[P-EM16] Space Plasma Physics: Theory and Simulation

[PEM16-06] Particle Simulation on low-frequency antenna characteristics in space plasma

*Koshiro Kusachi¹, Yohei Miyake², Hideyuki Usui³, Hirotsugu Kojima⁴, Ibuki Fukasawa⁴, Satoshi Kurita⁴ (1.Kobe University, 2.Education Center on Computational Science and Engineering, Kobe University, 3.Graduate school of system informatics Kobe University, 4.Research institute for sustainable humanosphere, Kyoto University)

Keywords:antenna impedance, particle simulation, low-frequency plasma wave, plasma dispersion relation

For the plasma wave observation in space, the electric field sensor using the dipole antenna is commonly equipped onboard scientific satellites. The antenna characteristics in space plasma are different from those on the ground due to the fluctuation in the electromagnetic field environment by plasma. Since the observed wave data are calibrated in consideration of the antenna characteristics, it is important to understand them quantitatively to improve the accuracy of observation data. While there are many studies on high-frequency antenna characteristics involving the electron dynamics [1][2][3], the study in the low-frequency range involving the ion dynamics is not really developed. The quantitative understanding of the antenna characteristics in the low-frequency range is required to realize a science mission for the polar formation exploration “FACTORS” which aims to observe ion-mode plasma waves causing the ion heating and acceleration.

In this research, we have been studying the low-frequency antenna characteristics from the point of view of antenna impedance by performing three-dimensional electromagnetic Particle-In-Cell simulations. In the simulation, we place a dipole antenna in the center of the domain filled with a large number of plasma particles. We also used the delta-gap feeding technique by which we give an electric pulse in the center of the antenna to obtain the antenna impedance as a function of frequency [4]. In the simulation results, we could observe the impedance resonance by lower hybrid waves and ion cyclotron harmonics. Based on the linear dispersion analysis, we found that the impedance resonance peaks are situated at frequencies, at which the associated ion plasma waves should have much shorter wavelengths than the antenna tip-to-tip length. This feature is highly contrast with the behavior of a common half-wave dipole antenna. We also studied the dependence of the antenna impedances on the parameters such as (1) ion temperature, (2) the angle of magnetic field to antenna, and (3) the intensity of magnetic field.


References

[1]D.T.Nakatani, H.H.Kuehl, “Input impedance of a short dipole antenna in a warm anisotropic plasma, 1, Kinetic theory”, Radio Science, Vol. 11 No. 5, pp. 433-444 (1976)

[2]S.Adachi, T.Ishizone and Y.Mushiake, “Transmission line theory of antenna impedance in a magnetoplasma”, Radio Science,Vol. 12 No. 1, pp. 23-31 (1977)

[3]Y.Miyake, H.Usui, H.kojima, Y.Omura, and H.Matsumoto “Electromagnetic Particle-In-Cell simulation on the impedance of a dipole antenna surrounded by an ion sheath”, Radio Science, Vol. 43, RS30004 (2008)

[4]Raymond Luebbers, Li Chen, Toru Uno, and Saburo Adachi, “Fdtd calculation of radiation patterns, impedance, and gain for a monopole antenna on a conducting box”, IEEE Transactions on Antennas and Propagation, Vol. 40 No. 12, pp. 1577-1583(1992)