Future Inversion of the Magnetic Field and Possible Changes in the Structure of the Magnetosphere

Geomagnetism and Aeronomy - IGRF-12 model data have been used to analyze the change in the global structure of internal sources of the Earth’s magnetic field. A decrease in the dipole...     

Simultaneous Observations of EMIC Waves,ELF/VLF Waves,and Energetic Particle Precipitation during Multiple Compressions of the Magnetosphere

Geomagnetism and Aeronomy - Simultaneous observations of ELF/VLF and EMIC waves from Van Allen Probe satellites in the daytime Earth’s magnetosphere and on the ground during multiple...     

Generation of EMIC Waves in the Magnetosphere and Precipitation of Energetic Protons: Comparison of the Data from THEMIS High Earth Orbiting Satellites and POES Low Earth Orbiting Satellites

Regions of the detection of electromagnetic ion-cyclotron (EMIC) waves on the THEMIS satellites near the equatorial plane and the precipitation of energetic protons on POES low Earth orbiting satellites are compared with the magnetospheric magnetic field model. It is confirmed that low Earth orbiting satellites detect the precipitation of energetic protons in the regon associated with observations of EMIC waves in the magnetosphere. This is consistent with the idea that protons are scattered in the loss cone as a result of ioncyclotron interaction. Thus, observations of fluxes of energetic protons in low Earth orbits can be used to monitor ion-cyclotron instability regions in the magnetosphere. Simultaneous observations at high and low Earth orbits contribute to the construction of a spatiotemporal pattern of the interaction region of EMIC waves and energetic protons. In addition, it is shown that proton precipitation associated with EMIC waves can cause errors in determining the latitude of the isotropic boundary (the equatorial boundary of isotropic fluxes of energetic protons), which is an indicator of the configuration of the magnetic field in the magnetosphere.     

Whistler Growth Rates in the Magnetosphere According to Measurements of Energetic Electron Fluxes on the Van Allen Probe A Satellite

Geomagnetism and Aeronomy - Measurements of the differential fluxes of energetic electrons in the equatorial region of the magnetosphere in the energy range from units of keV to hundreds of keV...     

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。     

Magnetic fields due to sea tides in the english channel

The M₂ (12.42-h period) magnetic field variation present at night in the United Kingdom can be interpreted in terms of sea tides, the main contribution being from the Atlantic Ocean. Osgood et al. (1970) observed a difference between the M₂-variations in the total magnetic field (F) variations at Sidmouth (0.8 km from the coast) and Exeter (16 km from the coast) of amplitude 0.8 γ, which must be due to local effects. Analysis of the phase of this difference between Exeter and Sidmouth has shown that it cannot be due entirely to tidally induced electric current systems confined to the English Channel. Measurements with two three-component magnetometers have shown that the night-time variations in the north-south (H) component of 12.42-h period are significantly different at Sidmouth and Exeter. The difference in H is in phase with the expected electric potential difference across Devon due to the difference in the phases of the sea tides in the English Channel and the Bristol Channel. The results of Donato and Rosser (1973) on micropulsations suggest the existence of a region of high conductivity under Exeter. If this connects the English Channel to the Bristol Channel, a current will flow beneath Exeter giving a difference in the M₂-variations in H at Exeter and Sidmouth. This difference in H dominates the M₂-variations in the total magnetic field (F) variations at Exeter and Sidmouth measured by Osgood et al. (1970).     

Influence of Cycle Variations in the Global Solar Magnetic Field on Characteristics of the Interplanetary Plasma

Geomagnetism and Aeronomy - Regularities of the spatial and temporal variation in the plasma parameters of the interplanetary medium in solar cycles 21–24 are studied based on the data from...     

Characteristics of the Energetic Electron Precipitation and Magnetospheric Conditions in 1994

The problem of the rapid depletion and saturation of the Earth’s outer radiation belt with energetic electrons is one of the central problems in the physics of the magnetosphere. The precipitation into the atmosphere and the escape of electrons from the magnetosphere are competing reasons for the depletion of the radiation belt. Long-term measurements of energetic electron precipitation (EEP) in the atmosphere in the experiment of the Lebedev Physical Institute (LPI) can be used to study the relative role of these phenomena. High fluence values of relativistic electrons in the outer belt is a necessary condition for EEP observation; however, the relation of the EEP rate to the condition of the belt is ambiguous, which is shown by the example of observations in 1994.     

Effect of Stress on the Magnetic Memory of Induced Magnetic Anisotropy of Rocks and Its Mathematical Model

When re-heated to temperatures below the Curie temperature and subsequently cooled in a constant magnetic field (H _T), rock samples which contain magnetic minerals can acquire an induced magnetic anisotropy (IMA). As the result of acquiring the IMA, a constriction develops in the hysteresis loop of the magnetization of these rocks at the values of the magnetizing field close or equal to the HT. Thus the IMA is capable of retaining the information on the palaeointensity of the geomagnetic field, i.e., if IMA was created in a rock in the geomagnetic field in a past geological epoch, it preserves the information on the intensity of that field. Investigations have shown, that when IMA is created in a rock under external stress, the stress has an impact on the magnetic memory. Here we also deal with the issue of how stress affects the magnetic memory of IMA. A mathematical model for the effect of stress on magnetic memory phenomena related to induced magnetic anisotropy in rocks containing multidomain magnetite and titanomagnetite grains is proposed herewith. The effect of temperature on the magnetic memory of rocks is discussed also.     

Variations in the Intensity of the Earth's Magnetic Field

The Earth's main magnetic field can be approximated by an axial, geocentric dipole. The remaining non-dipole field is much smaller and is a regional rather than a global feature – quite large changes can occur in a few ka. This review is concerned with changes in the dipole component of the geomagnetic field, and one of the problems is in separating the non-dipole from the dipole contributions to the field. Unlike the many determinations of the direction of the Earth's magnetic field in the past (which have led to fundamental contributions to our understanding of plate tectonics and shown that the field can on occasion reverse its polarity), estimates of the intensity of the field are comparatively few, especially before the Holocene. This is mainly the result of experimental difficulties in obtaining reliable measurements of the field. These problems are discussed in some detail and are followed by a short account of archaeomagnetic intensities and results from Hawaii where many of the first determinations were obtained. Measurements for the last 100 ka from both lavas and lacustrine and oceanic sediments are reviewed and results from different areas compared. An asymmetric saw-tooth pattern has been observed in some of the records over the last few Ma, and this rather controversial question is discussed. Finally an account is given of the far more limited data on palaeointensities in earlier times.A short discussion is given of the interpretation of coherent short wavelength variations which are observed in many marine magnetic profiles. Although short reversals of the field may be responsible for some of these tiny wiggles, it is more likely that in general they are the result of changes in the strength of the Earth's magnetic field.     

Magnetic topologies in the solar corona due to four discrete photospheric flux regions

Many dynamic phenomena in the solar corona are driven by the complex and ever-changing magnetic field. It is helpful, in trying to model these phenomena, to understand the structure of the magnetic field, i.e. the magnetic topology. We study here the topological structure of the coronal magnetic field arising from four discrete photospheric flux patches, for which we find that seven distinct, topologically stable states are possible; the changes between these are caused by six types of bifurcation. Two bifurcation diagrams are produced, showing how the changes occur as the relative positions and strengths of the flux patches are varied. A method for extending the analysis to higher numbers of sources is discussed.     

Relationship between the Drift of Medium-Scale Irregularities and the Orientation of Transverse Anisotropy of Small-Scale Irregularities in the F Region of the Midlatitude Ionosphere

Geomagnetism and Aeronomy - The characteristics of irregular ionospheric structures are studied with two different methods in the course of two independent, long-term experiments. The parameters of...     

Some Features of the Variation of the Magnetic Field Characteristics in the Umbra of Sunspots During Flares and Coronal Mass Ejections

The observed variations of the magnetic properties of sunspots during eruptive events (solar flares and coronal mass ejections (CMEs)) are discussed. Variations of the magnetic field characteristics in the umbra of the sunspots of active regions (ARs) recorded during eruptive events on August 2, 2011, March 9, 2012, April 11, 2013, January 7, 2014, and June 18, 2015, are studied. The behavior of the maximum of the total field strength B_max, the minimum inclination angle of the field lines to the radial direction from the center of the Sun α_min (i.e., the inclination angle of the axis of the magnetic tube from the sunspot umbra), and values of these parameters B_mean and α_mean mean within the umbra are analyzed. The main results of our investigation are discussed by the example of the event on August 2, 2011, but, in general, the observed features of the variation of magnetic field properties in AR sunspots are similar for all of the considered eruptive events. It is shown that, after the flare onset in six AR sunspots on August 2, 2011, the behavior of the specified magnetic field parameters changes in comparison with that observed before the flare onset.     

青藏高原东南缘地质构造基本形态与地震各向异性基本特征

青藏高原东南缘受印度板块NE向推挤和高原物质SE向挤出及四川盆地、华南块体阻挡的共同作用,成为高原物质SE向逃逸的关键通道。本文综述了青藏高原东南缘由不同震相和不同方法得到的不同深度的地震各向异性结果,结合区域内断裂分布、地表运动、构造应力以及深部结构等方面,全面分析了青藏高原东南缘上地壳至中下地壳及上地幔的介质各向异性与变形耦合特征。青藏高原东南缘壳幔地震各向异性的差异反映了区域内复杂的深部构造和壳幔变形。由于青藏高原形成机制、壳幔耦合状态和软弱层分布形态等科学问题尚处于学术探讨之中,有效结合不同数据和综合多种方法,有益于获得更加准确、精细的地壳—上地幔地震各向异性图像,对深部物质运动与动力模式进行更有效的约束。     

地电场日变幅各向异性度异常提取方法初步研究

首先建立地电场日变幅各向异性度(S值)方法:对不同测向的地电场日变幅换算成各向异性系数,进而提取异常信号的方法。通过对不同台站的映震结果的对比分析表明:(1)该方法能够较好地识别地震前兆信息异常,对于5级左右地震,在震前4个月之内,震中距200 km范围内各台能够记录到地震的短期异常,异常出现的早晚与各台震中距的远近有关;对于4级地震,震中距越近异常越明显;(2)在正常情况下,S值曲线一般在均值的2倍均方差以内波动;当出现异常时,异常判据为S值2日以上超过各台均值的2倍均方差、曲线形态发生畸变;(3)各台映震结果存在较大的差异性,这可能与地下介质电性结构、发震构造与各台构造关联性存在一定关系。     

1690年以来全球非偶极子磁场的变化特征

根据J Bloxham和A Jackson地磁场模型，计算和分析了1690-1990年期间非偶极子磁异常的变化特片。结构表明，1690年以来一直存在的变化磁异常有7个，在一定时期内出现的磁异常有3个，它们是1830年以后出现的北太平洋负磁异常、1850年以后出现的东南太平洋负磁异常和1690-1900年期间在南太平洋地区出现的负磁异常。各个磁异常的强度和中心位置随时间变化，变化趋势各不相同。与根据IGRF模型计算的20世纪的磁异常变化比较，除非洲负磁异常外，两种模型得出的其它磁异常在同一时段内的变化趋势基本一致。     

2004年12月26日印度尼西亚地震海啸灾害考察

印度洋地震海啸的灾害是严重的。本文介绍了印度尼西亚在这次地震海啸中的灾害情况，包括建筑物的破坏、生命线工程的破坏等。最后提出了几点建议。     

Model of Transport of Large-Scale Magnetic Field Fluctuations in the Solar Wind

We consider a model that couples the magnetic field fluctuations in the heliosphere with random shifts of force line footpoints on the Sun. This model generalizes the Giacalone (2001) model by taking into account the large-scale inhomogeneity of the solar wind velocity. This generalization aims to explain a number of specific features of the distribution of IMF directions, such as the change in the asymmetry of the distribution of IMF directions as a function of heliographic latitude and the solar cycle phase and the correlation of azimuthal angles and inclinations of the IMF; the sign of this correlation changes during the solar magnetic cycle. The simulation results have shown that the gradients of the solar wind speed can actually explain these specific features of the distribution of IMF directions, at least qualitatively.     

新沂台地电场频谱特征的分析与研究

运用快速傅里叶变换与小波分析对新沂地电场不同季节、不同年份的资料与地磁场H分量、连云港体应变资料进行频谱对比分析,结果显示:地电场EW向的,优势周期主要为12 h;地电场NS向的优势周期主要为8h、12h、24 h;地磁场H分量的优势周期主要为8h、12 h、24 h;体应变的优势周期主要为12 h、24h;并且在不同年份、不同季节各物理量的优势周期显著度也不尽相同.从各物理量对应性的结果显示:地电场EW向与体应变吻合度较高;地电场NS向与地磁场的吻合度较高.此对应结果解释了新沂台地电场产生的一种机制.