Observation and Theory of Magnetic Fields in Spiral Galaxies.

(1)从射电偏振数据中发现了螺旋星系中的双对称螺旋磁场。尽管导电气体有不同的旋转，但它们在圆盘中缠绕得相当松散。这与20年前让许多天文学家渴望旋臂的困境是一样的。我们通过同时考虑星际磁场的湍流扩散和垂直扩散的盘晕气体中的发电机作用来解决这个问题：由差动旋转产生的紧扭曲磁场通过湍流运动扩散到银晕中，并被发电机作用新产生的松散扭曲磁场所取代。(2)当各种介质的非线性动力学得到更广泛的发展时，上述问题的最终解才能得到。作为实现这一目标的几个步骤，我们研究了正弦型离散双Sine-Gordon方程中的扭结-反扭态和类呼吸模，DNA的局域结构涨落，以及量子自旋系统的去耦合胞格方法蒙特卡罗模拟。我们发现了一些在连续或/和离散介质中产生的混沌和非线性全局结构的例子。讨论了其在天体物理中的可能应用。(3)热力学和流体力学应用于旋转气体盘。一般的稳定性和不稳定性分析发现了一种新的模式，这种模式在气体介质中总是不稳定的。认为盘状气体的湍流运动是从这种不稳定性开始和发展起来的。如果这是真的，我们可能是第一个发现X射线吸积气体中的&lt；α&gt；P型粘性的基本过程。(4)用&lt；lambda&gt；=2.6 mm的CO射电发射(J=1-0)观测到了栅状星系M83中的分子气体。发现了分子气体的非圆运动和非对称凝聚。重力扭矩在M83中起作用。

(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.