Journal articles on the topic 'Ionospheric physics'
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Chernogor, L. F. "Physics of geospace storms." Kosmìčna nauka ì tehnologìâ 27, no. 1 (2021): 3–77. http://dx.doi.org/10.15407/knit2021.01.003.
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A review of our knowledge about the coupling of solar-terrestrial processes, manifestations of geospace storms, and variations in space weather is presented. Space weather effects are analyzed within the system paradigm concept. The system where geospace storms occur is a Sun–interplanetary medium–magnetosphere–ionosphere–atmosphere–Earth (interior spheres) aggregate (SIMMIAE). An early twenty-first- century geospace superstorm that occurred on November 7 – 10, 2004, is examined in detail. Clustered instrument observations of this storm effects are presented. The investigation of the physical effects of geospace storms is noted to be the most important field of study in space geophysics. The problem of subsystem coupling in the SIMMIAE system during a geospace storm is interdisciplinary in nature. Its solution requires an application of the system approach. The problem has a multifactor character. The subsystem response is determined by the simultaneous (synergetic) impact of a few disturbing factors. It is important to note that the SIMMIAE is an open, nonlinear, and nonstationary system. Within it, direct coupling and feedback processes, positive and negative linkages operate. Due to the myriads of manifestations of geospace storms, because of the unique nature of each storm, the investigation of occurring physical effects is far from complete. In addition to a thorough investigation of the storm’s physical effects, there is an urgent need to model and forecast the storms adequately and in detail. The solution to these problems will facilitate the survival and steady progress of our civilization, relying more and more on new state-of-the-art technology. The more technologically reliant our society is, the more vulnerable the civilization's infrastructure to solar and geospace storm impacts becomes. A classification of geostorms based on Akasofu's epsilon parameter has been advanced. Six types of geostorm have been introduced, and a geostorm index has been suggested. A classification of ionospheric storms and disturbances based on the magnitude of variations in the peak density of the F2 layer has been suggested. Five types of the ionospheric storm have been introduced. An ionospheric index characterizing the intensity of negative and positive ionospheric storms has been suggested. A classification of ionospheric storms and disturbances based on the magnitude of variations in the lower-ionosphere electron density has been proposed. Six types of the positive ionospheric storm have been introduced. The appropriate ionospheric index has been suggested. The physics-based model of the evolution of each group of ionospheric storms and disturbances has been determined. The linkages among magnetic, ionospheric, and atmospheric storms, as well as electric field disturbances, have been shown.
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Janhunen, P. "On the possibility of using an electromagnetic ionosphere in global MHD simulations." Annales Geophysicae 16, no. 4 (April 30, 1998): 397–402. http://dx.doi.org/10.1007/s00585-998-0397-y.
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Abstract. Global magnetohydrodynamic (MHD) simulations of the Earth's magnetosphere must be coupled with a dynamical ionospheric module in order to give realistic results. The usual approach is to compute the field-aligned current (FAC) from the magnetospheric MHD variables at the ionospheric boundary. The ionospheric potential is solved from an elliptic equation using the FAC as a source term. The plasma velocity at the boundary is the E × B velocity associated with the ionospheric potential. Contemporary global MHD simulations which include a serious ionospheric model use this method, which we call the electrostatic approach in this paper. We study the possibility of reversing the flow of information through the ionosphere: the magnetosphere gives the electric field to the ionosphere. The field is not necessarily electrostatic, thus we will call this scheme electromagnetic. The electric field determines the horizontal ionospheric current. The divergence of the horizontal current gives the FAC, which is used as a boundary condition for MHD equations. We derive the necessary formulas and discuss the validity of the approximations necessarily involved. It is concluded that the electromagnetic ionosphere-magnetosphere coupling scheme is a serious candidate for future global MHD simulators, although a few problem areas still remain. At minimum, it should be investigated further to discover whether there are any differences in the simulation using the electrostatic or the electromagnetic ionospheric coupling.Key words. Ionosphere · Ionosphere-magnetosphere interaction · Magnetospheric physics · Magnetosphere-ionosphere interaction · Space plasma physics · Numerical simulation studies
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Li, Minchi, Yu Liu, and Jiuhou Lei. "Design and fabrication of a magnetic filter source to produce ionospheric-like plasma." AIP Advances 13, no. 4 (April 1, 2023): 045208. http://dx.doi.org/10.1063/5.0126931.
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Generation of ionospheric-like plasma is important for laboratory investigations of ionospheric physics. In this work, the design and fabrication of a magnetic filter source for the ground simulation of ionospheric-like low density plasma are presented. Four groups of permanent magnets were placed at different regions to form a magnetic filter configuration, and filaments were used to produce the low-density plasmas. Operating with adjustable plasma source conditions can generate plasmas with variable density and energy similar to those of the ionosphere, which were measured using tailor-made plasma diagnostic tools. The results indicate that homogeneous distributed low-density plasmas on the order of 105 cm−3 were produced using the plasma source. In addition, ion and electron energies that are similar to those of the actual ionosphere were also achieved. Based on the plasma source, ionospheric plasma physics can be investigated in a controlled manner in the laboratory. In addition, it can also be extended to the calibration and testing of payloads for ionospheric plasma measurement before launching.
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SOJKA, J. J. "Ionospheric Physics." Reviews of Geophysics 29, S2 (January 1991): 1166–86. http://dx.doi.org/10.1002/rog.1991.29.s2.1166.
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Mitchell, C. N., I. K. Walker, S. E. Pryse, I. Kersley, I. W. McCrea, and T. B. Jones. "<i>Letter to the Editor:</i> First complementary observations by ionospheric tomography, the EISCAT Svalbard radar and the CUTLASS HF radar." Annales Geophysicae 16, no. 11 (November 30, 1998): 1519–22. http://dx.doi.org/10.1007/s00585-998-1519-2.
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Abstract. Experimental results are presented from ionospheric tomography, the EISCAT Svalbard radar and the CUTLASS HF radar. Tomographic measurements on 10 October 1996, showing a narrow, field-aligned enhancement in electron density in the post-noon sector of the dayside auroral zone, are related to a temporal increase in the plasma concentration observed by the incoherent scatter radar in the region where the HF radar indicated a low velocity sunwards convection. The results demonstrate the complementary nature of these three instruments for polar-cap ionospheric studies.Key words. Ionosphere · Auroral ionosphere · Polar ionosphere · Radio science (ionospheric physics)
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Ясюкевич, Юрий, Yury Yasyukevich, Илья Живетьев, and Ilya Zhivetiev. "Using network technology for studying the ionosphere." Solnechno-Zemnaya Fizika 1, no. 3 (September 27, 2015): 21–27. http://dx.doi.org/10.12737/10545.
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One of the key problems of ionosphere physics is the coupling between different ionospheric regions. We apply networks technology for studying the coupling of changing ionospheric dynamics in different regions. We used data from global ionosphere maps (GIM) of total electron content (TEC) produced by CODE for 2005–2010. Distribution of cross-correlation function maxima of TEC variations is not simple. This distribution allows us to reveal two levels of ionosphere coupling: «strong» (r>0.9) and «weak» (r>0.72). The ionosphere of the Arctic region upper 50° magnetic latitude is characterized by a «strong» coupling. In the Southern hemisphere, a similar region is bigger. «Weak» coupling is typical for the whole Southern hemisphere. In North America there is an area where TEC dynamics is «strongly» correlated inside and is not correlated with other ionospheric regions.
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Jee, Geonhwa. "Fundamentals of Numerical Modeling of the Mid-latitude Ionosphere." Journal of Astronomy and Space Sciences 40, no. 1 (March 2023): 11–18. http://dx.doi.org/10.5140/jass.2023.40.1.11.
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The ionosphere is one of the key components of the near-Earth’s space environment and has a practical consequence to the human society as a nearest region of the space environment to the Earth. Therefore, it becomes essential to specify and forecast the state of the ionosphere using both the observations and numerical models. In particular, numerical modeling of the ionosphere is a prerequisite not only for better understanding of the physical processes occurring within the ionosphere but also for the specification and forecast of the space weather. There are several approaches for modeling the ionosphere, including data-based empirical modeling, physics-based theoretical modeling and data assimilation modeling. In this review, these three types of the ionospheric model are briefly introduced with recently available models. And among those approaches, fundamental aspects of the physics-based ionospheric model will be described using the basic equations governing the mid-latitude ionosphere. Then a numerical solution of the equations will be discussed with required boundary conditions.
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Nielsen, E., and F. Honary. "Observations of ionospheric flows and particle precipitation following a Sudden Commencement." Annales Geophysicae 18, no. 8 (August 31, 2000): 908–17. http://dx.doi.org/10.1007/s00585-000-0908-y.
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Abstract. On May 4, 1998, at 0227 UT an interplanetary shock crossed the WIND spacecraft, and half an hour later a Sudden Commencement occurred. Coinciding with the Sudden Commencement a rapid intensification of the flux of particle precipitation into the ionosphere was observed. Evidence is presented that the ionospheric electric fields were influenced by the associated dynamic variations of the ionospheric conductivities. Following the initial phase the ionospheric flow speeds increased rapidly over the next 20 min to more than 2000 m/s, in agreement with an increased effective coupling of the solar wind energy to the magnetosphere following the interplanetary shock that caused the Sudden Commencement. These strong flows were meandering in latitude, a type of plasma flow modulation that has been reported before to occur during Omega band events: a string of alternating field-aligned currents propagating eastward. The riometer absorption was found to be at a minimum in regions associated with outward directed field aligned currents. The riometer absorption regions (the regions of particle precipitation) were drifting with E × B drift speed of the ionospheric electrons.Key words: Interplanetary physics (interplanetary shocks) - Ionosphere (electric fields and currents) - Magnetospheric physics (energetic particles, precipitating)
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Trigunait, A., M. Parrot, S. Pulinets, and F. Li. "Variations of the ionospheric electron density during the Bhuj seismic event." Annales Geophysicae 22, no. 12 (December 22, 2004): 4123–31. http://dx.doi.org/10.5194/angeo-22-4123-2004.
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Abstract. Ionospheric perturbations by natural geophysical activity, such as volcanic eruptions and earthquakes, have been studied since the great Alaskan earthquake in 1964. Measurements made from the ground show a variation of the critical frequency of the ionosphere layers before and after the shock. In this paper, we present an experimental investigation of the electron density variations around the time of the Bhuj earthquake in Gujarat, India. Several experiments have been used to survey the ionosphere. Measurements of fluctuations in the integrated electron density or TEC (Total Electron Content) between three satellites (TOPEX-POSEIDON, SPOT2, SPOT4) and the ground have been done using the DORIS beacons. TEC has been also evaluated from a ground-based station using GPS satellites, and finally, ionospheric data from a classical ionospheric sounder located close to the earthquake epicenter are utilized. Anomalous electron density variations are detected both in day and night times before the quake. The generation mechanism of these perturbations is explained by a modification of the electric field in the global electric circuit induced during the earthquake preparation. Key words. Ionosphere (ionospheric disturbances) – Radio Science (ionospheric physics) – History of geophysics (seismology)
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Joshi, Lalit Mohan, Samireddipelle Sripathi, Muppidi Ravi Kumar, and Esfhan Alam Kherani. "Simulating the dependence of seismo-ionospheric coupling on the magnetic field inclination." Annales Geophysicae 36, no. 1 (January 10, 2018): 25–35. http://dx.doi.org/10.5194/angeo-36-25-2018.
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Abstract. Infrasound generated during a seismic event upon reaching the ionospheric heights possesses the ability to perturb the ionosphere. Detailed modelling investigation considering 1-D dissipative linear dynamics, however, indicates that the magnitude of ionospheric perturbation strongly depends on the magnetic field inclination. Physics-based SAMI2 model codes have been utilized to simulate the ionosphere perturbations that are generated due to the action of the vertical wind perturbations associated with the seismic infrasound. The propagation of the seismic energy and the vertical wind perturbations associated with the infrasound in the model has been considered to be symmetric about the epicentre in the north–south directions. Ionospheric response to the infrasound wind, however, has been highly asymmetric in the model simulation in the north–south directions. This strong asymmetry is related to the variation in the inclination of the Earth's magnetic field north and south of the epicentre. Ionospheric monitoring generally provides an efficient tool to infer the crustal propagation of the seismic energy. However, the results presented in this paper indicate that the mapping between the crustal process and the ionospheric response is not a linear one. These results also imply that the lithospheric behaviour during a seismic event over a wide zone in low latitudes can be estimated through ionospheric imaging only after factoring in the magnetic field geometry. Keywords. Atmospheric composition and structure (pressure, density, and temperature) – history of geophysics (atmospheric sciences) – ionosphere (ionosphere–atmosphere interactions)
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Lockwood, M., and S. K. Morley. "A numerical model of the ionospheric signatures of time-varying magneticreconnection: I. ionospheric convection." Annales Geophysicae 22, no. 1 (January 1, 2004): 73–91. http://dx.doi.org/10.5194/angeo-22-73-2004.
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Abstract. This paper presents a numerical model for predicting the evolution of the pattern of ionospheric convection in response to general time-dependent magnetic reconnection at the dayside magnetopause and in the cross-tail current sheet of the geomagnetic tail. The model quantifies the concepts of ionospheric flow excitation by Cowley and Lockwood (1992), assuming a uniform spatial distribution of ionospheric conductivity. The model is demonstrated using an example in which travelling reconnection pulses commence near noon and then move across the dayside magnetopause towards both dawn and dusk. Two such pulses, 8min apart, are used and each causes the reconnection to be active for 1min at every MLT that they pass over. This example demonstrates how the convection response to a given change in the interplanetary magnetic field (via the reconnection rate) depends on the previous reconnection history. The causes of this effect are explained. The inherent assumptions and the potential applications of the model are discussed. Key words. Ionosphere (ionosphere-magnetosphere interactions; plasma convection) – Magnetospheric physics (magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)
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Polozov, Yuryi, and Oksana Mandrikova. "Regression analysis of ionospheric disturbance factors." E3S Web of Conferences 196 (2020): 02025. http://dx.doi.org/10.1051/e3sconf/202019602025.
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Investigation of interactions of the near-planet space parameters, Earth magnetic field and ionospheric parameters are of interest in the tasks of solar-terrestrial physics and applied researches related to space weather. Ionosphere is one of the important factors of space weather. Functioning of modern ground- and satellite-based engineering facilities depends much on its state. The paper makes a statistical estimate and analyzes complex effect from interplanetary magnetic field parameters, solar radiation and geomagnetic data on ionospheric disturbance development. Ionospheric disturbances were estimated on the basis of the method developed by the authors. The method applies wavelet transform and adaptive thresholds. The most significant factors of ionospheric disturbance occurrences were detected during the investigation and their significance was evaluated.
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Yang, Li-Xia, Chao Liu, Qing-Liang Li, and Yu-Bo Yan. "Electromagnetic wave propagation characteristics of oblique incidence nonlinear ionospheric Langmuir disturbance." Acta Physica Sinica 71, no. 6 (2022): 064101. http://dx.doi.org/10.7498/aps.71.20211204.
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Based on the generalized Zakharov model, a numerical model of electromagnetic wave propagating in the ionosphere at different angles is established by combining the finite difference time domain (FDTD) method of obliquely incident plasma with the double hydrodynamics equation and through equivalently transforming the two-dimensional Maxwell equation into one-dimensional Maxwell equation and the plasma hydrodynamics equation. In this paper. the dominant equation of Z-wave in obliquely incident nonlinear ionospheric plasma having been analyzed and deduced, the FDTD algorithm suitable for calculating the propagation characteristics of ionospheric electromagnetic wave is deduced. The simulation results prove the accuracy and effectiveness of this method for the Langmuir disturbance caused by electromagnetic wave heating the ionosphere at a small inclination angle. The results show that under small angle incidence, the high-power high-frequency electromagnetic wave excites the Langmuir wave near the O-wave reflection point in the ionospheric plasma. At the same time, the wave particle interaction causes the O-wave to convert into Z-wave and propagate into the higher region of the ionosphere. In this work, the electromagnetic wave propagation characteristics are further studied based on ionospheric plasma, which is helpful in laying the foundation of numerical algorithm for comprehensively and in depth analyzing the influence of ionospheric Langmuir disturbance on ionospheric radio wave propagation characteristics.
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Marshall, R. A., and F. W. Menk. "Observations of Pc 3-4 and Pi 2 geomagnetic pulsations in the low-latitude ionosphere." Annales Geophysicae 17, no. 11 (November 30, 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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Abdu, M. A. "Low latitude ionospheric physics." Journal of Atmospheric and Terrestrial Physics 57, no. 13 (November 1995): 1676. http://dx.doi.org/10.1016/0021-9169(95)90050-0.
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Farah, Ashraf. "Nequick2 Model Behaviour for Global Ionospheric Delay Mitigation During Solar Cycle-24." Artificial Satellites 53, no. 4 (December 1, 2018): 127–39. http://dx.doi.org/10.2478/arsa-2018-0010.
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Abstract The ionospheric delay is the major current source of potential range delay for single-frequency GNSS users. Different ionospheric delay mitigation methods have been developed to mitigate the ionospheric delay effects for single-frequency users. The NeQuick is a quick-run ionospheric electron density model particularly designed for trans-ionospheric propagation applications developed at the Aeronomy and Radio propagation Laboratory of the Abdus Salam International Centre for Theoretical Physics (ICTP), Italy. NeQuick2 is the latest version of the NeQuick ionosphere electron density model. NeQuick model been used by the European Space Agency (ESA) European Geostationary Navigation Overlay Service (EGNOS) project for assessment analysis and has been adopted for single-frequency positioning applications in the frame work of the European satellite navigation system (Galileo). NeQuick2 model adopted modifications related to the modeling of the F1 layer peak electron density, height and thickness parameter. Also, a new formulation of the shape parameter k has been adopted. This paper presents a global study for the behavior of the modified NeQuick2 model. The zenith ionospheric range delay correction by the model has been assessed using the highly accurate IGS-Global Ionospheric Maps (IGS-GIMs) for two different-latitude stations (Aswan, Egypt) (low-latitude) (24.1o N) and (Helsinki, Finland) (high-latitude) (60.2o N). The study was carried out during current solar cycle-24 over three different months that each of them reflects a different state of solar activity. It can be concluded that NeQuick2 model globally presents overestimation for ionospheric delay for quiet and medium ionospheric activity states respectively, while the model presents underestimation for high activity state of the ionosphere layer.
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Pokhotelov, O. A., M. Parrot, E. N. Fedorov, V. A. Pilipenko, V. V. Surkov, and V. A. Gladychev. "Response of the ionosphere to natural and man-made acoustic sources." Annales Geophysicae 13, no. 11 (November 30, 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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Moen, J., S. T. Berry, L. Kersley, and B. Lybekk. "Probing discrete auroral arcs by ionospheric tomography." Annales Geophysicae 16, no. 5 (May 31, 1998): 574–82. http://dx.doi.org/10.1007/s00585-998-0574-z.
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Abstract. Optical observations of 557.7 nm and 630.0 nm emissions from discrete auroral arcs in the post-noon sector have been related to localised field-aligned enhancements in the spatial distribution of E- and F-layer electron density respectively seen in images reconstructed by ionospheric tomography. Results from two case studies are presented in which meridian scanning photometer and all-sky camera observations on Svalbard have been compared to electron-density structures found by tomographic inversion of measurements made by reception of radio signals at a chain of four stations at high latitude. The F-layer features are long-lived and show exact correspondence to the red-line emissions. Transient arcs in green-line intensity result in E-region structures that are resolved in one case, but not in another where the dynamic auroral forms are separated by less than one degree of latitude. The signature of an inverted-V precipitation event is clearly evident in one example.Key words. Ionosphere (Auroral ionosphere) · Magnetospheric physics (Auroral phenomena) · Radio science (Ionospheric physics)
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Pushin, V. F., and L. F. Chernogor. "A SYNTHESIS OF TEMPORAL VARIATIONS IN DOPPLER SPECTRA RECORDED AT A QUASI-VERTICAL INCIDENCE BY THE HF DOPPLER RADAR WITH SPACED RECEIVERS." Radio physics and radio astronomy 26, no. 3 (September 14, 2021): 211–23. http://dx.doi.org/10.15407/rpra26.03.211.
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Purpose: The ionospheric channel is widely used for the communication, radio navigation, radar, direction finding, radio astronomy, and remote radio probing systems. The radio channel parameters are characterized by nonstationarity due to the dynamic processes in the ionosphere, and therefore their study is one of the topical problems of space radio physics and earth-space radio physics of geospace. This work aims at presenting the results of synthesis of temporal variations in the Doppler spectra obtained by the Doppler probing of the ionosphere at vertical and quasi-vertical incidence. Design/methotology/approach: One of the most effective methods of ionosphere research is the Doppler sounding technique. It has a high time resolution (about 10 s), a Doppler shift resolution (0.01–0.1 Hz), and the accuracy of Doppler shift measurements (~0.01 Hz) that permits monitoring the variations in the ionospheric electron density (10–4–10–3) or the study of the ionospheric plasma motion with the speed of 0.1-1 m/s and greater. The solution of the inverse radio physical problem, consisting in determination of the ionosphere parameters, often means solving the direct radio physical problem. In the Doppler sounding technique, it belongs with the construction of variations in Doppler spectra and comparing them with the Doppler spectra measurements. Findings: For the radio wave ordinary component, three echoes being produced by three rays are observed. Influence of the geomagnetic fi eld and large horizontal gradients in the electron density of δ≥10 % give rise to complex ray structures with caustic surfaces. The ionospheric disturbances traveling along the magnetic meridian form the skip zones. The longitudinal and transverse displacement of the ray reflection point attains a few tens of kilometers along the vil. Haidary to vil. Hrakove quasi-vertical radiowave propagation path, for which the great circle range is 50 km. For the vertical incidence, the signal azimuth at the receiver coincides with the traveling ionospheric disturbance azimuth. The synthesis of temporal variations in the HF Doppler spectra has been made and compared with the temporal variations in the Doppler spectra recorded with the V. N. Karazin Kharkiv National University radar. The estimate of δ=15 % obtained confirms the existence of large horizontal gradients in electron density. Conclusions: Temporal variations in Doppler spectra and in azimuth have been calculated for the vertical and quasi-vertical incidence with allowance for large horizontal gradients of the electron density caused by traveling ionospheric disturbances. Key words: ionosphere, Doppler sounding at oblique incidence, synthesis of temporal variations in HF Doppler spectra, traveling ionospheric disturbances, electron density
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Zhima, Zeren, Rui Yan, Jian Lin, Qiao Wang, Yanyan Yang, Fangxian Lv, Jianping Huang, et al. "The Possible Seismo-Ionospheric Perturbations Recorded by the China-Seismo-Electromagnetic Satellite." Remote Sensing 14, no. 4 (February 14, 2022): 905. http://dx.doi.org/10.3390/rs14040905.
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Driven by the objective of earthquake disaster prevention and mitigation, China launched the Zhangheng mission to build a stereoscopic earthquake monitoring system from the lithosphere to space. This report briefly presents the possible seismic ionospheric disturbances recorded by the first probe of the Zhangheng mission, which is known as the China-Seismo-Electromagnetic Satellite (CSES). The routine data preprocessing and seismo-ionospheric information analysis methods are briefly introduced. The possible seismo-ionospheric disturbances that appeared during the strong shallow earthquakes (with a magnitude over 7 and a depth shallower than 30 km) are analyzed by using CSES and other multi-source data. Investigating seismo-ionospheric mechanisms requires multidisciplinary knowledge involving geophysics, atmosphere/ionosphere physics, geochemistry/atmospheric chemistry, etc. We state that the results from the CSES scientific application center are preliminary, calling for international scientists to contribute to the seismo-ionospheric perturbation phenomena, which is one of the most challenging scientific problems.
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Palmroth, M., P. Janhunen, T. I. Pulkkinen, and H. E. J. Koskinen. "Ionospheric energy input as a function of solar wind parameters: global MHD simulation results." Annales Geophysicae 22, no. 2 (January 1, 2004): 549–66. http://dx.doi.org/10.5194/angeo-22-549-2004.
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Abstract. We examine the global energetics of the solar wind magnetosphere-ionosphere system by using the global MHD simulation code GUMICS-4. We show simulation results for a major magnetospheric storm (6 April 2000) and a moderate substorm (15 August 2001). The ionospheric dissipation is investigated by determining the Joule heating and precipitation powers in the simulation during the two events. The ionospheric dissipation is concentrated largely on the dayside cusp region during the main phase of the storm period, whereas the nightside oval dominates the ionospheric dissipation during the substorm event. The temporal variations of the precipitation power during the two events are shown to correlate well with the commonly used AE-based proxy of the precipitation power. The temporal variation of the Joule heating power during the substorm event is well-correlated with a commonly used AE-based empirical proxy, whereas during the storm period the simulated Joule heating is different from the empirical proxy. Finally, we derive a power law formula, which gives the total ionospheric dissipation from the solar wind density, velocity and magnetic field z-component and which agrees with the simulation result with more than 80% correlation. Key words. Ionosphere (modeling and forecasting) – Magnetospheric physics (magnetosphere-ionosphere interactions; storms and substorms)
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Chernigovskaya, Marina, Boris Shpynev, Denis Khabituev, Konstantin Ratovsky, Anastasiya Belinskaya, Aleksandr Stepanov, Vasily Bychkov, Svetlana Grigor'eva, Valery Panchenko, and Jens Mielich. "Studying the response of the mid-latitude ionosphere of the Northern Hemisphere to magnetic storms in March 2012." Solnechno-Zemnaya Fizika 8, no. 4 (December 24, 2022): 46–56. http://dx.doi.org/10.12737/szf-84202204.
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We have studied variations in ionospheric and geomagnetic parameters in the Northern Hemisphere during a series of magnetic storms in March 2012 by analyzing data from the Eurasian mid-latitude ionosonde chain, mid- and high-latitude chains of magnetometers of the global network INTERMAGNET. We have confirmed manifestations of the longitude inhomogeneity of ionospheric effects, which is associated with the irregular structure of the longitudinal variability of geomagnetic field components. The complex physics of the long magnetically disturbed period in March 2012 with switching between positive and negative phases of the ionospheric storm in the same period of the magnetic storm for different spatial regions is emphasized. The change in the effects of the ionospheric storm during this period might have been associated with the superposition in the mid-latitude region of the competing processes affecting the ionospheric ionization whose sources were in the auroral and equatorial ionosphere. We have compared the scenarios for the development of ionospheric disturbances under equinox conditions during magnetic storms in March 2012, October 2016, and March 2015.
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Chernigovskaya, Marina, Boris Shpynev, Denis Khabituev, Konstantin Ratovsky, Anastasiya Belinskaya, Aleksandr Stepanov, Vasily Bychkov, Svetlana Grigor'eva, Valery Panchenko, and Jens Mielich. "Studying the response of the mid-latitude ionosphere of the Northern Hemisphere to magnetic storms in March 2012." Solar-Terrestrial Physics 8, no. 4 (December 24, 2022): 44–54. http://dx.doi.org/10.12737/stp-84202204.
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We have studied variations in ionospheric and geomagnetic parameters in the Northern Hemisphere during a series of magnetic storms in March 2012 by analyzing data from the Eurasian mid-latitude ionosonde chain, mid- and high-latitude chains of magnetometers of the global network INTERMAGNET. We have confirmed manifestations of the longitude inhomogeneity of ionospheric effects, which is associated with the irregular structure of the longitudinal variability of geomagnetic field components. The complex physics of the long magnetically disturbed period in March 2012 with switching between positive and negative phases of the ionospheric storm in the same period of the magnetic storm for different spatial regions is emphasized. The change in the effects of the ionospheric storm during this period might have been associated with the superposition in the mid-latitude region of the competing processes affecting the ionospheric ionization whose sources were in the auroral and equatorial ionosphere. We have compared the scenarios for the development of ionospheric disturbances under equinox conditions during magnetic storms in March 2012, October 2016, and March 2015.
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Parker, James A. D., S. Eleri Pryse, Natasha Jackson-Booth, and Rachel A. Buckland. "Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC." Annales Geophysicae 36, no. 1 (January 25, 2018): 125–38. http://dx.doi.org/10.5194/angeo-36-125-2018.
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Abstract. The main ionospheric trough is a large-scale spatial depletion in the electron density distribution at the interface between the high- and mid-latitude ionosphere. In western Europe it appears in early evening, progresses equatorward during the night, and retreats rapidly poleward at dawn. It exhibits substantial day-to-day variability and under conditions of increased geomagnetic activity it moves progressively to lower latitudes. Steep gradients on the trough-walls on either side of the trough minimum, and their variability, can cause problems for radio applications. Numerous studies have sought to characterize and quantify the trough behaviour. The Electron Density Assimilative Model (EDAM) models the ionosphere on a global scale. It assimilates observations into a background ionosphere, the International Reference Ionosphere 2007 (IRI2007), to provide a full 3-D representation of the ionospheric plasma distribution at specified times and days. This current investigation studied the capability of EDAM to model the ionosphere in the region of the main trough. Total electron content (TEC) measurements from 46 GPS stations in western Europe from September to December 2002 were assimilated into EDAM to provide a model of the ionosphere in the trough region. Vertical electron content profiles through the model revealed the trough and the detail of its structure. Statistical results are presented of the latitude of the trough minimum, TEC at the minimum and of other defined parameters that characterize the trough structure. The results are compared with previous observations made with the Navy Ionospheric Monitoring System (NIMS), and reveal the potential of EDAM to model the large-scale structure of the ionosphere. Keywords. Ionosphere (midlatitude ionosphere; modelling and forecasting) – radio science (ionospheric physics)
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Bojilova, Rumiana, and Plamen Mukhtarov. "Analysis of the Ionospheric Response to Sudden Stratospheric Warming and Geomagnetic Forcing over Europe during February and March 2023." Universe 9, no. 8 (July 28, 2023): 351. http://dx.doi.org/10.3390/universe9080351.
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A study of the behavior of the main characteristics of the ionosphere over Europe during the 26–28 February 2023 ionospheric storm was carried out in this present work. The additional influence of sudden stratospheric warming on the ionosphere was considered. The behavior of the critical frequency of the ionosphere foF2 (characterizing the maximum electron density), the peak height of the F2-layer (hmF2), and Total Electron Content (TEC) were investigated through their relative deviations from the quiet conditions. The behavior of the TEC over Europe showed the geographic latitudinal dependence of the response. The variability in the ionospheric critical frequency was represented by the data of 10 ionospheric stations for vertical sounding located in two groups: (i) near the prime meridian and (ii) near the 25° E meridian. Some differences were found in the response compared to the TEC response, which was explained by the different responses of the top maximum region and bottom maximum region. The peak height of the F2 layer varied strongly during the storm, which was due to the forced drift of ionospheric plasma induced by additional electric fields. The present detailed analysis of the ionospheric response shows that the considered storm exhibited characteristic features inherent in the winter season but with some manifestations of reactions in equinox conditions.
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McWilliams, K. A., T. K. Yeoman, and G. Provan. "A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar." Annales Geophysicae 18, no. 4 (April 30, 2000): 445–53. http://dx.doi.org/10.1007/s00585-000-0445-8.
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Abstract. Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed ionospheric flow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic field lines, which occur during episodes of magnetic flux transfer to the terrestrial magnetosphere - flux transfer events or FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetary magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in different regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)
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Leyser, Thomas B., H. Gordon James, Björn Gustavsson, and Michael T. Rietveld. "Evidence of <i>L</i>-mode electromagnetic wave pumping of ionospheric plasma near geomagnetic zenith." Annales Geophysicae 36, no. 1 (February 21, 2018): 243–51. http://dx.doi.org/10.5194/angeo-36-243-2018.
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Abstract. The response of ionospheric plasma to pumping by powerful HF (high frequency) electromagnetic waves transmitted from the ground into the ionosphere is the strongest in the direction of geomagnetic zenith. We present experimental results from transmitting a left-handed circularly polarized HF beam from the EISCAT (European Incoherent SCATter association) Heating facility in magnetic zenith. The CASSIOPE (CAScade, Smallsat and IOnospheric Polar Explorer) spacecraft in the topside ionosphere above the F-region density peak detected transionospheric pump radiation, although the pump frequency was below the maximum ionospheric plasma frequency. The pump wave is deduced to arrive at CASSIOPE through L-mode propagation and associated double (O to Z, Z to O) conversion in pump-induced radio windows. L-mode propagation allows the pump wave to reach higher plasma densities and higher ionospheric altitudes than O-mode propagation so that a pump wave in the L-mode can facilitate excitation of upper hybrid phenomena localized in density depletions in a larger altitude range. L-mode propagation is therefore suggested to be important in explaining the magnetic zenith effect. Keywords. Space plasma physics (active perturbation experiments)
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Danilov, A. D., and A. V. Mikhailov. "F2-layer parameters long-term trends at the Argentine Islands and Port Stanley stations." Annales Geophysicae 19, no. 3 (March 31, 2001): 341–49. http://dx.doi.org/10.5194/angeo-19-341-2001.
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Abstract. The ionospheric sounding data at two southern hemisphere stations, the Argentine Islands and Port Stanley, are analyzed using a method previously developed by the authors. Negative trends of the critical frequency foF2 are found for both stations. The magnitudes of the trends are close to those at the corresponding (close geomagnetic latitude) stations of the northern hemisphere, as considered previously by the authors. The values of the F2 layer height hmF2 absolute trends ΔhmF2 are considered. The effect of ΔhmF2 dependence on hmF2 found by Jarvis et al. (1998) is reproduced. A concept is considered that long-term changes of the geomagnetic activity may be an important (if not the only) cause of all the trends of foF2 and hmF2 derived by several groups of authors. The dependence of both parameters on the geomagnetic index Ap corresponds to a smooth scheme of the ionospheric storm physics and morphology; thus, a principal cause of the foF2 and hmF2 geomagnetic trends is most probably a trend found in several publications in the number and intensity of ionospheric storms.Key words. Ionosphere (ionosphere-atmosphere interaction; ionospheric disturbances)
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Bößwetter, A., T. Bagdonat, U. Motschmann, and K. Sauer. "Plasma boundaries at Mars: a 3-D simulation study." Annales Geophysicae 22, no. 12 (December 22, 2004): 4363–79. http://dx.doi.org/10.5194/angeo-22-4363-2004.
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Abstract. The interaction of the solar wind with the ionosphere of planet Mars is studied using a three-dimensional hybrid model. Mars has only a weak intrinsic magnetic field, and consequently its ionosphere is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the interaction region. Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma, which could be identified as a bow shock (BS), ion composition boundary (ICB) and magnetic pile up boundary (MPB), where the latter both turn out to coincide. The simulation results regarding the shape and position of these boundaries are in good agreement with the measurements made by Phobos-2 and MGS spacecraft. It is shown that the positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the often unconsidered electron temperature of the ionospheric heavy ion plasma. Other consequences are rays of planetary plasma in the tail and heavy ion plasma clouds, which are stripped off from the dayside ICB region by some instability. Key words. Magnetospheric physics (solar wind interactions with unmagnetized bodies) – Space plasma physics (discontinuities; numerical simulation studies)
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Amm, O., A. Pajunpää, and U. Brandström. "Spatial distribution of conductances and currents associated with a north-south auroral form during a multiple-substorm period." Annales Geophysicae 17, no. 11 (November 30, 1999): 1385–96. http://dx.doi.org/10.1007/s00585-999-1385-6.
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Abstract. Using the method of characteristics to invert ground-based data of the ground magnetic field disturbance and of the ionospheric electric field, we obtain spatial distributions of ionospheric conductances, currents, and field-aligned currents (FACs) associated with a north-south auroral form that drifts westwards over northern Scandinavia around 2200 UT on December 2, 1977. This auroral form is one in a sequence of such north-south structures observed by all-sky cameras, and appears 14 min after the last of several breakups during that extremely disturbed night. Our analysis shows that the ionospheric Hall conductance reaches values above 200 S in the center of the form, and upward flowing FACs of up to 25 µA/m2 are concentrated near its westward and equatorward edge. The strong upward flowing FACs are fed by an area of more distributed, but still very strong downward-flowing FACs northeastward of the auroral form. In contrast to the conductances, the electric field is only slightly affected by the passage of the form. We point out similarities and differences of our observations and results to previously reported observations and models of 'auroral fingers', 'north-south aurora', and 'auroral streamers' which are suggested to be ionospheric manifestations of bursty bulk flows in the plasma sheet.Key words. Ionosphere (auroral ionosphere; electric fields and currents) · Magnetospheric physics (magnetosphere · ionosphere interactions)
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Blagoveshchensky, D. V., O. A. Maltseva, and A. S. Rodger. "Ionosphere dynamics over Europe and western Asia during magnetospheric substorms 1998–99." Annales Geophysicae 21, no. 5 (May 31, 2003): 1141–51. http://dx.doi.org/10.5194/angeo-21-1141-2003.
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Abstract. The temporal and spatial behaviour of the ionospheric parameters foF2 and h'F during isolated substorms are examined using data from ionospheric stations distributed across Europe and western Asia. The main purpose is finding the forerunners of the substorm disturbances and a possible prediction of these disturbances. During the period from March 1998 to March 1999, 41 isolated substorms with intensities I = 60 - 400 nT were identified and studied. The study separated occasions when the local magnetometers were affected by the eastward electrojet (positive substorms) from those influenced by the westward electrojet (negative substorms). The deviations of the ionospheric parameters from their monthly medians (DfoF2 and Dh'F) have been used to determine the variations through the substorm. Substorm effects occurred simultaneously (< 1 h) across the entire observatory network. For negative substorms, DfoF2-values increase > 6 h before substorm onset, To, reaching a maximum 2–3 h before To. A second maximum occurs 1–2 h after the end of the substorm. The Dh'F values 3–4 h before To have a small minimum but then increase to a maximum at To. There is a second maximum at the end of the expansion phase before dh'F drops to a minimum 2–3 h after ending the expansion phase. For positive substorms, the timing of the first maximum of the dfoF2 and dh'F values depends on the substorm length – if it is longer, the position is closer to To. The effects on the ionosphere are significant: DfoF2 and Dh'F reach 2–3 MHz (dfoF2 = 50–70% from median value) and 50–70 km (D h'F = 20–30% from median value), respectively. Regular patterns of occurrence ahead of the first substorm signature on the magnetometer offer an excellent possibility to improve short-term forecasting of radio wave propagation conditions.Key words. Ionosphere (ionospheric disturbances) – Magnetospheric physics (storms and substorms) Radio science (ionospheric physics)
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Pulkkinen, A., A. Thomson, E. Clarke, and A. McKay. "April 2000 geomagnetic storm: ionospheric drivers of large geomagnetically induced currents." Annales Geophysicae 21, no. 3 (March 31, 2003): 709–17. http://dx.doi.org/10.5194/angeo-21-709-2003.
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Abstract. Geomagnetically induced currents (GIC) flowing in technological systems on the ground are a direct manifestation of space weather. Due to the proximity of very dynamic ionospheric current systems, GIC are of special interest at high latitudes, where they have been known to cause problems, for example, for normal operation of power transmission systems and buried pipelines. The basic physics underlying GIC, i.e. the magnetosphere – ionosphere interaction and electromagnetic induction in the ground, is already quite well known. However, no detailed study of the drivers of GIC has been carried out and little is known about the relative importance of different types of ionospheric current systems in terms of large GIC. In this study, the geomagnetic storm of 6–7 April 2000 is investigated. During this event, large GIC were measured in technological systems, both in Finland and in Great Britain. Therefore, this provides a basis for a detailed GIC study over a relatively large regional scale. By using GIC data and corresponding geomagnetic data from north European magnetometer networks, the ionospheric drivers of large GIC during the event were identified and analysed. Although most of the peak GIC during the storm were clearly related to substorm intensifications, there were no common characteristics discernible in substorm behaviour that could be associated with all the GIC peaks. For example, both very localized ionospheric currents structures, as well as relatively large-scale propagating structures were observed during the peaks in GIC. Only during the storm sudden commencement at the beginning of the event were large-scale GIC evident across northern Europe with coherent behaviour. The typical duration of peaks in GIC was also quite short, varying between 2–15 min.Key words. Geomagnetism and paleo-magnetism (geomagnetic induction) – Ionosphere (ionospheric disturbances) – Magnetospheric physics (storms and substorms)
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Vybornov, F. I., and O. A. Sheiner. "Coronal mass ejections and high-speed solar wind streams effect on HF ionospheric communication channel." Journal of Physics: Conference Series 2131, no. 5 (December 1, 2021): 052096. http://dx.doi.org/10.1088/1742-6596/2131/5/052096.
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Abstract This article analyzes the degree of solar coronal mass ejections and high-speed solar wind streams influence on the ionospheric communication channel in the short-wavelength range. Regularities in the coronal mass ejections influence on the parameters of the ionosphere are revealed. It is shown that there is a decrease in the values of the used differential parameter of critical frequency of the ionosphere F2 layer after the onset of coronal mass ejections of the loop type, while no significant changes are observed from other types of coronal mass ejections. The contribution of the high-speed solar wind flux to the features of the behavior of ionospheric parameters is demonstrated. Deviations of critical frequency and maximum observed frequency of the ionosphere F2 layer indicate a change in conditions in the ionosphere, leading to disruption of radio communication in the short-wavelength range. The results of ground-based measurements of the ionospheric plasma parameters were obtained by the methods of oblique and vertical sounding of the ionosphere. The use of the method of oblique sounding made it possible to obtain data on the state of the ionosphere where there are no vertical sounding stations.
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Zhang, Yixin, Yang Liu, Junlei Mei, Chunxi Zhang, and Jinling Wang. "A Study on the Characteristics of the Ionospheric Gradient under Geomagnetic Perturbations." Sensors 20, no. 7 (March 25, 2020): 1805. http://dx.doi.org/10.3390/s20071805.
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The Earth’s ionosphere is greatly influenced by geomagnetic activities, especially geomagnetic storms. During a geomagnetic storm, the ionosphere suffers many perturbations, leading to a spatial gradient that are neglected during geomagnetically quiet periods. An ionospheric gradient generates potential hazards for a ground-based argumentation system (GBAS) by enlarging the errors in the delay corrections between ground monitor stations and users. To address this problem, this work investigates the characteristics of the ionospheric gradient under geomagnetic storms. Global Navigation Satellite System (GNSS) observations from the continuously operating reference station (CORS) network were used to analyze the ionospheric gradients during the geomagnetic storm on 8 September 2017. The statistical behavior of the ionospheric gradient was further discussed. Experiments show that strong geomagnetic perturbations lead to large ionospheric gradients, and the gradients also vary with the geomagnetic location.
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Lu, Weijun, Guanyi Ma, and Qingtao Wan. "A Review of Voxel-Based Computerized Ionospheric Tomography with GNSS Ground Receivers." Remote Sensing 13, no. 17 (August 29, 2021): 3432. http://dx.doi.org/10.3390/rs13173432.
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Ionized by solar radiation, the ionosphere causes a phase rotation or time delay to trans-ionospheric radio waves. Reconstruction of ionospheric electron density profiles with global navigation satellite system (GNSS) observations has become an indispensable technique for various purposes ranging from space physics studies to radio applications. This paper conducts a comprehensive review on the development of voxel-based computerized ionospheric tomography (CIT) in the last 30 years. A brief introduction is given in chronological order starting from the first report of CIT with simulation to the newly proposed voxel-based algorithms for ionospheric event analysis. The statement of the tomographic geometry and voxel models are outlined with the ill-posed and ill-conditioned nature of CIT addressed. With the additional information from other instrumental observations or initial models supplemented to make the coefficient matrix less ill-conditioned, equation constructions are categorized into constraints, virtual data assimilation and multi-source observation fusion. Then, the paper classifies and assesses the voxel-based CIT algorithms of the algebraic method, statistical approach and artificial neural networks for equation solving or electron density estimation. The advantages and limitations of the algorithms are also pointed out. Moreover, the paper illustrates the representative height profiles and two-dimensional images of ionospheric electron densities from CIT. Ionospheric disturbances studied with CIT are presented. It also demonstrates how the CIT benefits ionospheric correction and ionospheric monitoring. Finally, some suggestions are provided for further research about voxel-based CIT.
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Neudegg, D. A., S. W. H. Cowley, S. E. Milan, T. K. Yeoman, M. Lester, G. Provan, G. Haerendel, et al. "A survey of magnetopause FTEs and associated flow bursts in the polar ionosphere." Annales Geophysicae 18, no. 4 (April 30, 2000): 416–35. http://dx.doi.org/10.1007/s00585-000-0416-0.
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Abstract. Using the Equator-S spacecraft and SuperDARN HF radars an extensive survey of bursty reconnection at the magnetopause and associated flows in the polar ionosphere has been conducted. Flux transfer event (FTE) signatures were identified in the Equator-S magnetometer data during periods of magnetopause contact in January and February 1998. Assuming the effects of the FTEs propagate to the polar ionosphere as geomagnetic field-aligned-currents and associated Alfvén-waves, appropriate field mappings to the fields-of-view of SuperDARN radars were performed. The radars observed discrete ionospheric flow channel events (FCEs) of the type previously assumed to be related to pulse reconnection. Such FCEs were associated with \\sim80% of the FTEs and the two signatures are shown to be statistically associated with greater than 99% confidence. Exemplary case studies highlight the nature of the ionospheric flows and their relation to the high latitude convection pattern, the association methodology, and the problems caused by instrument limitations.Key words: Ionosphere (polar ionosphere) · Magnetospheric physics (magnetosphere-ionosphere interaction; solar wind-magnetosphere interactions)
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Wright, D. M., T. K. Yeoman, and J. A. Davies. "A comparison of EISCAT and HF Doppler observations of a ULF wave." Annales Geophysicae 16, no. 10 (October 31, 1998): 1190–99. http://dx.doi.org/10.1007/s00585-998-1190-7.
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Abstract. Since the middle of 1995, an HF Doppler sounder has been running almost continuously in northern Norway, with the receiver at Ramfjordmoen and the transmitter at Seljelvnes. Concurrent operation of the EISCAT UHF radar in common programme (CP-1) mode has made it possible to study the ionospheric signature of a magnetospheric ULF wave. These are the first results of such wave signatures observed simultaneously in both instruments. It has been demonstrated that the observed Doppler signature was mainly due to the vertical bulk motion of the ionosphere caused by the electric field perturbation of the ULF wave and the first direct observational confirmation of a numerical simulation has been achieved. The wave, which was Alfvénic in nature, was detected by the instruments 8° equatorward of the broad resonance region. The implications for the deduced wave modes in the ionosphere and the mechanism producing the HF Doppler variations are discussed.Key words. Magnetosphere-ionosphere interactions · MHD waves and instabilities · Radio science · Ionospheric physics
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Safargaleev, V., W. Lyatsky, N. G. Gazey, P. N. Smith, and V. Kriviliov. "The response of the azimuthal component of the ionospheric electric field to auroral arc brightening." Annales Geophysicae 18, no. 1 (January 31, 2000): 65–73. http://dx.doi.org/10.1007/s00585-000-0065-3.
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Abstract. We have analyzed the response of azimuthal component of the ionospheric electric field to auroral arc activity. We have chosen for analysis three intervals of coordinated EISCAT and TV observations on 18 February, 1993. These intervals include three kinds of arc activity: the appearance of a new auroral arc, the gradual brightening of the existing arc and variations of the arc luminosity. The arcs were mostly east-west aligned. In all cases, the enhancement of arc luminosity is accompanied by a decrease in the westward component of the ionospheric electric field. In contrast, an increase of that component seems to be connected with arc fading. The observed response is assumed to have the same nature as the "short circuit" of an external electric field by the conductor. The possible consequence of this phenomenon is discussed..Keywords. Ionosphere (electric fields and currents; ionospheric irregularities) · Magnetospheric physics (auroral phenomena)
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Gupta, J. K., and L. Singh. "Long term ionospheric electron content variations over Delhi." Annales Geophysicae 18, no. 12 (December 31, 2000): 1635–44. http://dx.doi.org/10.1007/s00585-001-1635-8.
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Abstract. Ionospheric electron content (IEC) observed at Delhi (geographic co-ordinates: 28.63°N, 77.22°E; geomagnetic co-ordinates: 19.08°N, 148.91°E; dip Latitude 24.8°N), India, for the period 1975–80 and 1986–89 belonging to an ascending phase of solar activity during first halves of solar cycles 21 and 22 respectively have been used to study the diurnal, seasonal, solar and magnetic activity variations. The diurnal variation of seasonal mean of IEC on quiet days shows a secondary peak comparable to the daytime peak in equinox and winter in high solar activity. IECmax (daytime maximum value of IEC, one per day) shows winter anomaly only during high solar activity at Delhi. Further, IECmax shows positive correlation with F10.7 up to about 200 flux units at equinox and 240 units both in winter and summer; for greater F10.7 values, IECmax is substantially constant in all the seasons. IECmax and magnetic activity (Ap) are found to be positively correlated in summer in high solar activity. Winter IECmax shows positive correlation with Ap in low solar activity and negative correlation in high solar activity in both the solar cycles. In equinox IECmax is independent of Ap in both solar cycles in low solar activity. A study of day-to-day variations in IECmax shows single day and alternate day abnormalities, semi-annual and annual variations controlled by the equatorial electrojet strength, and 27-day periodicity attributable to the solar rotation.Key words: Ionosphere (equatorial ionosphere) · Magnetospheric physics (magnetosphere · ionosphere interactions) · Radio science (ionospheric physics)
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Chisham, G., M. P. Freeman, I. J. Coleman, M. Pinnock, M. R. Hairston, M. Lester, and G. Sofko. "Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field." Annales Geophysicae 22, no. 12 (December 22, 2004): 4243–58. http://dx.doi.org/10.5194/angeo-22-4243-2004.
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Abstract. This study presents, for the first time, detailed spatiotemporal measurements of the reconnection electric field in the Northern Hemisphere ionosphere during an extended interval of northward interplanetary magnetic field. Global convection mapping using the SuperDARN HF radar network provides global estimates of the convection electric field in the northern polar ionosphere. These are combined with measurements of the ionospheric footprint of the reconnection X-line to determine the spatiotemporal variation of the reconnection electric field along the whole X-line. The shape of the spatial variation is stable throughout the interval, although its magnitude does change with time. Consequently, the total reconnection potential along the X-line is temporally variable but its typical magnitude is consistent with the cross-polar cap potential measured by low-altitude satellite overpasses. The reconnection measurements are mapped out from the ionosphere along Tsyganenko model magnetic field lines to determine the most likely reconnection location on the lobe magnetopause. The X-line length on the lobe magnetopause is estimated to be ~6–11 RE in extent, depending on the assumptions made when determining the length of the ionospheric X-line. The reconnection electric field on the lobe magnetopause is estimated to be ~0.2mV/m in the peak reconnection region. Key words. Space plasma physics (Magnetic reconnection) – Magnetospheric physics (Magnetopause, cusp and boundary layers) – Ionosphere (Plasma convection)
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Wild, J. A., S. E. Milan, S. W. H. Cowley, M. W. Dunlop, C. J. Owen, J. M. Bosqued, M. G. G. T. Taylor, et al. "Coordinated interhemispheric SuperDARN radar observations of the ionospheric response to flux transfer events observed by the Cluster spacecraft at the high-latitude magnetopause." Annales Geophysicae 21, no. 8 (August 31, 2003): 1807–26. http://dx.doi.org/10.5194/angeo-21-1807-2003.
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Abstract. At 10:00 UT on 14 February 2001, the quartet of ESA Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the post-noon sector on an outbound trajectory. At this time, the interplanetary magnetic field incident upon the dayside magnetopause was oriented southward and duskward (BZ negative, BY positive), having turned from a northward orientation just over 1 hour earlier. As they neared the magnetopause the magnetic field, electron, and ion sensors on board the Cluster spacecraft observed characteristic field and particle signatures of magnetospheric flux transfer events (FTEs). Following the traversal of a boundary layer and the magnetopause, the spacecraft went on to observe further signatures of FTEs in the magnetosheath. During this interval of ongoing pulsed reconnection at the high-latitude post-noon magnetopause, the footprints of the Cluster spacecraft were located in the fields-of-view of the SuperDARN Finland and Syowa East radars located in the Northern and Southern Hemispheres, respectively. This study extends upon the initial survey of Wild et al. (2001) by comparing for the first time in situ magnetic field and plasma signatures of FTEs (here observed by the Cluster 1 spacecraft) with the simultaneous flow modulations in the conjugate ionospheres in the two hemispheres. During the period under scrutiny, the flow disturbances in the conjugate ionospheres are manifest as classic "pulsed ionospheric flows" (PIFs) and "poleward moving radar auroral forms" (PMRAFs). We demonstrate that the ionospheric flows excited in response to FTEs at the magnetopause are not those expected for a spatially limited reconnection region, somewhere in the vicinity of the Cluster 1 spacecraft. By examining the large- and small-scale flows in the high-latitude ionosphere, and the inter-hemispheric correspondence exhibited during this interval, we conclude that the reconnection processes that result in the generation of PIFs/PMRAFs must extend over many (at least 4) hours of magnetic local time on the pre- and post-noon magnetopause.Key words. Ionosphere (plasma convection) – Magnetospheric physics (magnetosphere-ionosphere interactions; magnetospheric configuration and dynamics)
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Rishbeth, H. "The equatorial F-layer: progress and puzzles." Annales Geophysicae 18, no. 7 (July 31, 2000): 730–39. http://dx.doi.org/10.1007/s00585-000-0730-6.
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Abstract. This work reviews some aspects of the ionospheric F-layer in the vicinity of the geomagnetic equator. Starting with a historical introduction, brief summaries are given of the physics that makes the equatorial ionosphere so interesting, concentrating on the large-scale structure rather than the smaller-scale instability phenomena. Several individual topics are then discussed, including eclipse effects, the asymmetries of the `equatorial trough', variations with longitude, the semiannual variation, the effects of the global thermospheric circulation, and finally the equatorial neutral thermosphere, including `superrotation' and possible topographic influences.Keyword: Ionosphere (equatorial ionosphere)
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Vaishnav, Rajesh, Christoph Jacobi, Jens Berdermann, Erik Schmölter, and Mihail Codrescu. "Ionospheric response to solar EUV variations: Preliminary results." Advances in Radio Science 16 (September 4, 2018): 157–65. http://dx.doi.org/10.5194/ars-16-157-2018.
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Abstract. We investigate the ionospheric response to solar Extreme Ultraviolet (EUV) variations using different proxies, based on solar EUV spectra observed from the Solar Extreme Ultraviolet Experiment (SEE) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, the F10.7 index (solar irradiance at 10.7 cm), and the Bremen composite Mg-II index during January 2003 to December 2016. The daily mean solar proxies are compared with global mean Total Electron Content (GTEC) values calculated from global IGS TEC maps. The preliminary analysis shows a significant correlation between GTEC and both the integrated flux from SEE and the Mg II index, while F10.7 correlates less strongly with GTEC. The correlations of EUV proxies and GTEC at different time periods are presented. An ionospheric delay in GTEC is observed at the 27 days solar rotation period with the time scale of about ∼1–2 days. An experiment with the physics based global 3-D Coupled Thermosphere/Ionosphere Plasmasphere electrodynamics (CTIPe) numerical model was performed to reproduce the ionospheric delay. Model simulations were performed for different values of the F10.7 index while keeping all the other model inputs constant. Preliminary results qualitatively reproduce the observed ∼1–2 days delay in GTEC, which is might be due to vertical transport processes.
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Wild, J. A., T. K. Yeoman, P. Eglitis, and H. J. Opgenoorth. "Multi-instrument observations of the electric and magnetic field structure of omega bands." Annales Geophysicae 18, no. 1 (January 31, 2000): 99–110. http://dx.doi.org/10.1007/s00585-000-0099-6.
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Abstract. High time resolution data from the CUTLASS Finland radar during the interval 01:30-03:30 UT on 11 May, 1998, are employed to characterise the ionospheric electric field due to a series of omega bands extending ~5° in latitude at a resolution of 45 km in the meridional direction and 50 km in the azimuthal direction. E-region observations from the STARE Norway VHF radar operating at a resolution of 15 km over a comparable region are also incorporated. These data are combined with ground magnetometer observations from several stations. This allows the study of the ionospheric equivalent current signatures and height integrated ionospheric conductances associated with omega bands as they propagate through the field-of-view of the CUTLASS and STARE radars. The high-time resolution and multi-point nature of the observations leads to a refinement of the previous models of omega band structure. The omega bands observed during this interval have scale sizes ~500 km and an eastward propagation velocity ~0.75 km s-1. They occur in the morning sector (~05 MLT), simultaneously with the onset/intensification of a substorm to the west during the recovery phase of a previous substorm in the Scandinavian sector. A possible mechanism for omega band formation and their relationship to the substorm phase is discussed..Key words. Ionosphere (auroral ionosphere; electric fields and currents) · Magnetospheric physics (magnetosphere-ionosphere interactions)
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Liu, Congliang, Gottfried Kirchengast, Yueqiang Sun, Kefei Zhang, Robert Norman, Marc Schwaerz, Weihua Bai, Qifei Du, and Ying Li. "Analysis of ionospheric structure influences on residual ionospheric errors in GNSS radio occultation bending angles based on ray tracing simulations." Atmospheric Measurement Techniques 11, no. 4 (April 26, 2018): 2427–40. http://dx.doi.org/10.5194/amt-11-2427-2018.
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Abstract. The Global Navigation Satellite System (GNSS) radio occultation (RO) technique is widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source to RO at upper stratospheric altitudes, and a linear dual-frequency bending angle correction is commonly used to remove the first-order ionospheric effect. However, the higher-order residual ionospheric error (RIE) can still be significant, so it needs to be further mitigated for high-accuracy applications, especially from 35 km altitude upward, where the RIE is most relevant compared to the decreasing magnitude of the atmospheric bending angle. In a previous study we quantified RIEs using an ensemble of about 700 quasi-realistic end-to-end simulated RO events, finding typical RIEs at the 0.1 to 0.5 µrad noise level, but were left with 26 exceptional events with anomalous RIEs at the 1 to 10 µrad level that remained unexplained. In this study, we focused on investigating the causes of the high RIE of these exceptional events, employing detailed along-ray-path analyses of atmospheric and ionospheric refractivities, impact parameter changes, and bending angles and RIEs under asymmetric and symmetric ionospheric structures. We found that the main causes of the high RIEs are a combination of physics-based effects – where asymmetric ionospheric conditions play the primary role, more than the ionization level driven by solar activity – and technical ray tracer effects due to occasions of imperfect smoothness in ionospheric refractivity model derivatives. We also found that along-ray impact parameter variations of more than 10 to 20 m are possible due to ionospheric asymmetries and, depending on prevailing horizontal refractivity gradients, are positive or negative relative to the initial impact parameter at the GNSS transmitter. Furthermore, mesospheric RIEs are found generally higher than upper-stratospheric ones, likely due to being closer in tangent point heights to the ionospheric E layer peaking near 105 km, which increases RIE vulnerability. In the future we will further improve the along-ray modeling system to fully isolate technical from physics-based effects and to use it beyond this work for additional GNSS RO signal propagation studies.
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Ham, Young-Bae, Geonhwa Jee, Changsup Lee, Hyuk-Jin Kwon, Jeong-Han Kim, Nikolay Zabotin, and Terence Bullett. "Observations of the Polar Ionosphere by the Vertical Incidence Pulsed Ionospheric Radar at Jang Bogo Station, Antarctica." Journal of Astronomy and Space Sciences 37, no. 2 (June 2020): 143–56. http://dx.doi.org/10.5140/jass.2020.37.2.143.
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Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna that transmits 0.5–25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside ionosphere. With these observations, possible research applications will be briefly described in combination with other observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS.
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Foster, J. C., J. M. Holt, and L. J. Lanzerotti. "Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill." Annales Geophysicae 18, no. 1 (January 31, 2000): 111–19. http://dx.doi.org/10.1007/s00585-000-0111-1.
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Abstract. Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor ~2) near the 320 km Shuttle orbital altitude persisted for ~35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of ~6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a ~80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar ~80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (~95 s period) accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID) launched by the enhanced auroral activity. The most reasonable conclusion is that the ionospheric oscillations were a result of the coincident geomagnetic disturbance. The pronounced depletion of the bottomside ionosphere, however, accentuated the oscillatory behavior during the interval following the Shuttle OMS burn..Key words. Ionosphere (active experiments; ionospheric disturbances) · Magnetospheric physics (storms and substorms)
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Provan, G., and T. K. Yeoman. "Statistical observations of the MLT, latitude and size of pulsed ionospheric flows with the CUTLASS Finland radar." Annales Geophysicae 17, no. 7 (July 31, 1999): 855–67. http://dx.doi.org/10.1007/s00585-999-0855-1.
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Abstract. A study has been performed on the occurrence of pulsed ionospheric flows as detected by the CUTLASS Finland HF radar. These flows have been suggested as being created at the ionospheric footprint of newly-reconnected field lines, during episodes of magnetic flux transfer into the terrestrial magnetosphere (flux transfer events or FTEs). Two years of both high-time resolution and normal scan data from the CUTLASS Finland radar have been analysed in order to perform a statistical study of the extent and location of the pulsed ionospheric flows. We note a great similarity between the statistical pattern of the coherent radar observations of pulsed ionospheric flows and the traditional low-altitude satellite identification of the particle signature associated with the cusp/cleft region. However, the coherent scatter radar observations suggest that the merging gap is far wider than that proposed by the Newell and Meng model. The new model for cusp low-altitude particle signatures, proposed by Lockwood and Onsager and Lockwood provides a unified framework to explain the dayside precipitation regimes observed both by the low-altitude satellites and by coherent scatter radar detection.Key words. Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)
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Angrisano, Antonio, Salvatore Gaglione, Ciro Gioia, Marco Massaro, and Salvatore Troisi. "Benefit of the NeQuick Galileo Version in GNSS Single-Point Positioning." International Journal of Navigation and Observation 2013 (November 27, 2013): 1–11. http://dx.doi.org/10.1155/2013/302947.
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The GNSS measurements are strongly affected by ionospheric effects, due to the signal propagation through ionosphere; these effects could severely degrade the position; hence, a model to limit or remove the ionospheric error is necessary. The use of several techniques (DGPS, SBAS, and GBAS) reduces the ionospheric effect, but implies the use of expensive devices and/or complex architectures necessary to meet strong requirements in terms of accuracy and reliability for safety critical application. The cheapest and most widespread GNSS devices are single frequency stand-alone receivers able to partially correct this kind of error using suitable models. These algorithms compute the ionospheric delay starting from ionospheric model, which uses parameters broadcast within the navigation messages. NeQuick is a three-dimensional and time-dependent ionospheric model adopted by Galileo, the European GNSS, and developed by International Centre for Theoretical Physics (ICTP) together with Institute for Geophysics, Astrophysics, and Meteorology of the University of Graz. The aim of this paper is the performance assessment in single point positioning of the NeQuick Galileo version provided by ESA and the comparison with respect to the Klobuchar model used for GPS; the analysis is performed in position domain and the errors are examined in terms of RMS and maximum error for the horizontal and vertical components. A deep analysis is also provided for the application of the exanimated model in the first possible Galileo only position fix.
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Materassi, Massimo, Tommaso Alberti, Yenca Migoya-Orué, Sandro Maria Radicella, and Giuseppe Consolini. "Chaos and Predictability in Ionospheric Time Series." Entropy 25, no. 2 (February 17, 2023): 368. http://dx.doi.org/10.3390/e25020368.
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Modelling the Earth’s ionosphere is a big challenge, due to the complexity of the system. Different first principle models have been developed over the last 50 years, based on ionospheric physics and chemistry, mostly controlled by Space Weather conditions. However, it is not understood in depth if the residual or mismodelled component of the ionosphere’s behaviour is predictable in principle as a simple dynamical system, or is conversely so chaotic to be practically stochastic. Working on an ionospheric quantity very popular in aeronomy, we here suggest data analysis techniques to deal with the question of how chaotic and how predictable the local ionosphere’s behaviour is. In particular, we calculate the correlation dimension D2 and the Kolmogorov entropy rate K2 for two one-year long time series of data of vertical total electron content (vTEC), collected on the top of the mid-latitude GNSS station of Matera (Italy), one for the year of Solar Maximum 2001 and one for the year of Solar Minimum 2008. The quantity D2 is a proxy of the degree of chaos and dynamical complexity. K2 measures the speed of destruction of the time-shifted self-mutual information of the signal, so that K2−1 is a sort of maximum time horizon for predictability. The analysis of the D2 and K2 for the vTEC time series allows to give a measure of chaos and predictability of the Earth’s ionosphere, expected to limit any claim of prediction capacity of any model. The results reported here are preliminary, and must be intended only to demonstrate how the application of the analysis of these quantities to the ionospheric variability is feasible, and with a reasonable output.