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极光卵的尺度大小与太阳风-磁层-电离层能量耦合过程紧密相关,准确预测其大小对空间天气研究和预报具有非常重要的意义.本文基于模糊c均值聚类算法,从Polar卫星紫外极光图像中自动提取极光卵边界数据(~1215000个赤道向边界点和~3805000极向边界点),统计分析其与太阳风等离子体、行星际磁场、地磁指数等之间的相关特性,并构建了以行星际、太阳风为模型参数(模型1)和以行星际、太阳风及地磁指数为模型参数(模型2)的2种极光卵边界多元回归模型.以模型预测的极光卵边界与实际极光卵边界之间的平均绝对误差作为模型评价标准,将本文预测模型与Carbary(2005)模型和Milan(2009)模型进行了对比.结果表明,模型2对极光卵极向、赤道向边界预测的平均绝对误差为1.55和1.66地磁纬度,优于Carbary和Milan模型(Carbary模型极向、赤道向边界的平均绝对误差为2.18和5.47地磁纬度,Milan模型极向、赤道向边界的平均绝对误差为1.71地磁纬度和1.90地磁纬度). 相似文献
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行星际激波与地球磁层相互作用通常会导致日侧极光活动增强,随后沿着极光卵的晨昏两侧向夜侧扩展的激波极光.行星际激波也可能直接导致夜侧扇区极光活动增强,甚至沉降粒子能通量的数量级可以与典型亚暴相比拟.本文首次利用我国南极中山站和北极黄河站连续多年积累的极光观测数据,对行星际激波与地球磁层相互作用期间地面台站在夜侧扇区(18—06MLT)观测的极光响应进行了分析.对18个极光观测事件的分析结果表明:行星际激波与磁层相互作用可以在夜侧触发极光爆发和极光微弱增强或静态无变化事件;太阳风-磁层能量耦合的效率以及磁层空间的稳定性决定着行星际激波能否触发极光爆发. 相似文献
4.
极区电离层电流与极光电集流指数关系的定量分析 总被引：2，自引：0，他引：2
极区电离层电流体系主要是由场向电流产生的. 在平静状态下, 极区电流由一对晨昏电流涡组成, 而当亚暴发生时, 强度为几百万安培的西向电集流造成极区地磁场的剧烈扰动. 极光电集流的强度通常用极光电集流指数AL, AU, AE和AO来描述. 本文用国际磁层研究计划(IMS)执行期间, 由北半球71个高纬地磁台的资料所得到的极区电流函数, 定量分析极区电流特征与极光电集流指数的关系. 研究结果表明, AL, AU指数与AE指数有很好的线性关系, 所以可以用AE(乘以适当比例因子)近似代替AL和AU, AE指数可以近似表征极区总电流以及晨昏电流涡强度, 定量分析表明, AE指数的1 nT对应极区总电流1000 A. AE指数与最大西向电流密度有很好的正比关系, AE指数的1 nT对应地磁子夜最大西向电流密度1 A/km. 在夜间扇区的不同地方时, 电流密度随纬度变化的趋势大体相似, 最大西向电流密度一般位于地磁子夜附近和地磁纬度65°~70°处, 而东向电流密度在80°附近达到极大值. 分析还表明, 就5 min平均值而言, AE指数的饱和值约为700 nT, AL的饱和值约为−500 nT. 所以, 在研究磁层-电离层过程时, 使用饱和值以上的极光电集流指数需十分谨慎. 相似文献
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准确界定亚暴起始时刻是理解亚暴相关问题的关键.已有研究主要集中在两方面:一是从极光图像中人工挑选亚暴事件进行案例分析或统计分析来研究亚暴发生机制及亚暴期间的地磁环境;二是基于一些空间物理参数,如AE指数、SME(SuperMAG electrojet)指数、Pi2、正弯扰等,采用人眼判断或是模式识别的方法从中找出亚暴起始时刻.本文尝试采用模式识别的方法从紫外极光图像中自动地检测出亚暴膨胀期起始时刻.首先,将紫外极光图像通过网格化处理转换到磁地方时-地磁纬度(MLT-MLAT)直角坐标下,然后通过模糊c均值聚类方法提取亮斑,再考察亮斑强度是否增强、面积是否极向膨胀来判断是不是亚暴事件.本文方法在1996年12月-1997年2月这三个月的Polar卫星紫外极光图像上进行了实验验证.我们将检测到的亚暴起始时刻与Liou(J. Geophys. Res., 2010, 115: A12219)的人工标记进行了对比,并详细分析了与标记不一致的多检和漏检事件.本文提出的自动检测方法可以快速地从海量紫外极光图像中完成亚暴事件的初步筛选,方便研究人员进一步深入研究极光亚暴. 相似文献
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为研究极光电集流地磁纬度分布特征,利用北半球SME台站提供的极光电集流指数,通过时序叠加的方法,分析98-07年极光电集流中心地磁纬度随季节和世界时的分布特征.通过对磁扰程度的分级,分析极光电集流地磁纬度随地磁扰动程度的变化特征.结果表明:1)由于SME台站覆盖范围更广,更多地记录到最大的极光电集流强度,有利于研究极光电集流的变化特征;2)西向板光电集流纬度分布存在与强度相反的季节性变化特征,在春秋出现最低值,冬季、夏季出现最高值;3)在| SML|＜2000 nT时,西向极光电集流地磁纬度随着极光电集流强度的增强,近似以线性关系向低纬迁移.随后伴随SML的进一步增强,西向极光极光电集流中心地磁纬度仍有向低纬迁移的趋势,但主要是在磁纬62°N-63°N之间波动. 相似文献
7.
极光活动加剧和极光电集流增强是磁层-电离层能量耦合的两种重要表现形式,它们同为磁层带电粒子向电离层沉降的结果,但是变化规律却非常不同.本文用地基磁场资料,反演极区等效电流体系,研究地磁平静期和扰动期极光电集流带的运动特点.研究表明,Harang间断把极光电集流带分为两段：下午—黄昏段的东向电集流带较弱,而晨侧和子夜—凌晨段的西向电集流带较强.在亚暴膨胀相,随着AE指数增大,整个极光卵向赤道扩展,而极光电集流带却表现出分段差异的特点：下午—黄昏东向电集流带向低纬移动,晨侧西向电集流带也向赤道移动,而子夜—凌晨西向电集流带则向极移动.电动力学分析表明,在不同地方时段,控制电流的主要因素不同,因而,电流及其磁扰有不同的特点：下午—黄昏东向电集流和晨侧西向电集流组成了DP2电流体系,主要受控于磁层对流电场,反映了“驱动过程”的行为;而子夜—凌晨西向电集流是DP1电流体系的基本部分,主要受控于电导率,反映了“卸载过程”的特点. 相似文献
8.
作为太阳风引起的地磁扰动的系统辨识一文的姊妹篇,本文利用参数系统辨识方法,对太阳风-磁层耦合系统做了进一步的探讨.根据地磁扰动机制的理论研究,地磁扰动被认为是太阳风能量耦合进入磁层以及由此引起的一系列磁层内能量的输运和耗散的结果.在此基础上,对太阳风-磁层系统的非线性情况进行了讨论,建立了Dst指数与太阳风参量的非线性函数关系,给出了由此得到的地磁扰动计算结果.同时还利用1967年2月3-12日和1980年12月16-23日的两次事件,对已得到的函数关系进行了验证和讨论.验证结果不仅对模型的合理性、普适性做了很好的说明,也表明这种非线性函数关系作为定量的地磁预报模型,具有一定的可信度和实用性. 相似文献
9.
全天空成像观测是目前极光地面观测和反演磁层结构与动力学行为最有效的手段之一，本文介绍在参照WDC－C2极光数据中心ADPRS（AuroralDataProcessing＆RetrievingSystem）系统功能的基础上，采用视频图像采集技术，首次在微机上开发成功的一个极光全天空视频图像分析系统．该系统在图像处理用户界面的构建上采用了视窗编程技术，在全天空图像到地磁坐标／地理坐标的投影变换中首次引入了强度修正因子，其功能可与ADPRS系统媲美． 相似文献
10.
用１９７８年和１９８２年３６个磁暴期间的太阳风、行星际磁场（ＩＭＦ）和地磁资料，分析和检验已有的两类太阳风－磁层能量耦合函数．结果表明：Ａｋａｓｏｆｕ提出的耦合函数ε能大致地预报亚暴和磁暴的发生。ε开始起重要作用时即出现亚暴；电离层能耗达到饱和值是发生磁暴的标志。ε与磁层体系能耗之间有接近于对数量的线性关系．用１９７８－１９８６年的资料，分析环电流和极光区电离层能耗在１２１个太阳自转周内的分布表明，日面上可能存在相对持久的活动区域 相似文献
11.
《Journal of Atmospheric and Solar》2002,64(2):115-124
Auroras have been extensively studied using images obtained by space-borne experiments. We use global UVI images obtained from Polar and simultaneous plasma data obtained by the 3D instrument on Wind from the near-earth plasma sheet to study the dynamics of auroras with different size and intensity. Unstable phase space ion distributions are detected in the plasma sheet under diverse geomagnetic and solar wind IMF conditions (positive and negative Bz) and at all phases of a substorm. These results indicate that plasma instability processes with different disturbance levels operate in the plasma sheet and produce a continuum of auroral size and intensity. The criteria for triggering an instability are dependent on the local properties of the plasma distributions. These observations suggest a new framework to integrate previous and current results and a new way to examine the causal relationships of auroral and plasma sheet dynamics. 相似文献
12.
《Journal of Atmospheric and Solar》1999,61(11):829-840
The effect of the interplanetary magnetic field (IMF) By component on the dayside auroral oval from Viking UV measurements for March–November 1986 is studied. Observations of dayside auroras from Viking UV images for large positive (15 cases) and negative (22 cases) IMF By (∣By∣>4 nT), suggest that: (1) the intensity of dayside auroras tends to increase for negative IMF By and to decrease for positive By, so that negative IMF By conditions seem preferable for observations of dayside auroras; (2) for negative IMF By, the auroral oval tends to be narrow and continuous throughout the noon meridian without any noon gap or any strong undulation in the auroral distribution. For positive IMF By, a sharp decrease and spreading of auroral activity is frequently observed in the post-noon sector, a strong undulation in the poleward boundary of the auroral oval around noon, and the formation of auroral forms poleward of the oval; and (3) the observed features of dayside auroras are in reasonable agreement with the expected distribution of upward field-aligned currents associated with the IMF By in the noon sector. 相似文献
13.
D. Rees R. W. Smith F. Signernes K. Henriksen U. Brandstrom M. Harris G. Maskall 《Annales Geophysicae》1998,16(11):1461-1474
Two Doppler imaging systems (DIS) or wide-field imaging Fabry-Perot interferometers (FPI), have recently been commissioned, one at the Auroral Station, Adventdalen, Longyearbyen, Svalbard, and the second at the IRF, Kiruna, Sweden. These instruments can provide wide-field (600 * 800 km) images of neutral wind flows in the upper thermosphere, by measuring the Doppler shift of the atomic oxygen forbidden near 630 nm, which is emitted from an altitude of approximately 240 km. From the instrument in Svalbard, at mid-winter, it is possible to observe the dayside polar cusp and the polar cap throughout the entire day, whereas from Kiruna, the night-time auroral oval is observable during the hours of darkness. Measurements of thermospheric dynamics from the DIS can be used in conjunction with observations of ionospheric plasma flows and thermal plasma densities by the EISCAT-Svalbard radar (ESR) and by EISCAT, along with other complementary observations by co-located instruments such as the auroral large-scale imaging system (ALIS). Such combined data sets will allow a wide range of scientific studies to be performed concerning the dynamical response of the thermosphere and ionosphere, and the important energetic and momentum exchange processes resulting from their complex interactions. These processes are particularly important in the immediate vicinity of the polar cusp and within the auroral oval. Early results from Svalbard in late 1995 will be discussed. The DIS in Kiruna observed two interesting geomagnetic disturbances in early 1997, the minor geomagnetic storm of 10, 11 January, and the disturbed period from 7–10 February. During these events, the thermospheric wind response showed some interesting departures from the average behaviour, which we attribute to the result of strong and variable Lorenz forcing (ion drag) and Joule and particle heating during these geomagnetic disturbances. 相似文献
14.
Based on the DMSP F6 and F7 satellite observations, the characteristics of precipitating particles in different auroral precipitation regions of the dayside sector have been studied depending on the solar wind plasma density. Under quiet geomagnetic conditions (|AL| < 100 nT and B z > 0), a considerable increase in the fluxes of precipitating ions is observed in the zones of structured auroral oval precipitation (AOP) and soft diffuse precipitation (SDP). A decrease in the mean energy of precipitating ions is observed simultaneously with the flux growth in these regions. The global pattern of variations in the fluxes of precipitating ions, which shows the regions of effective penetration of solar wind particles into the magnetosphere at a change in the solar wind density from 2 to 20 cm?3, has been constructed. The maximal flux variation (ΔJ i = 1.8 · 107 cm?2 s?1, i.e., 3.5% of an increase in the solar wind particle flux) is observed in the SDP region on the dayside of the Earth. The dependence of precipitating ion fluxes in the low-latitude boundary layer (LLBL), dayside polar cusp, and mantle on the solar wind density at positive and negative values of the IMF B z component has been studied. In the cusp region, an increase in the precipitating ion flux is approximately 17% of an increase in the solar wind density. The IMF southward turning does not result in an appreciable increase in the ion precipitation fluxes either in the cusp or in the mantle. This fact can indicate that the reconnection of the geomagnetic field with southward IMF is not the most effective mechanism for penetration of solar wind particles into these regions. 相似文献
15.
S. I. Solovyev A. V. Moiseev E. S. Barkova K. Yumoto M. Engebretson 《Geomagnetism and Aeronomy》2006,46(1):41-51
The geomagnetic and auroral response to the variations in the solar wind dynamic pressure (Pd) are investigated in the periods of positive values of the IMF B z component. It is shown that the growth of Pd results in the intensification of luminosity along the auroral oval and in the poleward expansion of the poleward boundary of luminosity (PBL) in the nightside part of the oval by ～7° in latitude at a velocity of ～0.5 km/s and is accompanied by an enhancement of the DP2-type current system. A decrease in Pd, accompanied by an abrupt reversal of the IMF B y polarity from positive to negative, results in an enhancement of the westward electrojet and in a poleward shift of PBL and electrojet center. The conclusion has been made that the available three types of auroral response to Pd variations differ in the azimuthal velocity of the luminosity region or particle precipitation along the auroral oval: V 1 ～ 30–40 km/s, V 2 ～ 10, and V 3 ～ 1 km/s. 相似文献
16.
Y. I. Feldstein 《Geomagnetism and Aeronomy》2016,56(2):129-142
The auroral oval concept radically changed the view that existed for a century in geophysics on the patterns in aurora planetary spatial–temporal distributions. The auroral zone, which is located around the geomagnetic pole as a continuous ring at a constant angular distance of ~23°, was replaced by the auroral oval in 1960. The auroral oval spatial position reflects the shape of the Earth’s magnetosphere, which is compressed by the solar wind on the dayside and stretches into the magnetotail on the nightside. The oval is fixed relative to the direction toward the Sun and is located around the geomagnetic pole at altitudes of the upper atmosphere at an angular distance of ~12° at noon and ~23° at midnight. After an animated discussion over several subsequent years, the existence of the auroral oval was accepted by the scientific community as a paradigm of a new science, i.e., solar–terrestrial physics. The oval location indicates the zone where electron fluxes with energies varying from ~100 eV to ~20 keV precipitate into the upper atmosphere and is related to the structure of plasma domains in the Earth’s magnetosphere. The paper describes the scientific studies that resulted in the concept of the auroral oval existence. It has been shown how this concept was subsequently justified in the publications by Y.I. Feldstein and O.B. Khorosheva. The issue of the priority of the auroral oval concept introduction into geophysics has been considered. The statement that the concept of the oval is an archaic paradigm of solar–terrestrial physics has been called into question. Some scientific fields in which the term auroral oval or simply oval was and is the paradigm have been listed. 相似文献
17.
B.T. Tsurutani X.-Y. Zhou V.M. Vasyliunas G. Haerendel J.K. Arballo G.S. Lakhina 《Surveys in Geophysics》2001,22(2):101-130
Dayside near-polar auroral brightenings occur when interplanetary shocks impinge upon the Earth's magnetosphere. The aurora first brightens near local noon and then propagates toward dawn and dusk along the auroral oval. The propagation speed of this wave of auroral light is 10 km s-1 in the ionosphere. This speed is comparable to the solar wind speed along the outer magnetosphere. The fundamental shock-magnetospheric interaction occurs at the magnetopause and its boundary layer. Several physical mechanisms transferring energy from the solar wind directly to the magnetosphere and from the magnetosphere to the ionosphere are reviewed. The same physical processes can occur at other solar system magnetospheres. We use the Haerendel (1994) formulation to estimate the acceleration of energetic electrons to 50 keV in the Jovian magnetosphere/ionosphere. Auroral brightenings by shocks could be used as technique to discover planets in other stellar systems. 相似文献
18.
The interrelation between sudden increases in the solar wind dynamic pressure, auroral proton flashes on the dayside equatorward
of the oval, and geomagnetic pulsations in the Pc1 range is considered on the basis of simultaneous observations of the solar
wind plasma parameters, proton auroras on the IMAGE satellite, and geomagnetic pulsations at the Lovozero Observatory. It
is indicated that proton luminosity flashes were observed in 70% of cases equatorward of the auroral oval during sudden changes
in the solar wind pressure. In this case, flashes of proton auroras were observed in 85% of cases during sudden changes in
the pressure, which were related to interplanetary shocks. Increases in pressure during tangential discontinuities were accompanied
by flashes of proton auroras only in 45% of cases. When the ground station was conjugate to the region occupied by a proton
aurora flash, the appearance or intensification of existent pulsations in the Pc1 range was observed in 96% of cases. When
the ground station was not conjugate to the region of a proton luminosity flash, the response in geomagnetic pulsations was
observed in 32% of events. When a sudden change in the solar wind pressure was not accompanied by a proton luminosity flash,
the response in pulsations in the Pc1 range was hardly observed. 相似文献
19.
Polar and high latitude substorms and solar wind conditions 总被引：1，自引：0，他引：1
All substorm disturbances observed in polar latitudes can be divided into two types: polar, which are observable at geomagnetic latitudes higher than 70° in the absence of substorms below 70°, and high latitude substorms, which travel from auroral (<70°) to polar (>70°) geomagnetic latitudes. The aim of this study is to compare conditions in the IMF and solar wind, under which these two types of substorms are observable on the basis of data from meridional chain of magnetometers IMAGE and OMNI database for 1995, 2000, and 2006–2011. In total, 105 polar and 55 high latitude substorms were studied. It is shown that polar substorms are observable at a low velocity of solar wind after propagation of a high-speed recurrent stream during the late recovery phase of a magnetic storm. High latitude substorms, in contrast, are observable with a high velocity of solar wind, increased values of the Bz component of the IMF, the Ey component of the electric field, and solar wind temperature and pressure, when a high-speed recurrent stream passes by the Earth. 相似文献