要的意义. 相似文献
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Based on theoretical models of the ionosphere and the plasmasphere, the ion composition variations in the plasmasphere and the plasmapause structure were studied depending on the choice of the distribution model of the magnetospheric convection electric field at low and high geomagnetic activity at the equinox and the December solstice. Based on the model calculations performed, the plasmapause shape and size during an increase and decrease in geomagnetic activity were studied. It was revealed that the size of the plasmasphere mainly depends on the magnetic local time (MLT) sector and the level of geomagnetic activity, and it greatly depends on the maximum universal time during the equinox. The Earth’s plasmasphere asymmetry is manifested in the noon-midnight and morning-evening directions. The analysis results of daily and seasonal variations in the ionic composition of the Earth’s plasmasphere at a moderate solar activity level show that there is a certain increase in the ion concentrations of H+ and He+ in the winter period probably due to an increase in the exospheric density at the summer to winter transition. The data obtained are in good agreement with satellite observations which makes it possible to use the model proposed to study the plasmasphere under different geophysical conditions. 相似文献
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M. I. Verigin G. A. Kotova V. V. Bezrukikh V. V. Bogdanov A. V. Kaisin 《Geomagnetism and Aeronomy》2011,51(1):39-48
Based on the thermal plasma measurements in the Earth’s inner plasmasphere on the INTER-BALL-2 and MAGION-5 satellites it
has been indicated that the plasmaspheric ion temperature as a rule decreases during the main phase of magnetic storms; in
this case the plasma density increases or remains at the level typical of undisturbed conditions. The physical mechanism by
which the ion drift during a magnetic storm results in a temperature decrease is described. It is shown that the third adiabatic
invariant also remains in processes with a characteristic time shorter than the period of charged particle drift around the
Earth for cold equatorial plasma. The constructed model of the drift shell displacement from the Earth caused by a decrease
in the magnetic field in the inner magnetosphere during the development of a magnetic storm satisfactorily describes the decrease
in the proton temperature near the equatorial plane. 相似文献
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《Journal of Atmospheric and Solar》2007,69(3):303-313
We use magnetic field-aligned mapping between the ionosphere and the magnetosphere to intercompare ground-based observations of storm enhanced density (SED), and plasmasphere drainage plumes imaged from space by the IMAGE EUV imager, with the enhanced inner-magnetosphere/ionosphere SAPS electric field which develops during large storms. We find that the inner edge of the SAPS electric field overlaps the erosion plume and that plume material is carried sunward in the SAPS overlap region. The two phenomena, SED in the ionosphere and the erosion plume at magnetospheric heights, define a common trajectory for sunward-propagating cold plasma fluxes in the midnight—dusk–postnoon sector. The SAPS channel at ionospheric heights and its projection into the equatorial plane serve to define the sharp outer boundary of the erosion plume. The SAPS electric field abuts and overlaps both the plasmasphere boundary layer and the plasmasphere erosion plume from pre-midnight through post-noon local times. 相似文献