1988 Fiscal Year Final Research Report Summary
Study of Cosmic Electromagnetic Phenomena by using 3-D MHD Code
| Project/Area Number |
62540178
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Astronomy
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| Research Institution | National Astronomical Observatory (1988)
The University of Tokyo (1987) |
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Principal Investigator |
IKEUCHI Satoru National Astronomical Observatory, Professor, 理論天文学研究系, 教授 (90025461)
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| Co-Investigator(Kenkyū-buntansha) |
HABE Asao Hokkaido University, Research Associate, 理学部, 助手 (90180926)
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| Project Period (FY) |
1987 – 1988
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| Keywords | MHD Code / Magnitized Clouds / Critical Mass / Star Formation / Ambipolar Diffusion / 星間磁場 |
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| Research Abstract |
Developing the 3D MHD code, I have investigated the equilibrium structures of rotating, magnetized isothermal clouds under various conditions, and also have examined their evolution in consideration of magnetic field and angular momentum loss due to the ambipolar diffusion.
Till the present work, the equilibrium structures of rotating clouds without magnetic field or those of magnetized clouds without rotation have been studied. In this research, I have explored the equilibria of isothermal clouds considering both the rotation and magnetic field by using the MHD code. Further, the evolution of them has been followed. There are two kinds of equilibrium solutions for a fixed mass cloud: one is stable and the other is unstable. These two solutions coincide when the cloud has a critical mass, above which there are no equilibrium solutions for a given magnetic field and angular momentum distribution. The dependence of this critical mass upon magnetic field strength and total angular momentum has been made clear, and we have got a simple algebraic equation for it.Utilizing this equation, we can easily see the stability of clouds and magnetic field strength for o bserved clouds.
It is shown that the evolution of rotating, magnetized clouds is rather simple. At the innner region, the magnetic pressure dominates when the angular momentum loss is included and at the outer region the centrifugal force dom-inates. This results in the collapse of inner region to stars with keeping the outer, rotating disk. This evolutionary behavior sensitively depends upon the loss rate of magnetic field due to ambipolar diffusion and associated angular momentum loss. At present, the details of these physical essence are explored by means of a simple model.
The stability of clouds and configuration of interstellar magnetic field are strongly coupled, and their coupling will affect the formation and equilibrium figures of clouds. This is an important problem to be examined more.
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