南极中山站1991年地磁静日S_q变化

本文分析了１９９１年太阳活动峰年南极中山站地磁静日Ｓｑ变化，结果表明：１）地磁静日Ｓｑ变化叠加有很多扰动。Ｓｑ场是由Ｓ０ｑ场和Ｓｐｑ场所组成。２）Ｓ０ｑ场变化比较规则，其极昼月（夏季）的变幅比极夜月（冬季）大很多。在极昼月Ｓ０ｑ（Ｈ）变化出现有双峰图象。Ｓ０ｑ场主要是由高纬度极区电离层Ｓｑ电流体系所控制。３）Ｓｐｑ场的变化形态没有昼夜之分；它的变化强度为冬季小、夏季大。Ｓｐｑ场源主要是依赖于场向电流和电离层电导率。４）Ｓ０ｑ（Ｚ）变化比Ｓ０ｑ（Ｈ）变化要大，特别是在极夜的冬季，Ｓ０ｑ（Ｚ）的变幅比Ｓ０ｑ（Ｈ）大２／３倍。本文对北京地磁中心台磁静日资料也一并进行了分析。Ｓｑ变化主要是由北半球中、低纬电离层Ｓｑ电流体系所引起的     

A comparative study on the ionospheric current systems in the Antarctic and Arctic regions

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南极地区地磁扰日变化S_D场特征

利用南极地磁资料研究了地磁扰日变化ＳＤ场特征。１）ＳＤ场变化不如Ｓｑ场变化规则,无明显的昼夜差异;太阳活动高年（１９９１年）比下降年（１９９４年）ＳＤ场变化更强烈。２）极隙区中山站ＳＤ场变幅比亚极光区长城站和北半球低纬区北京台的ＳＤ场变幅大１０倍以上。３）中山站Ｓ０Ｄ（Ｈ）变化呈“正弦波”形态,与长城站和北京台Ｓ０Ｄ（Ｈ）变化形态相反。４）中山站Ｓ０Ｄ等效电流矢量在早晨－下午（０２～１５ｈ）矢量方向为反时针西向,下午－夜间（１５～０２ｈ）矢量方向为顺时针东向,这是由极区东向、西向电射流和极区电流涡旋所引起;长城站与北京台Ｓ０Ｄ等效电流矢量很小,这是由极区东向和西向电射流的影响所致。     

CHARACTERISTICS OF Sq VARIATION OF GEOMAGNETIC FIELD AT THE GREAT WALL STATION, ANTARCTICA IN WINTER

In this paper the characteristics of Sq variation of geomagnetic field in the region of the Chinese Great Wall Station (CGWS), Antarctica, in winter are analyzed from geomagnetic data obtained at the Geomagnetic Observatory of CGWS. The result enables us to reveal the following aspects: (1) The pattern of Sq variation at CGWS in early (Apr.) and Late winter (Sep.) is similar to that at Beijing Geomagnetic Observatory (BJO) at the middle latitude in the Northern Hemisphere. It may be controlled by the midlatitudinal ionospheric dynamo current. Amplitude of Sq variation is very small, and the harmonics in 8 hours or shorter periods in midwinter (June and July) is predominant because of the decreased effect of solar ultraviolet radiation and the dominant geomagnetic disturbance at high latitudes. (2) The vectors of Sq-equivalent current in the daytime are about five times more than that in the night. The direction of the vectors is clockwise in the daytime (08-15h) and counterclockwise in the night in earl     

南极长城站冬季地磁S_q变化特征

本文利用南极长城站1987年4月至9月的地磁资料,分析了长城站地区冬季地磁S_q变化特征。分析结果表明:(1)南极长城站在初冬(4月)与冬末(9月)月份的S_q变化形态与北半球中纬度的北京地磁台的S_q变化形态基本相似,这可能是由中纬度电离层中的发电机电流所控制的。在仲冬月份(6月与7月),由于太阳紫外辐射效应减少,高纬度的地磁扰动占主导地位,反映出S_q变幅很小和以8小时以下的较短周期谐波起主要作用,(2)在初冬与冬末月份的S_q等效电流矢量,白天比黑夜大约5倍;其矢量方向在白天(08—15时)为顺时针,黑夜为反时针。在仲冬月由于电离层中电流的影响相对减弱,S_q等效电流矢量很小,白天与黑夜基本一样;其矢量分布方向与初冬和冬末的矢量方向不同,这可能是极区的电离层电流或场向电流的影响造成的。     

极区电离层与磁层-电离层耦合

本文利用欧洲空间局设在北极区的非相干散射雷达系统EISCAT的观测资料讨论磁层-电离层耦合。磁静日和磁暴期间的观测样本比较表明,磁层基本过程对极区电离层有重要影响。这不仅说明极区电离层可看作这些过程的“全景屏幕”,也表明在南、北极区(特别是磁共轭点)进行同时观测的重要意义。文中还对进一步的南极研究课题提出了一些建议。     

Surface Integral Formulae for Geomagnetic Studies

Surface integral formulae are derived expressing any one of certain field quantities, namely current functions, magnetic potentials and normal components of magnetic fields, in terms of any one other, for current systems flowing in concentric spherical surfaces. In all, 36 such formulae are obtained, which should prove useful in many geomagnetic studies, especially in geomagnetic induction problems.     

南极中山站地磁脉动的观测分析

本文分析的是１９９２年２月９日至１９９３年２月９日在南极中山站记录的各种地磁脉动的观测资料，并对各种地磁脉动的激发机制进行了初步讨论。通过南极中山站地磁脉动观测资料分析，了解高纬地区地磁脉动的形态特征，对南极极隙区高空大气电磁环境、太阳风和磁层相互作用等现象有进一步的认识。     

A study of two polar magnetic substorms with a two-dimensional magnetometer array

Summary. The paper reports studies of the three-dimensional magnetospheric—ionospheric current systems which produced polar magnetic substorms on 1974 September 7 and September 18. The data were magnetic perturbation fields observed with a two-dimensional array of 23 three-component magnetometers located in western Canada beneath the auroral oval. In an earlier study of a substorm of September 11 (Bannister & Gough) the fields fitted calculated field for a Boström Type 1 current loop with field-aligned currents at east and west ends of the ionospheric segment, and with uniform current density across the width. The substorms here reported could not be modelled with uniform current density. An inverse method due to Oldenburg was therefore used to estimate current density distributions, and satisfactory fits of calculated to observed field resulted. Each substorm was modelled at six representative epochs. In general the principal ionospheric current seem by the array was westward. At four epochs of the September 7 substorm and throughout the September 18 substorm, significant eastward ionospheric current (or its equivalent in terms of the fields produced) was observed north of the westward electrojet. Northwestward bends in the ionospheric current segments were found at four epochs on September 7 and at three epochs on September 18. As in the September 11 substorm (Paper 1), these bends were either west of or close to magnetic midnight. In some cases the bends may follow the auroral oval, but in others they are sharper and may be associated with the Harang discontinuity. East of geomagnetic the ionospheric currents tend to run in a constant geomagnetic midnight latitude range. The developments of the three substorms, of September 7, 11 (Paper 1) and 18, are compared. They showed a variety of shifts in longitude, though all moved eastward relative to magnetic midnight.     

A description of the external and internal quiet daily variation currents at North American locations for a quiet-Sun year

Summary. An order 4, degree 12 spherical harmonic analysis of the smoothed quiet geomagnetic daily variations was used to separate the external and internal geomagnetic S _q field at North American locations for the quiet-Sun year, 1965. These fields were represented by a month-by-month display of equivalent current vortex systems with dominant, pre-noon foci. The focus reached 40° latitude near the June solstice and about 30° latitude near the December solstice. The daily range of S _q current amplitudes was largest in late July to early August and smallest in mid-December. Semi-annual variations of S _q currents dominated only the equatorial region. Daily maxima in mid-latitudes, occurred mostly near local noon in December to February and about 1 hr before noon in June to mid-October. The ratio of external to internal current amplitude vxied from about 1.5 to 1.9 in the middle latitudes with both annual and semiannual changes. An error treatment indicated that the analysis reproduced the form of the surface field with a correlation coefficient of about 0.9 and the amplitudes of the surface field to about 10 per cent of the S _q daily range.     

极光区高空物理过程与磁层-电离层耦合

极区高空物理现象之观测具有悠久历史。对极区地磁、电离层和极光现象的深入考察将地球物理的研究领域扩展到了外层空间,并提出了太阳风－磁层－电离层－热层间耦合这一重要课题。耦合物理机制的证实不仅是火箭、卫星探测的重要贡献,而且也是基于对地面雷达和遍及全球大陆的地磁台站、电离层垂测站之长期观测成果。对流电场、一区和二区场向电流、电离层扰动电流系（包括极光区电集流）,以及电导率的分布和变化乃是一有机整体,对其每一环节的深入认识均与对整体的全面了解密不可分。有关的理论和模式研究则有助于人们深入理解各个耦合过程的相互关系,以及其各发展阶段中不同物理过程的相对重要性。     

主要极地国家的极地科技体制探究——以美国、俄罗斯和澳大利亚为例

引领一国极地科学考察与研究的极地科技体制,已引起世界各国的广泛关注与重视。极地科技体制是指极地科学技术研究与管理的机构设置、职责范围、权属关系和管理方式的结构体系和组织架构,科学合理完善的极地科技体制是促进极地事业发展的前提和基础。文中重点研究分析了美国、俄罗斯和澳大利亚三个具有代表性极地国家的极地科技体制,并对上述三国的极地科技体制进行了概括总结,最后着眼于我国极地科技体制的现状,从学术和理论层面探讨了我国极地科技体制未来的改革方向,期待我国极地事业在"十三五"时期能够搭乘全面深化改革的便车实现跨越式发展,逐步形成适合我国国情并且相对完善的极地科技体制。     

A palaeomagnetic study of fracture fills in the Holy Cross Mountains of Central Poland and its application in dating tectonic processes

Calcite and sedimentary fills in fractures cutting the Upper Devonian carbonates in the Holy Cross Mountains (HCM) were dated palaeomagnetically by comparison with the apparent polar wander path (APWP). Haematite-bearing calcite possessed well-defined components of natural remanent magnetization (NRM), which were preserved under thermal demagnetization to temperatures of approximately 500 °C, when specimens disintegrated. Although not completely demagnetized, some specimens revealed a stable NRM component before destruction, thus making a component analysis possible. Five components were determined using density point distribution and cluster analysis. One has a mean that is similar to the present-day local geomagnetic vector. The remaining four components yielded palaeomagnetic poles located at: A (70.3°S, 5.5°E), B (71.3°S, 31.2°E), C (48.7°S, 351.0°E, virtual geomagnetic pole), and D (11.6°S, 312.3°E). Antipodal polarities found in the fracture fills, together with dissimilarities in magnetization found in calcite and hosting carbonates, indicate the lack of simultaneous remagnetization, and different times of remanence acquisition for the rocks under comparison. Taking both palaeomagnetically inferred palaeolatitudes and regional tectonics into consideration, a Mesozoic (Cretaceous?) age is estimated for palaeopoles A and B, a Permian age for pole C, and a Carboniferous age for pole D. These age determinations are in line with the calcite ages estimated from isotopic studies. A comparative palaeomagnetic study performed on a well-dated Upper Devonian neptunian dyke of limestone and a Lower Triassic clastic vein yielded virtual geomagnetic poles (VGPs) close to the APWP for Baltica. Generally, the remanence from fracture fills may be useful for dating related tectonics, karst phenomena and mineralization processes.     

Palaeomagnetic results from two basic volcanic formations in the western Himalayas and a Phanerozoic polar wandering curve for India

Summary. We present palaeomagnetic results from the Durgapipal and Rudraprayag formations, which are basic volcanic formations in the Lesser Himalayas of Uttar Pradesh State. NRM measurements and AF demagnetization stability tests were made on specimens cored from oriented block samples collected at representative sites. Mean stable remanent magnetic directions were used for calculating the Virtual Geomagnetic Pole (VGP) positions; where necessary tectonic corrections were applied.
The virtual geomagnetic north poles were found to be located at:

• (a). 

  Durgapipal (Permian): λ _p = 10° S, L_p = 42° W;
• (b). 

  Rudraprayag (Silurian-Devonian): λ _p = 30° S, L_p = 12° W.

A new, continuous Phanerozoic apparent polar wandering curve for the Indian subcontinent has been plotted from the available palaeomagnetic data and the VGP positions reported in this paper. As a result, the gap in the Indian palaeomagnetic data from the Lower Carboniferous to the Cambrian has been partially filled. The locations of the pole positions for the two formations on the Phanerozoic polar wandering curve for the Indian subcontinent, have been found to coincide with the stratigraphic ages assigned to them on the basis of rather limited geological and palaeontological evidence.
The Cambrian and Permian poles for the Salt Range in the NW Himalayas and the Permian pole for the Kumaon Himalayas are grouped along with the pole positions of contemporaneous formations of the Peninsular Shield. The palaeomagnetic data thus suggests that the two formations are autochthonous in nature.     

THE POLAR IONOSPHERE AND THE MAGNETOSPHERE-IONOSPHERE COUPLING

EISCAT (the Incoherent System at the northern polar region) data are used in discussion of the magnetosphere-ionosphere coupling. Comperison between samples in geomagnetic quiet days and during magnetic storms shows a significant effect of the basic magnetospheric processes on the features of the polar ionosphere. It not only demonstrates that the polar ionosphere can be regarded as a 'panoramic screen' of these process, but also indicates an importance of the simultaneous observation of southern and northern polar regions (especially, at the magnetic conjugate points). A few topics concerned are suggested for the further study of the southern polar region.     

Development of a polar magnetic substorm: a two-dimensional magnetometer array study

A polar magnetic substorm on 1974 September 11 was recorded by a two-dimensional array of 25 three-component magnetometers, so located that the westward ionospheric current passed over the array. The mean perturbation fields over five-minute intervals are presented at six representative epochs of the substorm, the first just before its onset and the sixth 21/2 hr later in the coda of the event. At four of the resulting 'time frames', the perturbation fields have been fitted, on a least-squares criterion, by calculated fields of three-dimensional current loops having downward field-aligned current at the east end of the ionospheric westward current, upward field-aligned current at the west end and closure in the magnetotail. The current density was constant across the width of each of these model currents. In three of the four time frames it proved necessary to introduce a bend to the northwest in the ionospheric current; this bend occurred within 27° (geomagnetic) west of geomagnetic midnight. An association with the Harang discontinuity is possible. The field-aligned current nearer to the array (in one time-frame the downward, east-end current, in two others the upward current at the west end) proved essential to secure any reasonable fit to the data. The ionospheric segment of the current loop moved at least 20° of longitude eastward, relative to the surface of the earth, between 07.48 and 08.58 UT. In this 70-min period the ionospheric segment moved at least 38° eastward relative to magnetic midnight.     

Annual variation of the geomagnetic field

Summary. Horizontal and vertical intensity data, obtained between 1957.0 and 1961.0 at 69 observatories, are analysed to determine the worldwide distribution of the annual variation of the geomagnetic field. Only data observed near local midnight are used, to avoid the small, but significant contamination from Sq. Over most of the world the variation is found to be small, with a clear dependence on latitude, but near the poles it is larger and more erratic. The non-polar variation is subjected to spherical harmonic analysis and separated into parts of internal and external origin. The polar variations are shown to be consistent with a north—south oscillation of the mean position of the auroral electrojets during the year. It is suggested that, with the exception of the polar effect, the annual variation is not due to ionospheric currents (as was hitherto believed), but results from an annual variation in the latitude of the ring current.     

Apparent polar wander of the mean-lithosphere reference frame

Apparent polar wander in the mean-lithosphere (= no-net-rotation = no-net-torque uniform drag) reference frame is compared with apparent polar wander in the hotspot reference frame over the past 100 Myr. Palaeo-magnetic poles and plate rotations previously used to determine an apparent polar wander path for the hotspot reference frame are here used to determine an apparent polar wander path in the mean-lithosphere reference frame. We find that the two paths are similar, especially for Late Cretaceous time, when a 10°–20° shift of the pole occurred. To first-order the hotspots and lithosphere (as a whole) moved in unison relative to the palaeomagnetic axis during Late Cretaceous time. A non-dipole field explanation for the apparent shift can probably be excluded. However, either motion of the time-averaged geomagnetic axis relative to the spin axis or polar wandering could have caused this shift, the latter being the more likely explanation.     

南极普里兹湾船载地磁三分量数据处理分析

船载地磁三分量测量仪(STCM)具有易携带、无时空限制、多参数测量等特点,在极地恶劣环境下,显然比拖曳磁力仪更具优势。对第29次南极科学考察获得的船载地磁三分量数据进行船磁干扰场的校正分离,获得相应的三分量数据以及总场。校正后地磁三分量数据与拖曳磁力数据进行对比,其标准差为47.56 n T,表明其在极区内工作性能良好,数据质量可靠。计算结果为我国首次在极区海域内获得的地磁三分量磁异常,有关的技术流程方法将为今后中国极地科考实施船载地磁三分量测量提供有效的技术支持。     

UT variation of internal Sq currents and the oceanic effect during 1980 March 1–18

Summary. UT variation of the internal part of S _q currents is examined using the geomagnetic data during 1980 March 1–18, and the effect of the ocean is found. The ratio of the internal currents to the external increases when the external current vortex comes above the Atlantic and Pacific Oceans, and the internal current vortex shifts to the oceans when the external vortex approaches the edge of the oceans. The existence of the ocean increases the total induced current by about 30 per cent and this amount is consistent with model calculations for S _q by previous workers.