Plenary meetings

December 2–3, 2016 Symposium on space plasma wave, Kyoto University Uji campus

Research 1: Space systems for utilization and maintenance of space environment (Hiroshi Yamakawa)

1. The electric sail is a new space propulsion system that uses multiple deployed and electrostatically charged wires to change interplanetary solar wind dynamic pressure into thrust force. It was first proposed by P. Janhunen (Journal of Propulsion and Power, 20, 4, 763-764, 2004). A new thrust model for the electric sail using the particle-in-cell method is investigated.
2. Geostationary satellites are located in geostationary orbits to keep a constant orbital position relative to the ground track. The charging phenomenon of the geostationary satellites is investigated numerically, and a charging model for geostationary satellites is proposed to evaluate active charging effects.
3. In order to prevent near-Earth asteroids from striking the Earth, the conventional concept of a gravity tractor is revisited by adding the Coulomb force effect to increase the asteroid trajectory control effect. This is realized by actively charging both the asteroid and a spacecraft positioned nearby the asteroid.

Publications, etc.

• K. Hoshi, H. Kojima, T. Muranaka, and H. Yamakawa, Thrust Calculation of Electric Solar Wind Sail by Particle-in-cell Simulation, Annales Geophysicae, Vol. 34, pp. 845-855, 2016, doi:10.5194/angeo-34-845-2016.
• K. Hoshi, H. Kojima, and H. Yamakawa, Particle-in-cell Simulation of Potential Structure around Electric Solar Sail Wind Tethers, The 30 ISTS Special Issue of Transaction of JSASS, Aerospace Technology Japan, Vol. 14, No. ists-30, pp. Pb-83-Pb-89, 2016.
• K. Hoshi, Y. Muranaka, H. Kojima, H. Usui, I. Shinohara, and H. Yamakawa, Numerical Analysis of Active Satellite Charging in the Geostationary Environment, Journal of Spacecraft and Rockets, Vol. 53, No. 4, pp. 589-598, 2016.
• K. Yamaguchi and H. Yamakawa, Near Earth Asteroid Deflection Mission Using Coulomb Force Attractor, The 30 ISTS Special Issue of Transactions of JSASS, Aerospace Technology Japan, Vol. 14, No, ists30, doi: 10.2322/tastj.14.Pd_119, 2016.

Research 2: Simulation study on substorms (Yusuke Ebihara)

Overview

We have investigated the mechanism underlying the generation of a substorm that disturbs the humanosphere.

Research Activity

We have been investigating the origin of the aurora by imitating aurora generation using supercomputer KDK.

Results

We have investigated the mechanism underlying the generation of the substorm that disturbs the humanosphere. Using a global magnetohydrodynamic (MHD) simulation, we investigated the mechanism underlying the generation of auroral arcs that appear in the growth phase of a substorm. When the interplanetary magnetic field (IMF) is northward, the plasma pressure distribution is found to be structured gradually due to the instability arising from the magnetosphere−ionosphere coupling. The structured plasma pressure distribution results in the structured distribution of the field-aligned current. The filament-like distribution of the field-aligned current may manifest north-south arcs, or sun-aligned arcs that can be seen during magnetic quiet time. When the IMF turns southward, the growth phase of a substorm commences and the structured plasma pressure distribution starts to move toward the equatorial plane. This process may be seen on the ground as equatorward-moving auroral arcs. The simulated auroral structure resembles the observed one. Previously, the auroral structures seen in the substorm growth phase were simple projections from the plasma sheet. On the basis of the simulation result, we suggest that the auroral structure in the growth phase is a projection of the plasma pressure distribution in the low-altitude magnetosphere, primarily in the lobe region.

Publications, etc.

Ebihara, Y., and T. Tanaka, Substorm simulation: Quiet and N-S arcs preceding auroral breakup, J. Geophys. Res., Vol. 121, pp. 1201-1218, doi:10.1002/2015JA021831, 2016.

Research 3: Study on dynamic variation of relativistic electron fluxes in the radiation belts (Yoshiharu Omura)

1. We have found that relativistic electrons in the Earth’s radiation belts are generated through nonlinear interaction with whistler-mode chorus emissions and that these electrons are precipitated by EMIC-triggered emissions.
2. Nonlinear wave processes are essential, and they are clarified by test particle simulations.

Publications, etc.

1. Y. Hsieh and Y. Omura, Nonlinear dynamics of electrons interacting with oblique whistler-mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 10.1002/2016JA022891, 2017.
2. Y. Kubota and Y. Omura, Rapid precipitation of radiation belt electrons induced by EMIC rising-tone emissions localized in longitude inside and outside the plasmapause, J. Geophys. Res. Space Physics, doi: 10.1002/2016JA023267, 2017.
3. J. C. Foster, P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, S. G. Claudepierre, Van Allen probes observations of prompt MeV radiation belt electron acceleration in non-linear interactions with VLF Chorus, J. Geophy. Res. Space Physics, doi: 10.1002/2016JA023429, 2017.
4. Y. Katoh and Y. Omura, Electron hybrid code simulation of whistler‑mode chorus generation with real parameters in the Earth’s inner magnetosphere, Earth, Planets and Space, 68, 192, 2016.

Research 4: Development of miniaturized plasma wave instruments for monitoring space electromagnetic environments (Hirotsugu Kojima)

We have aimed to achieve the ultra-miniaturization of plasma wave observation devices by making one in a single chip using ASIC technology. In FY2008 , in addition to the development of an analog circuit of a plasma wave observation device, we began work on the development of the digital part of the device. In order to connect the analog section and the digital section, an A/D converter is necessary, and in the chip we developed in FY2008, this A/D converter can be made into a chip. Furthermore, based on the field-programmable gate array (FPGA) develped at Kanazawa University, we also started to implement the on-board digital processing (digital filter and data compression) of a plasma wave receiver on the ASIC.

Publications, etc.

Ozaki, M., S. Yagitani, H. Kojima, K. Takahashi, H. Koji, T. Zushi, Y. Tokunaga, Development of an ASIC preamplifier for electromagnetic sensor probes for monitoring space electromagnetic environments, Earth, Planets and Space, doi: 10.1186/s40623-016-0470-9, 2016.

Research 5: Application research into new materials for space missions (Yoshikatsu Ueda)

During a survey of application technology, we discovered that water with micro-nano bubbles can be used in sustainable regions.

Publications, etc.

Hamamoto, S., N. Nihei, Y. Ueda, P. Moldrup, and T. Nishimura, Effects of Flow Rate and Gas Species on Micro- and Nano-Bubble Transport in Porous Media, Environmental Engineering, 2017 (in press).

Research 6: Microstructural analysis of wood-based, diamond-like carbon for improved resistance against atomic oxygen (Toshimitsu Hata, Hirotsugu Kojima)

Critical and rapid deterioration of the outer surface of a spacecraft is known to occur in low earth orbit (LEO) through interaction with atomic oxygen (AO) in complex space environments. Transmission electron microscopy (TEM) and electron energy-loss spectroscopy (TEM−EELS) revealed a quantitative structural change in wood-based, diamond-like carbon (DLC) during exposure to AO.

Research Activities

• Microstructural analysis of wood-based DLC before and after AO exposure.
• TEM observation of wood-based DLC before and after AO exposure.
• Structural analysis of wood-based DLC before and after AO exposure.