International Journal of Physics | Vol. 3, No. 3, March 2012 | pp. 19–26
DOI: 10.46882/2012/IJP/000027
Article Type: Original Research Paper
Title: Ionospheric Total Electron Content (TEC) Disturbance Profiles over Equatorial Latitudes During Severe Geomagnetic Storms
Names of Authors: G. I. Amadi¹, R. S. Greenwald²
Authors’ Affiliations: ¹Department of Physics, University of Lagos, Lagos, Nigeria; ²Space Physics and Engineering Department, Johns Hopkins University, Baltimore, USA
Abstract: Severe geomagnetic storms alter the global distribution of ionospheric plasma, inducing signal scintillation that can disrupt satellite navigation and communication links. This paper analyzes the spatial and temporal variations of Total Electron Content (TEC) across the equatorial ionosphere during the prominent geomagnetic storm events of 2011. Dual-frequency Global Positioning System (GPS) receiver networks situated within the West African equatorial coordinate zone were utilized to extract vertical TEC parameters. The storm dynamics were cross-referenced against solar wind indices and planetary Kp indicators. Our observations show that during the storm main phase, the equatorial ionization anomaly (EIA) expanded significantly, shifting up to 5 degrees poleward. This expansion caused a sharp daytime TEC enhancement of up to 45 TEC units (1 TECU = 10¹⁶ electrons/m²) over the magnetic equator, driven by intensified prompt penetration electric fields (PPEF). Conversely, the storm recovery phase displayed a prolonged negative ionospheric storm effect, with TEC values dropping 35% below quiet-time baseline averages due to thermospheric composition modifications (O/N₂ ratio reductions). These measured variations are valuable for calibrating regional empirical ionospheric models and correcting GPS positioning errors during space weather anomalies.
Keywords: Ionospheric total electron content; Geomagnetic storms; Equatorial ionization anomaly; GPS scintillation; Prompt penetration electric fields; Space weather; Thermospheric composition; Plasma dynamics.
Manuscript Timeline: Received: December 05, 2011; Revised: January 18, 2012; Accepted: February 11, 2012; Published: March 02, 2012.
Citation: Amadi, G. I., & Greenwald, R. S. (2012). Ionospheric Total Electron Content (TEC) Disturbance Profiles over Equatorial Latitudes During Severe Geomagnetic Storms. International Journal of Physics, 3(3), 19–26.
International Journal of Physics | Vol. 2, No. 8, August 2011 | pp. 60–67
DOI: 10.46882/2011/IJP/000020
Article Type: Original Research Paper
Title: Numerical Modelling of Fluid-Structure Interaction in Magnetohydrodynamic Channel Flows Under Non-Uniform Magnetic Fields
Names of Authors: I. J. Umar¹, P. A. Novak²
Authors’ Affiliations: ¹Department of Physics, Federal University of Technology, Minna, Nigeria; ²Department of Mechanical Engineering, Charles University, Prague, Czech Republic
Abstract: Magnetohydrodynamic (MHD) channel flows are central to developing liquid-metal cooling blankets for nuclear fusion reactors and electromagnetic pumps. This investigation presents a numerical model analyzing the fluid-structure interactions of an incompressible, viscous, electrically conducting fluid flowing through a deformable channel under a non-uniform transverse magnetic field. The coupled system balances the Navier-Stokes equations, Maxwell's electromagnetic equations, and elastic structural deformation mechanics, resolved using a monolithic finite-element solver. The magnetic Hartmann number (Ha) was varied up to 150 to observe changes in velocity profiles and wall shear stresses. Our simulations demonstrate that entering a localized magnetic field zone induces M-shaped velocity profiles and strong electric current loops within the fluid. These current paths generate a counteracting Lorentz force that suppresses turbulence intensity by up to 65%. However, the non-uniform magnetic gradients cause a localized pressure drop and introduce structural bending stresses along the thin channel walls, with peak stress scaling quadratically with the magnetic field intensity. This evaluation underscores the importance of structural wall reinforcement in regions featuring sharp magnetic transitions to prevent mechanical fatigue in high-field fluid handling systems.
Keywords: Magnetohydrodynamics; Fluid-structure interaction; Finite-element method; Hartmann number; Lorentz force; Velocity profiles; Channel flow; Fusion cooling.
Manuscript Timeline: Received: May 19, 2011; Revised: June 30, 2011; Accepted: July 22, 2011; Published: August 14, 2011.
Citation: Umar, I. J., & Novak, P. A. (2011). Numerical Modelling of Fluid-Structure Interaction in Magnetohydrodynamic Channel Flows Under Non-Uniform Magnetic Fields. International Journal of Physics, 2(8), 60–67.
International Journal of Physics | Vol. 2, No. 11, November 2011 | pp. 84–91
DOI: 10.46882/2011/IJP/000023
Article Type: Original Research Paper
Title: Thermoluminescence Response and Kinetic Parameters of Copper-Doped Lithium Borate Glass Dosimeters for Medical Radiation Mapping
Names of Authors: S. A. Jonah¹, A. M. El-Sayed²
Authors’ Affiliations: ¹Centre for Energy Research and Training, Ahmadu Bello University, Zaria, Nigeria; ²Department of Physics, Ain Shams University, Cairo, Egypt
Abstract: Accurate radiation dosimetry is critical in clinical radiotherapy to maximize tumor destruction while minimizing exposure to surrounding healthy tissues. This study evaluates the thermoluminescence (TL) characteristics of lithium borate (Li₂B₄O₇) glasses doped with copper impurities (0.1% to 0.5% mol) synthesized via melt-quench configurations. The fabricated glass samples were exposed to medical gamma rays from a Co-60 source across a dose range spanning 0.5 Gy to 50 Gy. The TL glow curves, measured at a constant heating rate of 5 K/s, displayed a well-defined, prominent dosimetric peak centered at 485 K. Computerized glow curve deconvolution (CGCD) methods were utilized to extract the defect trapping parameters. The analysis revealed second-order kinetic behavior with an activation energy of 1.12 eV and a frequency factor of 2.5 x 10¹¹ s⁻¹. The TL peak intensity displayed a linear response to radiation up to 25 Gy before exhibiting minor saturation tendencies. The fading rate was assessed at less than 4.5% over a 30-day storage period at room temperature. These stable characteristics indicate that copper-doped lithium borate glass serves as an effective, tissue-equivalent matrix for personal and clinical radiation monitoring.
Keywords: Thermoluminescence; Lithium borate glass; Radiotherapy dosimetry; Activation energy; Glow curve deconvolution; Trapping kinetics; Gamma radiation; Personal monitoring.
Manuscript Timeline: Received: August 02, 2011; Revised: September 15, 2011; Accepted: October 10, 2011; Published: November 05, 2011.
Citation: Jonah, S. A., & El-Sayed, A. M. (2011). Thermoluminescence Response and Kinetic Parameters of Copper-Doped Lithium Borate Glass Dosimeters for Medical Radiation Mapping. International Journal of Physics, 2(11), 84–91.
International Journal of Physics | Vol. 2, No. 7, July 2011 | pp. 52–59
DOI: 10.46882/2011/IJP/000019
Article Type: Original Research Paper
Title: Characterization of Wind Energy Potential and Power Density Distribution across Coastal Zones of Southern Nigeria
Names of Authors: C. U. Chiemeka¹, E. N. Lindqvist²
Authors’ Affiliations: ¹Department of Physics, University of Calabar, Calabar, Nigeria; ²Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark
Abstract: Expanding renewable energy infrastructure requires accurate, long-term assessment of wind speed variations and available wind power densities across regional terrains. This study evaluates the wind energy potential across four coastal locations in Southern Nigeria using a ten-year meteorological dataset (2000–2009) collected at a hub height of 10 meters. The wind speed distribution profiles were modeled using the two-parameter Weibull distribution function, with shape parameters (k) and scale parameters (c) estimated via maximum likelihood methods. The data show that the mean annual wind speed varies between 3.8 m/s and 5.4 m/s, with peak velocities recorded during the monsoon months of July and August. The highest annual wind power density was observed at the coastal station in Lagos, reaching 145.2 W/m², while the lowest was recorded in Calabar at 62.4 W/m². Extrapolating the wind profiles to a typical commercial turbine hub height of 80 meters increased the estimated power density to 320.5 W/m² in the prominent coastal zones. This profile classifies the Southern coastal strip as a Class 2 wind resource environment, indicating that it is highly suitable for small-to-medium scale wind farm development and decentralized power grid integration.
Keywords: Wind energy assessment; Weibull distribution; Power density; Coastal meteorology; Renewable resource; Scale parameter; Wind turbine; Power grid integration.
Manuscript Timeline: Received: April 12, 2011; Revised: May 25, 2011; Accepted: June 18, 2011; Published: July 09, 2011.
Citation: Chiemeka, C. U., & Lindqvist, E. N. (2011). Characterization of Wind Energy Potential and Power Density Distribution across Coastal Zones of Southern Nigeria. International Journal of Physics, 2(7), 52–59.
International Journal of Physics | Vol. 2, No. 9, September 2011 | pp. 68–75
DOI: 10.46882/2011/IJP/000021
Article Type: Original Research Paper
Title: Investigation of Deep Level Transient Spectroscopy Profiles in Electron-Irradiated Gallium Arsenide Schottky Barrier Diodes
Names of Authors: O. M. Kolawole¹, F. K. Richter²
Authors’ Affiliations: ¹Department of Physics, University of Jos, Jos, Nigeria; ²Institute of Solid State Physics, Technical University of Berlin, Berlin, Germany
Abstract: Semiconductor devices operating in high-radiation environments, such as aerospace systems and particle accelerators, experience structural degradation due to displacement damage. This study investigates the formation and electrical properties of deep-level defects in n-type gallium arsenide (GaAs) Schottky barrier diodes exposed to 1.0 MeV electron irradiation. Deep Level Transient Spectroscopy (DLTS) was employed to monitor capacitance transients across a temperature range of 77 K to 400 K. The irradiation fluence was systematically varied from 1.0 x 10¹⁴ to 5.0 x 10¹⁵ electrons/cm². The DLTS spectrums revealed three prominent electron traps, labeled E1, E2, and E3, located at 0.12 eV, 0.38 eV, and 0.57 eV below the conduction band edge, respectively. The dominant E3 trap, linked to arsenic vacancy-interstitial pairs, displayed an electron capture cross-section of 1.4 x 10⁻¹⁵ cm². Our data show that the trap concentration increases linearly with electron fluence, causing a severe reduction in carrier concentration and a 42% drop in diode forward current density. Isothermal annealing cycles executed at 500 K showed a 75% recovery of the electrical profiles within 60 minutes, driven by defect recombination pathways. These quantitative measurements refine defect kinetics parameters required for fabricating radiation-hardened arsenide devices.
Keywords: Deep level transient spectroscopy; Gallium arsenide; Electron irradiation; Schottky diodes; Electron traps; Capture cross-section; Defect annealing; Displacement damage.
Manuscript Timeline: Received: June 15, 2011; Revised: July 28, 2011; Accepted: August 20, 2011; Published: September 08, 2011.
Citation: Kolawole, O. M., & Richter, F. K. (2011). Investigation of Deep Level Transient Spectroscopy Profiles in Electron-Irradiated Gallium Arsenide Schottky Barrier Diodes. International Journal of Physics, 2(9), 68–75.
International Journal of Physics | Vol. 2, No. 1, January 2011 | pp. 1–9
DOI: 10.46882/2011/IJP/000013
Article Type: Original Research Paper
Title: Electronic and Topological Properties of Two-Dimensional Transition Metal Dichalcogenide Monolayers under Asymmetric Strain
Names of Authors: O. K. Oyewande¹, T. H. Kim²
Authors’ Affiliations: ¹Department of Physics, University of Ibadan, Ibadan, Nigeria; ²Department of Physics and Astronomy, Seoul National University, Seoul, South Korea
Abstract: Monolayers of transition metal dichalcogenides (TMDs) exhibit unique electronic and optical features that are missing in their bulk counterparts, making them promising candidates for flexible nanoelectronics and valleytronics. This paper examines the modulation of electronic band structures and topological invariants in molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) monolayers subjected to asymmetric uniaxial and biaxial tensile strains. The computations were executed using first-principles density functional theory (DFT) with the inclusion of spin-orbit coupling (SOC) effects. Our findings reveal that pristine monolayers exhibit a direct bandgap at the K point, which transitions to an indirect bandgap under a critical uniaxial strain of 2.5% for MoS₂ and 1.8% for WSe₂. Increasing the biaxial tensile strain beyond 6.5% induces a semiconductor-to-metal phase transition, driven by the differential orbital shifts of the transition metal d-states and chalcogen p-states. Furthermore, applying an asymmetric strain configuration breaks the local inversion symmetry, leading to a spin-splitting energy of up to 185 meV at the valence band maxima. This strain-engineered splitting enhances the valley-selective optical absorption coefficient, demonstrating a viable pathway for controlling spin and valley indices in mechanical strain-modulated nanoelectronic devices.
Keywords: Transition metal dichalcogenides; Density functional theory; Strain engineering; Electronic bandgap; Spin-orbit coupling; Semiconductor-to-metal transition; Monolayer MoS₂; Valleytronics.
Manuscript Timeline: Received: October 14, 2010; Revised: November 25, 2010; Accepted: December 16, 2010; Published: January 08, 2011.
Citation: Oyewande, O. K., & Kim, T. H. (2011). Electronic and Topological Properties of Two-Dimensional Transition Metal Dichalcogenide Monolayers under Asymmetric Strain. International Journal of Physics, 2(1), 1–9.