The response of geomagnetic spectral composition to solar wind during storm time

In this paper 16 geomagnetic storms in 1968–1978 recorded at 8 magnetic observatories located from polar to equatorial regions in the λ= 120°E longitudinal zone and its vicinity have been analysed. The horizontal component H traces of 27 h intervals have been sampled once every 1.5 min. The time sequences of the data thus obtained have been processed by the method of digital filtering and maximum entropy spectral analysis (MESA).The results of the analysis are compared with the associated solar wind parameters. It confirms that the geomagnetic disturbances are controlled by the solar wind in several ways, i.e. geomagnetic disturbances respond differently to various solar wind parameters or to the different ranges of them. The north-south component of the interplanetary magnetic field (IMF) B_z., the IMF latitude θ and the solar wind velocity V play the most important part in inducing geomagnetic storms.     

The calm before the storm: A punctuated equilibrium theory of international politics

Research has shown that policymaking in numerous domestic policies, across a multitude of polities, systematically produces a pattern of change that matches Punctuated Equilibrium Theory (PET), characterized by many incremental and occasional dramatic changes. The field of International Relations (IR), however, has paid surprisingly little attention to PET, even though the same pattern of change is also found in international politics. This study attempts to fill this gap and explains stability and change in international politics based on PET. Specifically, we detail the dynamics behind this pattern of behavior, both at the domestic and the international level, as well as their interplay. The empirical section shows that different indicators of international politics, including troop deployments, foreign aid and international trade, follow a leptokurtic pattern of change, which characterizes Punctuated Equilibrium, and whereby changes in countries' behavior are generally incremental, representing periods of relative stability, and punctuated by large changes that dramatically overthrow existing policies. Moreover, our results indicate that policy outputs where greater friction is at play are more punctuated than those policies that cannot as easily or directly be managed. This study urges future research to further explore the dynamics of stability and change at the aggregate, international level.     

The future of geomagnetic storm predictions: implications from recent solar and interplanetary observations

Within the last 7–8 years, there has been a substantial growth in our knowledge of the solar and interplanetary causes of geomagnetic storms at Earth. This review article will not attempt to cover all of the work done during this period. This can be found elsewhere. Our emphasis here will be on recent efforts that expose important, presently unanswered questions that must be addressed and solved before true predictability of storms can be possible. Hopefully, this article will encourage some readers to join this effort and perhaps make major contributions to the field.     

《野玫瑰》风波的再解读

<野玫瑰>是抗战中期西南联大教授陈铨的一个话剧作品,以美女、间谍、爱情、汉奸等元素反映沦陷区人民反对日本侵略者的斗争,情节曲折离奇,人物复杂多面,搬上舞台后立即引起轰动,受到国民政府教育部的嘉奖.然而在抗战中期国共冲突政治背景下,该剧的上演引发了国共两党在文化领域的一场激烈冲突,誉之者以为是现实主义杰作,贬之者斥之为是对中国人民抗战精神的亵渎.本文依据可靠史料重新解读风波的来垄去脉,辨析争论双方在政治理论、文艺表现手法等方面的不同取向,探讨争论背后的用意和故事.     

Diurnal variations in the D-region during a storm after-effect

Measurements of electron concentration in the D- and lower E-regions of the ionosphere are reported for seven rocket flights from South Uist, Scotland, in April 1973. They took place during a 12-hour period starting 30 hours after the main phase of a severe geomagnetic storm. The principal feature of the results is that the electron concentrations below 85 km varied between 4 and 10 times the concentrations found on normal days. The variability was correlated with changes in radio wave absorption.The observed electron concentrations are compared with results of other workers for storm conditions and in particular with the model of Spjeldvik and Thorne (1975), and are found to be in reasonable agreement.The possibility of changes in positive ion composition occurring during the post-storm period is inferred.     

A comparison of northern and southern hemisphere TEC storm behaviour

Changes in total electron content during magnetic storms are compared at stations with similar geographic and geomagnetic latitudes and eastward declinations in the northern and southern hemispheres.Mean patterns are obtained from 58 storms at ±35° and 28 storms at ± 20° latitude. The positive storm phase is generally larger (and earlier) in the southern hemisphere, while negative storm effects are larger in the north. These changes reduce the normal asymmetry in TEC between the two hemispheres. Composition changes calculated from the MSIS86 atmospheric model agree well with the maximum decreases in TEC in both seasons (when changes in the F-layer height are ignored). Recovery occurs with a time constant of about 35 h; this is 50% longer than in the MSIS86 model. There is a marked diurnal variation at 35°S, with a rapid overnight decay and enhanced values of TEC in the afternoon. This pattern is inverted (and weaker) at 35°N, where night-time decay is consistently slower than on undisturbed nights. These results require a diurnal change in composition of opposite sign in the two hemispheres, or enhanced westward winds at night changing to eastward near sunrise. There is some evidence for both these mechanisms. Following a night-time sudden commencement there is a large annual effect with daytime TEC increasing for storms near the June solstice and decreasing near December. Storms occurring between November and April tend to give large, irregular increases in TEC for several days, particularly at low latitudes. In summer and winter at both stations, the mean size of the negative phase does not increase for storms with K_p> 6. The size of the positive phase is proportional to the size of the change in a_p in winter, while in summer a positive phase is seen only for the larger storms.     

Low latitude auroras: the storm of 25 September 1909

Visual auroras at low latitudes are rare, documented for only five occasions since 1859. They are important from a theoretical point of view in terms of the lowest latitude at which particle precipitation can been observed. One of the great magnetic storms of the past 150 yr occurred on 25 September 1909, during the prolonged solar activity minimum around the beginning of the present century. A report of an auroral sighting at Singapore, not far from the magnetic equator, the lowest latitude ever reported for a visual aurora. has focussed attention on this event. This paper compiles and discusses the solar, magnetic, auroral, and telegraphic disturbance data related to the event. The data show that the lowest credible magnetic latitude for this event was between 30° and 36°. I conclude that the report of a visual auroral observation at Singapore, based on a single Australian newspaper item, was almost certainly not auroral at all, but rather resulted from cable disturbances, known to be associated with auroras, and confused with the aurora itself. Furthermore, consideration of the height at which particle precipitation would be observed leads to an estimate of a threshold magnetic latitude for a visual auroral event of the order of 15°, greater than that of 'Singapore. This result removes the necessity of theories of major storms to account for such a low latitude sighting.     

Swat in the eye of the storm: Interview with Akbar Ahmed

In this interview, Akbar Ahmed looks at the latest developments among the Swat Pathan, a people who have been the subject of classic ethnographies in anthropology for many years, but who are now at the centre of a bigger battle for control of this key geo-political region. What, if anything, can anthropologists contribute to understand and ameliorate the conflicts that rage in this region?     

More than a storm in a teacup: the defence and security implications of Scottish independence

In September 2014 the people of Scotland will vote on whether to become an independent nation, with the defence and security of Scotland proving to be one of the more vociferous areas of debate. This article argues that defence and security implications of this referendum are far more fundamental than either the ‘yes’ or ‘no’ campaigns have admitted. It makes four points. First, it suggests that the Scottish government's plans for defence and security in NATO and the EU are at odds with its proposed armed forces and that Scotland may well find itself having to make far greater commitments to defence to assure its allies. Second, it argues that a vote for independence will represent a game‐changing event for the remainder of the United Kingdom's defence and security, which will have significant consequences for the United Kingdom's partners and allies in NATO, the European Union and elsewhere. Third, the article contends that even a vote against independence will have a long‐term impact, in that the ‘West Lothian question’ and Scottish support for nuclear disarmament influence the 2015 Strategic Defence and Security Review. Finally, the article highlights how this issue has revealed weaknesses in the think‐tank and academic communities, particularly in Scotland. The independence vote does, therefore, represent ‘more than a storm in a tea cup’ and thus there needs to be far greater engagement with these issues within the United Kingdom and elsewhere.     

Winds,wind-shears and plasma densities during the initial phase of a magnetic storm from equatorial latitudes

Results of a sodium vapour release experiment carried out from SHAR (India), an equatorial rocket launching station, immediately after (⩽ 2 h) a storm sudden commencement (SSC) during the initial phase of a magnetic storm, followed by electron density measurements are presented. Many of the relevant atmospheric parameters, namely, neutral winds and their altitude variation, the magnitude of the shears in them, the neutral temperature with altitude by spectroscopic methods, diffusion measurements on the released trail, clues on the turbopause level and the electron densities including the structures (irregularities) in them were obtained. The results of the temperature measurements carried out independently on the sodium trail by means of a ground-based Fabry-Perot spectrometer, operating on the sodium D 1 line, resonantly scattered by the trail have already been reported by us (Ranjan Guptaet al., 1986). In this paper the effects of the excess temperature reported earlier and the rest of the measured parameters on the electron density profiles are evaluated using models and compared with the measurements.The formation of sharp layers of ionization have been explained on the basis of the electro-dynamical processes associated with the wind shears at a location, close to the edge of the equatorial electrojet belt. The significance of the changes in the neutral composition due to the enhanced neutral temperature and the low turbopause level, in increasing the base-level plasma densities by a factor of 3–5 are demonstrated and the possible role of plasma dynamics discussed.     

Travelling atmospheric disturbances as a possible explanation for daytime positive storm effects of moderate duration at middle latitudes

Using N-h profiles, critical frequency data, and the AE index, we find that daytime positive storm effects at middle latitudes are caused by uplifting of ionization and lag the onset of substorm activity by about 2.5 h. Since the increase in electron concentration lags the increase in layer height by about one hour, the perturbation responsible for positive storm effects should propagate with a high velocity (~500 m/s) from high to lower latitudes. Travelling atmospheric disturbances are offered as a possible explanation for short and medium duration events. A model calculation of the ionospheric response to such a perturbation supports our hypothesis.     

加拉帕戈斯 从火山到深海的世界尽头之旅

<正>锤头鲨,顾名思义,这种鲨鱼有着像锤子一样的脑袋,准确地说来,它们的脑袋长得如同一把榔头,而眼睛就长在头的左右两侧,距离非常远,看上去颇有几分怪异,不过也正是因为这样,锤头鲨才有了更为广阔的视野。锤头鲨的寿命通常有30～40岁。一般来说,锤头鲨的体长在4米左右,体重230公斤上下,生活在热带及温带海域。在今天,锤头鲨已经成为濒危动物,在加拉帕戈斯,你能够见到这些"水中巨头"的身影,其实还有赖于当地政府的保护,厄瓜多尔政府已经在加拉帕戈斯群岛的海洋保护区内为濒临灭绝的锤头鲨设立了禁猎区,让这些"水中巨头"可以有一片生存的净土。     

行摄西班牙 领略小而精致的别样风景

<正>西班牙,这个号称"出产阳光和海滩"的国家,是个享誉全球的旅游大国。截至2018年7月4日第42届世界遗产大会闭幕,西班牙共计拥有47项世界遗产,名列世界第3位。西班牙丰富的旅游资源,深厚的文化底蕴,以及热情的舞蹈,就像一个強大的磁场,吸引着世界游客频繁往来。建在云端的龙达小镇吃过早饭,我们从塞维利亚出发,前往西班牙安达卢西亚的龙达小镇参观。龙达小镇有3000多年的悠久历史。早在罗马帝国时代,一批旅人风尘仆仆地爬上这座750公尺的悬崖峭壁,发现这里地势险要,风景秀丽,河流丰沛,于是安营扎寨,建造出第一座房子。这白     

红树林里的小精灵 马来西亚沙巴Klias红树林湿地保护区

<正>在马来西亚沙巴州西南海岸的红树林保护区,居住着一种珍贵的灵长类野生动物——长鼻猴(proboscis monkey)。长鼻猴有着大得出奇的长鼻子,目前只有在马来西亚婆罗洲的沙巴、沙劳越等地的红树林中才能看到,属于世界濒危动物,也是马来西亚的国宝。