Research on the Formation and Activity of Galactic Nuclear Gas Disks Including Magnetohydrodynamical Processes

包括磁流体动力学过程的银河核气盘的形成和活动研究

基本信息

批准号：
16340052
负责人：
MATSUMOTO Ryoji
金额：
$ 9.54万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16340052/
关键词：
Galactic Disk Accretion Disk Magnetohydrodynamics Numerical Simulation Active Galactic Nuclei Astrophysical Jets Self Gravity Galactic Dynamo

项目摘要

Three-dimensional global magnetohydrodynamic (MHD) simulations have been carried out to study the mechanism of the formation and activity of galactic nuclear gas disks. The initial state is a gas torus threaded by weak toroidal magnetic fields. We assumed that the gas torus is rotating in the gravitational potential of stars and the dark matter. We found (1) magnetorotational instability growing in the torus drives magnetic turbulence, (2) interstellar gas in falls by transporting angular momentum through Maxwell stress and forms a nuclear gas disk, (3) galactic mean magnetic fields are amplified up to 1 micro G, (4) the direction of mean azimuthal magnetic fields reverses with period of about 1Gyr, and (5) the reversal of mean magnetic fields is driven by the buoyant escape of magnetic flux from the gas disk to the galactic halo. We also carried out global 3D MHD simulations of the nuclear gas disk and found that magnetic loops similar to those observed inside 1kpc of our galaxy are formed by the buoyant rise of the magnetic flux from the gas disk.Numerical simulations indicated that poloidal magnetic flux is carried toward the galactic center. We performed 2D and 3D global resistive MHD simulations of jet formation from disks threaded by vertical magnetic fields and showed that mass accretion is partly driven by the angular momentum extraction by jets. The stability of magnetically driven jets has been studied by using 3D MHD code in Cartesian coordinates. We found that although the kink instability grows in regions where magnetic field lines are strongly twisted, it does not disrupt the jet.We implemented 3D MHD simulation engine based on the Roe scheme to the MHD simulator CANS (Coordinated Astronomical Numerical Software). The manuals and web-pages of CANS have been translated into English and used in the Asian Winter School on Numerical Astrophysics, held in March 13-17, 2006, at Chiba University.

三维全球磁流体动力学（MHD）模拟已被用来研究星系核气盘的形成和活动机制。初始状态是由弱环形磁场穿过的气体环面。我们假设气环在恒星和暗物质的引力势中旋转。我们发现（1）环面中增长的磁旋转不稳定性驱动磁湍流，（2）星际气体通过麦克斯韦应力传输角动量并形成核气盘，（3）星系平均磁场被放大到1微G ，（4）平均方位磁场的方向以大约 1Gyr 的周期反转，并且（5）平均磁场的反转是由来自磁通量的浮逸逃逸驱动的气盘到银河晕。我们还对核气盘进行了全局 3D MHD 模拟，发现与我们银河系 1kpc 内部观察到的类似的磁环是由气盘磁通量的浮力上升形成的。数值模拟表明，极向磁通量为被带到银河系中心。我们对由垂直磁场穿过的圆盘形成的射流进行了 2D 和 3D 全局电阻 MHD 模拟，结果表明质量吸积部分是由射流提取的角动量驱动的。通过在笛卡尔坐标系中使用 3D MHD 代码研究了磁驱动射流的稳定性。我们发现，虽然扭结不稳定性在磁场线强烈扭曲的区域中增加，但它不会干扰射流。我们将基于 Roe 方案的 3D MHD 模拟引擎实现到 MHD 模拟器 CANS（协调天文数值软件）中。 CANS的手册和网页已被翻译成英文，并在2006年3月13日至17日在千叶大学举办的亚洲数值天体物理学冬季学校中使用。