日球层扰动变化的高纬地磁场响应

本文简要地论述了行星际过程与高纬地磁场扰动的关系,并对高纬极区地磁场变化对行星际过程的响应和地磁变化场的特点进行了分析研究和评述。     

行星际扰动对地磁活动的影响

利用第23太阳活动周中WIND和ACE资料,统计分析行星际扰动对不同水平地磁活动的影响,研究磁暴强度与不同行星际参数之间的相关性,结果发现:①从长期来看,地磁活动指数Dst与太阳风速度的相关性最好,相关性在太阳活动谷年时最高;②多磁暴时序叠加结果证实了导致小、中、强磁暴开始的经验行星际南向磁场条件,磁暴过程中行星际磁场...     

磁暴主相多阶发展行星际起因的初步分析

本文利用1998~2006年与磁云有关的80起中强磁暴(Dst*≤-50 nT),对其主相期间不同发展阶数磁暴的行星际起因进行了统计分析.重点研究了鞘区磁场单独作用、磁云本体单独作用、鞘区与磁云共同作用以及其他复杂行星际结构在磁暴主相多阶发展中的相对重要性,并对导致磁暴主相增加一阶的行星际起因做了初步分析.统计结果表明:(1)有一半以上的中强磁暴主相具有多个发展阶段,其中一阶磁暴和多阶磁暴(包括二阶和二阶以上磁暴)在中等磁暴(-100 nTDst*≤-50 nT)中所占比例分别为53.8%和46.2%,在强磁暴(Dst*≤-100 nT)中所占比例分别为42.6%和57.4%;(2)随着磁暴主相发展阶数的增加,磁暴主相的平均持续时间也随之延长;(3)鞘区磁场单独作用、磁云本体单独作用、鞘区与磁云共同作用、磁云与其他行星际结构共同作用都可能引起磁暴主相的多阶发展;(4)有46.5%的多阶磁暴是由鞘区磁场与磁云本体共同作用引起,有34.9%的多阶磁暴是由鞘区磁场单独作用和磁云本体单独作用引起,其余的多阶磁暴是由其他复杂行星际结构引起;(5)在鞘区磁场单独作用的事件中,鞘区磁场结构是影响磁暴主相多阶发展的重要因素之一;(6)磁暴主相的多阶发展与晨昏电场Ey、行星际磁场Bz南向分量的发展密切相关,随着Ey和Bz阶段性的发展,磁暴主相也呈现多阶发展的趋势,且每阶Dst*极小值与该阶Eymax和Bzmin有很好的线性相关性,线性耦合方程分别为Dstmin* =-34.62-11.89×Eymax 和Dstmin* =-5.90+8.50×Bzmin.     

中低纬度电离层对太阳风状态的响应

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△B2q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.     

1989年3月13日武昌地区太阳耀斑事件效应的观测结果

1989年3月13日太阳耀斑事件产生了丰富的地球物理效应。耀斑激波和耀斑粒子流引起强烈地磁暴。在武昌地区,磁暴急始发生于地方时3月13日09h30min,其初相期持续10小时（3月13日09h30min-19h20min）,主相期持续13小时（3月13日19h20min-3月14日08h20min）,至3月16日05h20min始恢复平静（图1）。     

中低纬度电离层对太阳风状态的响应

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S_q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,S_q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.     

1991年3月24日磁暴期间南极地区地磁脉动的分析

重点分析了1991年3月24日在南极中山站和长城站观测到的丰富的地磁脉动现象,给出了各种地磁脉动发生的时间和主要特征,并对两站各种地磁脉动做了比较分析．这不仅可以认识磁暴期间南极地区向日面与背日面、高纬与中纬地磁脉动的不同表现,也帮助我们了解南极地区磁暴期间地磁脉动形态和磁暴过程的关系。     

1991年3月24日磁暴期间南极地区地磁脉动的分析

重点分析了1991年3月24日在南极中山站和长城站观测到的丰富的地磁脉动现象,给出了各种地磁脉动发生的时间和主要特征,并对两站各种地磁脉动做了比较分析．这不仅可以认识磁暴期间南极地区向日面与背日面、高纬与中纬地磁脉动的不同表现,也帮助我们了解南极地区磁暴期间地磁脉动形态和磁暴过程的关系。     

行星际-赤道电场穿透效率的数值模拟研究

电场穿透作为强烈地磁活动期间太阳风-磁层-电离层电动力学耦合的重要形式,近年来一直是空间物理学最为活跃的课题之一.在过去的近40年里人们一直关注于观测证据的寻找以及物理过程的模拟,“电场穿透效率”这一重要定量化指标直到最近几年才得到重视.本文定义赤道电场增量与对应的行星际电场增量的比值为穿透效率,通过数值模拟的方法对穿透效率的地方时变化以及与中性风发电机的关系做了实验性讨论,在一定简化条件下结果表明：（1）不考虑跨极盖电势饱和的情况下,赤道电场增量与行星际电场增量呈线性关系,且中性风发电机并不影响电场穿透效率;（2）恒定重联线长度L的限定下,穿透效率具有明显地方时依赖性.例如对于L=2.6 RE,在9LT至23LT之间,穿透效率维持在10％左右;0LT至7LT之间,穿透效率迅速从2％上升至30％后又迅速回落到原始水平,形成尖峰.这些结果基本符合观测特征.     

地球磁场对太阳风的加卸载响应与川滇中强地震

川滇地区在１９９４～１９９６年间发生了多次中强地震。本文作者将磁暴的初始－主相－恢复过程作为地球磁场对太阳风加卸载的响应过程,计算分析了西南地区１０个地磁台站磁场垂直分量Ｚ的暴时场ＤＳｔ（ｚ）中的暴时扰日变化,以及ＤＳ（ｚ）场的加卸载响应比值Ｐ（ｚ）的时空分布,发现Ｐ（ｚ）的高值区即是未来４４天至１５个月内发生中强地震的地区。作者还对震区和非震区的Ｐ（ｚ）高值与地震和气象灾害之间的关系进行了粗略的讨论。     

地球磁场对太阳风的加卸载响应与地震

将磁暴过程作为地球磁场对太阳风的加卸响应，计算分析了北京地磁台１９６５．１－１９７９．１２和１９８９．１－１９９１．１２共１８年垂直分量Ｚ的暴时场Ｄｓｔ加卸载响应比值ｆＤ（Ｚ）的变化。     

特大地磁暴的一种行星际源:多重磁云

2001年3月31日观测到的大的多重磁云(Multi MC)事件造成了第23周太阳峰年(2000～2001)最大的地磁暴(Dst=-387nT). 通过分析ACE飞船的观测数据, 描述了这个多重磁云在1AU处的磁场和等离子体特征. 并且根据SOHO和GOES卫星的观测资料, 认证了它的太阳源. 在这次事件中, 由于多重磁云内部异常增强的南向磁场, 使之地磁效应变得更强, 它大大的延长了地磁暴的持续时间. 观测结果与理论分析表明, 多重磁云中子磁云的相互挤压使磁云内的磁场强度及其南向分量增强数倍, 从而加强了地磁效应. 因此, 研究认为多重磁云中子磁云之间的相互压缩是造成特大地磁暴的一种机制. 此外, 研究发现形成多重磁云的日冕物质抛射(CMEs)并不一定要来自同一太阳活动区.     

On the geomagnetic and ionospheric responses to an intense storm associated with weak IMF Bz and high solar wind dynamic pressure

A study of the geomagnetic storm of July 13–14, 1982, and its ionospheric response is presented using the low-latitude magnetic index, Dst, and interpreted using solar wind interplanetary data: proton number density, solar wind flow speed, interplanetary magnetic field southward component B _Z , and solar wind dynamic pressure. The F2 region structure response to the geomagnetic storm was studied using foF2 data obtained during the storm from a network of various ionosonde stations. Our results appear to show simultaneous abrupt depletion of foF2 that occurred at all latitudes in both the East Asian and African/European longitudinal zone during the period: 18:00–19:00 UT on July 13 and is as result of an abrupt increase in the dynamic pressure between 16:00 and 17:00 UT. The dynamic pressure increased from 3.21 to 28.07 nPa within an hour. The aforementioned abrupt depletion of foF2 simultaneously resulted in an intense negative storm with peak depletion of foF2 at about 19:00 at all the stations in the East Asian longitudinal zone. In the African/European longitudinal zone, this simultaneous abrupt depletion of foF2 resulted in intense negative storm that occurred simultaneously at the low latitude stations with peak depletion at about 20:00 UT on July 13, while the resulting negative storm at the mid latitude stations recorded peak depletion of foF2 simultaneously at about 2:00 UT on July 14. The present results indicate that most of the stations in the three longitudinal zones showed some level of simultaneity in the depletion of foF2 between 18:00 UT on July 13 and 2:00 UT on July 14. The depletion of foF2 during the main phase of the storm was especially strongly dependent on the solar wind dynamic pressure.     

昌黎地磁台地磁变化异常初探

根据磁暴报告，得出昌黎地磁台与同一纬度各台垂直分量△Z的最大幅度差值从几nT到60多nT的差异，初步探讨了昌黎地磁台及其地域地磁变化异常现象。     

用小波方法分析2000年7月13日地磁扰动

利用MORLET小波变换对2000年7月13日亚暴期间地磁场变化特征进行了分析。通过小波分析可以得到亚暴增长相、膨胀相,恢复相的发展过程．探讨了亚暴期间地磁脉动的特征。从小波谱中得到,一个谱结构是处于最高纬度的NAL台站更早出现较大的谱值,这说明此次事件中,地磁场首先在高纬区响应行星际扰动。另一个有明显谱结构的周期在：320～2000s之间,该周期范围的波谱几乎分布一天中的各个时段,但在1000～1700UT亚暴期间之间频带变宽并明显增强,这表明亚暴爆发将引起地磁场在高频端的强扰动。     

Heliospheric current sheet inclinations at Venus and Earth

We investigate the inclinations of heliospheric current sheet at two sites in interplanetary space, which are generated from the same solar source. From the data of solar wind magnetic fields observed at Venus (0.72 AU) and Earth (1 AU) during December 1978–May 1982 including the solar maximum of 1981, 54 pairs of candidate sector boundary crossings are picked out, of which 16 pairs are identified as sector boundaries. Of the remainder, 12 pairs are transient structures both at Venus and Earth, and 14 pairs are sector boundaries at one site and have transient structures at the other site. It implies that transient structures were often ejected from the coronal streamer belt around the solar maximum. For the 16 pairs of selected sector boundaries, we determine their normals by using minimum variance analysis. It is found that most of the normal azimuthal angles are distributed between the radial direction and the direction perpendicular to the spiral direction both at Venus and Earth. The normal elevations tend to be smaller than ≈45° with respect to the solar equatorial plane, indicating high inclinations of the heliospheric current sheet, in particular at Earth. The larger scatter in the azimuth and elevation of normals at Venus than at Earth suggests stronger effects of the small-scale structures on the current sheet at 0.72 AU than at 1 AU. When the longitude difference between Venus and Earth is small (<40° longitudinally), similar or the same inclinations are generally observed, especially for the sector boundaries without small-scale structures. This implies that the heliospheric current sheet inclination tends to be maintained during propagation of the solar wind from 0.72 AU to 1 AU. Detailed case studies reveal that the dynamic nature of helmet streamers causes variations of the sector boundary structure.     

磁暴时磁场变化率与地电场相关性研究

对2003年10月29日、10月30日两个典型大磁暴进行了分析,研究了磁暴期间磁场变化率与地电场的关系,以及磁暴期间磁暴、磁场变化率及地电场的周期成分。结果表明,磁暴期间H分量变化率与地电场东向分量观测数据显著相关,并且周期成分相同。     

Observations of the response time of high-latitude ionospheric convection to variations in the interplanetary magnetic field using EISCAT and IMP-8 data

We have combined ∼300 h of tristatic measurements of the field-perpendicular F region ionospheric flow measured overhead at Tromsø by the EISCAT UHF radar, with simultaneous IMP-8 measurements of the solar wind and interplanetary magnetic field (IMF) upstream of the Earth’s magnetosphere, in order to examine the response time of the ionospheric flow to changes in the north-south component of the IMF (B_z). In calculating the flow response delay, the time taken by field changes observed by the spacecraft to first effect the ionosphere has been carefully estimated and subtracted from the response time. Two analysis methods have been employed. In the first, the flow data were divided into 2 h-intervals of magnetic local time (MLT) and cross-correlated with the “half-wave rectifier” function V²B_s, where V is the solar wind speed, and B_s is equal to IMF B_z if the latter is negative, and is zero otherwise. Response delays, determined from the time lag of the peak value of the cross-correlation coefficient, were computed versus MLT for both the east-west and north-south components of flow. The combined data set suggests minimum delays at ∼1400 MLT, with increased response times on the nightside. For the 12-h sector centred on 1400 MLT, the weighted average response delay was found to be 1.3 ± 0.8 min, while for the 12-h sector centred on 0200 MLT the weighted average delay was found to increase to 8.8 ± 1.7 min. In the second method we first inspected the IMF data for sharp and enduring (at least ∼5 min) changes in polarity of the north-south component, and then examined concurrent EISCAT flow data to determine the onset time of the corresponding enhancement or decay of the flow. For the case in which the flow response was timed from whichever of the flow components responded first, minimum response delays were again found at ∼1400 MLT, with average delays of 4.8 ± 0.5 min for the 12-h sector centred on 1400 MLT, increasing to 9.2 ± 0.8 min on the nightside. The response delay is thus found to be reasonably small at all local times, but typically ∼6 min longer on the nightside compared with the dayside. In order to make an estimate of the ionospheric information propagation speed implied by these results, we have fitted a simple theoretical curve to the delay data which assumes that information concerning the excitation and decay of flow propagates with constant speed away from some point on the equatorward edge of the dayside open-closed field line boundary, taken to lie at 77° magnetic latitude. For the combined cross-correlation results the best-fit epicentre of information propagation was found to be at 1400 MLT, with an information propagation phase speed of 9.0 km s⁻¹. For the combined event analysis, the best-fit epicentre was also found to be located at 1400 MLT, with a phase speed of 6.8 km s⁻¹.     

安徽省地磁观测影响分析

地磁台站的观测数据除了受到磁暴等自然因素的影响外,还受到直流输电和人为等因素的影响。本文主要分析了直流输电对磁场影响的原理,定量计算了对地磁场影响的幅度,并和环境影响因素等做了对比分析。