Introduction to plasma astrophysics and cosmology     

Anthony L. Peratt 《Astrophysics and Space Science》1995,227(1-2):3-11

The year 1996 marks the Centennial Celebration of the founding of Plasma Astrophysics and Cosmology; its origins may be traced to the seminal research first published by Kristian Birkeland in 1896. This special workshop issue reports on advances in issues of importance to the plasma universe; topics as timely as when first raised a century ago.  相似文献   

等离子体湍动电场对Stark致宽函数的贡献     

章振大  林隽  王振 《中国天文和天体物理学报》1989,(1)

过去在用Stark效应研究天体活动过程的光谱时,一般仅考虑Holtsmark场的作用,所得出的电子密度只是一个上限。近来的研究表明,等离子体湍动电场在其中也起着重要的作用,而且当计及这种场的作用时,电子密度减小很多。本文给出Balmer线从H_3—H_(30)的Stark致宽函数S(α,α),它们是考虑到Holtsmark场和湍动场的联合作用以及对两者的不同比值而计算的,所给出的结果与Underhill等和Galdetskii等分别对纯Holtsmark场和纯湍动场而得到的类似数值不同。由于除了极少数外,大部分太阳耀斑和爆发日珥以及其他天体活动过程可能都处于弱或中等等离子体湍动状态,因而所算出的S(α,α)值可用于这些过程的氢线轮廓或半宽的分析。  相似文献   

Energy mode distribution: An analysis of the ratio of anti-Stokes to Stokes amplitudes generated by a pair of counterpropagating Langmuir waves     

F.J.R. Simes Júnior  M.V. Alves  F.B. Rizzato 《Journal of Atmospheric and Solar》2005,67(17-18):1680

Results from plasma wave experiments in spacecrafts give support to nonlinear interactions involving Langmuir, electromagnetic, and ion-acoustic waves in association with type III solar radio bursts. Starting from a general form of Zakharov equation (Zakharov, V.E., 1985. Collapse and self-focusing of Langmuir waves. Hand-book of Plasma Physics Cap.2, 81–121) the equations for electric fields and density fluctuations (density gratings) induced by a pair of counterpropagating Langmuir waves are obtained. We consider the coupling of four triplets. Each two triplets have in common the Langmuir pump wave (forward or backward wave) and a pair of independent density gratings. We numerically solve the dispersion relation for the system, extending the work of (Alves, M.V., Chian, A.C.L., Moraes, M.A.E., Abalde, J.R., Rizzato, F.B., 2002. A theory of the fundamental plasma emission of type- III solar radio bursts. Astronomy and Astrophysics 390, 351–357). The ratio of anti-Stokes (AS) (ω₀+ω) to Stokes (S) (ω₀-ω^*) electromagnetic mode amplitudes is obtained as a function of the pump wave frequency, wave number, and energy. We notice that the simultaneous excitation of AS and S distinguishable modes, i.e., with Re{ω}=ω_r≠0, only occurs when the ratio between the pump wave amplitudes, r is ≠1 and the pump wave vector k₀ is , W₀ being the forward pump wave energy. We also observe that the S mode always receives more energy.  相似文献   

Seasonal characterization of the equatorial electrojet height rise over Brazil as observed by the RESCO 50 MHz back-scatter radar     

C.M. Denardini  M.A. Abdu  E.R. de Paula  J.H.A. Sobral  C.M. Wrasse 《Journal of Atmospheric and Solar》2005,67(17-18):1665

In this paper, we present the seasonal characteristics of the post-noon rise of the equatorial electrojet 3-m irregularities scattering region observed over São Luís, Brazil (2.3S, 44.2W, dip:-0.5). The study is based on a 1 year data set collected by the 50 MHz coherent back-scatter radar (also known by the acronym RESCO), that started operation in 1998. Using a method to estimate the moments from each individual back-scattered power profiles that constitute the standard range–time–intensity (RTI) maps we were able to determine the following representative parameters of the electrojet: the total power back-scattered by the electrojet irregularities (EJP), the thickness of the electrojet back-scattered power profile (EJT), the height of the center of the back-scatter region, that is, the power profile, (EJC), and the noise level corresponding to each power profile (EJN). The parameterization was applied to all selected daily RTI maps from 2002. The analysis was carried out by grouping the data according to the radar beam angle (tilted 30 westward or eastward), the magnetic disturbance indices K_p and the season, which enables us to quantify the differences in the parameters on these bases. The results are presented and discussed here focusing on the post-noon ascent of the EJC. We will also present results on the east–west asymmetry in the radar back-scattered echo power confirming our previous results, and on the appearance of a scattering region after sunset during magnetically quiet conditions around the southern summer solstice.  相似文献   

电离层等离子体漂移的振荡          下载免费PDF全文

张顺荣  黄信榆 《地球物理学报》1994,37(1):10-16

根据中纬Ｗａｋｋａｎａｉ站与低纬Ｏｋｉｎａｗａ站的垂测数据，得出电离层峰区垂直漂移的频谱结构．结果表明，漂移除具有周期在２４ｈ之内的潮汐分量外，低纬站还呈现出值得特别注意的２．１ｄ的周期振荡．作者认为，低纬垂直漂移的振荡行为，主要是电场的波动分量引起；这种波动电场包含潮汐振荡与行星波两日振荡的成分．峰值电子浓度的振荡最直接地是由中性大气温度控制；而峰高的波动起伏，则主要是电场振荡的结果．  相似文献   

Equatorial spread-F initiation: Post-sunset vortex, thermospheric winds, gravity waves     

Erhan Kudeki  Ahmed Akgiray  Marco Milla  Jorge L. Chau  David L. Hysell 《Journal of Atmospheric and Solar》2007,69(17-18):2416

We present experimental evidence and modeling results which indicate that eastward thermospheric wind is the primary controlling factor of equatorial spread-F initiation in the post-sunset ionosphere. Eastward wind-driven Pedersen currents are able to polarize F-region density perturbations with westward tilting wavefronts into rapidly growing modes to trigger the formation of spread-F bubbles. The described process is so rapid that seeding requirements of spread-F initiation by external factors such as gravity waves are effectively eliminated.  相似文献   

气动雾化进样-微波等离子体炬质谱法快速测定水样中的钙离子   总被引：1，自引：1，他引：0  

杨美玲  钟涛  裴妙荣  张兴磊  乐长高  王广才  陈焕文 《岩矿测试》2015,34(5):586-591

环境水样中金属元素的分析通常采用电感耦合等离子体质谱法(ICP-MS),检出限低、线性范围宽,但仍存在使用功率高、耗气量大、分析成本高以及不适用于现场分析等不足。本文为降低金属元素分析成本,建立了微波等离子体炬(MPT)与有机质谱耦合的方式检测水样中钙离子的新方法。详细探究了载气流速和维持气流速对钙离子响应信号的影响,方法检出限为224.56 ng/L,相对标准偏差(RSD)为1.2%~9.8%,加标回收率在86.3%~110.4%之间。本方法无需样品预处理,分析速度快、灵敏度和精确度高,为环境水样中金属离子的测定提供了新途径,有望应用于金属离子的实时在线分析。  相似文献   

等离子质谱法测量土壤中铅、镉、铬的消解方法比对     

邢飞 《吉林地质》2015,(2)

通过高压罐密闭消解、微波消解与聚四氟乙烯坩埚常压消解,等离子质谱法测量土壤中重金属铅、镉、铬,结果表明三种方法均满足土壤质量评价要求,其中聚四氟乙烯坩埚常压消解除铬元素系统稍偏低。聚四氟乙烯坩埚常压消解具有简单,快速,稳定,方法线性范围为(0~200)ng/m L,相关系数均在0.999以上,铅、镉、铬检出限分别是0.7,0.03,3 ng/m L,能满足农业土壤重金属测量要求。  相似文献   

Ionospheric corrections via PIM and real-time data     

R. M. Campbell 《New Astronomy Reviews》1999,43(8-10)

We describe a method for removing ionospheric effects from single-frequency radio data a posteriori. This method is based on a theoretical climatological model developed by the USAF, which returns along the line of sight to the source. Together with a model of , ionospheric delay and Faraday rotation values ensue. If contemporaneous ionospheric data – GPS TEC observations or ionosonde profiles – exist, they can be incorporated to update the modeled n_e.  相似文献   

利用DEMETER卫星数据分析汶川地震前的电离层异常   总被引：19，自引：4，他引：15       下载免费PDF全文

曾中超  张蓓  方广有  王东峰  阴和俊 《地球物理学报》2009,52(1):11-19

DEMETER卫星由法国于2004年6月发射,高度约为665 km,圆轨道且经过极区,其主要目的是研究与地震有关的电离层异常.2008年5月12日6∶28（世界时）在四川省汶川县（31.02°N, 103.37°E）发生了M_s8.0级的特大地震.本文分析了在震前一周内DEMETER卫星观测到的电离层异常.这些异常主要包括：（1）卫星在震前4天和5天经过震中附近时,记录到电子浓度、电子温度和氧离子浓度出现剧烈变化（变化率均超过20%）;（2）在震前3天和7天,卫星探测到增强的电磁辐射.同时利用ELF频段（0~1250 Hz）的三分量电场和磁场数据,对异常电磁辐射作了进一步的分析（计算了电场功率谱、磁场功率谱、波矢方向和极化特性等）.另外,考查了观测期间的地磁指数,由此得出观测到的异常现象不大可能由地磁活动引起.最后,对震前出现的这些电离层异常的可能的物理机理进行了讨论.  相似文献