[P-EM17] 宇宙プラズマ科学

[PEM17-P15] Particle-in-Cell Simulations on Interferometry Technique Using Monopole Electric Field Sensors

*深澤 伊吹¹、三宅 洋平²、臼井 英之²、栗田 怜³、小嶋 浩嗣³ (1.京都大学大学院工学研究科電気工学専攻、2.神戸大学大学院システム情報学研究科、3.京都大学生存圏研究所)

キーワード：干渉計観測、プラズマ波動、PICシミュレーション

One of the principal parameters characterizing plasma waves is their phase velocities. Single-spacecraft interferometry observations can obtain the phase velocities of plasma waves in space. Those observations use the electric field signals picked up by two monopole electric field sensors. The phase velocity is calculated by the phase difference in the waveforms and distance between observation points. However, the complexity of the electric field observations introduced uncertainty. For instance, the distance introduced uncertainty due to the properties of the plasma. Moreover, distortions in the electric field wavefront arise from both the spacecraft body and the electric field sensors themselves. Evaluations based on realistic models of plasma environments are important for obtaining precise phase velocities from observations.
In this study, we use the full-PIC simulation to evaluate the interferometry technique and determine the equivalent length L_eq. We perform three-dimensional full particle-in-cell simulations to evaluate the interferometry technique applied to Langmuir waves excited by bump-on-tail instability. The sensor elements in the simulations are simple conductive rods with a particular length. The two waveforms picked up by each monopole sensor provide the time difference. The equivalent distance is calculated using the time difference and the phase velocity for the excited Langmuir waves. The simulation results reveal that the equivalent length for observing the Langmuir waves turns out to be slightly shorter than the sensor’s center-to-center distance. This is considered to be attributed to the distortion of the wavefront by the sensors and the spacecraft.