2007 Fiscal Year Final Research Report Summary
Generation of chorus emissions and acceleration of relativistic electrons associated with magnetic storms
| 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)
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| Project Period (FY) |
2005 – 2007
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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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[Journal Article] MHD simulation of the shock wave event on October 24, 20032007
Author(s)
Ogino, T., Y., Kajiwara, M., Nakao, K.S., Park, K., Fukazawa, Y., Yi
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Journal Title
Acta, Astronautica
Pages: 1-9
Description
「研究成果報告書概要(欧文)」より
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