Application of the method of potentials in problems of fracture mechanics

The theory of generalized elastic potentials is used for solving the problem of a space with cracks of arbitrary shape. Two solutions are proposed. In the first case, the solution is represented by a double-layer potential and a functional equation for determination of the unknown density is constructed in which difficulties stipulated by high polarity of the integrand may be eliminated. The other method consists of an analysis of a space with a thin smooth cavity and the solution of corresponding singular integral equations.Methods to improve the convergence of successive approximations used in solution of the equations are described and some particular cases of three-dimensional solids are considered. A special function is introduced on the external surface of the solid, which allows consideration of a whole space with cracks having fictitious stresses on their edges; this solution has some bearing on the main problem and also provides an integral equation for the auxiliary function. Another approach consists of the elimination of cracks by introduction of corresponding potentials and solution of the auxiliary problem for a continuous solid with special boundary conditions.     

Optimization of aerodynamic efficiency for twist morphing MAV wing

Twist morphing(TM) is a practical control technique in micro air vehicle(MAV) flight.However, TM wing has a lower aerodynamic efficiency(CL/CD) compared to membrane and rigid wing. This is due to massive drag penalty created on TM wing, which had overwhelmed the successive increase in its lift generation. Therefore, further CL/CDmaxoptimization on TM wing is needed to obtain the optimal condition for the morphing wing configuration. In this paper, two-way fluid–structure interaction(FSI) simulation and wind tunnel testing method are used to solve and study the basic wing aerodynamic performance over(non-optimal) TM, membrane and rigid wings. Then,a multifidelity data metamodel based design optimization(MBDO) process is adopted based on the Ansys-DesignXplorer frameworks. In the adaptive MBDO process, Kriging metamodel is used to construct the final multifidelity CL/CDresponses by utilizing 23 multi-fidelity sample points from the FSI simulation and experimental data. The optimization results show that the optimal TM wing configuration is able to produce better CL/CDmaxmagnitude by at least 2% than the non-optimal TM wings. The flow structure formation reveals that low TV strength on the optimal TM wing induces low CDgeneration which in turn improves its overall CL/CDmaxperformance.     

Short term topological changes of coronal holes associated with prominence eruptions and subsequent CMEs

We study the short-term topological changes of equatorial and polar coronal hole (CH) boundaries, such as a variation of their area and disintegration, associated to reconnection with nearby (within 15° distance) quiescent prominence magnetic fields leading to eruptions and subsequent Coronal Mass Ejections (CMEs). The examples presented here correspond to the recent solar minimum years 2008 and 2009. We consider a temporal window of one day between the CH topological changes and the start and end times of prominence eruptions and onset of CMEs. To establish this association we took into account observational conditions related to the instability of prominence/filaments, the occurrence of a CME, as well as the subsequent evolution after the CME. We found an association between short-term local topological changes in CH boundaries and the formation/disappearance of bright points near them, as well as, between short-term topological changes within the whole CH and eruptions of nearby quiescent prominences followed by the appearance of one or more CMEs.     

A Theoretic Interpretation of Movement of the Cusp Equatorward Boundary

A preliminary model is proposed to describe quantitatively the position and movement of cusp equatorward boundary. This integrated model, consisting of an empirical model of the magnetopause and a compressed dipolar model of Open/Closed field line, connects quantitatively the solar wind conditions, subsolar magnetopause and cusp equatorward boundary. It is shown that the increasing solar wind dynamic pressure and the increasing southward Interplanetary Magnetic Field (IMF) component drive the magnetopause to move inward and the cusp equatorward. This model is adopted to interpret quantitatively the cusp movement of August 14, 2001 observed by Cluster. The results show that the subsolar magnetopause moved earthward from 10.7 He to 9.0 Re during the period of 002300-002800 UT, and correspondingly the cusp equatorward boundary shifted equatorward. The observations of Cluster C1 and C4 show the cusp equatorward boundary that Cluster Cl and C4 were crossing during same interval moved equatorward by 4.6°. The cusp equatorward boundary velocity computed in the theoretical model (10.7km/s) is in good agreement with the observed value (9.4km/s) calculated from the data of CIS of Cluster C4 and C1.     

Space flight experiment on Chinese silkworm on board the Russian 10th Biosatellite.

Space flight experiments on Chinese silkworm (Bombyx mori L.) were conducted on board the Russian 10th Biosatellite for 12 days. The samples included silkworm eggs, larvae, cocoons, pupae and moths. The processes of spinning, cocooning, mating, oviposition, larval hatching, pupation and moth emergence all completed well in space. The following effects of space flight on silkworm development were observed: The times of hatching and oviposition in the flight group were 2 to 3 days earlier than in the control group; the hatching rate of diapause eggs during space flight seemed higher than that of the control group; the life span of 2 of the 7 varieties flown was shortened; genetical variations appeared in 3 varieties. The results showed that the embryonic stage was probably the period most sensitive to the space flight environment.     

Fine structure of the interplanetary shock front according to measurements of the ion flux of the solar wind with high time resolution

According to the data of the BMSW/SPEKTR-R instrument, which measured the density and velocity of solar wind plasma with a record time resolution, up to ~3 ×10^–2 s, the structure of the front of interplanetary shocks has been investigated. The results of these first investigations were compared with the results of studying the structure of the bow shocks obtained in previous years. A comparison has shown that the quasi-stationary (averaged over the rapid oscillations) distribution of plasma behind the interplanetary shock front was significantly more inhomogeneous than that behind the bow-shock front, i.e., in the magnetosheath. It has also been shown that, to determine the size of internal structures of the fronts of quasi-perpendicular (θ_BN > 45°) shocks, one could use the magnetic field magnitude, the proton density, and the proton flux of the solar wind on almost equal terms. A comparison of low Mach (М _А < 2), low beta (β₁ < 1) fronts of interplanetary and bow shocks has shown that the dispersion of oblique magnetosonic waves plays an essential role in their formation.     

Global Processes that Determine Cosmic Ray Modulation

The global processes that determine cosmic ray modulation are reviewed. The essential elements of the theory which describes cosmic ray behavior in the heliosphere are summarized, and a series of discussions is presented which compare the expectations of this theory with observations of the spatial and temporal behavior of both galactic cosmic rays and the anomalous component; the behavior of cosmic ray electrons and ions; and the 26-day variations in cosmic rays as a function of heliographic latitude. The general conclusion is that the current theory is essentially correct. There is clear evidence, in solar minimum conditions, that the cosmic rays and the anomalous component behave as is expected from theory, with strong effects of gradient and curvature drifts. There is strong evidence of considerable latitude transport of the cosmic rays, at all energies, but the mechanism by which this occurs is unclear. Despite the apparent success of the theory, there is no single choice for the parameters which describe cosmic ray behavior, which can account for all of the observed temporal and spatial variations, spectra, and electron vs. ion behavior.     

Critical Issues on Magnetic Reconnection in Space Plasmas

The idea of expedient energy transformation by magnetic reconnection (MR) has generated much enthusiasm in the space plasma community. The early concept of MR, which was envisioned for the solar flare phenomenon in a simple two-dimensional (2D) steady-state situation, is in dire need for extension to encompass three-dimensional (3D) non-steady-state phenomena prevalent in space plasmas in nature like in the magnetosphere. A workshop was organized to address this and related critical issues on MR. The essential outcome of this workshop is summarized in this review. After a brief evaluation on the pros and cons of existing definitions of MR, we propose essentially a working definition that can be used to identify MR in transient and spatially localized phenomena. The word “essentially” reflects a slight diversity in the opinion on how transient and localized 3D MR process might be defined. MR is defined here as a process with the following characteristics: (1) there is a plasma bulk flow across a boundary separating regions with topologically different magnetic field lines if projected on the plane of MR, thereby converting magnetic energy into kinetic particle energy, (2) there can be an out-of-the-plane magnetic field component (the so-called guide field) present such that the reconnected magnetic flux tubes are twisted to form flux ropes, and (3) the region exhibiting non-ideal MHD conditions should be localized to a scale comparable to the ion inertial length in the direction of the plasma inflow velocity. This definition captures the most important 3D aspects and preserves many essential characteristics of the 2D case. It may be considered as the first step in the generalization of the traditional 2D concept. As a demonstration on the utility of this definition, we apply it to identify MR associated with plasma phenomena in the dayside magnetopause and nightside magnetotail of the Earth’s magnetosphere. How MR may be distinguished from other competing mechanisms for these magnetospheric phenomena are then discussed.This revised version was published online in July 2005 with a corrected cover date.     

The homologous flare sites and the general solar activity

The homologous flares observed in the same region of a spotgroup testify the existence and the duration of a permanent instability. However, they also attest that the general magnetic configuration is not destroyed by these flares and that it changes $\text{slowly}$ up to the death of the site.The study of every flaring sites where more than ten flares occur has been performed in Meudon for the 1974–1980 period.One hundred and sixty-six sites have been analysed from the rotation where the A.R. is observed up to five rotations ahead. The basis of the study are the “Synoptic Maps”. A relation is found between the presence of crossing of “filament-phantom” corridors and the location of the homologous flare sites.¹