Study on ion-wave-electron interactions in space plasmas via spacecraft observations and computer experiments -Breakthrough of the magnetospheric physics-

本研究的主要目的是在新型观测系统研制、航天器观测数据分析和计算机实验的基础上，对空间等离子体中的离子波电子耦合进行研究。代表性成果如下：从航天器观测技术的角度来看，通过多个航天器对离子波电子耦合进行多次观测是研究离子波电子耦合的重要手段。因此，研制轻型等离子体波观测系统对未来的空间任务至关重要。我们利用数字技术和机载软件技术成功研制了轻型接收机。开发的等离子体波接收系统在SS-520-2火箭上，它在飞行过程中完美地工作。该接收系统为未来空间任务提供了一个典型的等离子体波接收系统模型。我们还研制了波粒相关器，实现了直接计算观测到的等离子体波与粒子之间的相关关系。我们通过计算机实验检验了它的性能和特点，并在一个FPGA芯片上进行了设计。在宇宙飞船的数据分析中，我们发现了哨声模式波触发日侧磁重联的证据。由于哨声模波与电子动力学有关，我们可以将哨声模波作为微观现象与磁重联作为宏观现象联系起来。在计算机实验中，我们重点研究了电子/离子束的不稳定性及其非线性演化。基于多次计算机实验，我们证明了它们的非线性演化的参数依赖性。

In the present study, the main objective is to study the ion-wave-electron coupling in space plasmas based on the development of new observation system, data analyses of spacecraft observations and computer experiments. The representative achievements are as follows. In the view point of spacecraft observation technique, the multiple observations via a fleet of spacecraft are important in order to study ion-wave-electron coupling. Therefore, the development of light-weight plasma wave observation system is essential for future space missions. We succeeded in developing the light-weight receiver using the digital technologies and onboard software technique. The developed plasma wave receiver system was onboard SS-520-2 rocket and it functioned perfectly during the flight. This receiver system I provides a typical model of plasma wave receiver system for future space missions. We also developed the wave-particle correlator, which realizes the direct calculation of correlation between observed plasma waves and particles. We examined its capability and characteristics using computer experiments and designed it on one FPGA chip. In the spacecraft data analyses, we found a proof that the whistler mode waves trigger the dayside magnetic reconnection. Since whistler-mode waves are related to electron dynamics, we can show the link of whistler mode waves as microscopic phenomena with the magnetic reconnection as the macroscopic phenomena. In the computer experiments, we focused on electron/ion beam instabilities and their nonlinear evolutions. Based on many runs of computer experiments, we showed the parametric dependence of their nonlinear evolutions.