On electromagnetic phenomena in Mercury’s magnetosphere

Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury’s and Earth’s magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury’s magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.     

Elemental Abundances in Coronal Structures

A great deal of evidence for elemental abundance variations among different structures in the solar corona has accumulated over the years. Many of the observations show changes in the relative abundances of high- and low-First Ionization Potential elements, but relatively few show the absolute elemental abundances. Recent observations from the SOHO satellite give absolute abundances in coronal streamers. Along the streamer edges, and at low heights in the streamer, they show roughly photospheric abundances for the low-FIP elements, and a factor of 3 depletion of high-FIP elements. In the streamer core at 1.5 R·, both high- and low-FIP elements are depleted by an additional factor of 3, which appears to result from gravitational settling. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determination of optimal parameters of a moving wall on airfoil

A problem is posed and solved on determining the optimal parameters of a moving wall installed on the airfoil surface to prevent the boundary layer separation. As the wall parameters, its initial and final position and motion velocity are taken. To solve the problem, the optimization methods with penalty functions are used. The conclusions were drawn on selecting the efficient parameters of the moving wall in terms of the minimum of energy expenditure and friction drag.     

Intensification of heat exchange on the convex surface of an annular channel with continuous flow swirling

In this paper, the results of an experimental study concerning average heat transfer in an annular channel with flow swirling by an endless screw and spherical grooves on the convex surface are presented. Also analyzed is the heat and hydraulic efficiency of grooves application under conditions being considered.     

Analysis of an arbitrarily loaded shell of revolution based on the finite element method in a mixed formulation

The volume finite element in the form of hexahedron with nodal unknowns as components of the displacement vector and stress tensor has been developed to analyze the shells of revolution. The displacement vector components for the inner point of the finite element and the components of its stress tensor are expressed through the nodal unknowns using the method of vector and tensor fields interpolation by the trilinear shape functions; that provides taking into account the finite element displacement as a whole solid. The variational principle in a mixed formulation is applied to form the matrix of hexahedron deformation. The efficiency of the proposed method for approximating the values being sought as vector and tensor fields in comparison with the traditional method for approximating the values being sought as scalar fields is confirmed by a numerical example.     

Microminiature Loran-C Receiver/Indicator

A Loran-C Receiver is used as an example to show how an analog system could be converted to a digital one to take advantage of the expanding integrated circuit technology. The digital equivalents of the analog servo elements are described. Criteria for the design of a phase-tracking servomechanism is developed in detail. The Loran performance requirements are used to illustrate their application. The noise performance of a critically damped Type II servomechanism is derived in detail. Since the system will be employed in aircraft, tracking velocity becomes an important consideration. An analysis is made showing that an adaptive control is desirable.     

Design and characteristics of a multiband communication satelliteantenna system

Feasibility studies on a multiband communication satellite antenna system and the key technologies involved in devising this system are described. The proposed multiband communication satellite utilizes four frequency bands: Ka (30/20 GHz), Ku (14/12 GHz), C (6/4 GHz), and S (2.6/2.5 GHz). It has six beam configurations, three multibeam and three shaped-beam. The following key technologies are presented: (1) a low-loss frequency selective subreflector (FSR) for compact feeds, (2) a low-loss and broadband frequency selective surface (FSS), and (3) a highly accurate and reliable mesh reflector     

IMF control of the Earth's magnetosphere

We review recent progress in the understanding of the IMF control on the Earth's magnetosphere through the reconnection process. Major points include, (1) the identification of the magnetopause structure under the southward IMF polarity to be the rotational discontinuity and the resulting inference that the reconnection line is formed in the equatorial region, and (2) the confirmation from several observational aspects that under the northward IMF the reconnection takes place in the polar cusp. The point (1) is consistent with the observed correlations of geomagnetic indices with IMF but raises an important theoretical issue, and the point (2) is accompanied by an interesting issue of explaining why the polar cap electron precipitation is more energetic under such IMF conditions. Critical studies have reaffirmed the view that the energy supplied by reconnection is partly transported directly to the ionosphere to drive the DP-2 type current system but at the same time it is partly stored in the magnetic field of the tail to be unloaded 0.5 1 hr later to produce the expansion phase of substorm.Presented at the Fifth International Symposium on Solar-Terrestrial Physics, held at Ottawa, Canada, May 1982.     

Performance of Digital Implementations of an Adaptive Processor

The performance of a digital implementation of an Applebaum-Howells type adaptive processor is analyzed for both a limiter and nonlimiter configuration. The performance is evaluated in terms of steady-state residue power, using either a single-pole filter or a perfect integrator to smooth the output of the correlation mixer. The latter filter is the more commonly used for digital implementations. It is shown that when using the perfect integrator filter for both the limiter and linear digital implementations, the steady-state average weight vector equals the optimum weight vector. Thus, for this filter, the steady-state residue power is the minimum possible for either implementation. When using the single-pole filter, neither implementation achieves the minimum possible steady-state residue power. The relative performance of the two implementations depends upon the relative gain settings. When the gains are adjusted to give comparable servo stability for the design maximum jammer power, a reasonable criterion for digital implementations because of analog to digital saturation, the limiter configuration always has smaller steady-state residue power.     

A Detection Algorithm for Optical Targets in Clutter

There is active interest in the development of algorithms for detecting weak stationary optical and IR targets in a heavy opticalclutter background. Often only poor detectability of low signal-to-noise ratio (SNR) targets is achieved when the direct correlation method is used. In many cases, this is partly obviated by using detection with correlated reference scenes [1, 2].This paper uses the experimentally justified assumption that most optical clutter can be modeled as a whitened Gaussian randomprocess with a rapidly space-varying mean and a more slowlyvarying covariance [2]. With this assumption, a new constant falsealarm rate (CFAR) detector is developed as an application of the classical generalized maximum likelihood ratio test of Neyman and Pearson. The final CFAR test is a dimensionless ratio. This test exhibits the desirable property that its probability of a false alarm(PFA) is independent of the covariance matrix of the actual noiseencountered. When the underlying noise processes are complex intime, similar considerations can yield a sidelobe canceler CFARdetection criterion for radar and communications. Performance analyses based on the probability of detection (PD)versus signal-to-noise ratio for several given fixed false alarm probabilities are presented. Finally these performance curves are validated by computer simulations of the detection process which use real image data with artificially implanted signals.