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H Saleem - One of the best experts on this subject based on the ideXlab platform.
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electrostatic wave instability and soliton formation with non thermal electrons in o h plasma of Ionosphere
Physics of Plasmas, 2019Co-Authors: Shaukat Ali Shan, Ibtehaj Hassan, H SaleemAbstract:It is pointed out that the presence of non-thermal electrons and protons in oxygen plasma of the Ionosphere plays a destructive role in the formation of electrostatic structures by nonlinear ion acoustic waves (IAWs). On the other hand, linear electrostatic perturbations at different IAW frequencies are excited by the field-aligned shear flow in oxygen-hydrogen plasma of the Upper Ionosphere, and non-thermal electrons cause an increase in the growth rate. The excitation of IAW and formation of solitary structures in the Ionosphere are investigated at altitudes of 600 km and 1000 km in the auroral region.
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ions shear flow and electron field aligned current produce ion acoustic waves in the oxygen hydrogen ionospheric plasma
Physics of Plasmas, 2017Co-Authors: H Saleem, Shaukat Ali Shan, Amanur RehmanAbstract:It is pointed out that the ion acoustic waves (IAWs) are excited either by field-aligned shear flows or electron parallel current in oxygen-hydrogen (O-H) plasma of Upper Ionosphere. The purely growing D'Angelo instability becomes ion acoustic wave instability in the presence of second kind of ions within the framework of multi-fluid plasma model. On the other hand, kinetic theory is used to show that the growth rate of current driven ion acoustic wave overcomes the ion Landau damping. Out of four real roots corresponding to negative shear flow, the two roots can become unstable. Thus, ion acoustic waves at different but very low real frequencies appear in O-H plasma of Ionosphere due to parallel shear flow and current, which is in agreement with satellite observations.
S M Stankov - One of the best experts on this subject based on the ideXlab platform.
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ionospheric specification with analytical profilers evidences of non chapman electron density distribution in the Upper Ionosphere
Advances in Space Research, 2015Co-Authors: Tobias Verhulst, S M StankovAbstract:Abstract In relation to the development of an operational ionospheric monitoring and imaging system, the most frequently used analytical ionospheric profilers (Chapman, Epstein, Exponential) were investigated in terms of suitability for topside Ionosphere modelling. For the purpose, topside sounder measurements onboard Alouette and ISIS satellites have been analysed. We have come to the conclusion that the use of the Chapman profiler should be exercised with precaution as there are evidences that there are conditions when other profilers are better fit for modelling purposes. This is highlighted during ionospheric disturbances (e.g. during geomagnetic storms), when the shape of the topside electron density distribution might be better described by an Epstein profiler rather than a Chapman profiler.
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a new method for reconstruction of the vertical electron density distribution in the Upper Ionosphere and plasmasphere
Journal of Geophysical Research, 2003Co-Authors: S M Stankov, N Jakowski, S Heise, Plamen Muhtarov, Ivan Kutiev, Rene WarnantAbstract:Ground-based Ionosphere sounding measurements alone are incapable of reliably modeling the topside electron density distribution above the F layer peak density height. Such information can be derived from Global Positioning System (GPS)-based total electron content (TEC) measurements. A novel technique is presented for retrieving the electron density height profile from three types of measurements: ionosonde (foF2, foE, M3000F2, hmf2), TEC (GPS-based), and O+-H+ ion transition level. The method employs new formulae based on Chapman, sech-squared, and exponential Ionosphere profilers to construct a system of equations, the solution of which system provides the unknown ion scale heights, sufficient to construct a unique electron density profile at the site of measurements. All formulae are based on the assumption of diffusive equilibrium with constant scale height for each ion species. The presented technique is most suitable for middle- and high-geomagnetic latitudes and possible applications include: development, evaluation, and improvement of theoretical and empirical ionospheric models, development of similar reconstruction methods utilizing low-earth-orbiting satellite measurements of TEC, operational reconstruction of the electron density on a real-time basis, etc.
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evaluation of analytical ionospheric models used in electron density profile reconstruction
Acta Geodaetica Et Geophysica Hungarica, 2002Co-Authors: S M StankovAbstract:New formulae based on the Sech-squared, Exponential and Chapman layers are introduced for a TEC-based electron density reconstruction technique using ionosonde and Upper ion transition level data. These analytical ionospheric models are implemented and tested as reconstruction tools with the help of satellite in-situ measurements of the ion and electron densities. Particular attention is drawn to the calculation quality of the scale height in the Upper Ionosphere, from hmF2 up to the O+-H+ transition height.
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a steady state f region model and its use for satellite data analysis
Annals of Geophysics, 1996Co-Authors: S M StankovAbstract:A steady-state mathematical model of the Earth's Upper Ionosphere and plasmasphere is presented. In the model the equations of continuity, momentum, and energy balance for O+, H+, and He+ ions are solved numerically along dipole magnetic field lines. As an extension of the model, a searching method is developed for de- termination of the boundary values in a self-consistent manner. Model results are compared with Atmosphere Explorer satellite measurements.
Shaukat Ali Shan - One of the best experts on this subject based on the ideXlab platform.
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electrostatic wave instability and soliton formation with non thermal electrons in o h plasma of Ionosphere
Physics of Plasmas, 2019Co-Authors: Shaukat Ali Shan, Ibtehaj Hassan, H SaleemAbstract:It is pointed out that the presence of non-thermal electrons and protons in oxygen plasma of the Ionosphere plays a destructive role in the formation of electrostatic structures by nonlinear ion acoustic waves (IAWs). On the other hand, linear electrostatic perturbations at different IAW frequencies are excited by the field-aligned shear flow in oxygen-hydrogen plasma of the Upper Ionosphere, and non-thermal electrons cause an increase in the growth rate. The excitation of IAW and formation of solitary structures in the Ionosphere are investigated at altitudes of 600 km and 1000 km in the auroral region.
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ions shear flow and electron field aligned current produce ion acoustic waves in the oxygen hydrogen ionospheric plasma
Physics of Plasmas, 2017Co-Authors: H Saleem, Shaukat Ali Shan, Amanur RehmanAbstract:It is pointed out that the ion acoustic waves (IAWs) are excited either by field-aligned shear flows or electron parallel current in oxygen-hydrogen (O-H) plasma of Upper Ionosphere. The purely growing D'Angelo instability becomes ion acoustic wave instability in the presence of second kind of ions within the framework of multi-fluid plasma model. On the other hand, kinetic theory is used to show that the growth rate of current driven ion acoustic wave overcomes the ion Landau damping. Out of four real roots corresponding to negative shear flow, the two roots can become unstable. Thus, ion acoustic waves at different but very low real frequencies appear in O-H plasma of Ionosphere due to parallel shear flow and current, which is in agreement with satellite observations.
Yk J Cho - One of the best experts on this subject based on the ideXlab platform.
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electrodynamics on extrasolar giant planets
The Astrophysical Journal, 2014Co-Authors: T T Koskinen, R V Yelle, P Lavvas, Yk J ChoAbstract:Strong ionization on close-in extrasolar giant planets (EGPs) suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the Upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive magnetohydrodynamics that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an Upper Ionosphere dominated by ionization of H and He and a lower Ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary Ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conductivity regimes on close-in EGPs and use a generalized Ohm's law to study the basic effects of electrodynamics in their atmospheres. We find that ion drag is important above the 10 mbar level where it can also significantly alter themore » energy balance through resistive heating. Due to frequent collisions of the electrons and ions with the neutral atmosphere, however, ion drag is largely negligible in the lower atmosphere below the 10 mbar level for a reasonable range of planetary magnetic moments. We find that the atmospheric conductivity decreases by several orders of magnitude in the night side of tidally locked planets, leading to a potentially interesting large-scale dichotomy in electrodynamics between the day and night sides. A combined approach that relies on UV observations of the Upper atmosphere, phase curve and Doppler measurements of global dynamics, and visual transit observations to probe the alkali metals can potentially be used to constrain electrodynamics in the future.« less
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electrodynamics on extrasolar giant planets
arXiv: Earth and Planetary Astrophysics, 2014Co-Authors: T T Koskinen, R V Yelle, P Lavvas, Yk J ChoAbstract:Strong ionization on close-in extrasolar giant planets suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the Upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive MHD that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an Upper Ionosphere dominated by ionization of H and He and a lower Ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary Ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conductivity regimes on close-in EGPs and use a generalized Ohm's law to study the basic effects of electrodynamics in their atmospheres. We find that ion drag is important above the 10 mbar level where it can also significantly alter the energy balance through resistive heating. Due to frequent collisions of the electrons and ions with the neutral atmosphere, however, ion drag is largely negligible in the lower atmosphere below the 10 mbar level for a reasonable range of planetary magnetic moments [abridged].
G Milinevsky - One of the best experts on this subject based on the ideXlab platform.
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model of the propagation of very low frequency beams in the earth Ionosphere waveguide principles of the tensor impedance method in multi layered gyrotropic waveguides
Annales Geophysicae, 2020Co-Authors: Yuriy Rapoport, V Grimalsky, V Fedun, O V Agapitov, J W Bonnell, A Grytsai, G MilinevskyAbstract:Abstract. The modeling of very low-frequency (VLF) electromagnetic (EM) beam propagation in the Earth–Ionosphere waveguide (WGEI) is considered. A new tensor impedance method for modeling the propagation of electromagnetic beams in a multi-layered and inhomogeneous waveguide is presented. The waveguide is assumed to possess the gyrotropy and inhomogeneity with a thick cover layer placed above the waveguide. The influence of geomagnetic field inclination and carrier beam frequency on the characteristics of the polarization transformation in the Earth–Ionosphere waveguide is determined. The new method for modeling the propagation of electromagnetic beams allows us to study the (i) propagation of the very low-frequency modes in the Earth–Ionosphere waveguide and, in perspective, their excitation by the typical Earth–Ionosphere waveguide sources, such as radio wave transmitters and lightning discharges, and (ii) leakage of Earth–Ionosphere waveguide waves into the Upper Ionosphere and magnetosphere. The proposed approach can be applied to the variety of problems related to the analysis of the propagation of electromagnetic waves in layered gyrotropic and anisotropic active media in a wide frequency range, e.g., from the Earth–Ionosphere waveguide to the optical waveband, for artificial signal propagation such as metamaterial microwave or optical waveguides.
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model of propagation of vlf beams in the waveguide earth Ionosphere principles of tensor impedance method in multilayered gyrotropic waveguides
Annales Geophysicae, 2019Co-Authors: Yuriy Rapoport, V Grimalsky, V Fedun, O V Agapitov, J W Bonnell, A Grytsai, G Milinevsky, Alex Liashchuk, A RozhnoiAbstract:Abstract. Modeling propagation of VLF electromagnetic beams in the waveguide earth-Ionosphere (WGEI) is of a great importance because variation in the characteristics of these waves is an effective instrument for diagnostics the influences on the Ionosphere from above (Sun-Solar Wind-Magnetosphere-Ionosphere), from below (the most powerful meteorological, seismogenic and other sources in the lower atmosphere and lithosphere/Earth, such as hurricanes, earthquakes, tsunamis etc.), from inside the Ionosphere (strong thunderstorms and lightning discharges) and even from the far space (such as gamma-flashes, cosmic rays etc.). Thus, VLF became one of the most universal instrument for monitoringthe Space Weather in the direct sense of this term, i.e. the state of the Sun-Earth space and the Ionosphere as it is particularly determined by all possible relatively powerful sources, wherever they are placed. This paper is devoted mostly to modelling VLF electromagnetic beam propagation in the WGEI. We present a new tensor impedance method for modelling propagation of electromagnetic beams (TIMEB) in a multi-layered/inhomogeneous waveguide. Suppose that such a waveguide, i.e. WGEI, possesses the gyrotropy and inhomogeneity with a thick cover layer placed above the waveguide. Note a very useful and attractive feature of the proposed TIMEB method: in spite of a large thickness of the waveguide cover layer, the proposed effective impedance approach reflects an impact of such a cover on the electromagnetic (EM) waves, which propagate in the waveguide. This impedance approach can be applied for EM waves/beams in layered gyrotropic/anisotropic active media in very wide frequency range, from VLF to optics. Moreover, this approach can be applied to calculations of EM waves/beams propagation in the media of an artificial origin such as metamaterial microwave or optical waveguides. The results of the modelling the propagation of VLF beams in the WGEI are included. The qualitative comparison between the theory and experimental observation of increasing losses of VLF waves in the WGEI is discussed. The new proposed method and its further development allows the comparison with the results of the future rocket experiment. This method allows to model (i) excitation of the VLF modes in the WGEI and their excitation by the typical VLF sources, such as radio wave transmitters and lightning discharges and (ii) leakage of VLF waves/beams into the Upper Ionosphere/magnetosphere.
