2006 Fiscal Year Final Research Report Summary
Magnetic reconnection in the Earth's magnetosphere
| Project/Area Number |
15340161
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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 | Tokyo Institute of Technology |
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Principal Investigator |
NAGAI Tsugunobu Tokyo Institute of Technology, Graduate School of Science and Engineering, Professor, 大学院理工学研究科, 教授 (60260527)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIMOTO Masaaki JAXA, Institute of Space and Astronautical Science, Professor, 宇宙科学研究本部, 教授 (30242811)
MACHIDA Shinobu Kyoto University, Professor, 理学研究科, 教授 (70209469)
SHINOHARA Iku JAXA, Institute of Space and Astronautical Science, Associate Professor, 宇宙科学研究本部, 助教授 (20301723)
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| Project Period (FY) |
2003 – 2006
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| Keywords | magnetic reconnection / substorm / magnetotail / Hall current / electron heating / magnetogydrodynamics / anomalous resistivity / simulation |
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| Research Abstract |
To understand magnetotail dynamics, it is essential to determine where magnetic reconnection takes place in the near-Earth plasma sheet during substorms. The Geotail spacecraft thoroughly surveyed the near-Earth magnetotail at radial distances of 10-31 Re during the years 1995-2003. Thirty-four clear reconnection events were identified using the criterion of strong electron acceleration. Various solar wind parameters prior to each reconnection events were examined in order to fine the factor controlling the location of the magnetic reconnection site in the magnetotail. The same analyses were carried out for fast tailward flow events. The most important factor was determined to be the solar wind energy input, which can be expressed by -Vx x Bs, where Vx is the x component of the solar wind velocity and Bs is the southward component of the interplanetary magnetic field. It is likely that higher energy input, rather than the total amount of energy input, primarily controls the location of magnetic reconnection; magnetic reconnection takes place closer to the Earth when the input energy is higher. A large number of simulations for magnetic reconnection in different codes were carried out. It is demonstrated that magnetic reconnection is quickly triggered only under the current sheet thickness smaller than ion inertial length. A multiple X lines commonly form spontaneously, and several X lines coexist and develop. In the developing phase of magnetic reconnection, electron two-stream instability provides electron acceleration and mixing. The nonlinear phase of the electron two-stream instability produces electrostatic solitary waves (ESWs), which are frequently observed by the spacecraft Geotail.
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