Open Access Original Research Article

W. I. A. Okuyade, T. M. Abbey

This paper presents a hydrodynamic model of flow in a bifurcating stream, in which the effects of environmental thermal differentials are investigated. The governing nonlinear and coupled equations are solved analytically using similarity transformation and perturbation series expansions methods. Solutions for the temperature, velocity and concentration are obtained and analyzed graphically. The results show that the heat exchange parameter reduces the velocity of the flow, and this enhances early deposition of the streambed loads. Furthermore, it is seen that free convection force increases the flow velocity, thus serving as a cushion for the adverse effect of heat exchange parameter on the flow.

Open Access Original Research Article

E. Comay

A gauge transformation of a simple electromagnetic system is analyzed. The Hamiltonian which is derived from the Dirac Lagrangian density is used for determining the state of an electron. The fact that this Hamiltonian is free of time differential operators plays a key role in the analysis and proves that this Hamiltonian is *not* invariant under a general gauge transformation. An application of a specific gauge transformation illustrates this fact. These results call for a further analysis of the role of gauge transformations in the theoretical structure of electrodynamics.

Open Access Original Research Article

Sunday E. Etuk, Okechukwu E. Agbasi, Nwokolo C. Samuel

In this research paper, measured monthly average daily radiometric data for global solar radiation on the horizontal surfaces and atmospheric parameters including relative humidity, sunshine hours, dew point temperature as well as the ambient temperatures (minimum and maximum) at Calabar, Nigeria obtained from the archives of the Nigeria Meteorological Agency, Oshodi Lagos, Nigeria for a 14-year period (2000-2013) were analysed and fifteen empirical models developed for predicting photo synthetically active radiation (PAR) for Calabar environment. The photo synthetically active radiation is estimated from measured global while the models are developed using extraterrestrial PAR, relative humidity, relative sunshine hours, dew point temperature as well as the relative ambient temperature (minimum and maximum) and clearness index. The performance of the models developed were tested for validation using mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE), Nash-Sutcliff equation (NSE), chi squares (χ2) and index of agreement (d). the linear, quadratic and polynomial regression models developed to estimate PAR judging from the model performance and validation test indicates that the proposed models could be used to estimate PAR in Calabar environ and other locations with similar climatological conditions across the globe.

Open Access Original Research Article

J. Z. G. Ma, J. P. St.- Maurice

Filamentary space-charge aurorae bring about cylindrical structures symmetric to local geomagnetic field lines in auroral ionosphere. It produces arbitrary structured electric fields. Developed from previous work on a backward mapping technique to solve ion velocities and transport properties under both collision-free and collisional conditions in cylindrically symmetric, uniformly charged auroral ionosphere, this paper studies the collision-free case by numerically solving the Boltzmann-Vlasov equation in the presence of three arbitrarily chosen electric field configurations: (1) an electric field which is proportional to the radius inside a space charge cylinder but drops off slowly outside the cylinder; (2) an electric field which is still proportional to the radius inside the space charge cylinder but drops off more quickly out side the cylinder; and, (3) an electric at the edge of the cylinder. Various shapes of non-Maxwellian ion velocity distributions and associated transport properties are obtained. In regimes where the electric field dropped outside the space-charge region, the evolving velocity distribution with time is found to have many possible types of shapes, such as, deformed pancake, horseshoe, teardrop, core-halo, etc. If the electric field drops sharply on both sides of the boundary of the region, the distribution develops into an ear-collar appearance with time. Under all electric field structures, the non-Maxwellian distributions and related transport parameters are localized to the region where the electric field permeates. The results are expected to be applicable to account for ongoing and future high-resolution observations.

Open Access Original Research Article

Hee J. Lee, Y. K. Lim

Plasma echo theory is revisited, and we apply it to a plasma slab bounded by a vacuum. Spatial echoes in a slab plasma are investigated by calculating the electric field produced by external charges and satisfying the boundary conditions at the interfaces. We determine the echo spots associated with the symmetric mode of the surface wave in the slab. Naturally, in the course of development, the dispersion relation of the electrostatic surface plasma wave in a slab geometry is derived kinetically by satisfying the specular reflection boundary condition for the distribution function. We show that echoes can occur at various spots. The diversity of echo occurrence spots is due to the boundary terms, and appears to be owing to the reflections of the waves from the interface.

Open Access Review Article

Anatolij Prykarpatski

It is a review of some new electrodynamics models of interacting charged point particles and related with them fundamental physical aspects, motivated by the classical A. M. Amper's magnetic and H. Lorentz force laws, as well as O. Jefimenko electromagnetic field expressions. Based on the suitably devised vacuum field theory approach the Lagrangian and Hamiltonian reformulations of some alternative classical electrodynamics models are analyzed in detail. A problem closely related to the radiation reaction force is analyzed aiming to explain the Wheeler and Feynman reaction radiation mechanism, well known as the absorption radiation theory, and strongly dependent on the Mach type interaction of a charged point particle in an ambient vacuum electromagnetic medium. There are discussed some relationships between this problem and the one derived within the context of the vacuum field theory approach. The R. Feynman's "heretical" approach to deriving the Lorentz force based Maxwell electromagnetic equations is also revisited, its complete legacy is argued both by means of the geometric considerations and its deep relation with the devised vacuum field theory approach. Based on completely standard reasonings, we reanalyze the Feynman's derivation from the classical Lagrangian and Hamiltonian points of view and construct its nontrivial relativistic generalization compatible with the vacuum field theory approach. The electron inertia problem is reanalyzed within the Lagrangian-Hamiltonian formalisms and the related Feynman proper time paradigm. The validity of the Abraham-Lorentz electromagnetic electron mass origin hypothesis within the shell charged model is argued. The electron stability in the framework of the electromagnetic tension-energy compensation principle is analyzed.