[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P16] Visualization of the propagation path of signals from the ground-based VLF transmitters in the inner magnetosphere based on the Arase/HFA observation

*Shuei Noda¹, Satoshi Kurita¹, Hirotsugu Kojima¹, Yoshiya Kasahara², Atsushi Kumamoto³, Fuminori Tsuchiya⁴, Yoshizumi Miyoshi⁵, Iku Shinohara⁶, Satoko Nakamura⁵, Masahiro Kitahara³ (1.Research Institute for Sustainable Humanosphere, 2.Emerging Media Initiative, Kanazawa University, 3.Department of Geophysics, Graduate School of Science, Tohoku University, 4.Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 5.Institute for Space-Earth Environment Research, Nagoya University, 6.Japan Aerospace Exploration Agency/Institute of Space and Astronautical Science)

In the Earth’s inner magnetosphere, various kinds of electromagnetic waves propagate and interact with charged particles trapped by the Earth’s magnetic fields. The interaction results in acceleration and loss of the trapped particles. It is known that man-made signals from the groundbased VLF transmitters can propagate into the magnetosphere through the ionosphere. Low altitude satellite measurements show that the VLF signals cause the precipitation loss of the radiation belt electrons into the atmosphere through pitch angle scattering. Thus it is important to understand the propagation characteristics of the signals from the VLF transmitters in the inner magnetosphere. For this purpose, we statistically investigated the VLF signals from the transmitters to identify the propagation path of these waves in the magnetosphere based on the plasma wave measurement performed by High Frequency Analyzer (HFA) onboard the Arase satellite. The statistical map of the VLF signal intensity was derived using the data obtained by HFA for three years. We successfully identified the geomagnetic longitude and altitude range where the VLF signals propagate in the magnetosphere and electric field intensities along the propagation paths. The propagation paths are the plausible location where pitch angle scattering by the VLF signals takes place. In addition, we also investigated the dependence of the electric field intensities of VLF signals on the seasons and MLT. In the presentation, we will show the propagation path and electric field intensities of the signals from the VLF transmitters in the inner magnetosphere, and their seasonal and MLT dependences.