利用地磁Z分量日变低点预报地震的新探索

在1984年地磁清理攻关时,我们曾对西南地区地磁低点位移与5级以上强震的关系进行了统计研究,其结论是:“由于西南地区地形复杂,气侯多变,地区差异大,导致低点位移频繁发生,虚报很多,相关系数接近1。因此,震磁关系不明显。本文进一步从地磁低点时间的规律性着手,分别对单台、多台低点时间进行统计研究:为区分磁暴影响,分别作了静、扰日对比;为查明气侯影响,作了季节统计对比;为查明低点位移与太阳黑子活动的关系,     

张北Ms6.2级地震前出现的地磁日变低点位移异常

１９９８年１月１０日张北发生Ｍｓ６．２级地震,地震前５ｄ￣２４ｄ,在全国范围内出现４次地磁日变低点位移异常现象。本文对地磁日变低点位移现象的物理基础进行了初步探讨,对地磁日变低点位移导演预报地震的方法作了简要介绍,对地磁日变低点位移异常与张北地震的关系进行了分析,认为张北地震前出现的地磁日变低点位移导演是该次地震的前兆反映。     

甘肃中强震前地磁“低点位移”现象研究

利用甘肃及邻近地区地磁垂直分量日变化极小值时间(低点时间)资料,分析了1995～2003年地磁"低点时间"在空间分布上的异常特征,即地磁"低点位移"现象,发现地磁"低点位移"现象除了有其自身的变化规律外,还与该区中强震的发生存在较好的相关性.1995～2003年的9年间,甘肃省中强震前均出现地磁"低点位移"现象.这表明地磁"低点位移"对该区地震的短临预测预报有一定的参考价值.     

安庆M4.8级地震前地磁低点位移现象研究

对安庆Ms4.8地震前中国大陆东部地区42个台站的地磁Z分量的幅度和相位进行分析,结果显示安庆地震前,华东地区出现地磁Z分量日变化幅度的极小值时间在空间上出现地磁低点位移现象,低点时间分界线沿郯庐断裂带呈现NNE走向,分界线两侧低点时间相差超过2h,地磁日变也出现明显的畸变,发震日期为异常发生后的29 (27±4)d,震中位于低点位移分界线附近,地磁低点位移的出现可能与安庆地震的孕育和发生相关.     

地磁低点位移现象及其与地震的关系

本文用中国地磁台网多年的资料,研究了地磁垂直分量日变极小值出现的时间(低点时间)在空间分布的异常特征,即低点位移现象。这种少见的地磁异常现象与地震的发生有较好的相关性,其发震日期为异常日以后的第27天或41天前后4天,发震地区在低点位移突变分界线附近。低点位移是一种复杂的地球物理现象,受多种因素影响,其机制仍处在探索阶段。      

汶川8.0级地震前地磁低点位移与内外源S_q等效电流体系关系的研究

本文利用球谐分析方法构建内外源Sq等效电流体系反演模型,对2008年汶川8.0级地震前的4月24日及5月9日两次地磁低点位移日前后共10日的内外源Sq等效电流体系进行逐日反演,并结合Dst磁暴指数分析研究地磁低点位移和电流体系之间的关系。研究发现:低点位移发生当日内外源等效电流体系南北半球电流涡中心强度都有减小的趋势,且内源场减小的幅度更大。低点位移发生日内源等效电流体系电流涡中心可能会发生纬向偏移现象。     

基于日变化相关的地磁低点位移异常可靠性分析方法

地磁低点位移法是20世纪提出的地震短临预测方法,该方法通过研究每日中国大陆地磁低点时间变化特征,给出地震短临预测意见,但不足之处是其仅研究了地磁日变化畸变的时间特征,未研究畸变幅度,因此虚报率高.本文通过分析低点位移线两侧台站地磁日变化的相关性,研究了地磁低点位移异常畸变幅度与地震的关系,并统计了2008-2018年出...     

利用地磁低点位移预测发震时间

四川及邻区是未来大震的重点监测地区，为了震情监视分析与预测，对四川地区出现的地磁“低点位移”与四川及邻区的中强地震对应进行了系统研究，认为地磁“低点位移”现象是客观存在的，“低点位移”作为一种地磁异常现象，与地震发生有较好的相关性。     

地磁低点位移线两侧异常变化的反相位现象及其解释

本文通过部分震例研究发现,在地磁低点位移异常日及附近,分布于低点位移线两侧的地磁垂直分量日变化畸变异常部分具有反相位变化特征,而水平分量无类似的现象.作者依据Biot-Savart定律推测,在低点位移异常期间,在低点位移线下方有一引起地磁垂直分量日变化畸变的电流通过,且该电流为线状分布,或仅在垂直面内有分布,埋深一般认为几十千米.作者同时分析认为,当这种电流的分布形成闭合圈或有东西分量时,地磁基本场对其产生的作用力对地震的发生可能有触发作用.     

新疆地区地磁低点位移异常与强震的关系

收集2008年1月1日～2018年12月31日的全国地磁台站垂直分量(Z)数据,运用地磁日变低点位移方法,提取并分析了新疆地区11次MS≥6.0地震前地磁垂直分量(Z)低点位移异常,结果表明,新疆地区强地震活动与地磁垂直分量低点位移异常之间有较好的对应关系;时间特征上地震发生日期一般为异常出现后的第27±4 d或41±...     

地磁低点位移与地磁场等效电流体系关系的初步研究

利用地磁内外源场分离的方法,反演得到了1997年11月8日玛尼地震和1998年１月10日张北地震前地下和空间等效电流体系的演化图象,并分析研究了地磁低点位移出现前后等效电流体系变化特征．结果表明,内、外场等效电流体系的变化与地震ldquo;低点位移rdquo;异常现象有着内在的联系,等效电流体系变化可能是地磁低点位移异常现象产生的原因之一。随着我国地磁台站的加密建设,势必可以得到更为精确的地磁场等效电流体系的演化特征,更有利于地震预测的研究。      

Hardness variation rate of precipitating electrons during <Emphasis Type="Italic">Pi</Emphasis>3 auroral pulsations

Photometric measurements of pulsating auroras have been carried out in the Pi3 range of geomagnetic pulsations with periods of 2–10 min with the use of auroral all-sky camera films obtained at the Lovozero Observatory. The new all-sky camera developed at the Polar Geophysical Institute uses the CCD matrix. This makes it possible to obtain simultaneous images in red, green, and blue spectral ranges and thus to investigate temporal luminosity variations in these spectral regions. The hardness of penetrating auroral electrons with a time resolution of a few seconds is qualitatively estimated. It is found that the energy of the electrons that cause auroras in the Pi3 pulsation range is not constant over the pulsation period. It is maximal at the lowest luminosity and minimal at its peaks. Luminosity pulsations are compared with geomagnetic pulsations, and it is established that large differences between luminosity variations in different parts of the sky explain the incomplete correspondence between the records of auroral and geomagnetic pulsations.     

Features of <Emphasis Type="Italic">Pc</Emphasis>5 pulsations in the geomagnetic field,auroral luminosity,and Riometer absorption

Simultaneous morning Pc5 pulsations (f ~ 3–5 mHz) in the geomagnetic field, aurora intensities (in the 557.7 and 630.0 nm oxygen emissions and the 471.0 nm nitrogen emission), and riometer absorption, were studied based on the CARISMA, CANMOS, and NORSTAR network data for the event of January 1, 2000. According to the GOES-8 satellite observations, these Pc5 geomagnetic pulsations are observed as incompressible Alfvén waves with toroidal polarization in the magnetosphere. Although the Pc5 pulsation frequencies in auroras, the geomagnetic field, and riometer absorption are close to one another, stable phase relationships are not observed between them. Far from all trains of geomagnetic Pc5 pulsations are accompanied by corresponding auroral pulsations; consequently, geomagnetic pulsations are primary with respect to auroral pulsations. Both geomagnetic and auroral pulsations propagate poleward, and the frequency decreases with increasing geomagnetic latitude. When auroral Pc5 pulsations appear, the ratio of the 557.7/630.0 nm emission intensity sharply increases, which indicates that auroral pulsations result from not simply modulated particle precipitation but also an additional periodic acceleration of auroral electrons by the wave field. A high correlation is not observed between Pc5 pulsations in auroras and the riometer absorption, which indicates that these pulsations have a common source but different generation mechanisms. Auroral luminosity modulation is supposedly related to the interaction between Alfvén waves and the region with the field-aligned potential drop above the auroral ionosphere, and riometer absorption modulation is caused by the scattering of energetic electrons by VLF noise pulsations.     

霍山"震情窗"地区流动地磁S异常与华东中强地震相关性的研究

以霍山“震情窗”地区流动地磁测线的S值变化,预测霍山“震情窗”相关地区－华东地区中强地震,研究结果表明：“震情窗”地区流动地磁测线的S值异常与距离霍山“震情窗”R＜500km的华东中强地震有明显的相关性。     

Regular Variations of Intensity of the Westward Auroral Electrojet according to the Geomagnetic <Emphasis Type="Italic">AL</Emphasis> Index

Diurnal and seasonal variations of the geomagnetic AL index are studied. It is found in disturbed days that the mode of AL diurnal variation depends on the angle between the Sun–Earth line prolongation in the direction towards the magnetotail and the plane of geomagnetic equator; on quiet days, AL depends on the angle of attack between the geomagnetic axis and the Earth–Sun line. Seasonal AL variations are characterized by annual variations with summer maximum and semiannual variations with equinoctial maxima. It is shown that the semiannual AL variations can be described by a simplified model of plasma convection in the magnetotail based on a plasma electron cooling mechanism.     

北半球电离层中纬槽发生率及其槽极小位置变化的统计研究

本文利用2014年9月到2017年8月全球高时空分辨率TEC数据对北半球四个经度带电离层中纬槽的发生率和槽极小位置的变化进行了统计研究.基于Kp指数,我们引入了一个包含地磁活动变化历史效应的地磁指数(Kp 9)来分析中纬槽位置变化与地磁活动水平的关系.通过与其他地磁活动指数的对比,发现槽极小纬度与Kp 9指数的相关性最好.此外,本文重点分析了中纬槽发生率及槽极小纬度的经度差异、季节变化、地方时变化以及与地磁活动强度等的关系.结果表明,中纬槽的发生率与经度关系不大,主要受到季节、地方时与地磁活动的影响.午夜中纬槽发生率在夏季较低,其随地方时的变化则呈现出负偏态分布的特点,在后半夜发生率更高,而地磁活动增强对中纬槽的发生具有明显的促进作用.对于槽极小纬度,其在四个经度带的分布差异不大,但月变化各不相同,其中-120°经度带呈单峰分布,在夏季槽极小纬度更高,而0°经度带夏季槽极小纬度更低.槽极小的位置显著依赖于地磁活动、地方时以及季节变化.一般说来,地磁活动越强,中纬槽纬度越低.中纬槽位置随地方时的变化有明显的季节差异,冬季昏侧槽极小纬度随地方时变化较快,弱地磁活动条件下22∶00 LT前即达到最低纬度,其后位置几乎保持不变,而两分季槽极小纬度从昏侧至午夜都在降低,夏季槽极小纬度从昏侧连续下降至03∶00 LT左右.     

The effect of the high-speed stream following the corotating interaction region on the geomagnetic activities

The high-speed stream following the corotating interaction regions (CIRs) was analyzed. As a result of the analysis, it is found that the geomagnetic field is continuously disturbed in the high-speed stream in question. The geomagnetic disturbances with long duration recurred several rotations between December 1993 and June 1994. These disturbances were associated with a large recurrent coronal hole expanding from the south pole of the Sun. High-speed solar wind from this coronal hole was observed by the IMP-8 satellite during this period. However, the observed intensities of the geomagnetic disturbances were different for each recurrent period. This is explained by the seasonal effect. The disturbed geomagnetic condition continued in the highspeed stream after the passage of the CIRs. The long duration of these disturbances can be explained by the continuous energy input into the Earths magnetosphere from the high-speed regions following the CIRs. This kind of long-duration geomagnetic disturbance in association with coronal holes has been observed in the declining phase of other solar cycles. The relation between the coronal-hole area and the maximum solar-wind velocity is not good for the well-developed large coronal hole analyzed here.     

对《转换函数与汶川大地震关系的初步研究》一文的分析

我们不能苟同该文作者的一些概念,认为该文用的计算公式以及所得的结果存在较多问题,其所得转换函数的量级以及与地震对应关系的分析叫人难以理解.     

Geomagnetic activity that corresponds to the median of the <Emphasis Type="Italic">F</Emphasis>2-layer critical frequency at various latitudes

On the basis of the F2-layer critical frequency foF2 for the noon at some European stations for 1958–2005, it is found that the geomagnetic activity corresponding to the foF2 median is systematically lower than that averaged over the month; the difference increases with an increase in latitude. Moreover, the dispersion of geomagnetic activity for the foF2 median at relatively high latitudes is lower than at middle latitudes. These regularities are related to the fact that high geomagnetic activity usually leads to a distinct deviation of foF2 from the typical average value, i.e., from the foF2 median, and such deviation is more substantial at relatively high latitudes. That is why the geomagnetic activity for the foF2 median is lower at relatively high latitudes than at middle latitudes.     

"Double low-points" anomaly in daily variation of vertical component of geomagnetic field before the MS8.0 Wenchuan earthquake

The "double low-points" anomaly in daily variation of vertical geomagnetic component was observed on May 9, 2008 at 13 geomagnetic observatories belonging to the geomagnetic observatory network center of China Earthquake Administration. These observatories distribute roughly on three belts with the intersection in western Sichuan. On May 12, three days after the anomaly appearance, the great M_S8.0 Wenchuan earthquake occurred. The "double low-points" anomaly in daily variation of vertical geomagnetic component is an anomalous phenomenon of regional geomagnetism, which does exist objectively. The possible cause is the change of extrinsic eddy current system resulting in geomagnetic daily quiet variation (S_q), or the delay of several hours between the intrinsic and the extrinsic eddy current systems. The relationship between the "double low-points" anomaly of daily geomagnetic variation and the earthquake reveals that the former possibly reflects the accelerative alteration of earthquake gestation in the deep Earth.