Poynting flux impulses and the ionospheric switching of geomagnetic substorms

Observations were made of impulse events in Poynting flux calculated from electric and magnetic disturbances encountered by the Polar satellite when on high-latitude field-lines in the magnetotail. These were found to be coincident within±6 min with impulsive spikes in cosmic radio background absorption in the D region of the ionosphere as detected by the Imaging Riometer for Ionospheric Studies riometer in Finland. They were also coincident with substorm onset at the same geomagnetic latitude as determined by a change of gradient in International Monitor for Auroral Geomagnetic Effects’ X-component magnetograms. The interpretation of the observations was that magnetospheric compression waves from the geomagnetic equator region of the magnetotail were coupling to progressively initiate field-guided Alfvén shear waves towards higher geomagnetic latitudes over a large volume of the magnetosphere. The study suggested that they were then able either directly or indirectly to ionise the D region of the ionosphere and in the process to cut deep electrically conducting channels between the magnetosphere and the ionosphere through which currents could flow and initiate the characteristic signature of geomagnetic substorms in ground magnetograms.     

Comparing the geomagnetic thresholds of cosmic rays for two empirical models of the magnetosphere during the period of an extreme geomagnetic storm in November 2003

The accuracy of determining the geomagnetic cutoff rigidity (the geomagnetic threshold) is closely related to that of describing the magnetic field of the magnetosphere with the model used for calculations. Geomagnetic thresholds are calculated for two empirical models of the magnetosphere, Ts0l and Ts04, constructed on the basis of the same initial experimental data. The Ts01 model describes the average magnetosphere for certain conditions in the solar wind and interplanetary field. The Ts01 model focuses on describing the large-scale evolution of magnetospheric currents during a storm. A comparison of the geomagnetic thresholds for Ts0l and Ts04 with experimental thresholds calculated by the Spectrographic Global Survey from data of the CR global network stations shows that the Ts01 model describes the magnetic field of the magnetosphere more realistically. Our study was conducted for the period of a strong geomagnetic storm in November 2003.     

Simulation of the electric field in Earth’s ionosphere during a geomagnetic storm

Previously, a global self-consistent model of the thermosphere, ionosphere, and protonosphere (GSM TIP) was used to study the ionospheric effects of geomagnetic storms in 2005, 2006, 2010, and 2011. In these studies, the input parameters of the model were specified using different dependences of variations of the potential difference across the polar caps and of the spatial distribution of Region 2 field-aligned currents during geomagnetic storms on the geomagnetic activity indices, solar wind parameters, and interplanetary magnetic field parameters. In the present work, we have tried to examine how correct was the choice of these relationships and how faithful are the obtained global distributions of the electric field in the ionosphere. For this, we present the results of a comparative analysis of the electric field in the ionosphere during geomagnetic storms of May 2–3, 2010, obtained using two models (GSM TIP and LC06) based on different approaches to solving this problem.     

地磁暴对电力系统的影响及防治策略

地磁暴是全球范围内地球磁场的剧烈扰动现象, 在电网中产生地磁感应电流(GIC)。电力变压器在GIC的作用下进入半波饱和状态, 其产生的谐波和增加的无功损耗影响电网电压稳定, 造成系统中继电保护装置误动, 随着电网电压等级的提高和电网规模的扩大, 地磁暴可能严重威胁电网安全运行。分析了变压器对GIC入侵后的响应, 以及次生灾害在电力系统中的传播过程, 阐明了磁暴对电力系统的影响机理, 分析了GIC对变压器、无功补偿设备和继电保护装置等设备的影响, 建立了GIC对系统电压稳定性影响的分析框架及基本方法, 最后提出了一种GIC优化治理策略, 与传统治理方法相比具有明显的优越性。     

地磁暴条件下电网连锁故障风险评估

地磁扰动会在高压电网中诱发产生地磁感应电流(GIC), 使得电力变压器等发生相继故障, 从而导致电力系统崩溃或者引起大停电事故, 研究地磁暴条件下电网连锁故障风险评估能够为预防其引起的电网事故提供重要参考。对地磁暴条件下电网连锁故障的机理进行了分析, 提出了地磁暴条件下电网连锁故障风险评估流程, 该流程可以识别各个地磁暴条件下电网的薄弱环节; 利用系统的负荷削减量来评估连锁故障各个阶段对系统的危害, 同时利用给定地磁暴条件下该薄弱环节导致电力系统崩溃所削减的临界负荷量来评估其对电力系统的危害。利用IEEE-RTS79系统对于所提出的流程进行验证, 验证结果表明所提出流程的可行性和有效性, 所得结果可以为量化和防范地磁暴电网风险提供参考。     

Katz Fractal Dimension of Geoelectric Field during Severe Geomagnetic Storms

We are concerned with the time series resulting from the computed local horizontal geoelectric field, obtained with the aid of a 1-D layered Earth model based on local geomagnetic field measurements, for the full solar magnetic cycle of 1996–2019, covering the two consecutive solar activity cycles 23 and 24. To our best knowledge, for the first time, the roughness of severe geomagnetic storms is considered by using a monofractal time series analysis of the Earth electric field. We show that during severe geomagnetic storms the Katz fractal dimension of the geoelectric field grows rapidly.     

我国磁层物理研究进展

我国磁层物理是在赵九章倡导下从１９５９年开始发展起来的,４０多年来,我国磁层物理有了很大进展。文章对我国磁层物理研究的主要成果作了概述,主要内容包括：磁层顶边界层的瞬时重联研究,磁层顶的不稳定性和反常输产业暴过程研究,磁尾动力学过程研究,极光加速区非线性波和粒子加速研究,行星磁了后是磁层物理发展趋势的展望。     

A Statistical Study of the Correlation between Geomagnetic Storms and M ≥ 7.0 Global Earthquakes during 1957–2020

In order to find out whether the geomagnetic storms and large-mega earthquakes are correlated or not, statistical studies based on Superposed Epoch Analysis (SEA), significance analysis, and Z test have been applied to the Dst index data and M ≥ 7.0 global earthquakes during 1957–2020. The results indicate that before M ≥ 7.0 global earthquakes, there are clearly higher probabilities of geomagnetic storms than after them. Geomagnetic storms are more likely to be related with shallow earthquakes rather than deep ones. Further statistical investigations of the results based on cumulative storm hours show consistency with those based on storm days, suggesting that the high probability of geomagnetic storms prior to large-mega earthquakes is significant and robust. Some possible mechanisms such as a reverse piezoelectric effect and/or electroosmotic flow are discussed to explain the statistical correlation. The result might open new perspectives in the complex process of earthquakes and the Lithosphere-Atmosphere-Ionosphere (LAI) coupling.     

地球变化磁场Z分量的混沌动力学特性分析

对地球变化磁场进行了混沌动力学特性分析,主要进行了以下两个方面的工作:1)运用多种方法对多个地磁台站同一时段变化磁场分量数据(分为磁扰较小和磁扰较大时段)进行了混沌特性分析,主要是为了以更充分的判据来验证地球变化磁场是否具有混沌特性;2)同一地磁台站不同时段变化磁场分量数据的混沌特性分析,主要是验证地球变化磁场是否具有变参数混沌特性.分析结果表明:1)变化磁场时间序列确实具有混沌特性;2)从混沌时间序列相空间重构的角度可初步认为模拟地球变化磁场动力学系统所必须的独立变量应该为6左右;3)变化磁场时间序列不仅具有混沌特性而且其参数也是在缓慢变化着的,具有变参数混沌系统的特性.     

First and second order non-equilibrium phase transition and evidence for non-extensive Tsallis statistics in Earth’s magnetosphere

In this paper strong evidence is provided for significant far from equilibrium phase transition processes in the Earth’s magnetosphere as revealed by the nonlinear analysis of in situ observations. These results constitute the solid base for the solution of the durable controversy about the chaotic or non-chaotic character of the magnetospheric dynamics. During the last two decades the concept of low dimensional chaos was supported by theoretical and experimental methods by our group in Thrace and others scientists, as an explicative paradigm of the magnetospheric dynamics including substorm processes. In parallel, the concept of self-organized criticality (SOC) and space-time intermittency was introduced as new and opposing to low dimensional chaos concepts for modeling the magnetospheric dynamics. Novel results concerning the nonlinear analysis of in situ space plasma data (magnetic-electric field, energetic particles and bulk plasma flow time series) obtained by the Geotail spacecraft presented in this paper for the first time reveal the following: (a) Coexistence of SOC and chaos states in the magnetospheric system and global phase transition from one state to the other during substorms. (b) Strong intermittent turbulent character of the magnetospheric system at the SOC or the low dimensional chaos states. (c) Clear indications for non-extensivity and q-Gaussian statistics during periods of low dimensional and chaotic dynamics of the magnetosphere. (d) Low dimensional and nonlinear space plasma dynamics in the day side magnetopause and bow shock dynamics. The dual character of the magnetospheric dynamics including low dimensional chaotic (coherent) and high dimensional turbulent states, as supported in this paper, is in agreement and verifies previous theoretical and experimental studies.     

Diurnal variations in cosmic ray intensity caused by high latitude magnetospheric-ionospheric current systems

Cosmic ray intensity measurements obtained with the neutron monitors at Thule (geomagnetic latitude, 84.8°) and McMurdo (geomagnetic latitude, −79.9°) in 2007–2009 were used to test the effect of the magnetic field generated by magnetospheric currents flowing along geomagnetic field lines in the high latitude region on cosmic ray intensity. The existence of such a relation in a region where the geomagnetic field lines are virtually radial should revise our concept of the unimpeded access that cosmic ray particles have to the Earth’s atmosphere.     

Satellite observations of electric fields in the innermagnetosphere and their effects in the mid-to-low latitude ionosphere

During geomagnetic disturbances, momentum and energy are transferred in significant quantities from interplanetary space to the magnetosphere-ionosphere system through the mediation of charged particles and electric fields. The most dramatic manifestations occur in the plasma sheet and the conjugate auroral ionosphere. However, electric fields observed during magnetic storms also penetrate the inner magnetosphere that maps to subauroral latitudes in the ionosphere. For example, a sudden commencement shock wave initiating the March 1991 magnetic storm created a new radiation belt within minutes. Particle and field measurements by Combined Release and Radiation Effects Satellite (CRRES) near the equatorial plane of the magnetosphere and by Defense Meteorological Satellite Program (DMSP) satellites in the topside ionosphere during the magnetic storm of June 1991 indicate that penetration electric fields energized the stormtime ring current and rapidly transported plasma within subauroral ion drift (SAID) structures at midlatitudes and in upward drafting plasma bubbles at low latitudes. Through enhanced transport or chemical reactions, the SAIDs dug deep plasma troughs at topside altitudes. Equatorial plasma bubbles developed while the ring current was unable to shield the electric field from the innermost magnetosphere     

Geomagnetically Induced Currents: Principles

The geospace, or the space environment near Earth, is constantly subjected to changes in the solar wind flow generated at the Sun. The study of this environment variability is called Space Weather. Examples of effects resulting from this variability are the occurrence of powerful solar disturbances, such as coronal mass ejections (CMEs). The impact of CMEs on the Earth’s magnetosphere very often greatly perturbs the geomagnetic field causing the occurrence of geomagnetic storms. Such extremely variable geomagnetic fields trigger geomagnetic effects measurable not only in the geospace but also in the ionosphere, upper atmosphere, and on and in the ground. For example, during extreme cases, rapidly changing geomagnetic fields generate intense geomagnetically induced currents (GICs). Intense GICs can cause dramatic effects on man-made technological systems, such as damage to high-voltage power transmission transformers leading to interruption of power supply, and/or corrosion of oil and gas pipelines. These space weather effects can in turn lead to severe economic losses. In this paper, we supply the reader with theoretical concepts related to GICs as well as their general consequences. As an example, we discuss the GIC effects on a North American power grid located in mid-latitude regions during the 13–14 March 1989 extreme geomagnetic storm. That was the most extreme storm that occurred in the space era age.     

Strong cosmic ray cutoff rigidity decreases during great magnetospheric disturbances

The theoretical and experimental cosmic ray cutoff rigidities during great magnetospheric disturbances in November 2004 and May 2005 have been determined. The theoretical geomagnetic cutoffs were calculated by the trajectory tracing method in the magnetic field of Tsyganenko’s magnetospheric model T03, which describes great magnetospheric disturbances (at Dst < 65 nT). The experimental geomagnetic cutoffs were determined by the spectrographic global survey method on the basis of the world network data. The cutoff rigidity decreases at Dst minima can reach 70–80% for theoretical cutoffs and ～40% for experimental cutoffs at mid latitudes.     

Geomagnetically induced currents during magnetic storms

The electric field which is induced by geomagnetic storms drives currents in technological systems, such as electric power transmission grids, oil and gas pipelines, telecommunication cables, and railway equipment. These geomagnetically induced currents (GIC) cause problems to the systems. In power grids, transformers may be saturated due to GIC resulting in harmful effects and possibly even to a collapse of the whole system, as occurred in Quebec in March 1989. Transformers may also suffer from permanent damage. In buried pipelines, GIC can enhance corrosion and interfere with corrosion control surveys. Telecommunication systems as well as railway equipment may also malfunction due to GIC. The electric and magnetic fields observed at the Earth's surface primarily depend on magnetospheric-ionospheric currents and secondarily on currents induced in the Earth. The physical background and modeling of GIC are discussed in this paper. Special attention is paid to basic principles necessarily understood to get an insight into GIC phenomena. Recent developments in the use of the Complex Image Method (CIM) permit fast and accurate computations of the electric field suitable for time-critical applications like GIC forecasting     

Electrodynamics of solar wind-magnetosphere-ionosphere interactions

The authors present a coherent picture of fundamental physical processes in three basic elements of the SW-I (solar wind-magnetosphere-ionosphere) coupling system: (i) the field-aligned potential structure which leads to the formation of auroral arcs; (ii) the magnetosphere coupling which leads to the onset of magnetospheric substorms; and (iii) the solar wind-magnetosphere dynamo which supplies the power for driving various magnetospheric processes. The field-aligned potential structure on auroral lines is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. The substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. The energy is transferred from the solar wind to the magnetosphere by a dynamo process primarily on open field lines     

Observation results of relativistic electrons detected by Fengyun-1 satellite and analysis of relativistic electron enhancement (REE) events

The space particle component detector on Fengyun-1 satellite which works at the sun-synchronous orbit of about 870 km altitude has detected relativistic electrons for a long time. In comparison with the SAMPEX satellite observations during 1999–2004, the relativistic electron data from Fengyun-1 satellite from June 1999 to 2005 are used to analyze the relativistic electron enhancement (REE) events at the low earth orbit, and the possible correlation among REE events at the low earth orbit, high-speed solar wind and geomagnetic storms is discussed. The statistical result presents that 45 REE events are found in total during this time period, and the strong REE events with the maximum daily average flux > 400 cm⁻²·sr^t-1·s⁻¹ occur mostly during the transition period from solar maximum to solar minimum. Among these 45 REE events, four strong REE events last a longer time period from 26-to 51-day and correlate closely with high speed solar wind and strong geomagnetic storms. Meanwhile, several strong geomagnetic storms occur continuously before these REE events, and these continuous geomagnetic storms would be an important factor causing these long-lasting strong REE events. The correlation analysis for overall 45 events indicates that the strength of the REE events correlates with the solar wind speed and the strength of the geomagnetic storm, and the correlation for strong REE events is much stronger than that for weak REE events.     

Theory for explosive ideal magnetohydrodynamic instabilities in plasmas

Flux tubes confined in tokamaks are observed to erupt explosively in some plasma disruptions and edge localized modes. Similar eruptions occur in astrophysical plasmas, for example, in solar flares and magnetospheric substorms. A single unifying nonlinear evolution equation describing such behavior in both astrophysical and tokamak plasmas is derived. This theory predicts that flux tubes rise explosively, narrow, and twist to pass through overlying magnetic field lines without reconnection.     

Dynamics of the Earth’s radiation belts

In this article, we provide a short review of the current state of the field of the radiation belts of the Earth. The main attention is given to the variations of energetic particle fluxes during geomagnetic storms. Electron and proton acceleration mechanisms in the terrestrial magnetosphere are discussed. The possibility of predicting various space weather parameters using the data on relativistic electrons of the outer radiation belt is discussed.     

Magnetospheric dynamics during the storm of February 14, 2009

The structure of the magnetic field in the magnetospheric during the storm of February 14, 2009 is studied. The model parameters that characterize the magnetospheric magnetic field are calculated every hour on the basis of solar wind data and the evolution of the magnetic field during the storm is reproduced using the A2000 model of the Earth’s magnetosphere. It is shown that extremely quiet geomagnetic conditions in 2009 promoted the expansion of the magnetosphere and were favorable for the formation of magnetic-island-like structures (plasmoids) in the geomagnetic tail. It is ascertained that negative variations in the B_z component could occur in the nightside magnetosphere in situations where the magnetic flux through the tail lobes exceeded certain thresholds, which depend on the parameters of the magnetospheric current systems. It is shown that the formation of magnetic islands decreases the magnetic flux through the tail lobes and prevents excessively strong development of the magnetic field in the tail.