Magnetic study of a metabasic dyke in Dhaiya,Dhanbad (Bihar)

Summary A metabasic dyke of pre-Cambrian age passing through Dhaiya village in Dhanbad, consists of metanorite, metadolerite and epidiorite. A magnetic study of this dyke has been undertaken. 14 magnetic traverses were taken with Schmidt vertical force variometer. Direction and intensity of N.R.M. have been determined for 15 oriented samples, with an astatic magnetometer. Magnetic susceptibility of 36 samples has been determined. Microscopic study (thin and polished sections) of samples has been done. The intensity of N.R.M. is upto 11.830×10^–3 c.g.s. units susceptibility varies from 53×10^–6 to 750×10^–6 c.g.s. units and the Koenigsberger ratio from 3.3 to 236.6. The magnetic profiles are interpreted taking into account both remanence and susceptibility. In case of metanorite and metadolerite, more than 80% of the anomaly is caused by remanence. Negative anomalies in some cases is due to negative inclination of remanent magnetization. Very low anomalies (less than 50 gammas) over epidiorite are due to loss of magnetism (both remanent and induced) of these rocks due to felspathization. A new mechanism has been proposed to account for the scatter in magnetic directions for metamorphosed igneous rocks. The rotation, during metamorphism, of magnetic grains (magnetite, ilmenite etc.) enclosed in the lenticular rock-forming minerals causes deviation of the magnetic vector from its original position. Two more causes have been suggested here to explain the variation of intensity of N.R.M. of metabasic rocks: (i) Ilmenite exsolved from titaniferous augite partly contributes to the N.R.M. (ii) magnetite dust injected into felspars by solutions during metamorphism, causing cloudiness in felspars, partly contributes to the N.R.M. The wide scatter in remanent magnetic direction in these rocks is due to the effects of metamorphism. The magnetic directions fall under two groups: one with positive inclination and the other with negative inclination; both the groups being, in general, magnetized normally in the horizontal direction. This indicates normal magnetization in northern and southern hemispheres respectively. This probably means that the place was in the northern and southern hemispheres at the time of original emplacement of the dolerite magma and of metamorphism respectively, the metamorphism, not affecting all the rocks uniformly.     

Magnetic study of the dolerite dyke near Amarpur,Dhanbad (Bihar)

Summary The dolerite dyke of post-lower Gondwana age reported earlier by the authors [5]²) has been taken for detailed magnetic study. Seven magnetic traverses have been taken across the dyke using Schmidt vertical force variometer. Negative anomalies varying from 1400 to 2200 gammas have been observed. Magnetic susceptibility of samples from the dyke has been determined on both cores and crushed material, using the Model MS-3 susceptibility bridge. The average susceptibility of 20 samples has been found to be 1930x10^–6 C.G.S. units. Direction and intensity of remanence on 10 oriented samples have been determined by an Astatic magnetometer. The average intensity of remanence has been found to be 3.13x10^–3 C.G.S. units and the average direction has a declination of 323° and inclination-68° (up dip). The Koenigsberger ratio varies from 1.6 to 5.6. The high negative magnetic anomalies have been explained in terms of remance-that more than 80% of the anomaly is due to remance and that negative anomalies are due to negative inclination of remanent direction of the rocks. The magnetic direction for the dyke gave the position for Dhanbad as 51° south latitude in Jurassic period. This is in conformity with the deductions made by other workers from the palaeomagnetic studies of the Deccan and Rajmahal traps. The virtual geomagnetic pole in Jurassic period as deduced from the palaeomagnetism of the dyke has a position of latitude 8 1/2°N and longitude 71°W, in the southern Carribean. On palaeomagnetic evidence this dyke has been correlated with Rajmahal traps of eastern Bihar.     

A satellite study of dayside auroral conjugacy

A study of dayside auroral conjugacy has been done using the cleft/boundary layer auroral particle boundaries observed by the DMSP-F7 satellite in the southern hemisphere and the global UV auroral images taken by the Viking spacecraft in the northern hemisphere. The 22 events have been studied on the basis of an internal IGRF 1985 magnetic field; it is shown that there is a displacement of up to 4^° in latitude from the conjugate points with the northern aurora appearing to be located poleward of the conjugate point. No local time dependence of the north-south auroral location difference was seen. The use of a more realistic magnetic field model for tracing field lines which incorporates the dipole tilt angle and Kp index, the Tsyganenko 1987 long model plus the IGRF 1985 internal magnetic field model, appears to organize the data better. Although with this external plus internal model some tracings did not close in the opposite hemisphere, 70% of those that did indicated satisfactory conjugacy. The study shows that the degree of auroral conjugacy is dependent upon the accuracy of the magnetic field model used to trace to the conjugate point, especially in the dayside region where the field lines can either go to the dayside magnetopause near the subsolar point or sweep all the way back to the flanks of the magnetotail. Also the discrepancy in the latitude of northern and southern aurora can be partially explained by the displacement of the neutral sheet (source region of the aurora) by the dipole tilt effect.     

Meridional distribution of tropospheric ozone from measurements aboard commercial airliners

Aboard commercial airliners twenty registrations of the ozone concentration of the upper troposphere were carried out within a period of 14 months between Europe and South Africa. Nearly each of these meridional ozone profiles shows an approximately constant ozone content between 25°S and 25°N with a pronounced seasonal variation. Most of these profiles show two marked peaks of the ozone concentration at about 30°N and between 40° and 45°N. Though the number of these registrations is not sufficient for statistical computations, the first results confirm the meridional ozone distribution, which was expected from studies with ozone-radiosonde soundings. Moreover a strong asymmetry of the northern and southern hemisphere is confirmed by these ozone measurements.     

Latitudinal Profiles of the Photospheric Magnetic Field in Solar Cycles 19–21

For various groups of photospheric magnetic fields differing in strength, averaged synoptic maps have been obtained from the data of the Kitt Peak National Solar Observatory (1976–2003). The latitudinal profiles of magnetic field fluxes are considered individually for each 5-G field strength interval. Changes in the maxima of the latitude profiles and their localization in the latitude are studied. The results are evidence that the latitudinal distribution of the magnetic fields changes significantly at field strengths of 5, 15, and 50 G. The magnetic flux for groups of fields differing in strength decreases monotonically as the strength increases, starting from B > 5 G; the fluxes of the southern hemisphere exceed those of the northern hemisphere. A very special group is formed by the weakest fields with B < 5 G, which are opposite in phase to stronger fields in terms of localization and time changes.     

High altitude observations of electron temperature and a possible north–south asymmetry

Measurements of electron temperature made by the thermal electron energy distribution (TED) instrument on board the EXOS-D (Akebono) satellite have been analysed. From the data taken between 1989 and 1995, averaged daytime and nighttime temperature profiles for different geophysical conditions have been produced. These profiles represent the averaged thermal electron temperature between 1000 and 8000 km altitude for conditions of high (F10.7>150) and low (F10.7<120) solar activity. Results indicate that increased solar activity has a marked effect on the electron temperature. At 8000 km altitude, the typical low-latitude daytime electron temperature is around 8000 K. The nighttime electron temperature at 8000 km is around 4000 K. The averaged daytime difference between high and low solar activity conditions is around 1000 K at altitudes above 2500 km. Between 1000 and 2000 km altitude this situation is reversed, and the electron temperature is comparatively higher during periods of low solar activity during both day and night. Composition changes in the region are proposed as a mechanism for this reversal. In addition, there is evidence of an asymmetry in thermal electron temperature between the northern and southern hemispheres. The averaged electron temperature is found to be comparatively higher in the northern hemisphere during the daytime and comparatively higher in the southern hemisphere during the nighttime. This difference between hemispheres is particularly evident during the nighttime, and during the rapid heating and cooling periods around sunrise and sunset. Possible reasons for the asymmetry are discussed. Profiles are also presented for conditions of high (Ap>30) and low (Ap<20) magnetic activity. Analysis has confirmed that geomagnetic activity has little effect on electron temperature below L=2.2.     

On the mean zonal and meridional circulations and the flux of moisture in the northern hemisphere during the summer season

Summary The mean zonal and meridional wind components of the northern hemisphere at different pressure levels for the summer season June–August have been determined and the mean meridional mass circulation has been computed as a function of latitude. From the mass circulation the meridional flux of moisture is computed for the latitudinal belt 0°–45° N. Using the horizontal divergence of this flux the average difference between precipitation and evapotranspiration from the earth's surface is evaluated.     

Reversed polarity patches at the CMB and geomagnetic field reversal

The International Geomagnetic Reference Field models (IGRF) for 1900–2000 are used to calculate the geomagnetic field distribution in the Earth’ interior from the ground surface to the core-mantle boundary (CMB) under the assumption of insulated mantle. Four reversed polarity patches, as one of the most important features of the CMB field, are revealed. Two patches with +Z polarity (downward) at the southern African and the southern American regions stand out against the background of ™Z polarity (upward) in the southern hemisphere, and two patches of ™Z polarity at the North Polar and the northern Pacific regions stand out against the +Z background in the northern hemisphere. During the 1900–2000 period the southern African (SAF) patch has quickly drifted westward at a speed of 0.20–.3° /a; meanwhile its area has expanded 5 times, and the magnetic flux crossing the area has intensified 30 times. On the other hand, other three patches show little if any change during this 100-year period. Extending upward, each of the reversed polarity patches at the CMB forms a chimney-shaped “reversed polarity column” in the mantle with the bottom at the CMB. The height of the SAF column has grown rapidly from 200km in 1900 to 900km in 2000. If the column grows steadily at the same rate in the future, its top will reach to the ground surface in 600–700 years. And then a reversed polarity patch will be observed at the Earth’s surface, which will be an indicator of the beginning of a magnetic field reversal. On the basis of this study, one can describe the process of a geomagnetic polarity reversal, the polarity reversal may be observed firstly in one or several local regions; then the areas of these regions expand, and at the same time, other new reversed polarity regions may appear. Thus several poles may exist during a polarity reversal.     

Magnetic Susceptibility Screening of Anthropogenic Impact on the Danube River Sediments in Northwestern Bulgaria - Preliminary Results

Several events of anthropogenic impacts on the floodplain river sediments of the Danube along a section near the town of Oryakhovo (NW Bulgaria) have been detected using magnetic technique. In the field, magnetic susceptibility was measured using three susceptibility meters – MS2D, KT-5 and SM30. The differences in the surface susceptibility values measured with the different instruments are ascribed to the various penetration depths which depend on several parameters like sensor diameter, frequency and field strength. This is supported by the detailed laboratory study on penetration depth and sensitivity of the new SM30 susceptibility meter and the comparison with the already existing data for the other two sensors. Boundaries between different flooding events are clearly linked with significant variability of the measured susceptibility values corresponding to one and the same level. Sediment cores, taken at different distances from the water level, show the history of depositional events and corresponding degree of anthropogenic pollution. Identification of the magnetic phases responsible for the signal was carried out by means of thermomagnetic (T) curves. The main carrier is magnetite with Tc of 580°C or oxidized magnetite with Tc of 600°C. A second kink at about 300°C is better expressed for samples with lower susceptibilities. It may correspond to several minerals, e.g. maghemite, pyrrothite, titanomagnetite, as well as different mineral transformations of paramagnetic minerals (decomposition, dehydroxilation, etc. for example siderite, lepidocrocite). The samples showing strong magnetic enhancement are characterized by the predominance of magnetite. Optical microscopy on magnetic extracts shows the presence of small spherical particles, typical for the anthropogenic magnetic phases from high-temperature technological processes. Well expressed susceptibility variations along the cores suggest the presence of several stages of different degree of pollution, covering an estimated period of about 30 years.     

Observations on the distribution of dissolved mercury in the ocean

The concentration of dissolved mercury in sea water has been determined in a number of areas in the northern and southern hemispheres and an attempt has been made to correlate the values found for certain areas with natural physical phenomena. The average concentrations found ranged from 11.2 ng l^?1 in the southern hemisphere to 33.5 ng l^?1 for the northern hemisphere; an increase suspected to be the result of dispersion of industrial pollution by jet streams. Local effects including upwelling, volcanic action, land run-off and heavy suspended matter loads are also discussed.     

耀斑日面位置与磁扰关系的不对称性

本文探討了耀斑日面位置与磁扰关系的不对称性。經分析研究,得到（βγ+γ+β_f）型活动区耀斑的磁扰效应有明显的南北不对称性,但（β_p+β）型活动区耀斑却无此南北不对称效应。在太阳南半球,不論那种磁場类型活动区,发生在西边的耀斑要比东西或中心子午线附近耀斑的影响强,而在北半球只有（β_p+β）型活动区耀斑才有这种东西不对称性效应。在最近三个太阳黑子周內,这些不对称是經常存在的,而在春秋季表現最为明显。     

The average tropospheric ozone content and its variation with season and latitude as a result of the global ozone circulation

Evaluations of radiosonde soundings over North America and Europe, measurements aboard commercial airlines, and permanent ozone registrations at nineteen ground-based stations between Tromsö, Norway, and Hermanus, South Africa, yield three belts of higher ozone intrusion from the stratosphera and maximum values of the annual means at about 30°N, at between 40°–45°N and at about 60°N. A marked decrease of the annual mean values of the tropospheric ozone is detected towards the equator and the pole, respectively.In the northen hemisphere the maximum of the annual cycle of the tropospheric ozone concentration occurs in spring at high latitudes and in summer at mid-latitudes.For the tropical region from 30°S to 30°N a strong asymmetry of the northern and southern hemisphere occurs. This fact is discussed in detail. The higher troposphere of the tropics seems to be a wellmixed reservoir and mainly supplied with ozone from the tropopause gap region in the northern hemisphere. The ozone distribution in the lower troposphere of the whole tropics seems to be controlled by the up and down movements of the Hadley cell. The features of large-scale and seasonal variation of tropospheric ozone are discussed in connection with the ozone circulation in the stratosphere, the dynamic processes near the tropopause and the destruction rate at the earth's surface.     

A Geophysical Study Of The Ophiolite Complex And The Sedimentary Basins In The Northwest Part Of The Chalkidiki Peninsula (N. Greece)

The present work focuses on the study of the main ophiolite complex ofNorthern Greece, which is one of the dominant geological features in thebroader Aegean area, by the use of geophysical (gravity and magnetic)data. This ophiolite complex, which trends in a NW-SE direction, startsat the eastern part of the borders of Greece with F.Y.R.O.M. and continuesup to the southern part of the Chalkidiki Peninsula. The ophiolites mainlyconsist of dense, high-susceptibility peridotitic and gabbroic rocks. As aresult, the southwestern part of the ophiolitic complex, which crosses thenorthwestern part of the Chalkidiki-Peninsula, gives rise to both highamplitude aeromagnetic and Bouguer anomaly values. On the other hand,the Axios-Thermaikos basin, which is situated at the western border of theophiolitic complex, exhibits a deep sedimentary cover that results in lowBouguer anomaly values. The corresponding Bouguer anomaly decreasesto the southwest, indicating an increase of the sedimentary layer thicknessin that direction.2.5-D inversion was applied to both the aeromagnetic and the Bouguergravity data along several profiles. All the profiles were oriented normalto the main trend of the ophiolitic complex. Information from two deepboreholes, as well as the surface occurrence of the ophiolites was used asconstrains to the inversion scheme. The produced model shows an averagesedimentary thickness of 2.5 km along the coastline. From the joint inversionof the Bouguer and aeromagnetic anomaly data the existence of two ophioliticstripes is revealed. The first ``external' one is located in the southwest part, while the other ``internal' one to the northeast part of the belt. In the internal one, the depth extent of the ophiolites was estimated to range between 1 to 4 km. Moreover, the ophiolites were found to dip towards the northeast, but their dip varies from 20–45° in the northern part to 10–15° in the southern part of the stripe. For the ``external' stripe the extent of the ophiolitic bodies varies from northwest to southeast, reaching its highest depth of 5 km to the south. This stripe is also dipping towards the northeast with a dip of 10–15°.     

Correlation of magnetitic susceptibility with18O/16O data in late orogenic granites of the southern Appalachian Piedmont

Initial magnetic susceptibility (generally indicative of magnetite content) has been determined for 445 samples from 17 granites located in the southern Appalachian Piedmont of Georgia and South Carolina. These values have been correlated with whole rock δ¹⁸O data from the same plutons, yielding a pronounced inverse relationship. It has previously been shown for the southern Piedmont that low oxygen isotopic (¹⁸O-enriched) values usually occur in S-type granites (Wenner [1], this issue). It follows, then, that I-type granites are characterized by high susceptibilities (χ > 1 × 10^?4 G/Oe), and S-type granites by low susceptibilities (χ < 1 × 10^?4 G/Oe). An interesting result of this work has been the observation that some S-type granites exhibit good within-site clusters of remanent magnetic directions while I-type granites generally do not.     

极区Hall电流经度差异特征的统计学研究:CHAMP卫星观测

本文利用2001至2010年间CHAMP(CHallenging Minisatellite Payload)卫星标量磁力仪(Overhauser Magnetometer)观测的磁场数据,反演得到电离层霍尔(Hall)电流,并且对极区电离层Hall电流的特征进行了统计学研究.研究主要关注平静期,即重联电场小于2 mV·m~(-1)条件下,在磁纬60°至90°范围内的Hall电流在不同太阳活动、季节、磁经度、磁地方时等条件下的变化特征.研究发现:Hall电流具有明显的经度差异,在南北半球呈现显著一波经度结构,而且南北半球反相,即北半球电流密度呈现峰-谷-峰结构,而南半球呈现谷-峰-谷结构.Hall电流密度的经度结构与太阳活动紧密相关,太阳活动高年经度差异最大,太阳活动中年经度差异次之,太阳活动低年经度差异最小.研究发现,在磁地方时为10-14MLT的白天,影响Hall电流的因素主要是太阳辐射;而磁地方时为21-03MLT的夜晚,除了电导率的影响之外,可能存在其他的重要的物理过程影响着Hall电流的经度分布.本文还研究了与电流相关的焦耳热的经度分布情况,发现其在南北半球分别呈现单峰、单谷结构,经度差异亦十分明显.     

Gravity and magnetic signatures of volcanic plugs related to Deccan volcanism in Saurashtra, India and their physical and geochemical properties

The Bouguer anomaly and the total intensity magnetic maps of Saurashtra have delineated six circular gravity highs and magnetic anomalies of 40-60 mGal (10⁻⁵m/s²) and 800-1000 nT, respectively. Three of them in western Saurashtra coincide with known volcanic plugs associated with Deccan Volcanic Province (DVP), while the other three in SE Saurashtra coincide with rather concealed plugs exposed partially. The DVP represents different phases of eruption during 65.5±2.5 Ma from the Reunion plume. The geochemical data of the exposed rock samples from these plugs exhibit a wide variation in source composition, which varies from ultramafic/mafic to felsic composition of volcanic plugs in western Saurashtra and an alkaline composition for those in SE Saurashtra. Detailed studies of granophyres and alkaline rocks from these volcanic plugs reveal a calc-alkaline differentiation trend and a continental tectonic setting of emplacement. The alkaline plugs of SE Saurashtra are associated with NE-SW oriented structural trends, related to the Gulf of Cambay and the Cambay rift basin along the track of the Reunion plume. This indicates a deeper source for these plugs compared to those in the western part and may represent the primary source magma. The Junagadh plug with well differentiated ring complexes in western Saurashtra shows well defined centers of magnetic anomaly while the magnetic anomalies due to other plugs are diffused though of the same amplitude. This implies that other plugs are also associated with mafic/ultramafic components, which may not be differentiated and may be present at subsurface levels. Paleomagnetic measurements on surface rock samples from DVP in Saurashtra suggest a susceptibility of 5.5×10⁻² SI units with an average Koenigsberger ratio (Q_n) of almost one and average direction of remanent magnetization of D=147.4° and I=+56.1°. The virtual geomagnetic pole (VGP) position computed from the mean direction of magnetization for the volcanic plugs and Deccan basalt of Saurashtra is 30°N and 74°W, which is close to the VGP position corresponding to the early phases of Deccan eruption. Modeling of gravity and magnetic anomalies along two representative profiles across Junagadh and Barda volcanic plugs suggest a bulk density of 2900 and 2880 kg/m³, respectively and susceptibility of 3.14×10⁻² SI units with a Q_n ratio of 0.56 which are within the range of their values obtained from laboratory measurements on exposed rock samples. The same order of gravity and magnetic anomalies observed over the volcanic plugs of Saurashtra indicates almost similar bulk physical properties for them. The inferred directions of magnetization from magnetic anomalies, however, are D=337° and 340° and I=−38° and −50° which represent the bulk direction of magnetization and also indicate a reversal of the magnetic field during the eruption of these plugs. Some of these plugs are associated with seismic activities of magnitude ≤4 at their contacts. Based on this analysis, other circular/semi-circular gravity highs of NW India can be qualitatively attributed to similar subsurface volcanic plugs.     

行星际磁场对极尖区位形变化的统计研究

利用Cluster卫星数据,选取2001—2010年期间的616个极尖区穿越事件,研究了行星际磁场（IMF）的大小和方向对极尖区位形的影响.结果表明：当B_z为北向时,随着B_x负向的增大,极尖区的磁不变纬度向高纬方向（极区）移动;当B_z为南向时,随着B_x负向增大,极尖区的磁不变纬度略微向低纬度方向（赤道）移动.B_x正向增大时,极尖区并没有明显移动.B_x对极尖区影响在南半球较为显著,在北半球没有明显规律性变化.此外,随着行星际磁场锥角的增大（>90°）,极尖区也随之向高纬移动.当B_z南向时,随着B_y的负向增大,极尖区在北半球向晨侧移动,在南半球向昏侧移动.而当B_z南向增加时,南北半球两个极尖区的磁不变纬度都朝赤道方向移动;但北向B_z时几乎没有移动.     

A deformed Pliocene-Quaternary alluvial and red paleosol succession in the Eastern Betics: Paleomagnetic,rock-magnetic and sedimentological pilot study

Summary An integrated pilot paleomagnetic and sedimentological study has been conducted in the Neogene-Quaternary infilling materials of the Bajo Segura Basin (Eastern Betics, SE Spain). The studied sediments belong to the youngest (late Pliocene-Quaternary) lithostratigraphic unit of the basin (P-Q unit). The statistical analysis of tectonic striations and stylolitic dissolutions on the conglomerate limestone clasts indicates a NNW-SSE maximum compression direction. This is in accordance with the principal susceptibility axes, determined from the anisotropy of magnetic susceptibility measurements (AMS) of the interbedded siltstones where the Kmax axis group in a subhorizontal N 080° E direction.A total of 45 core samples have been collected from 16 stratigraphic siltstone levels encompassing the described section at Crevillente with the aim to establish a magnetochronology. Upwards in the section the NRM intensity and bulk susceptibility vary from 10^–2 to 10^–3 A/m and from 1550 to 100 × 10^–6 SI, respectively. The mean characteristic remanent magnetization (ChRM) after bedding correction (Dec/Inc = 10°/60°, ₉₅ = 8.7°, k = 15.9) is deviated slightly towards the E from the reference N direction, and could reflect a deflection related to the observed magnetic fabric although no clear correlation exists with AMS parameters. The derived magnetostratigraphy reveals only one reversal boundary within the upper third of the section, delimiting an upper reversal magnetozone which has been tentatively correlated with the Olduwai subchron close to the Plio-Pleistocene boundary.Pilot and preliminary rock-magnetic experiments and standard X-ray difraction (XRD) analysis have been performed on typical samples in order to establish the carriers of magnetization and characterize the sedimentological and magnetic-acquisition processes in these sediments. Magnetic carriers seem to be dominated by magnetite with a relative grain size within the PSD state (pseudo single-domain) threshold, but closer to the MD (multi domain) threshold, which favours the detrital origin for the magnetite.     

Global and regional N2O measurements

Real-time N₂O measurements have been madein situ at the South Pole, Antarctica, north and south of the equator from on board the Alpha Helix and over the Pacific Ocean on several aircraft flights from the U.S. to New Zealand, Australia and 90°S. In addition, an automated EC-GC has been operated for the past year intermittently monitoring N₂O in surface air at a rural site in the wheatlands of eastern Washington state. The data obtained are consistent and in agreement with the data obtained from the analyses of a large number of samples collected both from ground stations and a variety of aircraft flights made in the southern and northern hemisphere. The observed global data show no interhemispheric differences. The present concentration of N₂O in the troposphere is measured to be 330±3 ppbv. Its vertical distribution in the troposphere is very uniform. A small decrease (2–3 percent) across the tropopause is characteristically observed in the high altitude Learjet flights.     

外源S_q等效电流体系电流涡中心电流强度与太阳活动关系

本文选取了INTERMAGNET地磁台网2001年到2012年的地磁数据,对其进行世界时(UT)到地方时(LT)的转换后利用自然正交分量法(NOC)从所选资料中提取出太阳静日变化Sq成分,再通过球谐分析方法建立模型分离内、外源Sq成分,逐日反演出内、外源Sq等效电流体系,并得到外源Sq等效电流体系南北电流涡中心电流强度.本文将外源Sq等效电流体系南北电流涡中心电流强度与同一时期的Dst指数进行了对比分析,研究表明它们之间具有同步变化的规律,且北半球电流涡中心电流强度在磁暴发生时的异常现象远高于南半球.对F10.7cm太阳射电流量与外源Sq等效电流体系南、北半球电流涡中心电流强度的长短周期分析发现,Sq等效电流表现出明显的11年周期特点,与太阳活动周期一致.外源南、北半球电流涡中心电流强度和F10.7cm年均值的相关系数分别达到了0.93和0.90,说明太阳活动是导致外源Sq电流体系变化的最直接也最主要的因素,这可能与电离层电导率受控于太阳的电磁辐射相关.