HR: 0830h
AN: SM11C-1187    [PDF]
TI: Rheometry experiment for a wire antenna aboard spacecraft at low frequencies
AU: * Imachi, T
EM: imachi@reg.is.t.kanazawa-u.ac.jp
AF: Department of Information and System Engineering, Kanazawa University, 2-40-20 Kodatsuno, Kanazawa, 920-8667 Japan
AU: Yagitani, S
AF: Graduate School of Natural Science and Technology, Kanazawa University, 2-40-20 Kodatsuno, Kanazawa, 920-8667 Japan
AU: Nagano, I
AF: Graduate School of Natural Science and Technology, Kanazawa University, 2-40-20 Kodatsuno, Kanazawa, 920-8667 Japan
AU: Higashi, R
AF: Graduate School of Natural Science and Technology, Kanazawa University, 2-40-20 Kodatsuno, Kanazawa, 920-8667 Japan
AU: Esaki, S
AF: Graduate School of Natural Science and Technology, Kanazawa University, 2-40-20 Kodatsuno, Kanazawa, 920-8667 Japan
AU: Tsutsui, M
AF: Information Communication Engineering Department, Kyoto Sangyo University, Motoyama, Kamigamo, Kyoto, 603-8555 Japan
AU: Matsumoto, H
AF: Radio Science Center for Space & Atmosphere, Kyoto University, Gokasho, Uji, 610-0011 Japan
AB: Observation of plasma waves in the space is an important subject of scientific spacecraft missions. The sensor frequently used to measure the low frequency AC electric field of plasma waves is a wire antenna. It is necessary for an accurate measurement to estimate the effective length of each wire antenna accurately, because it is closely related to the gain of the sensor, and the inaccuracy of it affects greatly to the quantitative studies of plasma waves. In most researches related to plasma waves, the effective length of a wire antenna has been assumed to be a half of its physical length. However, on the other hand, when we measure electrostatic or quasi-static field, the intensity is calculated from a voltage between probes, placed at both tips of the antenna, divided by the distance between them. In this case the antenna effective length is treated as the same as the physical length of the wire. What makes difference between them? To investigate this problem, we estimated frequency dependency of the effective length in quasi-static frequency range, by using ``Rheometry experiment''[1], and analyzed the result of the experiment by theoretical calculation of equivalent circuits. The result of the experiment shows that the effective length is a half of their physical length in higher frequencies (more than several kHz), however, in very low frequencies(less than several hundred Hz), it depends on the structure of the antenna. And according to the theoretical calculation, we found that this phenomina can be explained by the static potential along the wire of the antenna, not by electric current distribution. We will show the detailed result. [1] H.O.Rucker et al., Radio Science, Vol.31, No.6, pp.1299, 1996
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2708 Current systems (2409)
DE: 2712 Electric fields (2411)
DE: 2794 Instruments and techniques
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting