| Project/Area Number |
17340146
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Kyoto University |
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Principal Investigator |
OMURA Yoshiharu Kyoto University, Research Institute for Sustainable Humanosphere, Professor (50177002)
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| Co-Investigator(Kenkyū-buntansha) |
USUI Hideyuki KYOTO UNIVERSITY, Research Institute for Sustainable Humanosphere, Associate Professor (10243081)
OGINO Tatsuki Nagoya University, Solar-Terrestrial Environment Laboratory, Professor (00109274)
加藤 雄人 京都大学, 生存圏研究所, 非常勤研究員 (60378982)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥15,900,000 (Direct Cost: ¥14,700,000、Indirect Cost: ¥1,200,000)
Fiscal Year 2007: ¥5,200,000 (Direct Cost: ¥4,000,000、Indirect Cost: ¥1,200,000)
Fiscal Year 2006: ¥5,100,000 (Direct Cost: ¥5,100,000)
Fiscal Year 2005: ¥5,600,000 (Direct Cost: ¥5,600,000)
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| Keywords | chorus / whistler-mode wave / simulation / relativistic electron / Particle acceleration / wave-particle interaction / magnetosphere / radiation belt |
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| Research Abstract |
Whistler-mode chorus waves are eletromagnetic emissions that have been observed by spacecraft in the magmetospheres of Earth, Jupiter, Saturn, and Uranus, with frequencies in the range 0.05-0.8 Ω, where Ωis the local electron gyrofrequency. At Earth chorus emissions have also been recorded on the ground Chorus emissions am observed at the time of magnetic field disturbance such as magnetic storms and suhstorms. Chorus waves comprise discrete emissions of short duration (<10-1sec), with frequency typically increasing in time (rising tones), and, when connected to an audio amplifier, sound like bird song at dawn or chirping crickets. Theoretical and modeling studies and observational evidence have established electron acceleration by gyroresonant wave-particle interaction with chorus waves as a key mechanism for generating relativistic (>1 MeV) electrons in the Earth's outer radiation belt during geomagnetically disturbed periods. After nearly four decades of chorus wave observations and numerical studies, only recently have computer simulations been performed that successfully model the generation of chorus emissions with a rising tone. We have found that in the simulation of chorus generation, some resonant electrons are rapidly energized by the processes of relativistic turning acceleration (RTA) and ultra-relativistic acceleration (URA). RTA and URA are particular forms of nonlinear wave trapping of resonant electrons by coherent whistler-mode waves and constitute viable mechanisms for the generation of relativistic electrons in the radiation belts of magnetized planets. The computer simulations reveal that nonlinear wave growth due to the rising tone is the key ingredient in the generation of chorus waves.
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