Study on Global Structure of Space Plasma Wave Energy by Using Large Scale Ray-Tracing

该项目的主要目标是：(1)扩展我们的射线追踪技术，用于计算地球磁层中VLF和ELF波的射线路径；(2)将该技术应用于Akebono卫星观测的VLF和ELF波，以解释这些波现象。总结了重要的研究结果：最初为超级计算机开发的VLF哨声模式和ELF离子回旋模式的射线追踪计算机程序被移植到工作站，并完成了各种图形程序，将计算结果显示在显示器上，并根据要求获得硬拷贝。将上述射线追迹系统应用于akakebono卫星观测的波资料如下：a)利用星载VLF波仪观测到用于地面导航的Omega信号（10.2KHz），确定了其信号强度和波法向在磁层中的空间分布。如果给出合适的磁层等离子体模型，这些结果可以与射线追踪技术的理论计算结果进行比较。我们已经开发了一种方法来制作等离子体密度模型，该模型最适合沿卫星轨道实际观测到的电子密度。用等离子体模型进行射线追迹的结果与Akebono的观测结果吻合得很好。b)利用星载极低频波仪发现了新的极低频发射现象，这种现象只存在于磁赤道区100Hz以下的频率范围内。这些发射与氦离子和氧离子的离子回旋频率密切相关，因此它们被解释为由超热质子的各向异性温度产生的离子回旋模式发射。为了证实这一假设，我们使用了射线追踪技术，我们的解释是令人满意的。

The main objectives of this project were (1) to extend our ray tracing technique for calculating ray paths of VLF and ELF waves in the earth magnetosphere and (2) to apply this technique to the VLF and ELF waves observed by Akebono satellite for interpretation of these wave phenomena. Important results are summarized :1. The computer programs for ray tracing of VLF whistler mode and ELF ion cyclotron mode, both originally developed for supercomputers, were transplanted to workstations and completed various graphic routines to represent the results of calculation on a display and to get hardcopies on request.2. Application of the above ray tracing system to the wave data observed by the Akebono Satellite are as follows :a) By the VLF wave instruments on-board the satellite, Omega signals (10.2KHz) for ground navigation have been observed and spatial distributions of their signal intensity and wave normal direction in the magnetosphere were determined. These results can be compared with those theoretically calculated by ray tracing technique, if an appropriate Plasma model in the magnetosphere is given. We have developed a method to make a plasma density model which best fits the electron density actually observed along the satellite trajectory. It was found the results of ray tracing using the plasma model thusmade satisfactorily agree with those observed by Akebono.b) By the ELF wave instrument on-board the satellite, new ELF emission phenomena were discovered, which exist only in the magnetic equatorial region in the frequency range below 100Hz. These emissions are closely related with ion cyclotron frequency of Helium and Oxygen ions, so that they are interpreted as ion cyclotron mode emissions generated by an anisotropic temperature of super-thermal protons. In order to confirm this hypothesis, our ray tracing technique has been used and our interpretation was found to be satisfactory.