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Liu, Moran, Chen Zhou, Xiang Wang, Bin Bin Ni i Zhengyu Zhao. "Numerical simulation of oblique ionospheric heating by powerful radio waves". Annales Geophysicae 36, nr 3 (13.06.2018): 855–66. http://dx.doi.org/10.5194/angeo-36-855-2018.
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<p><strong>Abstract.</strong> In this paper, we investigate the ionospheric heating by oblique incidence of powerful high-frequency (HF) radio waves using three-dimensional numerical simulations. The ionospheric electron density and temperature perturbations are examined by incorporating the ionospheric electron transport equations and ray-tracing algorithm. The energy distribution of oblique incidence heating waves in the ionosphere is calculated by the three-dimensional ray-tracing algorithm. The calculation takes into consideration the electric field of heating waves in the caustic region by the plane wave spectral integral method. The simulation results show that the ionospheric electron density and temperature can be disturbed by oblique incidence of powerful radio waves, especially in the caustic region of heating waves. The oblique ionospheric heating with wave incidence parallel and perpendicular to the geomagnetic field in the mid-latitude ionosphere is explored by simulations, results of which indicate that the ionospheric modulation is more effective when the heating wave propagates along the magnetic field line. Ionospheric density and temperature striations in the caustic region due to thermal self-focusing instability are demonstrated, as well as the time evolution of the corresponding fluctuation spectra.</p>
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Aburjania, G. D., K. Z. Chargazia, G. V. Jandieri, A. G. Khantadze i O. A. Kharshiladze. "On the new modes of planetary-scale electromagnetic waves in the ionosphere". Annales Geophysicae 22, nr 4 (2.04.2004): 1203–11. http://dx.doi.org/10.5194/angeo-22-1203-2004.
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Abstract. Using an analogy method the frequencies of new modes of the electromagnetic planetary-scale waves (with a wavelength of 103 km or more), having a weather forming nature, are found at different ionospheric altitudes. This method gives the possibility to determine spectra of ionospheric electromagnetic perturbations directly from the dynamic equations without solving the general dispersion equation. It is shown that the permanently acting factor-latitude variation of the geomagnetic field generates fast and slow weakly damping planetary electromagnetic waves in both the E- and F-layers of the ionosphere. The waves propagate eastward and westward along the parallels. The fast waves have phase velocities (1–5)km s–1 and frequencies (10–1–10–4), and the slow waves propagate with velocities of the local winds with frequencies (10–4–10–6)s–1 and are generated in the E-region of the ionosphere. Fast waves having phase velocities (10-1500)km s–1 and frequencies (1–10–3)s–1 are generated in the F-region of the ionosphere. The waves generate the geomagnetic pulsations of the order of one hundred nanoTesla by magnitude. The properties and parameters of the theoretically studied electromagnetic waves agree with those of large-scale ultra-low frequency perturbations observed experimentally in the ionosphere. Key words. Ionosphere (ionospheric disturbances; waves propagation; ionosphere atmosphere interactions)
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Onohara, A. N., I. S. Batista i H. Takahashi. "The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling". Annales Geophysicae 31, nr 2 (7.02.2013): 209–15. http://dx.doi.org/10.5194/angeo-31-209-2013.
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Abstract. The main purpose of this study is to investigate the vertical coupling between the mesosphere and lower thermosphere (MLT) region and the ionosphere through ultra-fast Kelvin (UFK) waves in the equatorial atmosphere. The effect of UFK waves on the ionospheric parameters was estimated using an ionospheric model which calculates electrostatic potential in the E-region and solves coupled electrodynamics of the equatorial ionosphere in the E- and F-regions. The UFK wave was observed in the South American equatorial region during February–March 2005. The MLT wind data obtained by meteor radar at São João do Cariri (7.5° S, 37.5° W) and ionospheric F-layer bottom height (h'F) observed by ionosonde at Fortaleza (3.9° S; 38.4° W) were used in order to calculate the wave characteristics and amplitude of oscillation. The simulation results showed that the combined electrodynamical effect of tides and UFK waves in the MLT region could explain the oscillations observed in the ionospheric parameters.
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Husin, Asnawi, i Buldan Muslim. "EFEK GELOMBANG TSUNAMI ACEH 2004 PADA GANGGUAN IONOSFER BERGERAK SKALA MENENGAH DARI PENGAMATAN JARINGAN GPS SUMATRA". Komunikasi Fisika Indonesia 16, nr 2 (31.10.2019): 130. http://dx.doi.org/10.31258/jkfi.16.2.130-137.
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Medium Scale Travelling Ionospheric Disturbance (MSTID), thought to be manifestation of atmospheric gravity wave (AGW) in the ionospheric altitude that propagates horizontally and effects on in the electron density structure of ionosphere. These atmospheric gravity waves sourced from lower atmospheric activities such as typhoons, volcanic eruptions and tsunamis. Wave energy by its coupling induction process can travel to the ionosphere region. It has been understood that the TID's wave structure have an impact on the propagation of radio waves in the ionosphere so that it will affect the performance of navigation satellite-based positioning measurements. Based on Aceh tsunami in December 2004, this study aimed to investigation of the induction of atmospheric gravity waves in the ionosphere using total electron content (TEC) data from the Sumatra GPS network (Sumatra GPS Array, SUGAR). The detection technique of TEC changes due to AGW induction with a filter to separate medium scale disturbance at the ionospheric pierce point at an altitude of 350 km (IPP, Ionospheric Pierce Point). The results show the horizontal wavelength of a medium-scale TID around 180 ± 12 Km with a velocities of around 376 ± 9 ms-1. Based on two-dimensional map, the TID moves to the southeast.
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Rothkaehl, H., A. Krakowski, I. Stanislawska, J. Błęcki, M. Parrot, J. J. Berthelier i J. P. Lebreton. "Wave and plasma measurements and GPS diagnostics of the main ionospheric trough as a hybrid method used for Space Weather purposes". Annales Geophysicae 26, nr 2 (26.02.2008): 295–304. http://dx.doi.org/10.5194/angeo-26-295-2008.
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Abstract. The region of the main ionospheric trough is a unique region of the ionosphere, where different types of waves and instabilities can be generated. This region of the ionosphere acts like a lens, focusing a variety of indicators from the equator of plasmapause and local ionospheric plasma. This paper reports the results of monitoring the mid-latitude trough structure, dynamics and wave activity. For these purposes, the data gathered by the currently-operating DEMETER satellite and past diagnostics located on IK-19, Apex, and MAGION-3 spacecraft, as well as TEC measurements were used. A global-time varying picture of the ionospheric trough was reconstructed using the sequence of wave spectra registered and plasma measurements in the top-side ionosphere. The authors present the wave activity from ULF frequency band to the HF frequency detected inside the trough region and discuss its properties during geomagnetic disturbances. It is thought that broadband emissions are correlated with low frequency radiation, which is excited by the wave-particle interaction in the equatorial plasmapause and moves to the ionosphere along the geomagnetic field line. In the ionosphere, the suprathermal electrons can interact with these electrostatic waves and excite electron acoustic waves or HF longitudinal plasma waves. Furthermore, the electron density trough can provide useful data on the magnetosphere ionosphere dynamics and morphology and, in consequence, can be used for Space Weather purposes.
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He, L. M., L. X. Wu, S. J. Liu i S. N. Liu. "Superimposed disturbance in the ionosphere triggered by spacecraft launches in China". Annales Geophysicae 33, nr 11 (9.11.2015): 1361–68. http://dx.doi.org/10.5194/angeo-33-1361-2015.
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Abstract. Using GPS dual-frequency observations collected by continuously operating GPS tracking stations in China, superimposed disturbances caused by the integrated action of spacecraft's physical effect and chemical effect on ionosphere during the launches of the spacecrafts Tiangong-1 and Shenzhou-8 in China were firstly determined. The results show that the superimposed disturbance was composed of remarkable ionospheric waves and significant ionospheric depletion emerged after both launches. Meanwhile, we found for the first time that the ionospheric waves were made up of two periods of wave by wavelet analysis. The first period of ∼ 4 min shows one event in the near stations and two sub-events in the few far stations. The second period of ∼ 9 min shows only one event in all the observed stations. Finally, the time characteristics for ionospheric waves and depletions were examined.
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Zhang, X., i L. Tang. "Traveling ionospheric disturbances triggered by the 2009 North Korean underground nuclear explosion". Annales Geophysicae 33, nr 1 (30.01.2015): 137–42. http://dx.doi.org/10.5194/angeo-33-137-2015.
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Abstract. Underground nuclear explosions (UNEs) can induce acoustic-gravity waves, which disturb the ionosphere and initiate traveling ionospheric disturbances (TIDs). In this paper, we employ a multi-step and multi-order numerical difference method with dual-frequency GPS data to detect ionospheric disturbances triggered by the North Korean UNE on 25 May 2009. Several International GNSS Service (IGS) stations with different distances (400 to 1200 km) from the epicenter were chosen for the experiment. The results show that there are two types of disturbances in the ionospheric disturbance series: high-frequency TIDs with periods of approximately 1 to 2 min and low-frequency waves with period spectrums of 2 to 5 min. The observed TIDs are situated around the epicenter of the UNE, and show similar features, indicating the origin of the observed disturbances is the UNE event. According to the amplitudes, periods and average propagation velocities, the high-frequency and low-frequency TIDs can be attributed to the acoustic waves in the lower ionosphere and higher ionosphere, respectively.
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Pavelyev, A. G., K. Zhang, J. Wickert, T. Schmidt, Y. A. Liou, V. N. Gubenko, A. A. Pavelyev, R. R. Salimzjanov i Y. Kuleshov. "Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals". Atmospheric Measurement Techniques Discussions 4, nr 2 (1.03.2011): 1465–92. http://dx.doi.org/10.5194/amtd-4-1465-2011.
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Abstract. Conditions for communication, navigation, and remote sensing in the ionosphere and atmosphere depend strongly on the ionospheric impact on the radio waves propagation. By use of the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data a description of different types of the ionospheric contributions to the RO signals at the altitudes 30–90 km of the RO ray perigee is introduced and compared with results of measurements obtained earlier in the communication link satellite-to-Earth at frequency 1.5415 GHz. An analytical model is introduced for description of the radio waves propagation in a stratified medium consisting of sectors having the spherically symmetric distributions of refractivity. Model presents analytical expressions for the phase path and refractive attenuation of radio waves. Model is applied for analysis of the radio waves propagation effects along a prolonged path including the atmosphere and two parts of the ionosphere. Model explains significant amplitude and phase variations at the altitudes 30–90 km of the RO ray perigee as connected with influence of the inclined ionospheric layers. An innovative eikonal acceleration technique is described and applied for the identification of the inclined ionospheric layers contributions and their location. Possibility to separate the influence of layered structures from contributions of irregularities and turbulence is analyzed.
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Pokhotelov, D., W. Lotko i A. V. Streltsov. "Simulations of resonant Alfvén waves generated by artificial HF heating of the auroral ionosphere". Annales Geophysicae 22, nr 8 (7.09.2004): 2943–49. http://dx.doi.org/10.5194/angeo-22-2943-2004.
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Abstract. Numerical two-dimensional two-fluid MHD simulations of dynamic magnetosphere-ionosphere (MI) coupling have been performed to model the effects imposed on the auroral ionosphere by a powerful HF radio wave transmitter. The simulations demonstrate that modifications of the ionospheric plasma temperature and recombination due to artificial heating may trigger the ionospheric feedback instability when the coupled MI system is close to the state of marginal stability. The linear dispersion analysis of MI coupling has been performed to find the favorable conditions for marginal stability of the system. The development of the ionospheric feedback instability leads to the generation of shear waves which resonate in the magnetosphere between the heated ionospheric E-region and the strong gradient in the speed at altitudes of 1-2 RE. The application of the numerical results for the explanation of observations performed by low-orbiting satellites above the high-latitude ionosphere heated with a high power ground-based HF transmitter is discussed.
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Rapoport, Yuriy G., Oleg K. Cheremnykh, Volodymyr V. Koshovy, Mykola O. Melnik, Oleh L. Ivantyshyn, Roman T. Nogach, Yuriy A. Selivanov i in. "Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment". Annales Geophysicae 35, nr 1 (5.01.2017): 53–70. http://dx.doi.org/10.5194/angeo-35-53-2017.
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Abstract. We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs), which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG) at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs) with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1). Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1) of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2) of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz) and VLF (kHz) ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system, measurements of electromagnetic and acoustic fields, study of the variations in ionospheric transparency for the radio emissions from galactic radio sources, optical measurements, and the impact on atmospheric aerosols. The proposed approach can be useful for better understanding the mechanism of the acoustic channel of seismo-ionospheric coupling.
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Leonovich, A. S., i V. A. Mazur. "Penetration to the Earth's surface of standing Alfvén waves excited by external currents in the ionosphere". Annales Geophysicae 14, nr 5 (31.05.1996): 545–56. http://dx.doi.org/10.1007/s00585-996-0545-1.
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Abstract. The problem of boundary conditions for monochromatic Alfvén waves, excited in the magnetosphere by external currents in the ionospheric E-layer, is solved analytically. Waves with large azimuthal wave numbers m»1 are considered. In our calculations, we used a model for the horizontally homogeneous ionosphere with an arbitrary inclination of geomagnetic field lines and a realistic height disribution of Alfvén velocity and conductivity tensor components. A relationship between such Alfvén waves on the upper ionospheric boundary with electromagnetic oscillations on the ground was detected, and the spatial structure of these oscillations determined.
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Rogov, D. D., V. M. Vystavnoi, N. F. Blagoveshchenskaya, P. E. Baryshev i A. S. Kalishin. "RUSSIAN HIGH-LATITUDE NETWORK OF OBLIQUE IONOSPHERIC SOUNDING". Meteorologiya i Gidrologiya, nr 4 (2021): 5–13. http://dx.doi.org/10.52002/0130-2906-2021-4-5-13.
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The network for monitoring the high-latitude ionosphere by the method of oblique ionospheric sounding deployed in the Russian Arctic region is considered. The study describes the main results of operational data processing for studying the high-latitude ionosphere and determining the conditions for the optimum operation of radio communication systems and over-the-horizon radars in this region. The study demonstrates the potential of the network as a tool for the remote diagnostics of parameters of small-scale artificial ionospheric irregularities induced by powerful HF radio waves in the mid-latitude ionospheric F-region.
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Li, Qingfeng, Zeyun Li i Hanxian Fang. "Using 3D Ray Tracing Technology to Study the Disturbance Effect of Rocket Plume on Ionosphere". Atmosphere 13, nr 7 (20.07.2022): 1150. http://dx.doi.org/10.3390/atmos13071150.
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In this paper, the initial neutral atmospheric parameters, background ionospheric parameters and geomagnetic field parameters of the ionosphere are obtained by NRLMSISE-00 model, IRI-2016 model and IGRF-13 model, respectively. Considering the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, a three-dimensional dynamic model of chemical substances released by rocket plume disturbing the ionosphere is constructed. The influence of the disturbance on the echo path of high frequency radio waves with different incident frequencies is simulated by using three-dimensional digital ray-tracing technology. Using this model, the process of ionospheric disturbance caused by the main chemical substances H2 and H2O in the rocket plume under three different release conditions: fixed-point release at 300 km, vertical path at 250–350 km and parabolic path at 250–350 km, and the influence of the ionospheric cavity on the radio wave propagation of high frequency radio waves at different frequencies are simulated. The main purpose of the article is to focus on the effect of the cavity generated by the rocket exhaust on the propagation of radio waves. It mainly studies the perturbation effect on the ionosphere under different release conditions, considers the neutral gas diffusion process, ion chemical reaction and plasma diffusion process, and establishes the three-dimensional dynamics of the ionospheric electron density and the spatiotemporal distribution of the plume plasma learning model. Finally, the three-dimensional ray-tracing algorithm is used to simulate the propagation path of the radio wave through the disturbance area. We considered three different release conditions, including fixed-point release, vertical path and parabolic path. The ionospheric disturbances produced by these different releases are compared and analyzed, and their effects on the propagation path of radio waves are studied.
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Streltsov, A. V., i T. R. Pedersen. "Excitation of zero-frequency magnetic field-aligned currents by ionospheric heating". Annales Geophysicae 29, nr 6 (27.06.2011): 1147–52. http://dx.doi.org/10.5194/angeo-29-1147-2011.
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Abstract. Time-dependent, three-dimensional numerical simulations of the reduced MHD model describing shear Alfvén waves in the magnetosphere provide an interesting prediction superficially similar to results of several ionospheric heating experiments conducted at high altitudes. In these experiments, heating of the ionospheric F-region with a constant/zero-frequency beam of HF waves causes luminous structures in the ionosphere in the form of a ring or a solid spot with a characteristic size comparable to the size of the heated spot. Simulations suggest that spots/rings or similar optical appearance might be associated with a magnetic field-aligned current system produced by the ionospheric heating. Two of the most interesting features of this current system are (1) strong localization across the ambient magnetic field and (2) distinctive non-symmetrical luminous signatures (ring/spot) in magnetically conjugate locations in the ionosphere.
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Panasenko, Sergii, Dmytro Kotov, Taras Zhivolup, Olexander Koloskov i Volodymyr Lisachenko. "Simultaneous ionosonde investigations of the ionospheric F2 layer critical frequency and peak height at both ends of the geomagnetic tube". PHYSICS OF ATMOSPHERE AND GEOSPACE 1, nr 1 (31.12.2020): 31–44. http://dx.doi.org/10.47774/phag.01.01.2020-3.
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Based on the results of simultaneous ionosonde observations during low solar and weak magnetic activities, a coupling was found between diurnal and quasi-periodic variations in ionospheric parameters over magnetically conjugated regions, where the Ukrainian Antarctic Station (UAS) and Millstone Hill Observatory are located. A significant impact of the summer hemisphere on the nighttime variations of the F2 layer critical frequency foF2 in the magnetically conjugated region in the winter hemisphere was found. The most characteristic manifestation of this impact is the control of foF2 variations over the UAS not by the local sunset (sunrise), but by the sunset (sunrise) over Millstone Hill. It was found that the sunset over Millstone Hill leads to an increase in foF2 over the UAS, while the sunrise leads to a decrease in foF2 with a subsequent sharp increase. Both phenomena are associated with changes in the photoelectron flux from the northern hemisphere, corresponding changes in the electron temperature in the ionosphere above the UAS and the effect of these changes on the compression or rarefaction of the ionospheric plasma and changes in the plasmaspheric fluxes of H + ions. It was shown that the transition from nighttime to daytime conditions over both observation points was characterized by a significant decrease in the F2 layer peak height, and the difference in the values of this ionospheric parameter over Millstone Hill and UAS at night is due to seasonal differences in the thermospheric circulation and the difference in the behavior of the ionospheric parameters in the Northern and Southern hemispheres. Manifestations of atmospheric gravity waves, caused by the passage of local sunrise terminators, as traveling ionospheric disturbances with periods of about 90 and 75 – 120 mins over Millstone Hill and UAS, respectively, were found. These waves were most likely generated in the region located between the ionospheric F1 and F2 layers, where the sharp gradients in the electron and ion densities occur during changes in the intensity of solar radiation. It is confirmed that wave disturbances in atmospheric and ionospheric parameters can be transferred between magnetically conjugated regions by slow magnetohydrodynamic waves generated both at the heights of the ionospheric dynamo region due to the modulation of atmospheric and ionospheric parameters by atmospheric waves and the occurrence of external currents, and at the top of the plasmaspheric tube, where sharp plasma compression and heating or rarefaction and cooling occur during the passage of the solar terminator. Keywords: the ionosphere, F2 region, ionosonde measurements, geomagnetic field tube, magnetoconjugate region coupling, atmospheric gravity waves, traveling ionospheric disturbances, generation of slow magnetohydrodynamic waves
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Ueda, H. O., Y. Omura i H. Matsumoto. "Computer simulations for direct conversion of the HF electromagnetic wave into the upper hybrid wave in ionospheric heating experiments". Annales Geophysicae 16, nr 10 (31.10.1998): 1251–58. http://dx.doi.org/10.1007/s00585-998-1251-y.
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Abstract. Excitation of upper hybrid waves associated with the ionospheric heating experiments is assumed to be essential in explaining some of the features of stimulated electromagnetic emissions (SEE). A direct conversion process is proposed as an excitation mechanism of the upper hybrid waves where the energy of an obliquely propagating electromagnetic pump wave is converted into the electrostatic upper hybrid waves due to small-scale density irregularities. We performed electromagnetic particle-in-cell simulations to investigate the energy conversion process in the ionospheric heating experiments. We studied dependence of the amplitude of the excited wave on the propagation angle of the pump wave, scale length of the density irregularity, degree of the irregularity, and thermal velocity of the plasma. The maximum amplitude is found to be 37 of the pump amplitude under an optimum condition.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; wave-particle interactions).
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Pokhotelov, O. A., M. Parrot, E. N. Fedorov, V. A. Pilipenko, V. V. Surkov i V. A. Gladychev. "Response of the ionosphere to natural and man-made acoustic sources". Annales Geophysicae 13, nr 11 (30.11.1995): 1197–210. http://dx.doi.org/10.1007/s00585-995-1197-2.
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Abstract. A review is presented of the effects influencing the ionosphere which are caused by acoustic emission from different sources (chemical and nuclear explosions, bolides, meteorites, earthquakes, volcanic eruptions, hurricanes, launches of spacecrafts and flights of supersonic jets). A terse statement is given of the basic theoretical principles and simplified theoretical models underlying the physics of propagation of infrasonic pulses and gravity waves in the upper atmosphere. The observations of "quick" response by the ionosphere are pointed out. The problem of magnetic disturbances and magnetohydrodynamic (MHD) wave generation in the ionosphere is investigated. In particular, the supersonic propagation of ionospheric disturbances, and the conversion of the acoustic energy into the so-called gyrotropic waves in the ionospheric E-layer are considered.
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Waters, C. L., T. K. Yeoman, M. D. Sciffer, P. Ponomarenko i D. M. Wright. "Modulation of radio frequency signals by ULF waves". Annales Geophysicae 25, nr 5 (4.06.2007): 1113–24. http://dx.doi.org/10.5194/angeo-25-1113-2007.
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Abstract. The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1–100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B0, giving an e×B0 drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF) Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere.
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Afraimovich, E. L., N. P. Perevalova, A. V. Plotnikov i A. M. Uralov. "The shock-acoustic waves generated by earthquakes". Annales Geophysicae 19, nr 4 (30.04.2001): 395–409. http://dx.doi.org/10.5194/angeo-19-395-2001.
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Abstract. We investigate the form and dynamics of shock-acoustic waves generated by earthquakes. We use the method for detecting and locating the sources of ionospheric impulsive disturbances, based on using data from a global network of receivers of the GPS navigation system, and require no a priori information about the place and time of the associated effects. The practical implementation of the method is illustrated by a case study of earthquake effects in Turkey (17 August and 12 November 1999), in Southern Sumatra (4 June 2000), and off the coast of Central America (13 January 2001). It was found that in all instances the time period of the ionospheric response is 180–390 s, and the amplitude exceeds, by a factor of two as a minimum, the standard deviation of background fluctuations in total electron content in this range of periods under quiet and moderate geomagnetic conditions. The elevation of the wave vector varies through a range of 20–44°, and the phase velocity (1100–1300 m/s) approaches the sound velocity at the heights of the ionospheric F-region maximum. The calculated (by neglecting refraction corrections) location of the source roughly corresponds to the earthquake epicenter. Our data are consistent with the present views that shock-acoustic waves are caused by a piston-like movement of the Earth’s surface in the zone of an earthquake epicenter.Key words. Ionosphere (ionospheric disturbances; wave propagation) – Radio science (ionospheric propagation)
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Gong, Hongwei, Hanxian Fang i Zeyun Li. "Numerical Simulation of Ionospheric Disturbances Due to Rocket Plume and Its Influence on HF Radio Waves Propagation". Universe 8, nr 6 (15.06.2022): 331. http://dx.doi.org/10.3390/universe8060331.
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In this paper, the ionospheric disturbances of CO2, which is released by rocket exhaust plumes, was simulated. The effect of this disturbance on the propagation of high-frequency (HF) radio waves at different incident frequencies was also simulated by using three-dimensional digital ray tracing technique. The results show that CO2 can effectively dissipate the background electrons and form ionospheric holes after being released in the ionosphere. At the peak height of ionospheric electron density (about 300 km), the electrons are dissipated fastest and the radius of ionospheric hole is also largest. This is due to the fact that the diffusion coefficient of CO2 usually increases with height while the electron density just increases before reaching its peak height and then decreases with height, and the chemical reaction rate between ions and CO2 also becomes largest at the peak height of electron density (about 300 km). Around 100 s after the release of CO2, when the radio waves at a frequency of 8 MHz pass through the ionosphere with an elevation range of 85~95°, the “secondary focusing effect” can occur, and we believe that this is due to the reflection of HF shortwaves on the walls of the ionospheric holes. With time going on, this phenomenon disappears at 300 s and only one focus is left at this time. For the HF shortwaves at same incident frequency, the focusing effect of waves displays a weakening trend with time increasing, and the height of focus center also ascends gradually. At the same time after CO2 releasing, with the increasing of radio waves frequency, the focusing effect also becomes weaker and the focus center displays an ascending trend.
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Hysell, D. L., E. Kudeki i J. L. Chau. "Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>". Annales Geophysicae 23, nr 7 (14.10.2005): 2647–55. http://dx.doi.org/10.5194/angeo-23-2647-2005.
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Abstract. Vertical shear in the zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside F region ionosphere made at Jicamarca from about 1600–2200 LT. The relative importance of the factors controlling the shear, which include competition between the E and F region dynamos as well as vertical currents driven in the E and F regions at the dip equator, is presently unknown. Bottom-type scattering layers arise in strata where the neutral and plasma drifts differ widely, and periodic structuring of irregularities within the layers is telltale of intermediate-scale waves in the bottomside. These precursor waves appear to be able to seed ionospheric interchange instabilities and initiate full-blown equatorial spread F. The seed or precursor waves may be generated by a collisional shear instability. However, assessing the viability of shear instability requires measurements of the same parameters needed to understand shear flow quantitatively - thermospheric neutral wind and off-equatorial conductivity profiles. Keywords. Ionosphere (Equatorial ionosphere; ionospheric irregularities) – Space plasma physics (Waves and instabilities)
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Wang, Jin, Gang Chen, Tao Yu, Zhongxin Deng, Xiangxiang Yan i Na Yang. "Middle-Scale Ionospheric Disturbances Observed by the Oblique-Incidence Ionosonde Detection Network in North China after the 2011 Tohoku Tsunamigenic Earthquake". Sensors 21, nr 3 (2.02.2021): 1000. http://dx.doi.org/10.3390/s21031000.
Pełny tekst źródłaStreszczenie:
The 2011 Tohoku earthquake and the following enormous tsunami caused great disturbances in the ionosphere that were observed in various regions along the Pacific Ocean. In this study, the oblique-incidence ionosonde detection network located in North China was applied to investigate the inland ionospheric disturbances related to the 2011 tsunamigenic earthquake. The ionosonde network consists of five transmitters and 20 receivers and can monitor regional ionosphere disturbances continuously and effectively. Based on the recorded electron density variations along the horizontal plane, the planar middle-scale ionospheric disturbances (MSTIDs) associated with the 2011 Tohoku tsunamigenic earthquake were detected more than 2000 km west of the epicenter about six hours later. The MSTIDs captured by the Digisonde, high-frequency (HF) Doppler measurement, and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellite provided more information about the far-field inland propagation characteristics of the westward propagating gravity waves. The results imply that the ionosonde network has the potential for remote sensing of ionospheric disturbances induced by tsunamigenic earthquakes and provide a perspective for investigating the propagation process of associated gravity waves.
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Martines-Bedenko, Valeriy, Vyacheslav Pilipenko, Viktor Zakharov i Valeriy Grushin. "INFLUENCE OF THE VONGFONG 2014 HURRICANE ON THE IONOSPHERE AND GEOMAGNETIC FIELD AS DETECTED BY SWARM SATELLITES: 2. GEOMAGNETIC DISTURBANCES". Solar-Terrestrial Physics 5, nr 4 (17.12.2019): 74–80. http://dx.doi.org/10.12737/stp-54201910.
Pełny tekst źródłaStreszczenie:
Strong meteorological disturbances in the atmosphere, accompanied by the generation of waves and turbulence, can affect ionospheric plasma and geomagnetic field. To search for these effects, we have analyzed electromagnetic measurement data from low-orbit Swarm satellites during flights over the typhoon Vongfong 2014. We have found that there are “magnetic ripples” in the upper ionosphere that are transverse to the main geomagnetic field fluctuations of small amplitude (0.5–1.5 nT) with a predominant period of about 10 s caused by small-scale longitudinal currents. Presumably, these quasiperiodic fluctuations are produced by the satellite’s passage through the quasiperiodic ionospheric structure with a characteristic scale of ~70 km induced by the interaction of acoustic waves excited by the typhoon with the E-layer of the ionosphere. In one of the flights over the typhoon, a burst of high-frequency noise (~0.3 Hz) was observed, which can be associated with the excitation of the ionospheric Alfven resonator by atmospheric turbulence.
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Martines-Bedenko, Valeriy, Vyacheslav Pilipenko, Viktor Zakharov i Valeriy Grushin. "INFLUENCE OF THE VONGFONG 2014 HURRICANE ON THE IONOSPHERE AND GEOMAGNETIC FIELD AS DETECTED BY SWARM SATELLITES: 2. GEOMAGNETIC DISTURBANCES". Solnechno-Zemnaya Fizika 5, nr 4 (17.12.2019): 90–98. http://dx.doi.org/10.12737/szf-54201910.
Pełny tekst źródłaStreszczenie:
Strong meteorological disturbances in the atmosphere, accompanied by the generation of waves and turbulence, can affect ionospheric plasma and geomagnetic field. To search for these effects, we have analyzed electromagnetic measurement data from low-orbit Swarm satellites during flights over the typhoon Vongfong 2014. We have found that there are “magnetic ripples” in the upper ionosphere that are transverse to the main geomagnetic field fluctuations of small amplitude (0.5–1.5 nT) with a predominant period of about 10 s caused by small-scale longitudinal currents. Presumably, these quasiperiodic fluctuations are produced by the satellite’s passage through the quasiperiodic ionospheric structure with a characteristic scale of ~70 km induced by the interaction of acoustic waves excited by the typhoon with the E-layer of the ionosphere. In one of the flights over the typhoon, a burst of high-frequency noise (~0.3 Hz) was observed, which can be associated with the excitation of the ionospheric Alfven resonator by atmospheric turbulence.
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Marshall, R. A., i F. W. Menk. "Observations of Pc 3-4 and Pi 2 geomagnetic pulsations in the low-latitude ionosphere". Annales Geophysicae 17, nr 11 (30.11.1999): 1397–410. http://dx.doi.org/10.1007/s00585-999-1397-2.
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Abstract. Day-time Pc 3–4 (~5–60 mHz) and night-time Pi 2 (~5–20 mHz) ULF waves propagating down through the ionosphere can cause oscillations in the Doppler shift of HF radio transmissions that are correlated with the magnetic pulsations recorded on the ground. In order to examine properties of these correlated signals, we conducted a joint HF Doppler/magnetometer experiment for two six-month intervals at a location near L = 1.8. The magnetic pulsations were best correlated with ionospheric oscillations from near the F region peak. The Doppler oscillations were in phase at two different altitudes, and their amplitude increased in proportion to the radio sounding frequency. The same results were obtained for the O- and X-mode radio signals. A surprising finding was a constant phase difference between the pulsations in the ionosphere and on the ground for all frequencies below the local field line resonance frequency, independent of season or local time. These observations have been compared with theoretical predictions of the amplitude and phase of ionospheric Doppler oscillations driven by downgoing Alfvén mode waves. Our results agree with these predictions at or very near the field line resonance frequency but not at other frequencies. We conclude that the majority of the observations, which are for pulsations below the resonant frequency, are associated with downgoing fast mode waves, and models of the wave-ionosphere interaction need to be modified accordingly.Key words. Ionosphere (ionosphere irregularities) · Magnetospheric physics (magnetosphere-ionosphere interactions) · Radio science (ionospheric physics)
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Kotik, Dmitriy, Ekaterina Orlova i Vladimir Yashnov. "Peculiarities of ULF wave characteristics in a multicomponent ionospheric plasma". Solnechno-Zemnaya Fizika 8, nr 4 (24.12.2022): 57–65. http://dx.doi.org/10.12737/szf-84202205.
Pełny tekst źródłaStreszczenie:
We have examined the properties of low-frequency electromagnetic waves in multicomponent ionospheric plasma in the 1–30 Hz band, using the magnetoionic theory. Complex permittivity tensor components and refractive indices of normal waves (ordinary and extraordinary) were calculated at altitudes from 80 to 750 km. The calculations show that the refractive indices are highly dependent on frequency and height. Polarization of ordinary and extraordinary waves is elliptical over the entire range of the frequencies investigated. The refractive index and the polarization of normal waves are demonstrated to tend to magnetohydrodynamic (MHD) values only at frequencies lower than 1 Hz. The group velocity vector of an extraordinary wave is not directed along the magnetic field, as follows from the MHD approximation, but it lies inside a cone within ±(5–10) degrees, depending on frequency. The group velocity vector of an ordinary wave is practically independent of the angle with the geomagnetic field as in the MHD approximation. The proposed method for calculating the characteristics of normal waves in the ionosphere can be used to study ULF wave propagation from both natural and artificial ionospheric sources, which arise under the action of powerful HF radio waves in the lower and upper ionosphere.
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Kotik, Dmitriy, Ekaterina Orlova i Vladimir Yashnov. "Peculiarities of ULF wave characteristics in a multicomponent ionospheric plasma". Solar-Terrestrial Physics 8, nr 4 (24.12.2022): 55–62. http://dx.doi.org/10.12737/stp-84202205.
Pełny tekst źródłaStreszczenie:
We have examined the properties of low-frequency electromagnetic waves in multicomponent ionospheric plasma in the 1–30 Hz band, using the magnetoionic theory. Complex permittivity tensor components and refractive indices of normal waves (ordinary and extraordinary) were calculated at altitudes from 80 to 750 km. The calculations show that the refractive indices are highly dependent on frequency and height. Polarization of ordinary and extraordinary waves is elliptical over the entire range of the frequencies investigated. The refractive index and the polarization of normal waves are demonstrated to tend to magnetohydrodynamic (MHD) values only at frequencies lower than 1 Hz. The group velocity vector of an extraordinary wave is not directed along the magnetic field, as follows from the MHD approximation, but it lies inside a cone within ±(5–10) degrees, depending on frequency. The group velocity vector of an ordinary wave is practically independent of the angle with the geomagnetic field as in the MHD approximation. The proposed method for calculating the characteristics of normal waves in the ionosphere can be used to study ULF wave propagation from both natural and artificial ionospheric sources, which arise under the action of powerful HF radio waves in the lower and upper ionosphere.
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Santoso, Anwar, Buldan Muslim i Siti Inayah Fitriyani. "DETEKSI EFEK GEMPABUMI PADA IONOSFER MENGGUNAKAN DATA GNSS". Komunikasi Fisika Indonesia 17, nr 1 (26.03.2020): 1. http://dx.doi.org/10.31258/jkfi.17.1.1-6.
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Seismic activities such as earthquakes can cause atmospheric and infrared gravitational waves. If the earthquake happens to be strong enough (M> 6 SR), these waves can spread to the ionosphere altitude in the form of atmospheric and infrasonic gravitational waves. The monitoring system of ionospheric wave that associated with earthquakes from network of GNSS data has been much developed in Indonesia by using the sliding Fast Fourier Transform (SFFT) programfor disturbed ionospheric TEC positions. The results of previous studies, differential TEC showed irregular fluctuations in the order of several tens of seconds until to several tens of minutes with average amplitude less than 0.01 TECU. At times the ionospheric is not disturbed (regular), the amplitude can reaching greater than 0.01 TECU. As a case study, in this paper a methodological examination will be conducted on the events of Aceh earthquake on December 26, 2004 (M = 9.2 SR), Tohoku March 11, 2011 (M = 9 SR) and Yogyakarta May 27, 2006 (M = 6.2 SR).
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Hayes, Laura A., i Peter T. Gallagher. "A Significant Sudden Ionospheric Disturbance Associated with Gamma-Ray Burst GRB 221009A". Research Notes of the AAS 6, nr 10 (26.10.2022): 222. http://dx.doi.org/10.3847/2515-5172/ac9d2f.
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Abstract We report the detection of a significant sudden ionospheric disturbance in the D-region of Earth’s ionosphere (∼60–100 km), which was associated with the massive γ-ray burst GRB 221009A that occurred on 2022 October 9. We identified the disturbance over northern Europe—a result of the increased ionization by X- and γ-ray emission from the GRB-using very low frequency radio waves as a probe of the D-region. These observations demonstrate that an extra-galactic GRB (z ∼ 0.151) can have a significant impact on the terrestrial atmosphere and illustrates that the Earth’s ionosphere can be used as a giant X- and γ-ray detector. Indeed, these observations may provide an insight into the impacts of GRBs on the ionospheres of planets in our solar system and beyond.
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Kong, Jian, Lulu Shan, Xiao Yan i Youkun Wang. "Analysis of Ionospheric Disturbance Response to the Heavy Rain Event". Remote Sensing 14, nr 3 (21.01.2022): 510. http://dx.doi.org/10.3390/rs14030510.
Pełny tekst źródłaStreszczenie:
Meteorological activities in the troposphere would affect electron concentrations and distributions in the ionosphere, thereby exciting ionospheric disturbance. To explore the ionospheric anomalies during severe convective weather, the ionospheric phenomenon during the heavy rainfall in Sichuan Province on 9 July 2013 was analyzed based on GNSS data. The Total Electron Content (TEC) are evaluated by carrier phase smoothed pseudoranges. Then, the dTEC (detrend TEC) sequences are obtained by using the cubic smoothing spline. They show obvious N-shaped ionospheric disturbances and have propagation characteristics, with the maximum of 0.4 TECU. Frequency domain analysis using continuous wavelet transform (CWT) also reached similar conclusions—that there are obvious ionospheric disturbances with different frequencies and intensity. Based on the isotropic assumption and feature points method, the horizontal propagation velocity of the disturbances in the ionosphere is estimated to be approximately 150 m/s. Then, Sichuan Province is divided into 1° × 1° grids, and the disturbance trigger source is determined via the grid searching method to be the central of Sichuan Province. Finally, the mechanisms causing ionospheric disturbance are discussed. During the heavy rainfall, the strong convection may excite gravity waves (GWs), which are driven by terrain and background wind fields to propagate upwards to the ionosphere and release energy, causing ionospheric disturbances.
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Galushko, V. G., V. V. Paznukhov, Y. M. Yampolski i J. C. Foster. "Incoherent scatter radar observations of AGW/TID events generated by the moving solar terminator". Annales Geophysicae 16, nr 7 (31.07.1998): 821–27. http://dx.doi.org/10.1007/s00585-998-0821-3.
Pełny tekst źródłaStreszczenie:
Abstract. Observations of traveling ionospheric disturbances (TIDs) associated with atmospheric gravity waves (AGWs) generated by the moving solar terminator have been made with the Millstone Hill incoherent scatter radar. Three experiments near 1995 fall equinox measured the AGW/TID velocity and direction of motion. Spectral and cross-correlation analysis of the ionospheric density observations indicates that ST-generated AGWs/TIDs were observed during each experiment, with the more-pronounced effect occurring at sunrise. The strongest oscillations in the ionospheric parameters have periods of 1.5 to 2 hours. The group and phase velocities have been determined and show that the disturbances propagate in the horizontal plane perpendicular to the terminator with the group velocity of 300-400 m s-1 that corresponds to the ST speed at ionospheric heights. The high horizontal group velocity seems to contradict the accepted theory of AGW/TID propagation and indicates a need for additional investigation.Key words. Ionosphere (wave propagation) · Meteorology and atmospheric dynamics (waves and tides)
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Liu, Tong, Zhibin Yu, Zonghua Ding, Wenfeng Nie i Guochang Xu. "Observation of Ionospheric Gravity Waves Introduced by Thunderstorms in Low Latitudes China by GNSS". Remote Sensing 13, nr 20 (15.10.2021): 4131. http://dx.doi.org/10.3390/rs13204131.
Pełny tekst źródłaStreszczenie:
The disturbances of the ionosphere caused by thunderstorms or lightning events in the troposphere have an impact on global navigation satellite system (GNSS) signals. Gravity waves (GWs) triggered by thunderstorms are one of the main factors that drive short-period Travelling Ionospheric Disturbances (TIDs). At mid-latitudes, ionospheric GWs can be detected by GNSS signals. However, at low latitudes, the multi-variability of the ionosphere leads to difficulties in identifying GWs induced by thunderstorms through GNSS data. Though disturbances of the ionosphere during low-latitude thunderstorms have been investigated, the explicit GW observation by GNSS and its propagation pattern are still unclear. In this paper, GWs with periods from 6 to 20 min are extracted from band-pass filtered GNSS carrier phase observations without cycle-slips, and 0.2–0.8 Total Electron Content Unit (TECU) magnitude perturbations are observed when the trajectories of ionospheric pierce points fall into the perturbed region. The propagation speed of 102.6–141.3 m/s and the direction of the propagation indicate that the GWs are propagating upward from a certain thunderstorm at lower atmosphere. The composite results of disturbance magnitude, period, and propagation velocity indicate that GWs initiated by thunderstorms and propagated from the troposphere to the ionosphere are observed by GNSS for the first time in the low-latitude region.
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Tang, Chen, Chen i Louis. "Statistical Observation of Thunderstorm-Induced Ionospheric Gravity Waves above Low-Latitude Areas in the Northern Hemisphere". Remote Sensing 11, nr 23 (21.11.2019): 2732. http://dx.doi.org/10.3390/rs11232732.
Pełny tekst źródłaStreszczenie:
Gravity waves (GWs) generated in the lower atmosphere can propagate upwards to ionospheric height. In this study, we investigated the correlation between ionospheric GWs detected by Global Navigation Satellite System (GNSS)-derived total electron content data and thunderstorm events recorded by a local lightning-detection network in the low-latitude region of Southern China during a four-year period, from 2014 to 2017. Ionospheric GWs were detected on both thunderstorm and non-thunderstorm days. Daytime ionospheric GW activity on high-thunderstorm days showed a similar convex-function-like diurnal variation to thunderstorm activity, which is different to the concave-function-like pattern on non-thunderstorm days. Daytime ionospheric GW activity on low-thunderstorm days showed an approximately linear rising trend and was of a larger magnitude than that of high-thunderstorm days, suggesting it may be mixed by non-thunderstorm origins. Night-time enhancement of ionospheric GW activity was observed on thunderstorm days but not on non-thunderstorm days. Furthermore, ionospheric GW activity on thunderstorm days showed a positive correlation to solar activity. These findings can effectively distinguish thunderstorm-related ionospheric GWs from those of non-thunderstorm origins and provide more comprehensive knowledge of thunderstorm–ionosphere coupling in low-latitude areas.
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Khantadze, A. G., G. V. Jandieri, A. Ishimaru, T. D. Kaladze i Zh M. Diasamidze. "Electromagnetic oscillations of the Earth's upper atmosphere (review)". Annales Geophysicae 28, nr 7 (1.07.2010): 1387–99. http://dx.doi.org/10.5194/angeo-28-1387-2010.
Pełny tekst źródłaStreszczenie:
Abstract. A complete theory of low-frequency MHD oscillations of the Earth's weakly ionized ionosphere is formulated. Peculiarities of excitation and propagation of electromagnetic acoustic-gravity, MHD and planetary waves are considered in the Earth's ionosphere. The general dispersion equation is derived for the magneto-acoustic, magneto-gravity and electromagnetic planetary waves in the ionospheric E- and F-regions. The action of the geomagnetic field on the propagation of acoustic-gravity waves is elucidated. The nature of the existence of the comparatively new large-scale electromagnetic planetary branches is emphasized.
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Hocke, K., i K. Schlegel. "A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995". Annales Geophysicae 14, nr 9 (30.09.1996): 917–40. http://dx.doi.org/10.1007/s00585-996-0917-6.
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Abstract. Recent investigations of atmospheric gravity waves (AGW) and travelling ionospheric disturbances (TID) in the Earth\\'s thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS), the results are presented in the first part of the review. The second part describes the progress towards understanding the AGW/TID characteristics. It points to the AGW/TID relationship which has been recently revealed with the aid of model-data comparisons and by the application of new inversion techniques. We describe the morphology and climatology of gravity waves and their ionospheric manifestations, TIDs, from numerous new observations.
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Freeshah, Mohamed, Xiaohong Zhang, Erman Şentürk, Muhammad Arqim Adil, B. G. Mousa, Aqil Tariq, Xiaodong Ren i Mervat Refaat. "Analysis of Atmospheric and Ionospheric Variations Due to Impacts of Super Typhoon Mangkhut (1822) in the Northwest Pacific Ocean". Remote Sensing 13, nr 4 (11.02.2021): 661. http://dx.doi.org/10.3390/rs13040661.
Pełny tekst źródłaStreszczenie:
The Northwest Pacific Ocean (NWP) is one of the most vulnerable regions that has been hit by typhoons. In September 2018, Mangkhut was the 22nd Tropical Cyclone (TC) over the NWP regions (so, the event was numbered as 1822). In this paper, we investigated the highest amplitude ionospheric variations, along with the atmospheric anomalies, such as the sea-level pressure, Mangkhut’s cloud system, and the meridional and zonal wind during the typhoon. Regional Ionosphere Maps (RIMs) were created through the Hong Kong Continuously Operating Reference Stations (HKCORS) and International GNSS Service (IGS) data around the area of Mangkhut typhoon. RIMs were utilized to analyze the ionospheric Total Electron Content (TEC) response over the maximum wind speed points (maximum spots) under the meticulous observations of the solar-terrestrial environment and geomagnetic storm indices. Ionospheric vertical TEC (VTEC) time sequences over the maximum spots are detected by three methods: interquartile range method (IQR), enhanced average difference (EAD), and range of ten days (RTD) during the super typhoon Mangkhut. The research findings indicated significant ionospheric variations over the maximum spots during this powerful tropical cyclone within a few hours before the extreme wind speed. Moreover, the ionosphere showed a positive response where the maximum VTEC amplitude variations coincided with the cyclone rainbands or typhoon edges rather than the center of the storm. The sea-level pressure tends to decrease around the typhoon periphery, and the highest ionospheric VTEC amplitude was observed when the low-pressure cell covers the largest area. The possible mechanism of the ionospheric response is based on strong convective cells that create the gravity waves over tropical cyclones. Moreover, the critical change state in the meridional wind happened on the same day of maximum ionospheric variations on the 256th day of the year (DOY 256). This comprehensive analysis suggests that the meridional winds and their resulting waves may contribute in one way or another to upper atmosphere-ionosphere coupling.
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Foroodi, Zahra, Mahdi Alizadeh, Harald Schuh i Lung-Chih Tsai. "Alternative Approach for Tsunami Early Warning Indicated by Gravity Wave Effects on Ionosphere". Remote Sensing 13, nr 11 (30.05.2021): 2150. http://dx.doi.org/10.3390/rs13112150.
Pełny tekst źródłaStreszczenie:
The rapid displacement of the ocean floor during large ocean earthquakes or volcanic eruptions causes the propagation of tsunami waves on the surface of the ocean, and consequently internal gravity waves (IGWs) in the atmosphere. IGWs pierce through the troposphere and into the ionospheric layer. In addition to transferring energy to the ionosphere, they cause significant variations in ionospheric parameters, so they have considerable effects on the propagation of radio waves through this dispersive medium. In this study, double-frequency measurements of the Global Positioning System (GPS) and ionosonde data were used to determine the ionospheric disturbances and irregularities in response to the tsunami induced by the 2011 Tohoku earthquake. The critical frequency of the F2 layer (foF2) data obtained from the ionosonde data also showed clear disturbances that were consistent with the GPS observations. IGWs and tsunami waves have similar propagation properties, and IGWs were detected about 25 min faster than tsunami waves in GPS ground stations at the United States west coast, located about 7900 km away from the tsunami’s epicenter. As IGWs have a high vertical propagation velocity, and propagate obliquely into the atmosphere, IGWs can also be used for tsunami early warning. To further investigate the spatial variation in ionospheric electron density (IED), ionospheric profiles from FORMOSAT-3/COSMIC (F3/C) satellites were investigated for both reference and observation periods. During the tsunami, the reduction in IED started from 200 km and continued up to 272 km altitude. The minimum observed reduction was 2.68 × 105 el/cm3, which has happened at 222 km altitude. The IED increased up to 767 km altitude continuously, such that the maximum increase was 3.77 × 105 el/cm3 at 355 km altitude.
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Tsugawa, Takuya. "Message from the Winner". Journal of Disaster Research 18, nr 2 (1.02.2023): 83. http://dx.doi.org/10.20965/jdr.2023.p0083.
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I am very honored to receive the JDR Award for the Most Cited Paper 2022, and I am very grateful to the editorial board and staff of the Journal of Disaster Research. The paper, “Total Electron Content Observations by Dense Regional and Worldwide International Networks of GNSS,” reviews our research related to ionospheric observations using GNSS receiver networks. Since the late 1990s, the rapid development of GNSS receiver networks has made it possible to observe the ionosphere in two dimensions with high temporal and spatial resolution, revealing new features of various ionospheric phenomena. Ionospheric observation using GNSS receiver networks has become an indispensable method of observation in the space weather field. After the 2011 Tohoku Earthquake, it was revealed that various atmospheric waves excited by earthquakes and tsunamis propagated up to the ionosphere and caused ionospheric variations, suggesting the possibility of tsunami monitoring using ionospheric observations. We are also working on the standardization of ionospheric data formatting to achieve even higher spatial resolution and wider coverage of ionospheric observation using GNSS receiver networks through international cooperation. Encouraged by this award, we will continue our research and development efforts with a view to applying this technology not only to space weather but also to natural disasters such as earthquakes and tsunamis.
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ELIASSON, BENGT. "FULL-SCALE SIMULATIONS OF IONOSPHERIC LANGMUIR TURBULENCE". Modern Physics Letters B 27, nr 08 (13.03.2013): 1330005. http://dx.doi.org/10.1142/s0217984913300056.
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This brief review is devoted to full-scale numerical modeling of the nonlinear interactions between electromagnetic (EM) waves and the ionosphere, giving rise to ionospheric Langmuir turbulence. A numerical challenge in the full-scale modeling is that it involves very different length- and time-scales. While the EM waves have wavelengths of the order 100 meters, the ionospheric Langmuir turbulence involving electrostatic waves and nonlinear structures can have wavelengths below one meter. A full-scale numerical scheme must resolve these different length- and time-scales, as well as the ionospheric profile extending vertically hundreds of kilometers. To overcome severe limitations on the timestep and computational load, a non-uniform nested grid method has been devised, in which the EM wave is represented in space on a relatively coarse grid with a spacing of a few meters, while the electrostatic wave turbulence is locally resolved on a much denser grid in space at the critical layer where the turbulence occurs. Interpolation and averaging schemes are used to communicate values of the EM fields and current sources between the coarse and dense grids. In this manner, the computational load can be drastically decreased, making it possible to perform full-scale simulations that cover the different time- and space-scales. We discuss the simulation methods and how they are used to study turbulence, stimulated EM emissions, particle acceleration and heating, and the formation of artificial ionospheric plasma layers by ionospheric Langmuir turbulence.
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Milan, S. E., M. Lester, T. K. Yeoman, T. R. Robinson, M. V. Uspensky i J. P. Villain. "HF radar observations of high-aspect angle backscatter from the E-region". Annales Geophysicae 22, nr 3 (19.03.2004): 829–47. http://dx.doi.org/10.5194/angeo-22-829-2004.
Pełny tekst źródłaStreszczenie:
Abstract. We present evidence for the observation of high-aspect angle HF radar backscatter from the auroral electrojets, and describe the spectral characteristics of these echoes. Such backscatter is observed at very near ranges where ionospheric refraction is not sufficient to bring the sounding radio waves to orthogonality with the magnetic field; the frequency dependence of this propagation effect is investigated with the Stereo upgrade of the CUTLASS Iceland radar. We term the occurrence of such echoes the "high-aspect angle irregularity region" or HAIR. It is suggested that backscatter is observed at aspect angles as high as 30°, with an aspect sensitivity as low as 1dB deg–1. These echoes are distinguished from normal electrojet backscatter by having low Doppler shifts with an azimuthal dependence that appears more consistent with the direction of the convection electric field than with the expected electron drift direction. This is discussed in terms of the linear theory dispersion relation for electrojet waves. Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere)
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Xu, Xin, Ling Huang, Shun Wang, Yicai Ji, Xiaojun Liu i Guangyou Fang. "VLF/LF Lightning Location Based on LWPC and IRI Models: A Quantitative Study". Remote Sensing 14, nr 22 (16.11.2022): 5784. http://dx.doi.org/10.3390/rs14225784.
Pełny tekst źródłaStreszczenie:
The group velocity of lightning electromagnetic signals plays an important role in lightning location systems using the time difference of arrival (TDOA) method. Accurate estimation of group velocity is difficult due to the space- and time-varying properties of the Earth’s ionospheric waveguide. Besides, the analytical solution of the group velocity is difficult to obtain from the classic mode theory, especially when higher-order modes, anisotropic geomagnetic background, diffuse ionosphere profile, and propagation path segmentation are all taken into consideration. To overcome these challenges, a novel numerical method is proposed in this paper to estimate the group velocity of the lightning signal during ionospheric quiet periods. The well-known Long Wavelength Propagation Capability (LWPC) code is used to model the propagation of VLF/LF radio waves. Since LWPC uses a simplified ionospheric model which is unable to describe the subtle variations of ionospheric parameters over time and space, the IRI-2016 model is incorporated into the numerical modeling process to provide more accurate ionosphere parameters. Experimental results of a VLF/LF lightning location network are demonstrated and analyzed to show the effectiveness of our method. The proposed method is also applicable when there is a sudden ionospheric disturbance as long as the parameters of the ionosphere are obtained in real time by remote sensing methods.
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Xu, Xiang, Chen Zhou, Run Shi, Binbin Ni, Zhengyu Zhao i Yuannong Zhang. "Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes". Annales Geophysicae 34, nr 9 (21.09.2016): 815–29. http://dx.doi.org/10.5194/angeo-34-815-2016.
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Abstract. Powerful high-frequency (HF) radio waves can be used to efficiently modify the upper-ionospheric plasmas of the F region. The pressure gradient induced by modulated electron heating at ultralow-frequency (ULF) drives a local oscillating diamagnetic ring current source perpendicular to the ambient magnetic field, which can act as an antenna radiating ULF waves. In this paper, utilizing the HF heating model and the model of ULF wave generation and propagation, we investigate the effects of both the background ionospheric profiles at different latitudes in the daytime and nighttime ionosphere and the modulation frequency on the process of the HF modulated heating and the subsequent generation and propagation of artificial ULF waves. Firstly, based on a relation among the radiation efficiency of the ring current source, the size of the spatial distribution of the modulated electron temperature and the wavelength of ULF waves, we discuss the possibility of the effects of the background ionospheric parameters and the modulation frequency. Then the numerical simulations with both models are performed to demonstrate the prediction. Six different background parameters are used in the simulation, and they are from the International Reference Ionosphere (IRI-2012) model and the neutral atmosphere model (NRLMSISE-00), including the High Frequency Active Auroral Research Program (HAARP; 62.39° N, 145.15° W), Wuhan (30.52° N, 114.32° E) and Jicamarca (11.95° S, 76.87° W) at 02:00 and 14:00 LT. A modulation frequency sweep is also used in the simulation. Finally, by analyzing the numerical results, we come to the following conclusions: in the nighttime ionosphere, the size of the spatial distribution of the modulated electron temperature and the ground magnitude of the magnetic field of ULF wave are larger, while the propagation loss due to Joule heating is smaller compared to the daytime ionosphere; the amplitude of the electron temperature oscillation decreases with latitude in the daytime ionosphere, while it increases with latitude in the nighttime ionosphere; both the electron temperature oscillation amplitude and the ground ULF wave magnitude decreases as the modulation frequency increases; when the electron temperature oscillation is fixed as input, the radiation efficiency of the ring current source is higher in the nighttime ionosphere than in the daytime ionosphere.
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KALADZE, T. D., H. A. SHAH, G. MURTAZA, L. V. TSAMALASHVILI, M. SHAD i G. V. JANDIERI. "Influence of non-monochromaticity on zonal-flow generation by magnetized Rossby waves in the ionospheric E-layer". Journal of Plasma Physics 75, nr 3 (czerwiec 2009): 345–57. http://dx.doi.org/10.1017/s0022377808007678.
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AbstractThe influence of non-monochromaticity on low-frequency, large-scale zonal-flow nonlinear generation by small-scale magnetized Rossby (MR) waves in the Earth's ionospheric E-layer is considered. The modified parametric approach is used with an arbitrary spectrum of primary modes. It is shown that the broadening of the wave packet spectrum of pump MR waves leads to a resonant interaction with a growth rate of the order of the monochromatic case. In the case when zonal-flow generation by MR modes is prohibited by the Lighthill stability criterion, the so-called two-stream-like mechanism for the generation of sheared zonal flows by finite-amplitude MR waves in the ionospheric E-layer is possible. The growth rates of zonal-flow instabilities and the conditions for driving them are determined. The present theory can be used for the interpretation of the observations of Rossby-type waves in the Earth's ionosphere and in laboratory experiments.
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Kong, Qiaoli, Changsong Li, Kunpeng Shi, Jinyun Guo, Jingwei Han, Tianfa Wang, Qi Bai i Yanfei Chen. "Global Ionospheric Disturbance Propagation and Vertical Ionospheric Oscillation Triggered by the 2022 Tonga Volcanic Eruption". Atmosphere 13, nr 10 (16.10.2022): 1697. http://dx.doi.org/10.3390/atmos13101697.
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The Tonga volcano erupted on 15 January 2022, at 04:15:45 UTC, which significantly influenced the atmosphere and space environment, at the same time, an unprecedented opportunity to monitor ionospheric anomalies is provided by its powerful eruption. In current studies of traveling ionospheric disturbance (TID) triggered by the 2022 Tonga volcanic eruption, the particular phenomenon of ionospheric disturbances in various parts of the world has not been reasonably explained, and the vertical ionospheric disturbances are still not effectively detected. In this paper, we calculate the high-precision slant total electron content (STEC) from more than 3000 ground-based GPS stations distributed around the world, then we obtain the radio occultation (RO) data from near-field COSMIC-2 profiles and investigate the horizontal TID and the vertical ionospheric disturbances by the singular spectrum analysis (SSA). Horizontal TID propagation captured by GPS STEC results indicates that acoustic-gravity waves dominate the energy input at the beginning of the ionospheric disturbance with an approximate speed of 1050 m/s initially. With the dissipation of the shock energy, lamb waves become a dominant mode of ionospheric disturbances, moving at a more stable speed of about 326 m/s to a range of 16,000 km beyond the far-field. Local characteristics are evident during the disturbance, such as the ionospheric conjugation in Australia and the rapid decay of TID in Europe. The shock-Lamb-tsunami waves’ multi-fluctuation coupling is recorded successively from the COSMIC-2 RO observation data. The shock and Lamb waves can perturb the whole ionospheric altitude. In contrast, the disturbance caused by tsunami waves is much smaller than that of acoustic-gravity waves and Lamb waves. In addition, influenced by the magnetic field, the propagation speed of TID induced by Lamb waves is higher towards the northern hemisphere than towards the southern hemisphere.
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Mingaleva, G. I., V. S. Mingalev i I. V. Mingalev. "Simulation study of the high-latitude F-layer modification by powerful HF waves with different frequencies for autumn conditions". Annales Geophysicae 21, nr 8 (31.08.2003): 1827–38. http://dx.doi.org/10.5194/angeo-21-1827-2003.
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Abstract. The large-scale high-latitude F-region modification by high power radio waves is investigated using a numerical model of the convecting high-latitude ionosphere developed earlier. Simulations are performed for the point with geographic coordinates of the ionospheric heater near Tromsø, Scandinavia for autumn conditions. The calculations are made for distinct cases, in which high power waves have different frequencies, both for nocturnal and for day-time conditions. The results of modeling indicate that the frequency of HF waves ought to influence significantly the large-scale F-region modification by high power radio waves in the high-latitude ionosphere.Key words. Ionosphere (active experiments; modeling and forecasting; plasma temperature and density)
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Dumbrava, Zinaida F., Vladimir P. Sivokon, Yuriy A. Teslyuk i Sergey Y. Khomutov. "Ionosphere disturbance during cosmodrome “Vostochniy” launches". E3S Web of Conferences 62 (2018): 01008. http://dx.doi.org/10.1051/e3sconf/20186201008.
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It is known that during spacecraft launches ionospheric plasma properties are modified in the result of impact of shock-acoustic waves generated during carrier rocket supersonic motion. As a rule, investigation of ionospheric plasma variations is carried out by the signals of Global Navigation Satellite Systems GPS/GLONASS that implies ground station network. There is no such a system near the “Vostochniy” cosmodrome that makes it necessary to search for an alternative solution. One of them may be the application of ionosphere vertical and oblique sounding stations. Based on the analysis of such station data, the possibility of evaluation of ionosphere modification during “Vostochniy” cosmodrome launches is shown.
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Rahayu, R. W., M. N. Cahyadi, B. Muslim, I. M. Anjasmara, E. Y. Handoko i I. N. Muafiry. "Three-dimensional Tomography of Coseismic Ionospheric Disturbances from the 2016 West Sumatera Earthquake". IOP Conference Series: Earth and Environmental Science 936, nr 1 (1.12.2021): 012022. http://dx.doi.org/10.1088/1755-1315/936/1/012022.
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Abstract Global Navigation Satellite System (GNSS) is a navigation system that uses satellite signals to determine its position, which consists of several satellites arranged in a constellation system. GNSS transmits signals to receivers on Earth. The GNSS receiver determines the user’s position, speed, and time by processing the signals transmitted by the satellites. The initial purpose of launching the GNSS was for navigation purposes, but along with its development, GNSS can be used for the purposes of observing deformation of the earth’s crust and in studying the atmosphere. The delayed wave data when passing through the ionosphere can be used to obtain Total Electron Content (TEC) values which then used to study ionospheric disturbances. Ionospheric disturbances are caused by various phenomena, the most common one is the ionospheric disturbances caused by the induction of acoustic and gravitational waves excited by co seismic crustal motions from large earthquakes. Ionospheric disturbances that happened before an earthquake are called Pre-seismic Ionospheric Disturbances and those that occur after an earthquake are called Co-seismic Ionospheric Disturbances (CID). Most studies of ionospheric disturbances still provide information on the timing and value of TEC anomalies in 2D form. Therefore, in this study, a 3D ionosphere profile modelling using computed 3D tomography will be carried out. The 3D information provided is in the form of time, ionosphere altitude and TEC anomaly value by utilizing GNSS data. The TEC anomaly value is obtained from the calculation of linear combination of the ionosphere. This study aims to obtain a spatial and temporal analysis of the CID caused by the West Sumatra Earthquake on March 2, 2016.
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Blaunstein, N. "Diffusion spreading of middle-latitude ionospheric plasma irregularities". Annales Geophysicae 13, nr 6 (30.06.1995): 617–26. http://dx.doi.org/10.1007/s00585-995-0617-7.
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Abstract. In contrast to the way that the spreading of irregularities in a plasma is usually considered, the diffusion spreading of irregularities stretched along the geomagnetic field B is examined using a three-dimensional rigorous numerical model of quasi-neutral diffusion in the presence of a magnetic field, in conjunction with the actual height variations of the diffusion and conductivity tensors in the ionosphere. A comparison with the earlier constructed approximate model of unipolar diffusion was made. As in the previous case, the same peculiarities of irregularity spreading in the inhomogeneous background ionospheric plasma were observed. The accuracy of the approximate model for describing the process of spreading of anisotropic ionospheric irregularities is established. Time relaxation effects of real heating-induced ionospheric irregularities on their scale transverse to B are presented using the approximate analytical model for the case of a quasi-homogeneous ionospheric plasma. The calculated results have a vivid physical meaning and can be directly compared with experimental data on the radiophysical observations of artificial heating-induced irregularities created by powerful radio waves in the ionosphere.
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Menk, F. W., T. K. Yeoman, D. M. Wright, M. Lester i F. Honary. "High-latitude observations of impulse-driven ULF pulsations in the ionosphere and on the ground". Annales Geophysicae 21, nr 2 (28.02.2003): 559–76. http://dx.doi.org/10.5194/angeo-21-559-2003.
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Abstract. We report the simultaneous observation of 1.6–1.7 mHz pulsations in the ionospheric F-region with the CUTLASS bistatic HF radar and an HF Doppler sounder, on the ground with the IMAGE and SAMNET magnetometer arrays, and in the upstream solar wind. CUTLASS was at the time being operated in a special mode optimized for high resolution studies of ULF waves. A novel use is made of the ground returns to detect the ionospheric signature of ULF waves. The pulsations were initiated by a strong, sharp decrease in solar wind dynamic pressure near 09:28 UT on 23 February 1996, and persisted for some hours. They were observed with the magnetometers over 20° in latitude, coupling to a field line resonance near 72° magnetic latitude. The magnetic pulsations had azimuthal m numbers ~ -2, consistent with propagation away from the noon sector. The radars show transient high velocity flows in the cusp and auroral zones, poleward of the field line resonance, and small amplitude 1.6–1.7 mHz F-region oscillations across widely spaced regions at lower latitudes. The latter were detected in the radar ground scatter returns and also with the vertical incidence Doppler sounder. Their amplitude is of the order of ± 10 ms-1. A similar perturbation frequency was present in the solar wind pressure recorded by the WIND spacecraft. The initial solar wind pressure decrease was also associated with a decrease in cosmic noise absorption on an imaging riometer near 66° magnetic latitude. The observations suggest that perturbations in the solar wind pressure or IMF result in fast compressional mode waves that propagate through the magnetosphere and drive forced and resonant oscillations of geomagnetic field lines. The compressional wave field may also stimulate ionospheric perturbations. The observations demonstrate that HF radar ground scatter may contain important information on small-amplitude features, extending the scope and capability of these radars to track features in the ionosphere.Key words. Ionosphere (Ionosphere-magnetosphere interactions; ionospheric disturbances) – Magnetospheric physics (MHD waves and instabilities)
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Arnold, N. F., T. B. Jones, T. R. Robinson, A. J. Stocker i J. A. Davies. "Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data". Annales Geophysicae 16, nr 10 (31.10.1998): 1392–99. http://dx.doi.org/10.1007/s00585-998-1392-z.
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Abstract. Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.Key words. Ionosphere (ionosphere – atmosphere interactions) · Meteorology and atmospheric dynamics (thermospheric dynamics) · Radio science (ionospheric propagations)