The flare process in a topologically non-equilibrium magnetohydrodynamical system

The existing models for solar flares fail to treat in an appropriate manner the energy release mechanisms based on a step-like transformation of the magnetic field energy from magnetic field to energy of the hydrodynamical motion of the medium and dissipation of these motions through shock waves into heat.In considering an example of the relaxation process in a topologically non-equilibrium magnetohydrodynamical system resulting from the merging of two magnetic loops that possess balanced longitudinal currents, this paper suggests one such energy release mechanism. Due to a certain degree of universality for different topologically non-equilibrium systems, a variety of characteristics of the relaxation process obtained may form the basis for constructing a model of solar flares based on a step-like transformation of the magnetic field energy in topologically non-equilibrium magnetohydrodynamical systems.     

Calculation of the sound velocity in stratified seawater based on a set of fundamental equations

An algorithm for calculating the sound velocity in seawater is developed based on the analytical treatment of a fundamental set of thermo-hydrodynamics equations using perturbation theory methods with the IES 80 empirical equation of state. The calculation procedure makes it possible to determine any single quantity of the set of basic physical parameters “pressure-temperature-salinity-sound speed” from the values of the other three. The calculated data fit well with the UNESCO tables. These methods can be used to control the accuracy of sea measurements on a real time basis if the redundancy condition is satisfied. Due to the increased number of recorded parameters, it is possible to identify the sensor that introduces the largest error.     

Laboratory simulation of energy release in solar flares

A laboratory simulation method is proposed for energy release processes occurring in a fragment of the flare current sheet on the Sun. The method relies on the assumption that the spatial scale of such processes is represented by the current sheet's thickness whose values can be close for both the solar and laboratory conditions. It is shown that in an extended current sheet, current dissipation on anomalous resistivity that ensures the specific power of energy release close to that observed in a flare, is the main energy release mechanism. A rapid compression of the sheet by external magnetic fields can provide the condition for switching on a powerful energy release. The tearing instability developing in a homogeneous neutral sheet, leads to the formation of magnetic islands in which the energy release is localized.     

Numerical analysis and visualization of fine structures of the fields of two-dimensional attached internal waves

In the linear approximation, we compute the patterns of two-dimensional perturbations formed in a viscous exponentially stratified fluid in the process of motion of a plate at an arbitrary angle to the horizon. The exact solution of the problem obtained in quadratures and satisfying the physically meaningful boundary conditions is numerically analyzed. The properties of the fields are computed and described in broad ranges of all parameters of the problem, including the length and velocity of motion of the plate, the characteristics of stratification and viscosity of the medium, and the slope of the path. In the picture of currents, we distinguish two groups of waves and compact nonwave singularities near the edges of a source of generation. The results of comparison with the available data of independently performed calculations and experiments reveal the existing agreement between the computed and observed pictures of the currents.     

A prominence model in a simple magnetic arcade

This paper offers an evolution scenario for a simple magnetic arcade where the frozen-in magnetic field decreases with the ascent of its arches together with the plasma. Uplift is produced by the movement of photospheric plasma with a frozen-in magnetic field, which is divergent with respect to a neutral line. A decrease in magnetic field leads to the appearance in the arcade of a height range of arches, with no high-temperature thermal equilibrium present, and to a variation of the nonequilibrium range with time. Uplift of the arcade is accompanied by the consecutive entry of new arches into this range. All arches entering the nonequilibrium range experience a transient process. Some of the earlier inquiries into the physics of this process were instrumental, in the first place, in identifying those arches which – through the production of an ascending plasma flow from the base of the arcade – are involved in the formation of a prominence (with magnetic dips appearing and evolving at the tops of these arches) and, secondly, in synthesizing a computational algorithm for the final state of the transient process, the quasi-steady-state dynamic structure of the prominence. The arcade evolution scenario, combined with the computational algorithm, constitutes a unified prominence model, a model for the transition from a simple static magnetic arcade to a quasi-steady dynamic prominence structure. The model has been used in numerical calculations of parameters of two classes of prominences: in and outside active regions. Results of the calculations are in good agreement with observations.