甚低频电磁波方法预报地磁暴

通过观察甚低频电磁波的相位变化,预测太阳耀斑的级别.当太阳耀斑爆发时,太阳表面首先会发出大量电磁辐射(主要是X射线),甚低频电磁波能很好地感应到此辐射;其次还喷射出大量带电低能粒子流,这会引起地磁暴,且通常在耀斑爆发1~2d之后到达地球.给出了一个预报地磁暴的实例.两事件的时间间隔约为28h,太阳风的速度约为1 484.1km/s.     

甚低频法预报“神舟”三号发射期间的太阳耀斑爆发情况

太阳发生耀斑时,辐射出大量的X射线和高能粒子等,使得电离层的物质瞬间被大量电离,电离层的电子浓度急速变化,电离层的等效反射高度随之变化,从而引发甚低频信号相位异常现象。基于在河南新乡用甚低频接收机监测到的“神州”三号发射和返回期间的甚低频信号的相位异常情况,对相位异常的数据用最小二乘法进行了处理分析并给出了预测的耀斑级别,和美国的GOES卫星观测到的数据进行比较,结果吻合恰好,验证了此方法的可行性。     

基于软件无线电的甚低频法探矿接收机

对隐伏矿体的定位预测,已成为当今社会找矿实践与勘察分析的当务之急.基于软件无线电的甚低频法探矿接收机的研制设计,为我国探矿事业的顺利发展提供了良好的催化剂.此接收机可以接收3个台、每个台3个不同的频率共9路甚低频(VLF)信号.这些信号导入地下后是一些强大的电磁波信号,经过抗混叠滤波器,A/D转换器等,最后有信号分析仪分析计算出感应电磁场的垂直分量和水平分量并判断出零交点的准确位置,最后做出相应的仿真,验证了该方法的可行性.     

中纬度地区粒子沉降和太阳耀斑对甚低频传播的影响分析

通过观测俄罗斯Alpha甚低频导航台到中纬度地区(新乡)之间的甚低频(VLF)信号的相位变化数据,发现在2002-07-17-2002-07-20期间,VLF信号发生了多次相位超前现象,观测到在2002-07-19和2002-07-20发生了高能粒子沉降事件,并分析出此次事件是由2002-07-17和2002-07-18发生的太阳耀斑引起.通过与美国发布的GOES卫星数据进行对比,发现两者的数据有很好的一致性.粒子沉降和太阳耀斑都会使甚低频信号的相位发生相位超前.粒子沉降大多数情况发生在极区,本次在新乡地区观测到高能粒子沉降,是一次极为宝贵的观测数据,对研究中纬度地区的高能粒子沉降有很大的作用.     

短波通信环境甚低频法监测预报仪的设计

太阳耀斑爆发会引起电离层出现突然骚扰(SID)事件,使得甚低频信号相位的突然超前。这会造成短波通信不稳定,甚至短波通信中断。设计了利用甚低频方法监测短波通信环境的预报仪,给出了系统结构和软件功能。并且画出短波通信环境预报程序的流程图,进行了一个监测实例。该预报仪采用软件无线电技术进行设计,可靠性高,一致性好。     

Fast acceleration of “killer” electrons and energetic ions by interplanetary shock stimulated ULF waves in the inner magnetosphere

Energetic electrons and ions in the Van Allen radiation belt are the number one space weather threat. Understanding how these energetic particles are accelerated within the Van Allen radiation belt is one of the major challenges in space physics. This paper reviews the recent progress on the fast acceleration of "killer" electrons and energetic ions by ultralow frequency (ULF) waves stimulated by the interplanetary shock in the inner magnetosphere. Very low frequency (VLF) wave-particle interaction is considered to be one of the primary electron acceleration mechanisms because electron cyclotron resonances can easily occur in the VLF frequency range. Recently, using four Cluster spacecraft observations, we have found that, after interplanetary shocks impact the Earth’s magnetosphere, energetic electrons in the radiation belt are accelerated almost immediately and continue to accelerate for a few hours. The time scale (a few days) for traditional acceleration mechanisms, based on VLF wave-particle interactions to accelerate electrons to relativistic energies, is too long to explain our observations. Furthermore, we have found that interplanetary shocks or solar wind pressure pulses, with even small dynamic pressure changes, can play a non-negligible role in radiation belt dynamics. Interplanetary shocks interaction with the Earth’s magnetosphere manifests many fundamental space physics phenomena including energetic particle acceleration. The mechanism of fast acceleration of energetic electrons in the radiation belt responding to interplanetary shock impacts consists of three contributing parts: (1) the initial adiabatic acceleration due to strong shock-related magnetic field compression; (2) followed by the drift-resonant acceleration with poloidal ULF waves excited at different L-shells; and (3) particle acceleration due to the quickly damping electric fields associated with ULF waves. Particles end up with a net acceleration because they gain more energy in the first half of this cycle than they lose in the second. The results reported in this paper cast a new light on understanding the acceleration of energetic particles in the Earth’s Van Allen radiation belt. The results of this study can likewise be applied to interplanetary shock interaction with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.     

甚低频远程遥控信号传输特性分析及接收方法

分析甚低频电磁波传播路径与方式,给出场强的计算公式。推导了海水中的基本电磁波方程,分析了电磁波的入水深度和入水后相位的变化,特别是电场和磁场分量从水面传播到水下时场强的衰减,并初步估算了甚低频遥控信号的入水深度。采用正交天线,不论信号来自任何方向,它接收到的都是最大值。     

外周化学感受器活动对心率变异性的影响

采用给健康、麻醉的豚鼠吸入纯氮气 (N2 )和纯氧气 (O2 )的方法 ,以兴奋或抑制外周化学感受器 ,观察外周化学感受器兴奋对心率变异性的影响 .吸入N2 引起TV、VLF、VLF/HF和LF/HF比值显著增加 ( p <0 0 5～ 0 0 0 1 ) .吸入纯氧后VLF和LF显著减少 ( p <0 0 5 ) .实验表明 :VLF随外周化学感受器的不同活动状态而改变 ,外周化学感受器兴奋对VLF的形成起了重要作用     

连续两次特大粒子沉降对南极VLF传播影响的观测和分析

通过观测1991-07-19至1991-07-20连续发生两次特大粒子沉降时,Omega导航系统G台与南极中山站之间甚低频(VLF)信号传播的相位变化情况,比较正常情况下G台--中山站的相位变化曲线,分析出VLF信号相位出现的异常变化。再与NGDC发布的GOES卫星观测的高能粒子流量作对比,研究连续两次特大粒子沉降对南极VLF信号传播造成的影响。结果表明高能粒子沉降与VLF信号相位异常超前现象之间存在着很好的相关性。     

1997-03-09日全食的甚低频观测与分析

在1997-03-09发生日全食期间,在河南省新乡市对Alpha甚低频(VLF)信号的观测试验发现,日全食对VLF信号传播特性有很大的影响,明显引起VLF相位滞后.讨论了日全食对VLF信号传播影响的机理,并用"波导模"理论对这种影响进行了理论计算.计算结果表明:VLF传播路径穿越日全食主食带的情况下,VLF相速比正常情况减小的最大值约为0.101%~0.118%;VLF传播路径穿越80%日偏食带的情况下,该值约为0.064%~0.082%.