SHIGENOBU HIROSE AND JULIAN H. KROLIK

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1 SHIGENOBU HIROSE AND JULIAN H. KROLIK
VERTICAL STRUCTURE OF GAS PRESSURE-DOMINATED ACCRTION DISKS WITH LOCAL DISSIPATION OF TURBULENCE AND RADIATIVE TRANSPORT 局所的乱流散逸と輻射輸送を含む ガス圧優勢降着円盤の垂直構造 SHIGENOBU HIROSE AND JULIAN H. KROLIK AND JAMES M. STONE 2006, ApJ, 640, 901

2 ABSTRACT 降着円盤の local patch の 垂直構造を計算 Relaxation Period 以降 Steady State
MRI driven MHD turbulence による heating～Radiative cooling Shearing box で rad-MHD を解くことで self-consistently ３D & Energy Conserving code (元はZEUS３D+FLD module) Relaxation Period 以降 Steady State Photosphere ～7H Conventional analytic model では ～3H 磁気圧がdisk atmosphere を押し上げる 散逸はmidplaneの3H以内に分布 Tgas～Trad(Photoshpere上空でも) Radiation flux は 散逸の変動と時間差 ×tcoolで同調 Away from midplane では散逸の変動は強い Top と Bottom surface の flux に大きな asymmetry 散逸に Long-timescale asymmetry Disk全体で垂直方向の energy flow は Radiative Diffusion が dominate

3 CONTEXT

4 Shearin box & Grid and Boundary condition
Height z outflow boundary 12H 8+8=16H 256 grids H 300rg -H Azimuth y 6.62M◉ periodic boundary 8H 64 grids -12H Radius x H=cg/Ω : scale height 2H 32 grids shearing periodic boundary Δx=Δz=H/16=Δy/2

5 全エネルギー保存の為の項 Density floor,Energy floor,Velocity capの散逸への寄予は1%程度

6 (殆ど)Shakura-Sunyaev と同じ F:τ≧1でF0(=σT4) 0.01csのrandom perturbation
INITIAL CONDITION (殆ど)Shakura-Sunyaev と同じ F:τ≧1でF0(=σT4) 0.01csのrandom perturbation Pgas Twisted azimuthal flux tube x=z=0, max poloidal B:2.16×106 G, β=24 max MRI wavelength:1.59×106 cm = 7.2 grid Pmag Prad

7 RESULT 計算時間:60 orbit 5-10 orbit 以降は steady
Time-average は orbit で取った

8 Mean Vertical Profiles: Gas Density
Exponetial Initial : (nearly)Gaussian

9 Mean Vertical Profiles: Pressure
Pgas dominant Pmag >Prad dominant Pgas-supported disk body + Pmag-supported atmosphere β(mid) ~ 40 β(7H) ~ 0.03 Pgas Pmag Mid plane Prad

10 Mean Vertical Profile: Temperature
Tgas~Trad→LTE high z τ1/4Teffではoverestimate ∵dissipationが強い τ1/4Teff Boundary の影響

11 Mean Vertical Profile: Dissipation & Stress
Midplane 内に Asymmetry structure stressの殆どがmidplane内で生成 α～0.016(vertically integrated) α～1(midplane) α～0.01(|z|>6H)

12 Thermal Balance: Net Energy Flow
Radial surfaceになされる仕事 Magnetic stress:77% Reynolds stress Outgoing energy Radiation diffusion:99.71% Radiation advection:0.14% Mater:0.25% Poynting flux:0.10%

13 Thermal Balance: Dissipation Rate

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16 Thermal Balance: Cooling
f =1/2(Photosphereと定義) Photosphere の Fluctuationは 1-2 orbit f =1/3

17 Internal Fluctuation: Gas Density and Magnetic Intensity

18 Internal Fluctuation: Top-Bottom Asymmetry

19 Internal Fluctuation: Magnetic Field Line Structure
Azimuthal が predominant midplane では short scale で tangled (MRI に該当) mid-altitude では smooth high-altitude では disordered (Random fluid motion)