Observational Manifestation of Chaos in the Gaseous Disk of the Grand Design Spiral Galaxy NGC 3631

The main goal of the paper is to demonstrate the presence of chaotic trajectories in the gaseous disk of a real spiral galaxy. As an example we have chosen NGC 3631. First, we show the stationarity of the 3-D velocity field restored from the observed line-of-sight velocity field of the gaseous disk. That allows to analyse behaviour of the trajectories of the fluid particles (gas clouds) in the disk, calculating the corresponding observed streamlines. We estimate the Lyapunov characteristic numbers using their independence of the metrics and show the existence of chaotic trajectories outside the vortices which are present in the velocity field, and in the vicinity of the saddle point. Related spectra of the stretching numbers for some trajectories are also calculated.     

Discrete energy release in microwave emission in the preflare stage

Examples of solar microwave precursors and estimates of their energetic characteristics are discussed based on spectral investigations of the preflare activity.     

Microwave spectrum analysis as solar energy release diagnostics

The possibilities of using spectrographic observations of microwave radio emission as a solar flare plasma diagnostic are discussed. The spectral fine structure of the emission is interpreted in the context of plasma emission mechanisms. The balance equations for particles and plasma turbulence together with the transfer equations for electromagnetic waves in a plasma are solved for a model containing a diverging magnetic loop. As a result of the analysis of the blip-type spectral feature, the structure of energy release region and the unperturbed plasma concentration in the preflare loop are evaluated. The number of accelerated electrons and the intensity of the plasma turbulence in the source region are estimated using the properties of the weak continuum emission following the blip. Based on the degree of circular polarization of both the narrow band and the continuum emission, estimates for the external magnetic field strength and the angular width of the radiating plasma turbulence have been obtained.     

Progress in the Study of Galaxies: Structures,Collective Phenomena and Methods

The review contains the important achievements in dynamics of the galactic disks. Among them there are I. New structures discovered recently: • giant vortices (including giant anticyclone in the Solar vicinity); • slow bar; • inner oscillating structure within spiral arms similar that of enveloped soliton; • chaotic streamlines in the velocity field of the gaseous disk of a real galaxy. II. New collective phenomina discovered recently: • new overreflection instability initiating ‘mini-spiral’ in the innermost central parsec of Galaxy; • large-scale convection caused by nonlinear interaction of density wave with disk gas; • non-kolmogorovian spectrum of weak turbulence corresponding to the observed one in the • Solar vicinity. III. New methods worked out recently: • reconstruction of full three-dimensional vector field of gas velocity from the observed line-of- • sight velocity field; • observational test for verification of the wave-nature of the spiral arms; • observational test to distinguish two types of vertical motions: warp and z-motions in the • density wave; • derivation of correct system of two-dimensional dynamical equations from the initial three- • dimensional one. This revised version was published online in June 2006 with corrections to the Cover Date.