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.     

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。     

Association of large geomagnetic storms with halo CMEs and CIRs observed during 1997–2007

In the present study, we have analysed large geomagnetic storms associated with storm time index (D_st) decrease of more than 100 nT observed during 1997–2007 and found 90 geomagnetic storms falling in our selection criteria. We have analyzed the association of the above selected 90 large geomagnetic storms with three types of solar drivers: single front-side halo CME (S-type), multiple front-side halo CMEs (M-type) and corotating interaction region, CIR (C-type). It is found that 58% storms were caused by single front-side halo CME (S-type), whereas 30% storms were caused by multiple front-side halo CMEs (M-type). Rest 12% storms were caused by corotating interaction region (CIR). We find that there is an east-west asymmetry and north-south asymmetry as well. We have also shown the association of the selected 90 large geomagnetic storms with three types of surface source region: active region, quiet region and coronal holes. We find that 62% storms were caused by active region whereas 10% storms were caused by quiet region. 12% storms were caused by coronal holes. Surface source region of rest 16% storms are unknown due to data gap.     

Behavior of the cosmic-ray vector anisotropy before interplanetary shocks

The behavior of the galactic cosmic ray density and vector anisotropy during geomagnetic storms with sudden storm commencements has been investigated based on the global survey data. It is shown that the average anisotropy significantly increases directly before a sudden storm commencement; the larger the subsequent Forbush decrease, the larger the increase in anisotropy. The averaged values of the CR anisotropy and density start to be affected by the shock wave approximately 5 h before its arrival. Changes in the anisotropy direction (especially for west Forbush sources) can be observed much earlier.     

Effect of NO concentration disturbances on the global distribution of ionospheric parameters during geomagnetic storms

The role of nitric oxide (NO) in the ionospheric effects during geomagnetic storm on May 1–3, 2010, is examined. The studies are performed using a global self-consistent model of the thermosphere, ionosphere and protonosphere (GSM TIP). Two versions of calculations are used: (1) based on an analytical approximation of the NO concentration and (2) self-consistent calculation of the global distribution of nitric oxide over the ionosphere. It is shown that, during a geomagnetic disturbance, the NO concentration at high latitudes shows an increase, which under the influence of the horizontal circulation of neutral gas leads to an increase in the concentration of NO at mid-latitudes ～1 day after the start of the perturbation. Simulated values of foF2 are compared to experimental data obtained at a number of Russian mid-latitude stations. It is noted that the self-consistent calculations of the NO concentration better describes the spatial-temporal behavior of ionospheric parameters during geomagnetic storms.     

Evaluation of the Kushida Method of short-term earthquake prediction

Kushida and Kushida found that FM radio waves from stations at distances over-the-horizon are received before earthquakes. Based on this finding, since the mid-1990’s, the Kushidas have been practicing “Earthquake Precursor Detection Experiment”. The performance of the Kushida method during 2000–2003 has been evaluated by checking their predictions against the actual seismicity. During the period, there were 92 Kushida predictions mentioning the possibility of M ≥ 5.5 event, whereas there were 49 M ≥ 5.5 earthquakes in the Japanese region. If the criteria for successful prediction are set as: the errors in date is less than one day, epicentral position is roughly within specified area, and error in M is less than 0.5, the success rate was 20% and the alarm rate was 12%. If we relax the criteria to: the errors in dates within 10 days, epicenter within additional 100 km of specified area and the magnitude error less than 1.0, the success rate was 40% and the alarm rate was 27%. These rates may look insufficient for a practical prediction method. Considering, however, the fact that no other short-term prediction has ever been made in Japan so far it is a significant achievement. Moreover, it was found that in almost all failed predictions, meaningful signals were detected although the interpretations were incorrect. This indicates that the method is promising provided further investigation is carried out. The same evaluation at the M ≥ 6.0 level showed that the general performance was similar to the M ≥ 5.5 level, except that both success rate and alarm rate were lower at the M ≥ 6.0 level. If this unexpected finding is real, it might be inherent to the methodology using scattering of short-wave length radio waves as suggested by M. Hayakawa and may contain important information in understanding the earthquake physics and LAI-coupling. The results of the present study indicate strongly that the earthquake prediction research using anomalous transmission of VHF FM radio waves should be enhanced in parallel with complementary research in other frequency ranges.     

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。     

Possible triggering of solar activity to big earthquakes (<Emphasis Type="Italic">Ms</Emphasis>≥8) in faults with near west-east strike in China

This paper studies the relationship between solar activity and big earthquakes (Ms≥8) that occurred in China and western Mongolia. It is discovered that the occurrence dates of most of the big earthquakes in and near faults with west-east strike are close to the maximum years of sunspot numbers, whereas dates of some big earthquakes which are not in such faults are not close to the maximum years. We consider that it is possibly because of the appearance of many magnetic storms in the maximum years of solar activity. The magnetic storms result in anomalies of geomagnetic field and then produce eddy current in the faults gestating earthquake with near west-east strike. Perhaps the gestated big earthquakes occur easily since the eddy current heats the rocks in the faults and therefore decreases the shear resistant intensity and the static friction limit of the rocks.     

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.     

太阳与地磁活动对超低轨重力卫星电推进系统工作的影响

面向当前第25太阳活动周, 评估太阳与地磁活动对超低轨重力卫星电推进系统工作的影响。通过对超低轨道重力卫星进行轨道仿真和分析GOCE任务数据, 得出大气阻力的变化规律, 并获得了太阳活动极大年附近任务和极小年附近任务对携带工质量的影响、地磁暴对电推进系统保持"无拖曳"工作的影响。结果表明: 其余情况相同下, 卫星在太阳活动低年附近任务的工作轨道高度可较高年降低约20 km, 有利于提高重力信号强度。强地磁暴通常引起超低轨道卫星阻力增加30%~90%, 飞行控制需为克服地磁暴影响留足够的推力裕度。推力器设计应保证最大推力的10%~70%推力区间具有高比冲, 且着重考虑此区间的寿命问题。      

计及地磁暴影响的电力系统事故链仿真模型

地磁暴影响下地磁感应电流(GIC) 流过变压器中性点, 引起变压器无功损耗增加, 在强地磁暴环境中, 系统的无功补偿装置可能过载, 母线电压下降, 可能引发连锁故障, 继而导致大停电事故。对比事故链各环节特点和因磁暴导致的电力系统停电事故的发展规律, 使用事故链模型来仿真实现地磁暴条件下的电网停电过程。基于自组织临界理论和非故障线路的安全稳定裕度来确定连锁故障的传播路径。结合IEEERTS79系统参数, 估算各母线的地理位置, 借助PowerWorld仿真软件, 以该系统为例, 研究结果验证了所提事故链模型可以反映给定电网条件下, 地磁暴参数对电力系统事故链集与薄弱环节辨识的影响, 研究结果可为量化和防治磁暴电网灾害提供依据。     

Ionospheric effects of geomagnetic storms at mid latitudes

Previously, we studied the ionospheric effects of the sequence of geomagnetic storms on September 9–14, 2005 using a global self-consistent model “Thermosphere-Ionosphere-Protonosphere” (GSM TIP). Differences between the predicted and observed effects of the ionospheric storms may be due to the use of the three-hour K _p index of geomagnetic activity in modeling the time dependence of model input parameters, use of the dipole approximation of the geomagnetic field, and disregard in simulations for solar flares that occurred during this period. We tried to eliminate two of these three reasons. First, we used the A _E index of geomagnetic activity with minute resolution in modeling the time dependence of the model input parameters. Second, we took into account the effects of solar flares. In addition, GSM TIP model was supplemented by an empirical model describing the precipitation of high-energy electrons. The results of the simulation of the behavior of various ionospheric parameters over the Yakutsk, Irkutsk, Millstone Hill, and Arecibo stations on September 9 and 10, 2005 in the new formulation of the problem, presented in the current work, are in better agreement with the available experimental data than the results of previous calculations.     

Solar, geomagnetic and seismic activity

Summary An 11-y modulation of large Italian earthquakes has been successfully identified and found to be positively linked to sunspot activity. The seismic activity appears to be modulated by the 11-y sunspot cycle through the coherent variation of geomagnetic activity. It is proposed that the two phenomena are linked by the influence of a magnetostriction process on stresses in the crust. An implication of this model is that geomagnetic storms may directly trigger large earthquakes.

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Riassunto L'analisi dei valori annuali delle macchie solari, della variazione geomagnetica interdiurna e dei grossi terremoti italiani ha permesso di identificare una significativa diretta modulazione undecennale dell'attività sismica da parte dell'attività solare attraverso la coerente variazione dell'attività geomagnetica con un relativo effetto magnetostrittivo sulle rocce crostali. Il modello proposto si rivela di pratica importanza per la previsione dei terremoti innescati da tempeste magnetiche.

     

Possible triggering of solar activity to big earthquakes (Ms ≥ 8) in faults with near west-east strike in China

This paper studies the relationship between solar activity and big earthquakes (Ms≥8) that occurred in China and western Mongolia. It is discovered that the occurrence dates of most of the big earthquakes in and near faults with west-east strike are close to the maximum years of sunspot numbers, whereas dates of some big earthquakes which are not in such faults are not close to the maximum years. We consider that it is possibly because of the appearance of many magnetic storms in the maximum years of solar activity. The magnetic storms result in anomalies of geomagnetic field and then produce eddy current in the faults gestating earthquake with near west-east strike. Perhaps the gestated big earthquakes occur easily since the eddy current heats the rocks in the faults and therefore decreases the shear resistant intensity and the static friction limit of the rocks.     

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.     

Wave ionosphere perturbations with small periods under magnetic storm conditions

The characteristics of total electron content (TEC) variations obtained using the data of middle-latitude stations for receiving GPS satellite signals were studied. An analysis showed that perturbations of diurnal TEC variations during a geomagnetic storm were determined by strengthening of harmonics with periods of 4–5 and 6–8 h. Perturbations in diurnal TEC variations were retained for several days after a geomagnetic storm. An analysis of the frequency and amplitude characteristics of perturbed variations showed that differences between variations at different latitudes could be explained by the propagation of Poincaré planetary waves in an atmospheric wave channel. The atmospheric channel was formed because of increased heating of pole regions during geomagnetic storms. A comparative analysis of observations made at different stations was used to estimate the width of the atmospheric channel and Poincaré wave frequencies and wave vector components.     

Assessing Earthquake Forecast Performance Based on b Value in Yunnan Province,China

Many studies have shown that b values tend to decrease prior to large earthquakes. To evaluate the forecast information in b value variations, we conduct a systematic assessment in Yunnan Province, China, where the seismicity is intense and moderate–large earthquakes occur frequently. The catalog in the past two decades is divided into four time periods (January 2000–December 2004, January 2005–December 2009, January 2010–December 2014, and January 2015–December 2019). The spatial b values are calculated for each 5-year span and then are used to forecast moderate-large earthquakes (M ≥ 5.0) in the subsequent period. As the fault systems in Yunnan Province are complex, to avoid possible biases in b value computation caused by different faulting regimes when using the grid search, the hierarchical space–time point-process models (HIST-PPM) proposed by Ogata are utilized to estimate spatial b values in this study. The forecast performance is tested by Molchan error diagram (MED) and the efficiency is quantified by probability gain (PG) and probability difference (PD). It is found that moderate–large earthquakes are more likely to occur in low b regions. The MED analysis shows that there is considerable precursory information in spatial b values and the forecast efficiency increases with magnitude in the Yunnan Province. These results suggest that the b value might be useful in middle- and long-term earthquake forecasts in the study area.     

Recurrent solar wind streams

A new approach to investigating the statistical relationship between certain solar features and recurrent wind streams is presented. This approach is based, on a comparative analysis of the distributions of lifetimes of a set of solar features, recurrent geomagnetic disturbances, and geomagnetic “calms.” Correlation coefficients of 0.81, 0.85, 0.79, and 0.77 are found for the distributions of several solar features—filaments, large-scale magnetic fields, coronal features, and coronal holes, respectively—and recurrent geomagnetic disturbances. A correlation factor of 0.97 between the distributions of geomagnetic “calms” and active regions is found. The combined evidence indicates that no specific type of solar feature is responsible for the recurrent stream activity. Rather, the configuration of the large-scale magnetic field of the Sun appears to control the permanently existing corpuscular activity. Since prominences trace polarity division lines of the large-scale magnetic field structure of the Sun, they have been checked as a possible general predictor of recurrent corpuscular activity; their parameters could present the most reliable indices that relate closely with trends in geomagnetic disturbances. A comparative analysis of cyclic variations of sunspot numbers, the total number of prominences, the relative number of low-height (<-20″) prominences, and recurrent geomagnetic storms is made for solar cycle N16. The relative number of low-height prominences is found to correlate broadly (0.83) with recurrent wind streams. P. K. Shternberg State Astronomical Institute, Moscow, Russia; National Solar Observatory, Sacramento Peak, U.S. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 2, pp. 145–151, February, 1998.     

A study of non-extensivity in the Earth’s magnetosphere

Magnetic storms are undoubtedly among the most important phenomena in space physics and also a central subject of space weather. The non-extensive Tsallis entropy has been recently introduced, as an effective complexity measure for the analysis of the geomagnetic activity D _st index. Tsallis entropy has been shown to sensitively detect the complexity dissimilarity between pre-storm activity and intense magnetic storms in the Earth’s magnetosphere. Here, we show that the D _st time series obey a modified form of the Gutenberg-Richter law for the case of non-extensive statistics, thus providing evidence for universality in magnetic storm and earthquake occurrence.