The nature of isostructural spinodal decomposition in the Al-Zn system

The electronic structure and thermodynamic properties of disordered Al-Zn alloys are investigated in the coherent potential approximation by the KKR-ASA method. Analysis of the electronic density of states and the Fermi surfaces of disordered alloys reveals the presence of eight electronic topological transitions in the concentration interval from 0 to 70 at. % Zn. It is shown that the passage of the Fermi level through two minima of the density of states, which are due to the superposition of different types of electronic topological transitions, gives rise to singularities in the concentration dependence of the second derivative of the thermodynamic potential at points corresponding to the boundaries of the region of isostructural decomposition of the high-temperature solid solution, according to the phase diagram of the Al-Zn system. Fiz. Tverd. Tela (St. Petersburg) 39, 593–596 (April 1997)     

The origin of the solar magnetic cycle

After summarizing the relevant observational data, we discuss how a study of flux tube dynamics in the solar convection zone helps us to understand the formation of sunspots. Then we introduce the flux transport dynamo model and assess its success in modelling both the solar cycle and its departures from strictly periodic behaviour.     

Forbush decreases in the 19th solar cycle

The 19th solar cycle was characterized by abnormally high solar activity; unfortunately, the possibilities of observing it were limited. Ground-based observations of cosmic rays and geomagnetic activity are among the few types of continuous measurements that allow statements about the events of 19th cycle and their comparison with events of other cycles. Comparison of the events in cosmic rays with solar and geomagnetic activities shows that the number and strength of magnetic storms in the 19th cycle correspond to an abnormally high number of sunspots. However, large Forbush decreases were lacking in this cycle. The most powerful ICMEs of the 19th cycle were generally weaker than the greatest ones in later periods.     

Proper orthogonal decomposition of solar photospheric motions

The spatiotemporal dynamics of the solar photosphere is studied by performing a proper orthogonal decomposition (POD) of line of sight velocity fields computed from high resolution data coming from the MDI/SOHO instrument. Using this technique, we are able to identify and characterize the different dynamical regimes acting in the system. Low-frequency oscillations, with frequencies in the range 20-130 microHz, dominate the most energetic POD modes (excluding solar rotation), and are characterized by spatial patterns with typical scales of about 3 Mm. Patterns with larger typical scales of approximately 10 Mm, are associated to p-modes oscillations at frequencies of about 3000 microHz.     

The subharmonics of the 22-year solar cycle

Summary We briefly discuss the existence in various aspects of solar activity of the precise periodicities of Hale cycle (22y), Gleissberg cycle (88y) and of 132y recently discovered by our group. We consider also the possible harmonics of 11y and 5.5y, and make the hypothesis that the Sun behaves as a nonlinear system forced by an oscillator having the Hale frequency. The frequencies of 1c/88y and of 1c/132y might be two subharmonics of Hale frequency. The forcing elementx inside the Sun might be identified with the torsional oscillator suggested by Bracewell. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

On the chaotic nature of turbulence observed in benchmark analysis of nonlinear plasma simulation

Simulational results of two dissipative interchange turbulence (Rayleigh-Taylor-type instability with dissipation) models with the same physics are compared. The convective nonlinearity is the nonlinear mechanism in the models. They are shown to have different time evolutions in the nonlinear phase due to the different initial value which is attributed to the initial noise. In the first model (A), a single pressure representing the sum of the ion and electron components is used (one-fluid model). In the second model (B) the ion and electron components of the pressure fields are independently solved (two-fluid model). Both models become physically identical if we set ion and electron pressure fields to be equal in the model (B). The initial conditions only differ by the infinitesimally small initial noise due to the roundoff errors which comes from the finite difference but not the differentiation. This noise grows in accordance with the nonlinear development of the turbulence mode. Interaction with an intrinsic nonlinearity of the system makes the noise grow, whose contribution becomes almost the same magnitude of the fluctuation itself in the results. The instantaneous deviation shows the chaotic characteristics of the turbulence. (c) 1997 American Institute of Physics.     

Stochastic relaxation oscillator model for the solar cycle

We perform a detailed analysis of the sunspot number time series to reconstruct the phase space of the underlying dynamical system. The features of this phase space allow us to describe the behavior of the solar cycle in terms of a simple relaxation oscillator in two dimensions. The absence of systematic self-crossings suggests that the complexity of the sunspot time series does not arise as a consequence of chaos. Instead, we show that it can be adequately modeled through the introduction of a stochastic fluctuation in one of the parameters of the dynamic equations.     

太阳日冕物质抛射的磁流体力学性质

太阳是离地球最近的一颗恒星,太阳日冕物质抛射是太阳大气中最剧烈的一种活动现象.当日冕物质抛射爆发时,大量的等离子体物质从接近太阳日面的低日冕被抛出,瞬时释放出巨大的能量.当一部分这些物质和能量传播到地球附近时,可以造成短波通讯中断、卫星工作失常等破坏性现象.文章作者认为,是缠绕的太阳磁场提供了足够的能量,使这些日冕物质可以克服恒星的重力以及周边磁场的束缚抛射出来;而磁螺度在日冕中的不断积累,不仅为日冕物质抛射提供了能量基础,而且使爆发在一定程度上成为一种日冕演化的必然.     

Relativistic SCRs during the events of solar cycle 19

Two major ground-level SCR events in solar cycle 19 are analyzed: the events of May 4 and November 12, 1960. The characteristics of relativistic solar protons (RSPs) have been obtained using the up-to-date method based on the data from the ground based network of neutron monitors. The event of May 4, 1960, occurred against a quiet background, and during the event of 12.11.1960 two shocks, caused by previous flares in the same active region, approached the Earth. The RSP dynamics, related to disturbances in the interplanetary medium, is studied. The solar proton spectra, obtained from the ground-based measurements, are compared to the direct balloon measurements performed at that time.     

Characteristics of solar proton events near the minimum of the 23rd cycle of solar activity

Analysis and systematization of proton activity in the declining phase near the minimum of the 23rd cycle of solar activity in the period 2004–2005 have been performed. Flux, spectral, energy, and some temporal characteristics of the solar proton events observed in the near-Earth space during the noted period are investigated and reported.     

Formation process of Si nanoparticles in rare gas observed by a decomposition method

We have investigated the formation process of silicon nanoparticles after laser ablation of silicon targets in argon gas. The nanoparticles exhibit bright photoluminescence in the visible wavelength range and can be applied to opto-electronic devices. In order to observe silicon nanoparticles, we have developed a decomposition method. The nanoparticles were probed by detecting light emission resulting from decomposition using a second laser. This method enables us to observe nanoparticles that cannot be observed directly by the methods applied so far. We have observed that the nanoparticles grow in time periods of 1.0-1.8 ms following ablation in Ar gas at 5 Torr when Si targets are ablated at 5 J/cm² with a pulse width of 7 ns. The nanoparticles begin to grow above ablation spots slightly apart from the targets just after thermalization of the plume. We also found that the growth is delayed at higher fluxes of ablation laser light.     

Hysteresis of a solar EUV flux and the relation of its characteristics to the solar cycle amplitude

The phenomenon of a difference between solar EVV fluxesI (<130 nm) measured for the same solar indices but in cycles of different amplitudes is studied. The difference can reach 15–20%. The phenomenon is explained in terms of a two-component model of solar EUV variations (from the active regions and the undisturbed solar surface). It follows from this model that in powerful cycles the fluxesI must be greater than in weak cycles for the same solar index F_10.7. The results of the HI line measurements from SME are presented as an example of the possibility of solar cycle amplitude prediction about two years before the solar maximum epoch.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1237–1241, October, 1996.     

Interaction of high-speed and transient fluxes of solar wind at the maximum of solar cycle 24

The interaction of the interplanetary coronal mass ejection (ICME) and the high-speed solar wind flux (HSSWF) associated with the coronal hole (CH) is considered. By the examples of two events at the maximum of solar cycle 24 from June 4 to June 16 and from June 30 to July 10, 2012 it is shown that the temperature-dependent parameters of the SW ionic composition appear closer to the values in the HSSWF than in the ICME due to mixing of fluxes in the corona when the ICME source is near the CH boundary.     

3D Modeling of the solar corona in different stages of the solar magnetic cycle over the period 1870 to 1991

Three-dimensional (3D) modeling of the solar corona has been carried out on the basis of the magnetic field distribution on H-alpha charts for the epochs of solar eclipses that occur near the epoch of the polar magnetic field reversal. Analysis of the 3D modeling shows that:

1. Besides the global neutral sheet, two high-latitude coronal neutral sheets are also observed during the epoch of the polar magnetic field reversal.
2. The observed structure of the coronal streamers is due to a projection of the folds of corrugated neutral sheets on the picture plane rather than due to the peculiar configuration of the magnetic field lines.

     

Lithium experiment on solar neutrinos to weight the CNO cycle

The measurement of the flux of beryllium neutrinos with an accuracy of about 10% and CNO neutrinos with an accuracy of 20–30% will enable one to find the flux of pp neutrinos in the source with an accuracy better than 1% using the luminosity constraint. The future experiments on νe^? scattering will enable one to measure with very good accuracy the flux of beryllium and pp neutrinos on the Earth. The ratio of the flux of pp neutrinos on the Earth and in the source will enable one to find with very good accuracy a mixing angle θ_⊙. A lithium detector has high sensitivity to CNO neutrinos and can find the contribution of the CNO cycle to the energy generated in the Sun. This will be a stringent test of the theory of stellar evolution and combined with other experiments will provide a precise determination of the flux of pp neutrinos in the source and a mixing angle θ_⊙. The work on the development of the technology of a lithium experiment is now in progress.     

利用天然气冷量的朗肯循环发电流程的工艺模拟

高压天然气集输过程中节流会使天然气温度有明显的下降,提出了分别采用丙烷和混合工质的朗肯循环回收天然气的冷量进行发电。采用HYSYS软件对两种工艺分别进行了工艺模拟,结果表明采用混合工质时由于冷热流体间换热温差明显减小,因而循环效率提高了约40%。在夏季当天然气输量为55×104Nm2/d时,可以产生48.42kW的功率,冷能有效能的利用效率约为23.06%。     

Various decomposition techniques for linear equations of continuum mechanics

Various methods of decomposition of a sufficiently general linear set of equations, special cases of which are frequently encountered in continuum mechanics, are described. These methods are based on splitting the sets of coupled 3D equations into several simpler independent equations. In addition to the firstorder decomposition, we also considered higher order decompositions. Examples of the decomposition of sets of equations describing slow motions of viscous and viscoelastic incompressible fluids and viscous compressible barotropic fluids and gases are presented. The obtained results can be used for the exact or numerical solution of 3D problems of continuum mechanics and physics.     

Interoccurrence times in the Bak-Tang-Wiesenfeld sandpile model: a comparison with the observed statistics of solar flares

A sequence of bursts observed in an intermittent time series may be caused by a single avalanche, even though these bursts appear as distinct events when noise and/or instrument resolution impose a detection threshold. In the Bak-Tang-Wiesenfeld sandpile, the statistics of quiet times between bursts switches from Poissonian to scale invariant on raising the threshold for detecting instantaneous activity, since each zero-threshold avalanche breaks into a hierarchy of correlated bursts. Calibrating the model with the time resolution of GOES data, qualitative agreement with the interoccurrence time statistics of solar flares at different intensity thresholds is found.