| Project/Area Number |
60540156
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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 | Faculty of Science, Nagoya University |
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Principal Investigator |
FUJIMOTO Mitsuaki Department of Physics, Nagoya University, 理学部, 教授 (70022580)
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| Co-Investigator(Kenkyū-buntansha) |
HANAWA Tomoyuki Department of Physics, Nagoya University, 理学部, 助手 (50172953)
HOMMA Shigeo Department of Engineering, Nagoya University, 理学部, 助手 (50023297)
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| Project Period (FY) |
1986 – 1987
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1986: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1985: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | Galaxies / Magnetic fields / Turbulent diffusion / Soliton / Lattice / Accretion disk / 降着円盤 / 回転ガス円盤 |
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| Research Abstract |
(1) Bisymetric spiral magnetic fields have been found in spiral galaxies from radio polarization data. They are wound rather loosely in the disk in spite of the differential rotation of electrically-conducting gas. This is the same dilemma as the one that tantalized many astronomers for the spiral arms two decades ago. We solved this problem by taking into account both the turbulent diffusion of interstellar magnetic fields and the associated dynamo action in the disk-halo gas in vertical spread: The tightly-twisted magnetic fields, generated by the differential rotation, diffuse out into the galactic halo by the turbulent motion and are replaced by the loosely-twisted ones newly generated by the dynamo action.
(2) Final solution of the above problem is to be obtained when the nonlinear dynamics of various kinds of media are more generally developed. As several steps towards this goal, we have worked on the kink-antikink states and breather-like modes in sine-form discrete double Sine-Gordon equation, the local structural fluctuation of DNA, and the decoupled cell method Monte Carlo simualtion for quantum spin system. We have found some examples of chaos and nonlinear global structures generated in continuous or/and discrete media. A possible appication to astrophysics was discussed.
(3) Therodynamics and hydromagnetics are applied to rotating gaseous disks. A general stabiltity-and-instability analysis has found a new type of mode which is always unstable in the gaseous media in differential rotation. It is suggested that the turbulent motion of disk gas is initiated and developed from this instabiltiy. If it is true, we could be the first to find a basic process for the <alpha> P-type viscosity in the X-ray emitting accretion gas.
(4) Molecular gas in the barred galaxy M83 has been observed by <lambda> =2.6 mm radio emission of CO (J=1-0). Noncircular motion and asymmetyric condensation of molecular gas are found. Gravitational torque is operative in M83.
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