Reflection of Large Tectonic Structures of the Eastern Part of the Arctic Ocean in the Lithospheric Magnetic Field

Geomagnetism and Aeronomy - The article considers maps of the field of lithospheric magnetic anomalies—images of the deep structures of the Arctic Ocean—constructed from observations by...     

Hydroacoustic wave in the external alternating magnetic field

The electromagnetic fields induced by hydroacoustic waves, propagating in a liquid conducting medium in an alternating magnetic field, have been considered. The equation, relating the induced magnetic field to the undisturbed antenna field and acoustic wave parameters, has been obtained. The spatial—temporal pattern of the induced field has been constructed in the case when acoustic wave propagates along a direct line with an alternating current.     

2004年11月7-8日巨磁暴期间场向电流的分布特征

利用CHAMP卫星磁场数据分析研究了2004年11月7日至8日巨磁暴(Dst<-200 nT)期间大尺度场向电流的分布特征.把方向相同且时间连续的一段场向电流定义为一个电流片,分析结果表明,伴随磁暴的发展,在卫星飞过的两个扇区(早上扇区0200-0400MLT及下午扇区1400-1600MLT)中的大尺度场向电流分布呈现不同的纬向分布特征:随着地磁扰动的增强,早上扇区电流片分布范围向高纬扩展;而下午扇区电流片分布范围则显著地向低纬扩展.与地磁活动SYM-H和AE指数对比分析得出,早上扇区的大尺度电流片的分布特征更多地受到亚暴活动的影响,而下午扇区的电流片分布则明显反映出磁暴环电流活动的特征.     

张家口—渤海地震带岩石圈磁场时空变化特征

利用2016—2018年3期华北地区流动地磁矢量原始测量资料, 经数据计算获得2期华北地区和张家口—渤海地震活动带及邻区岩石圈磁场时空变化模型。 研究结果显示: 张家口—渤海地震带岩石圈磁场变化空间分布不均匀, 具有明显的分区特征, 在张家口段(西段)与北京段(中西段)分界处和北京段(中西段)与唐山段(中东段)分界处岩石圈磁场各要素具有明显的异常变化, 如水平矢量存在转向和幅值变化, 磁偏角与磁倾角具有正负异常高梯度带的特征, 这与张家口—渤海地震带构造分段性特征密切相关。 张家口—渤海地震带位于燕山块体与华北平原块体之间, 两者运动的平动速率之差是张家口—渤海地震带左旋走滑的直接动力来源, 而各断裂带左旋走滑速率之差很可能是岩石圈磁场空间变化分段性分布的主要原因。     

Resonance properties of Psi5/Psc5 in geostationary orbit

It has been indicated that the magnetic field variations, registered by the geostationary satellites in the range 150–600 s after 14 SI/SC events, include transverse wave components that show the spectral—polarization properties of standing Alfvén waves. The amplitude of these waves increases with increasing pulse amplitude, the period increases with decreasing magnetic field magnitude, and the rotation direction and magnetic field vector orientation reverse their signs near the noon and midnight meridians.     

Plane discontinuities in collisionless plasmas: An analysis as applied to the magnetopause

Types of plane discontinuities possible in collisionless kinetics—thin current sheets with a nonzero normal component of the magnetic field—are considered. In a general case the electromagnetic field energy is transformed at such a discontinuity to the energy of ion flows. In addition to the known MHD discontinuities, the discontinuities that exist in the presence of pairs of interpenetrating flows on both sides of a discontinuity are studied. The application of the theory to an analysis of observations on the magnetopause has been considered.     

The experience of using the rock magnetic methods for assessing the prospects of magnetic exploration in the territory of archaeological monuments of the Barabinsk forest steppe

The results of studying the magnetic properties of the components of the natural environment of the Barabinsk forest steppe accommodating the archaeological monuments dated to VI century B.C. to II century A.D. are presented. The rock magnetic model is constructed for a two-layer medium composed of modern soil and an underlying blanket substratum deposits (clay loam, sandy loam, sand). It is shown that the magnetism of the humic horizon of the soil depends on the topographic position and soil type, whereas the magnetic characteristics of the underlying substratum deposits are persistent throughout the studied territory. The ratio of the magnetic susceptibilities of the humus horizon to the substratum is K = 3–6 for the automorphic soil, K = 1–2.5 for semihydromorphic soil, and K = 0.8–1.0 for hydromorphic soil. Based on subdividing the studied territory in accordance with the values of K and the calculated amplitudes of the microanomalies of the magnetic field, the areas where application of the magnetic survey is highly promising, moderately efficient, and unpromising are outlined. The particular cases of the absence of magnetic anomalies above the archaeological objects, the false anomalies, and the chaotic patterns of the low-amplitude anomalies—all the situations when the magnetic survey is inefficient—are explained from the standpoint of the model.     

Ultra-Low Geomagnetic Field Intensity in the Devonian Obtained from the Southern Ural Rock Studies

Izvestiya, Physics of the Solid Earth - Abstract—In order to determine the Earth’s magnetic field intensity in the Devonian, a collection of rocks of the Baymak-Buribay formation of the...     

DEMETER卫星监测的极低频和超低频电磁场数据分析

分析了DEMETER卫星上测量的极低频(ELF, 3—30 Hz)和超低频(SLF, 30—300 Hz)水平磁场. 其统计变化规律与地面上实测的此频段大气噪声变化规律一致, 并且数值差异也符合电波传播规律, 说明卫星上监测的电磁场来源于地面. 同时对DEMETER卫星上测量的ELF和SLF归一化波阻抗进行了深入地分析, 由电子密度与离子密度计算出的归一化波阻抗与由实测电磁场计算出的归一化波阻抗均有差异. 现有观测资料并不完全“自洽”, 尚有问题需深入研究.      

Study of Geoelectrical Responses to Space Weather Anomalies: Auroral Latitudes,Yenisei-Khatanga Regional Trough

Izvestiya, Physics of the Solid Earth - Abstract—The paper presents the results of analysis of the geoelectric (telluric) field variability during the Earth’s magnetic field...     

Evolution of the Large-Scale Geomagnetic Field over the Last 12 000 Years

Geomagnetism and Aeronomy - Abstract—The ERDA and IGRF-12 geomagnetic field models are used to study the behavior of Earth’s large-scale magnetic field. The unusualness of the modern...     

Topological semi-dynamos

Abstract

Magnetic field generation in a continuous medium in processes without self-excitation—the so-called semi-dynamo, involving as essential elements both magnetohydrodynamic processes and the presence of an impressed e.m.f.—has been studied for the case of the topological pumping effect on the magnetic field generation by an impressed e.m.f. operating in a three-dimensional Bénard convection layer.

Under conditions of interest for astrophysical applications the magnetic flux produced can exceed substantially that excited by the e.m.f. in the absence of motion.

The results obtained permitted an evaluation of the general quasi-steady magnetic field of the Sun generated by an azimuthal Coriolis e.m.f. which is active in the outermost layers of the convective envelope, taking into account small-scale convective and turbulent motions. In the polar regions of the Sun this field can reach ～10^?1 G.     

Dynamics of equilibrium upset and electromagnetic energy transformation in the geomagnetotail: A theory and simulation using particles. 3. Versions of formation of thin current sheets

The final part of the study is devoted to the process of rapid reconfiguration of the geomagnetotail after the upset of the equilibrium, i.e., to substorm activation. Such a version of spontaneous formation of nonlinear kinetic small-scale structures at the site occupied by an initial current sheet (CS), which results in the formation of a specific equilibrium current structure with strong ion anisotropy (forced kinetic current sheet, FKCS), has been revealed in the course of numerical simulation. This reconfiguration “channel” is realized when the relative value of the magnetic field component normal to CS is smaller than a certain critical value. In this case the disturbance intensity is SPONTANEOUSLY settled at a certain final level at the late stages. The obtained results are compared with the previous study of the system evolution under the action of the external trigger. The physical causes and specific features of different CS evolution regimes are considered. The studied plasma mechanisms are responsible for the effects of rapid energy transformation—magnetic field “annihilation”—that took place in the geomagnetotail.     

The geomagnetic field in the 20th century

The continuous spatial-temporal model of variations in the main geomagnetic field in the 20th century has been elaborated. All available data—from the navigation to the satellite surveys at the beginning and end of the century, respectively—have been used to construct the model. Since the accuracy of measurements was different during the century and the data are nonuniformly distributed over the Earth’s surface, the methods for regulating solutions based on global parameters of the magnetic field and its secular variation, invariant on the simulation interval, have been used to correct the model. The secular variation model has been represented as the sum of the models obtained by means of expansion in terms of natural orthogonal components. The conclusions that the character of field variations is complex have been made and the spatial and temporal characteristics of the secular variations of different origin have been estimated based on the simulation results.     

Trends in the F2 ionospheric layer due to long-term variations in the Earth's magnetic field

The Earth's magnetic field presents long-term variations with changes in strength and orientation. Particularly, changes in the dip angle (I) and, consequently, in the sin(I)cos(I) factor, affect the thermospheric neutral winds that move the conducting plasma of the ionosphere. In this way, a lowering or lifting of the F2-peak (hmF2) is induced together with changes in foF2, depending on season, time and location. A simple theoretical approximation, developed in a previous work, is extended to a worldwide latitude–longitude grid to assess hmF2 and foF2 trends due to Earth's magnetic field secular variations. Compared to the greenhouse gases effects over the ionosphere, the Earth's magnetic field may be able to produce stronger trends which vary with season, time and location. However, to elucidate the origin of F2-region trends, long-term variations in the three possible known mechanisms should be considered altogether—greenhouse gases, geomagnetic activity and Earth's magnetic field.     

Seismic,Atmospheric-Wave,Electrical, and Magnetic Effects of Powerful Atmospheric Fronts

Izvestiya, Physics of the Solid Earth - Abstract—Disturbances of seismic noise, magnetic field, electrical characteristics of the surface atmosphere and microbaric variations caused by the...     

Long-term variations of solar magnetic fields derived from geomagnetic data

There are limited homogeneous instrumental observations of the sunspot magnetic fields, but the Earth is a sort of a probe reacting to interplanetary disturbances which are manifestation of the solar magnetic fields. We find correlations between some parameters of geomagnetic activity (the geomagnetic activity “floor”—the minimum value under which the geomagnetic activity cannot fall in a sunspot cycle, and the rate of increase of the geomagnetic activity with increasing sunspot number), and sunspot magnetic fields (the sunspot magnetic field in the cycle minimum, and the rate of increase of the sunspot magnetic field from cycle minimum to cycle maximum). Based on these correlations we are able to reconstruct the sunspot magnetic fields in sunspot minima and maxima since sunspot cycle 9 (mid 19th century).     

Certain regularities of solar activity variations during the 11-year cycle

The relationships between a number of the main characteristic parameters of the cycle—amplitude, half-width, and growth phase duration—and the approximation parameters, which make it possible to estimate the average behavior of 11-year activity, have been derived based on the obtained analytical representations of the regularities in the solar activity variations during the cycle. Quasibiennial variations proceeding against a background of the cycle are distinctly associated with the solar magnetic field structure and the structure representation variations in the corona and in the flux of the solar neutrino radiation. This makes it possible to state that all these processes are parts of the common physical mechanism of solar variability.     

中国境内各阶非偶极子磁场的时空变化

为了研究中国境内各阶非偶极子(ND)磁场,通过最新的地磁场模型CALS10K.1b计算了10000 BC—AD 1990年ND磁场在中国境内的时空及能量变化;22,23和24极子磁场零值线主要呈现出从我国中北部向东南部移动,从北部向东部移动,以及从东南部向西北部移动的趋势;除了26极子磁场,其余ND磁场在1500年以后均有“翘尾”现象,其所占主磁场的比值在10000 BC—AD 1500年呈震荡变化,从1500年开始快速上升;除了22极子磁场,其它各阶ND磁场能量随时间变化的趋势基本一致. 在5650 BC年左右,各阶ND磁场能量值均出现高值并随阶数的增大而衰减,反映了在该时间点通过地核发电机产生的磁场能量随径向距离而近似线性衰减,地磁场能量主要源自地球液态外核. 将CALS10K.1b模型结果与IGRF11模型对比后,得出CALS10K.1b模型所计算的ND磁场及能量值较为可靠,而两者差异主要源于数据和建模方法的不同.      

20世纪中国地区主磁场变化研究

为了研究2 0世纪中国地区主磁场变化, 首先使用最新的全球模型IGRF11, CALS3K. 4 (3K. 4) 和GUFM1进行计算, 并分析了1900—1990年的主磁场年变率均值的变化; 然后基于1960—2000年以10年为间隔的实测数据, 结合全球模型CM4与区域模型泰勒(Taylor)多项式(TY)模型分析了中国地区主磁场的年变率分布及年变率均值, 并与上述几种全球模型进行了比较． 结果显示: 20世纪利用IGRF11, GALS3K.4和GUFM1模型得到的主磁场的年变率均值均很接近. 它们所绘制的1960—2000年中国地区的主磁场年变率分布类似． 其原因主要是由于它们的建模原理相同且截断阶数接近所致． 基于实测点绘制的年变率分布与全球模型基本一致, X分量的年变率逐年减少, Y、 Z、 F分量的年变率均呈现先减小后增大的趋势．但两者也存在一定差异, 主要原因是由于更高密度的实测点及使用区域模型所致． 结果还显示了基于实测值绘制的年变率均值变化与CM4较为接近. 作者认为 CM4模型可以较好地反映中国地区主磁场的变化．