Joule effect

Abstract: The assimilative mapping of ionospheric electrodynamics (AMIE) algorithm has been applied to derive the realistic time-dependent large-scale global distributions of the ionospheric convection and particle precipitation during a recent Geospace Environment Modeling (GEM) campaign period: March 28-29, 1992. The AMIE outputs are then used as the inputs of the National Center for Atmospheric Research thermosphere-ionosphere general circulation model to estimate the electrodynamic quantities in the ionosphere and thermosphere. It is found that the magnetospheric electromagnetic energy dissipated in the high-latitude ionosphere is mainly converted into Joule heating, with only a small fraction (6%) going to acceleration of thermospheric neutral winds. Our study also reveals that the thermospheric winds can have significant influence on the ionospheric electrodynamics. On the average for these 2 days, the neutral winds have approximately a 28% negative effect on Joule heating and approximately a 27% negative effect on field-aligned currents. The field-aligned currents driven by the neutral wind flow in the opposite direction to those driven by the plasma convection. On the average, the global electromagnetic energy input is about 4 times larger than the particle energy input.

Abstract: This paper concerns the determination of the electric current requirements for an anti-icing technique based on the Joule effect. The minimum current intensity needed for preventing ice accretion depends on several conductor parameters, including external diameter, electrical resistance, as well as surface geometry (number and diameter of external strands). It depends also on meteorological conditions, such as air temperature, wind velocity, and liquid water content. The study comprises the elaboration of a mathematical model and the laboratory experiments for validation. This research work is mainly concerned with power-line conductor and atmospheric parameters. Therefore, four different types of single A1/S1 power-line conductors are investigated. The analytical model was validated with the experiments performed in the wind tunnel of CIGELE Icing Research Pavilion at the University of Quebec, Chicoutimi. In order to complete the mathematical model, it is necessary to assess the overall heat transfer coefficient (HTC) for stranded conductors. The HTC measurements are presented for conductors with different surface geometries

Abstract: We study the mutual influence of thermal and magnetic evolution in a neutron star's crust in axial symmetry. Taking into account realistic microphysical inputs, we find the heat released by Joule effect consistent with the circulation of currents in the crust, and we incorporate its effects in 2D cooling calculations. We solve the induction equation numerically using a hybrid method (spectral in angles, but a finite--differences scheme in the radial direction), coupled to the thermal diffusion equation. We present the first long term 2D simulations of the coupled magneto-thermal evolution of neutron stars. This substantially improves previous works in which a very crude approximation in at least one of the parts (thermal or magnetic diffusion) has been adopted. Our results show that the feedback between Joule heating and magnetic diffusion is strong, resulting in a faster dissipation of the stronger fields during the first million years of a NS's life. As a consequence, all neutron stars born with fields larger than a critical value (about 5 10^13 G) reach similar field strengths (approximately 2-3 10^{13} G) at late times. Irrespectively of the initial magnetic field strength, after $10^6$ years the temperature becomes so low that the magnetic diffusion timescale becomes longer than the typical ages of radio--pulsars, thus resulting in apparently no dissipation of the field in old NS. We also confirm the strong correlation between the magnetic field and the surface temperature of relatively young NSs discussed in preliminary works. The effective temperature of models with strong internal toroidal components are systematically higher than those of models with purely poloidal fields, due to the additional energy reservoir stored in the toroidal field that is gradually released as the field dissipates.

Abstract: A thermal–electrical model was developed for sparks generated by electrical discharge in a liquid media. A cylindrical shape has been used for the discharge channel created between the electrodes. The discharge channel being an electrical conductor will dissipate heat, which can be explained by the Joule heating effect. The amount of heat dissipated varies with the thermal–physical properties of the conductor; as a result, the maximum temperature reached is different. In the present model, the radii value of the conductor is a function of the current intensity and pulse duration. The thermal–physical values used in the model are the average of both the ambient and melting value. Copper and iron are the materials used for anode and cathode, respectively. The Finite Element Analysis (FEA) results were compared with the experimental values of the table of AGIE SIT used by other researchers [D.D. DiBitonto, P.T. Eubank, M.R. Patel, M.A. Barrufet, Theoretical models of the electrical discharge machining process—I: a simple cathode erosion model, Journal of Applied Physics, 66(9) (1989) 4095–4103; M.R. Patel, M.A. Barrufet, P.T. Eubank, D.D. DiBitonto, Theoretical models of the electrical discharge machining process—II: the anode erosion model, Journal of Applied Physics, 66(9) (1989) 4104–4111; P.T. Eubank, M.R. Patel, M.A. Barrufet, B. Bozkurt, Theoretical models of the electrical discharge machining process—III: the variable mass, cylindrical plasma model, Journal of Applied Physics, 73(11) (1993) 7900–7909]. In order to show the universality of the model it was obtained results for all current intensity values of the table. The Tool Wear Ratio (TWR) and Material Removal Rate (MRR) as well as surface roughness results agree reasonably well with the researcher's values found for that table and itself.