共查询到19条相似文献，搜索用时 156 毫秒
1.
本文讨论了行星际磁场B2分量变化时内磁层和中低纬度电离层的响应.指出B2变化引起的磁层大尺度对流电场的变化在一定条件下有可能透入内磁层,并沿磁力线映射到中低纬度电离层,在那里产生电场和电流体系,从而使Sq电流体系发生畸变,并在地面磁场中反映出来.数值计算表明,当△B2<0时,Sq电流体系的焦点向东和向高纬移动,地面磁场会观测到数伽马的变化.这就为中低纬地磁观测诊断磁层和太阳风状态提供了一种可能性.此外,本文还用上述物理过程解释了赤道地区一些高空物理现象,如B2倒转时电离层漂移速度的变化,赤道磁场异常以及赤道q型偶现E层的消失等等. 相似文献
2.
磁层亚暴与磁层暴（Ⅱ）:太阳风参数对Dst的影响机制研究 总被引：1，自引：0，他引：1
为了研究地磁活动指数Dst受太阳风参数影响,包括行星际磁场（IMF）南向分量Bst、太阳风速度V?和太阳风-磁层发电机电动势U调制的机制,应用太阳风-磁层-电离层输入-输出[I（t）-O（t）]电网络模型,对磁层亚暴与磁层暴过程中,Bz（t）-Dst、V-a（t）-Dst和U（t）-Dst的激励-响应特性进行模拟。研究表明,Bz是形成亚暴与磁层暴的前提条件,Vst是形成亚暴与磁层暴的充分条件,二者统一于电动势Ust研究结果与观测结果一致。 相似文献
3.
本文用随时间变化的对流模式,讨论了电导率日夜不均匀性对磁层-电离层耦合过程及大尺度场向电流日变化形态的影响,以Senior-Blanc随时间变化的简单模式为基础,计入电导率日夜变化加以发展,对驱动势随时间变化为阶梯函数的情况进行了讨论。修正模式表明电导率日夜不均匀性对磁层-电离层弛豫过程产生影响,在不同地方时,二区场向电流发展状况不同,达到平衡时间也各异。在某些条件下,中午前后甚至可能达不到平衡。模式计算给出的电位及场向电流图象与观测基本特点相符。这说明S-B模式反映了电场耦合中的主要物理过程,也表明电离层电导率日夜变化的调制作用。 相似文献
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5.
用中国地磁台站的资料,研究了Sq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Sq变化.对1973年的资料研究表明,Sq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Sq变化.由此提出了一种新的地磁指数--Sq指数,用来描述Sq发电机电流强度的逐日变化. 相似文献
6.
利用ISEE－1和ISEE-2飞船观测的磁场数据，分析了地球内磁层场向电流的统计特征，包括场向电流的空间（L值和地方时）分布；流进和流出电离层的场向电流随地方时的变化；场向电流发生率与地磁活动水平（以AL指数表征）、行星际磁场（IMF）Bz的关系，电流强度和密度随地磁活动水平的变化等．发现，场向电流大都发生在夜间，且集中在L为6-10区域内，场向电流发生率，强度和密度随地磁活动增强而增大，行星际磁场南向时的发生率远远高于北向时的发生率．这些结果表明，内磁层场向电流的产生是太阳风和磁层、电离层间电动耦合增加的结果． 相似文献
7.
高纬电离层特性的实例研究 总被引：1，自引：0，他引：1
本文利用EISCAT雷达资料讨论磁层-电离层耦合的高纬电离层效应。研究表明,即使在夏季极昼情况下,磁扰期间的磁层过程对高纬电离层形态的影响也远大于太阳紫外辐射的作用。高能粒子沉降使电离层E层的电子密度大大增加;而磁层对流速度变大会使F层内电离复合加强。因而,磁扰时经常出现ne（E层）>e（F层）的情况。此现象不仅与宁静时完全相反,而且与中低纬电离层形态变化也有很大差别。 相似文献
8.
本文在Hibberd方法的基础上提出了一种分离变化磁场几种主要成分的方法,使用这种方法可以定量地给出每天Sq型变化、Dst变化和其他不规则变化。用东亚地磁台链资料进行了检验,结果表明:中低纬度电离层Sq型电流体系的空间结构相当稳定,即使在磁暴期间,该电流体系的结构也无十分明显的变化;磁扰期间复杂的地磁变化主要来自磁层环电流、场向电流和高纬度电离层电流:Sq逐日变化主要表现在幅度上,这反映了电离层发电机电流体系具有较稳定的空间结构和逐日变化的强度。 相似文献
9.
本文用数值计算方法对极盖区边界变化、其上驱动电势突然增减以及粒子沉降边界随时间变化等情况下,中低纬电离层电位分布及赤道电急流变化进行了研究。结果表明,赤道电急流明显地受到磁层-电离层电动耦合的影响。在白天到午夜的大部分时间内,当驱动势增强和扰动源向低纬扩展时,产生扰时附加东向赤道电急流;反之,有较强的磁层源西向电急流。计算结果解释了观测的主要现象,也表明观测结果的复杂性可能与过程不同阶段上电急流位相变化有关。 相似文献
10.
本文讨论了一种地球磁层的亚暴机制。当行星际磁场有大的南向分量时,磁层的位形可由基本闭式转变为开式。磁鞘中的阿尔文波可以携带超过10~(18)尔格/秒的能流传入磁层尾部,并将能量耗散于等离子体片中。等离子体片中的粒子被加热和加速后,注入近地空间,产生环电流和极区亚暴。计算了剪切流场中阿尔文波的传播过程,以及磁层中阿尔文波的耗散。将本文的结算与[4]中的结果合在一起,可以说明当行星际磁场转向南时,容易发生地球磁层亚暴,但这两者并非一一对应的关系,行星际磁场没有南向分量时也可以发生地球磁层亚暴。 相似文献
11.
《Journal of Atmospheric and Solar》2007,69(3):265-278
Recent observations have quantified the auroral wind O+ outflow in response to magnetospheric inputs to the ionosphere, notably Poynting energy flux and precipitating electron density. For moderate to high activity periods, ionospheric O+ is observed to become a significant or dominant component of plasma pressure in the inner plasma sheet and ring current regions. Using a global circulation model of magnetospheric fields and its imposed ionospheric boundary conditions, we evaluate the global ionospheric plasma response to local magnetospheric conditions imposed by the simulation and evaluate magnetospheric circulation of solar wind H+, polar wind H+, and auroral wind O+. We launch and track the motions of millions of test particles in the global fields, launched at randomly distributed positions and times. Each particle is launched with a flux weighting and perpendicular and parallel energies randomly selected from defined thermal ranges appropriate to the launch point. One sequence is driven by a two-hour period of southward interplanetary magnetic field for average solar wind intensity. A second is driven by a 2-h period of enhanced solar wind dynamic pressure for average interplanetary field. We find that the simulated ionospheric O+ becomes a significant plasma pressure component in the inner plasma sheet and outer ring current region, particularly when the solar wind is intense or its magnetic field is southward directed. We infer that the reported empirical scalings of auroral wind O+ outflows are consistent with a substantial pressure contribution to the inner plasma sheet and plasma source surrounding the ring current. This result violates the common assumption that the ionospheric load is entirely confined to the F layer, and shows that the ionosphere is often an important dynamic element throughout the magnetosphere during moderate to large solar wind disturbances. 相似文献
12.
R. G. Rastogi 《Annales Geophysicae》1997,15(10):1309-1315
A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V × Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field. 相似文献
13.
《Journal of Atmospheric and Solar》2007,69(3):212-222
We have used a global time-dependent magnetohydrodynamic (MHD) simulation of the magnetosphere and particle tracing calculations to determine the access of solar wind ions to the magnetosphere and the access of ionospheric O+ ions to the storm-time near-Earth plasma sheet and ring current during the September 24–25, 1998 magnetic storm. We found that both sources have access to the plasma sheet and ring current throughout the initial phase of the storm. Notably, the dawnside magnetosphere is magnetically open to the solar wind, allowing solar wind H+ ions direct access to the near-Earth plasma sheet and ring current. The supply of O+ ions from the dayside cusp to the plasma sheet varies because of changes in the solar wind dynamic pressure and in the interplanetary magnetic field (IMF). Most significantly, ionospheric O+ from the dayside cusp loses access to the plasma sheet and ring current soon after the southward turning of the IMF, but recovers after the reconfiguration of the magnetosphere following the passage of the magnetic cloud. On average, during the first 3 h after the sudden storm commencement (SSC), the number density of solar wind H+ ions is a factor of 2–5 larger than the number density of ionospheric O+ ions in the plasma sheet and ring current. However, by 04:00 UT, ∼4 h after the SSC, O+ becomes the dominant species in the ring current and carries more energy density than H+ ions in both the plasma sheet and ring current. 相似文献
14.
Keiichiro Fukazawa Tomoharu Aoyama Tatsuki Ogino Kiyohumi Yumoto 《Journal of Atmospheric and Solar》2010,72(13):1019-1023
It is well known that the cross polar cap potential is saturated under a strong interplanetary electric field and is often said to be related to the ionospheric currents. To investigate the other factors influencing this phenomenon, a global magnetohydrodynamics simulation not including the feedback from the ionosphere to the magnetosphere was conducted. The simulation results showed that an increase in the southward IMF causes a smaller increase in the cross polar cap potential than that caused by an increase in the solar wind velocity. This difference was caused by the transportation of reconnected magnetic field lines towards the tail. 相似文献
15.
H. Prez-de-Tejada 《Journal of Atmospheric and Solar》2005,67(17-18):1786
The general features of the region of interaction of the solar wind with the ionosphere of Venus and Mars are compared using data obtained with the Mariner 5 and the Pioneer Venus Orbiter (PVO) spacecraft for Venus and with the Phobos II, the Mars Global Surveyor (MGS) and the Mars Express spacecraft for Mars. Despite the overall weak intrinsic global magnetic field that is present in both planets there are significant differences in the manner in which the interplanetary magnetic field accumulates and is organized around and within their ionosphere. Such differences are unrelated to the crustal magnetic field remnants inferred from the MGS measurements around Mars. In fact, while in Venus and Mars there is a region in which the magnetic field becomes enhanced as it piles up in their plasma environment it is shown that such a region exhibits different regimes with respect to changes in the ion composition measured outside and within the ionosphere. At Venus the region of enhanced magnetic field intensity occurs in general above the ionopause which represents the boundary across which there is a change in the ion composition with dominant solar wind protons above and planetary O+ ions below. At Mars the region of enhanced magnetic field is located below a magnetic pileup boundary across which there is also a comparable change in the ion composition (solar wind protons above and planetary O+ ions below). It is argued that this difference in the relative position of the region of enhanced magnetic field with respect to that of a plasma boundary that separates different ion populations results from the peculiar response of the ionosphere of each planet to the oncoming solar wind dynamic pressure. While at Venus the peak ionospheric thermal pressure is in general sufficient to withhold the incident solar wind kinetic pressure there is a different response in Mars where the peak ionospheric thermal pressure is in general not large enough to deviate the solar wind. In this latter case the ionosphere is unable to force the solar wind to move around the ionosphere and as a result the oncoming electron population can reach low altitudes where it is influenced by neutral atmospheric particles (the solar wind proton population is replaced at the magnetic pileup boundary which marks the upper extent of the region where the interplanetary magnetic field becomes enhanced). Peculiar conditions are expected near the magnetic polar regions and over the terminator plane where the solar wind is directed along the sides of the planet. 相似文献
16.
用Ｋａｍｉｄｅ－Ｍａｔｓｕｓｈｉｔａ方法，在行星际磁场具有较小的北向分量，且｜Ｂｙ｜＞＞｜Ｂｋ｜时，对磁语和磁扰状态以及Ｂｒ＞０和Ｂｙ＜０等不同情况，分别计算了场向电流引起的电离层电势、电场和电流体系．结果表明，极隙区场向电流的存在使高纬向日面区域的电势发生畸变，当Ｂｙ＞０时，无论是磁扰还是磁静日，极隙区电场具有显著的北向分量；等离子体对流有较大的西向分量；电离层电流为东向电流．当Ｂｙ＜０时，电场和等离子体对流的方向与Ｂｙ＞０时相反；电离层电流在磁抗日有西向分量，但在磁静日没有西向分量．电导率对电场和电流体系的影响十分明显，磁扰极光带电导率增强使电流涡从背阳面向向阳而漂移，与静日相比，磁扰时极隙区场向电流引起的电场畸变更为明显，但电场和电流强度的大小却基本保持不变． 相似文献
17.
《Journal of Atmospheric and Solar》2002,64(2):145-157
The solar wind, magnetosphere, and ionosphere are intrinsically coupled through magnetic field lines. The electrodynamic state of the high-latitude ionosphere is controlled by several geophysical processes, such as the location and rate of magnetic reconnection at the magnetopause and in the magnetotail, and the energisation and precipitation of solar wind and magnetospheric plasmas. Amongst the most observed ionospheric manifestation of solar wind/magnetospheric processes are the convection bursts associated with the so-called flux transfer events (FTEs), magnetic impulse events (MIEs), and travelling convection vortices (TCVs). Furthermore, the large-scale ionospheric convection configuration has also demonstrated a strong correspondence to variations in the interplanetary medium and substorm activity. This report briefly discusses the progress made over the past decade in studies of these transient convection phenomena and outlines some unsettled questions as well as future research directions. 相似文献
18.
本文利用中低纬日本地区(131°E,35°N)GPS-TEC格点化数据,分析了2001—2009年间109个共转相互作用区(CIR)事件、45个日冕物质抛射(CME)事件引起的地磁扰动期间电离层的响应.结果表明,电离层暴的类型随太阳活动的变化而有不同的变化,CIR事件引发的电离层正相暴、正负双相暴多发生在太阳活动下降年,负相暴多发生在高年,负正双相暴多发生在低年;CME事件引发的电离层正相暴和负相暴多发生在高年.CIR和CME引发的不同类型的电离层暴的季节性差异不大,在夏季多发生正负双相暴.电离层暴发生时间相对地磁暴的时延大部分在-6~6h之间,但CIR引发的电离层暴时延范围更广,在-12~24h之间,而CME引发的电离层暴时延主要在-6~6h之间.中低纬的电离层暴多发生在主相阶段,其中CIR引发的双相暴也会发生在初相阶段.电离层负暴多发生在AE最大值为800~1200nT之间.CIR引起的电离层扰动持续时间较长,一般在1~6天左右,而CME引起的电离层扰动持续时间一般在1~4天左右. 相似文献
19.
V. M. Mishin M. Foerster T. I. Saifudinova A. D. Bazarzhapov Yu. A. Karavaev L. A. Sapronova S. I. Solovyev 《Geomagnetism and Aeronomy》2007,47(4):429-441
The interval 0000-1400 UT of the superstorm of November 20, 2003, has been studies based on the ACE/WIND data and the MIT2 magnetogram inversion technique. The distributions of the electric potential and currents, field-aligned currents, and Joule heat in the ionosphere have been calculated. The variable magnetotail length and powers coming into the magnetosphere, ionosphere and ring current have been estimated. The selected superstorm intervals, when it became possible to identify the disturbance mode produced by the interaction between the variable solar wind dynamic pressure and IMF effects, have been described. Spontaneous substorms, two types of driven responses to changes in IMF or in the solar wind dynamic pressure (P d ), zero events at simultaneous jumps of IMF and P d , and a previously unknown mode of saturation of the ionospheric electric field at a redistribution of the energy coming into the magnetosphere between the ionosphere and ring current are among the selected modes. 相似文献