1997 Fiscal Year Final Research Report Summary
Structure and Stability of Advection-Dominated Accretion Disks
| Project/Area Number |
08640328
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
KATO Shoji Kyoto Univ.Graduate School of Science, Professor, 大学院・理学研究科, 教授 (80011534)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Accrefion Disks / Advection-Dominated Accretion Disks / Two-Temperature Disks / Thermal Instabilcty / Turbulence |
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| Research Abstract |
1)Construction of Advection-Dominated Accretion Disks
After having constructed one-temperature advection-dominated disk models in collaboration with Prof. E.Narayan, we proceeded to make two-temperature advectiondominated disk models. First we made such disk models, taking only bremsstrahlung as cooling processes of electron gas. After this success, we constructed more general models, taking Compton and synchrotron processes into account as cooling processes of electron gas.
2)Thermal Instability of Advection-Dominated Accretion Disks
Examination of thermal instability of advection-dominated disks is of importance in relation to understanding origins of time variations of X-ray stars and active galactic nulei. Since advection-dominated disks are relatively thick in the vertical direction, their thermal instability should be studied by a method different from that used for standard disks. Our analyzes show that advection-dominated accretion disks are weakly unstable against local perturbations, if turbulent heat conduction is negligible.
3)Turbulence in non-magnetized Keplerian disks
Keplerian disks are highly stable against axially symmetric perturbations (Rayleigh criterion). In this sense, it is usually supposed that magnetic field will be necessary to make the disks turbulent (Balbus-Hawley instability). We think this argument is not always correct, and constructed a possible model of hydrodynamic turbulence in Keplerian disks.
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