| Project/Area Number |
14540417
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Space and upper atmospheric physics
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| Research Institution | Kochi National College of Technology |
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Principal Investigator |
IMAI Kazumasa Kochi National College of Technology, Department of Electrical Engineering, Professor, 電気工学科, 教授 (20132657)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Takehiko Kumamoto University, Faculty of Education, Associate Professor, 教育学部, 助教授 (10297632)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2004: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | Jupiter / Natural Radio Emissions / Decametric Wave / Magnetosphere / Dynamic Spectrum / Modulation Lanes / Model / Radio Source |
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| Research Abstract |
Frequency-time dynamic spectra of Jupiter's decametric radio emission display a complex structure on several different time scales. One of the characteristic spectral patterns on a time scale of a few tens of seconds are the modulation lanes discovered by Riihimaa in 1968. We developed a model for the mechanism responsible for their production in which the free parameters can be adjusted to provide a very close fit with the observations [Imai et al., 1992a,1992b,1997,2002]. In our model, we propose the existence of a grid-like interference screen composed of field-aligned columns of enhanced or depleted plasma density located along the longitudinal direction near Io's orbit.
We made a statistical analysis of Io-A and Io-B source modulation lanes observed by wideband spectrographs at Oulu, Florida, and Nancay. Using the modulation lane method it was possible to make relatively precise measurements of the value of the cone half-angle of the hollow-cone emission beam and the System III source locations for the Io-A and Io-B sources. The measured cone half-angles for the two sources were both within about 3 degrees of 60 degrees. And the measured typical ranges of source System III longitude are 130 to 205 degrees for Io-A and 125 to 215 degrees for Io-B. These results show that the radio active regions of Io-A and Io-B are sharing the same source System III longitude. Based on these results, we are able to show for the first time a more realistic view of the location and beaming of Jupiter's radio sources using a 3D computer graphic animation (http://jupiter.kochi-ct.jp/cg/). This can provide a very important piece of information in the investigation of the mechanism responsible for Jupiter's decametric radio emission.
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