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Gotowa bibliografia na temat „Ionospheric studies”

Autor: Grafiati

Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Ionospheric studies"

Su, Ke, i Shuanggen Jin. "Three Dual-Frequency Precise Point Positioning Models for the Ionospheric Modeling and Satellite Pseudorange Observable-Specific Signal Bias Estimation". Remote Sensing 13, nr 24 (15.12.2021): 5093. http://dx.doi.org/10.3390/rs13245093.

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Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) enables the estimation the ionospheric vertical total electron content (VTEC) as well as the by-product of the satellite Pseudorange observable-specific signal bias (OSB). The single-frequency PPP models, with the ionosphere-float and ionosphere-free approaches in ionospheric studies, have recently been discussed by the authors. However, the multi-frequency observations can improve the performances of the ionospheric research compared with the single-frequency approaches. This paper presents three dual-frequency PPP approaches using the BeiDou Navigation Satellite System (BDS) B1I/B3I observations to investigate ionospheric activities. Datasets collected from the globally distributed stations are used to evaluate the performance of the ionospheric modeling with the ionospheric single- and multi-layer mapping functions (MFs), respectively. The characteristics of the estimated ionospheric VTEC and BDS satellite pseudorange OSB are both analyzed. The results indicated that the three dual-frequency PPP models could all be applied to the ionospheric studies, among which the dual-frequency ionosphere-float PPP model exhibits the best performance. The three dual-frequency PPP models all possess the capacity for ionospheric applications in the GNSS community.

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Safi’i, A. N., Susilo, D. Ramdani i B. Muslim. "Utilization of Indonesia’s regional ionosphere model to improve the accuracy of GPS measurements to support disaster mitigation studies". IOP Conference Series: Earth and Environmental Science 950, nr 1 (1.01.2022): 012097. http://dx.doi.org/10.1088/1755-1315/950/1/012097.

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Abstract Ionospheric can cause severe degradation of GPS (Global Positioning System) functionality and decrease coordinate accuracy. Increasing the precision of GPS station coordinates will improve accuracy in many applications. Many applications can use GPS for deformation studies, such as geodynamic studies, active fault studies, volcanic deformation monitoring, land subsidence studies, and hazard mitigation studies. We can use global ionospheric correction to produce better coordinates by utilizing post-processing GPS data. With the increasing number of GPS stations in Indonesia, it is possible to develop regional ionosphere models. This study computes regional ionospheric models from real-time streaming GPS data and uses them in GPS processing. Regional ionospheric models can increase the accuracy of GPS station coordinates by 5% -10% compared to global ionosphere models (igsg and codg).

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Savastano, Giorgio, Attila Komjathy, Esayas Shume, Panagiotis Vergados, Michela Ravanelli, Olga Verkhoglyadova, Xing Meng i Mattia Crespi. "Advantages of Geostationary Satellites for Ionospheric Anomaly Studies: Ionospheric Plasma Depletion Following a Rocket Launch". Remote Sensing 11, nr 14 (23.07.2019): 1734. http://dx.doi.org/10.3390/rs11141734.

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In this study, we analyzed signals transmitted by the U.S. Wide Area Augmentation System (WAAS) geostationary (GEO) satellites using the Variometric Approach for Real-Time Ionosphere Observation (VARION) algorithm in a simulated real-time scenario, to characterize the ionospheric response to the 24 August 2017 Falcon 9 rocket launch from Vandenberg Air Force Base in California. VARION is a real-time Global Navigation Satellites Systems (GNSS)-based algorithm that can be used to detect various ionospheric disturbances associated with natural hazards, such as tsunamis and earthquakes. A noise reduction algorithm was applied to the VARION-GEO solutions to remove the satellite-dependent noise term. Our analysis showed that the interactions of the exhaust plume with the ionospheric plasma depleted the total electron content (TEC) to a level comparable with nighttime TEC values. During this event, the geometry of the satellite-receiver link is such that GEO satellites measured the depleted plasma hole before any GPS satellites. We estimated that the ionosphere relaxed back to a pre-perturbed state after about 3 h, and the hole propagated with a mean speed of about 600 m/s over a region of 700 km in radius. We conclude that the VARION-GEO approach can provide important ionospheric TEC real-time measurements, which are not affected by the motion of the ionospheric pierce points (IPPs). Furthermore, the VARION-GEO measurements experience a steady noise level throughout the entire observation period, making this technique particularly useful to augment and enhance the capabilities of well-established GNSS-based ionosphere remote sensing techniques and future ionospheric-based early warning systems.

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Janhunen, P. "On the possibility of using an electromagnetic ionosphere in global MHD simulations". Annales Geophysicae 16, nr 4 (30.04.1998): 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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Ratovsky, Konstantin G., Maxim V. Klimenko, Yury V. Yasyukevich, Vladimir V. Klimenko i Artem M. Vesnin. "Statistical Analysis and Interpretation of High-, Mid- and Low-Latitude Responses in Regional Electron Content to Geomagnetic Storms". Atmosphere 11, nr 12 (2.12.2020): 1308. http://dx.doi.org/10.3390/atmos11121308.

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Geomagnetic storm is one of the most powerful factors affecting the state of the Earth’s ionosphere. Revealing the significance of formation mechanisms for ionospheric storms is still an unresolved problem. The purpose of the study is to obtain a statistical pattern of the response in regional electron content to geomagnetic storms on a global scale to interpret the results using the upper atmosphere model (the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere), to make the detailed comparison with the thermospheric storm concept, and to compare the obtained pattern with results from previous statistical studies. The regional electron content is calculated based on the global ionospheric maps data, which allows us to cover the midlatitude and high-latitude zones of both hemispheres, as well as the equatorial zone. Most of the obtained statistical pattern agrees with the thermospheric storm concept and with the previous statistical studies: ionospheric responses at ionospheric storm main phases including their seasonal dependences for the high- and midlatitudes and some features of ionospheric responses at recovery phases. However, some of the statistical patterns are inconsistent with the thermospheric storm concept or contradicts the previous statistical studies: negative midlatitude ionospheric responses at recovery phases in the local winter, the domination of the spring response in the equatorial zone, seasonal features of the positive after-effects, the interhemispheric asymmetry of ionospheric responses, and the prestorm enhancement. We obtained that the contribution of electric field to the interpretation of the zonal and diurnal averaged storm-time regional electron content (REC) disturbances is insignificant. The positive after-storm effects at different latitudes are caused by n(O) disturbances.

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Parker, James A. D., S. Eleri Pryse, Natasha Jackson-Booth i Rachel A. Buckland. "Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC". Annales Geophysicae 36, nr 1 (25.01.2018): 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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Inyurt, Samed, Selcuk Peker i Cetin Mekik. "Monitoring potential ionospheric changes caused by the Van earthquake (<i>M</i><sub>w</sub>7.2)". Annales Geophysicae 37, nr 2 (15.03.2019): 143–51. http://dx.doi.org/10.5194/angeo-37-143-2019.

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Abstract. Many scientists from different disciplines have studied earthquakes for many years. As a result of these studies, it has been proposed that some changes take place in the ionosphere layer before, during or after earthquakes, and that the ionosphere should be monitored in earthquake prediction studies. This study investigates the changes in the ionosphere created by the earthquake with a magnitude of Mw=7.2 in the northwest of Lake Erçek, which is located to the north of the province of Van in Turkey on 23 October 2011 and at 13:41 local time (−3 UT) with the epicenter of 38.75∘ N, 43.36∘ E using the TEC values obtained by the global ionosphere models (GIMs) created by IONOLAB-TEC and CODE. In order to see whether the ionospheric changes obtained by the study in question were caused by the earthquake or not, the ionospheric conditions were studied by utilizing indices providing information on solar and geomagnetic activities (F10.7 cm, Kp, Dst). One of the results of the statistical test of the TEC values obtained from both models is positive and negative anomalies obtained for the times before, on the day of and after the earthquake, and the reasons for these anomalies are discussed in detail in the last section of the study. As the ionospheric conditions on the analyzed days were highly variable, it was thought that the anomalies were caused by geomagnetic effects, solar activity and the earthquake.

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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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Perrone, Loredana, Angelo De Santis, Cristoforo Abbattista, Lucilla Alfonsi, Leonardo Amoruso, Marianna Carbone, Claudio Cesaroni i in. "Ionospheric anomalies detected by ionosonde and possibly related to crustal earthquakes in Greece". Annales Geophysicae 36, nr 2 (14.03.2018): 361–71. http://dx.doi.org/10.5194/angeo-36-361-2018.

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Abstract. Ionosonde data and crustal earthquakes with magnitude M≥6.0 observed in Greece during the 2003–2015 period were examined to check if the relationships obtained earlier between precursory ionospheric anomalies and earthquakes in Japan and central Italy are also valid for Greek earthquakes. The ionospheric anomalies are identified on the observed variations of the sporadic E-layer parameters (h′Es, foEs) and foF2 at the ionospheric station of Athens. The corresponding empirical relationships between the seismo-ionospheric disturbances and the earthquake magnitude and the epicentral distance are obtained and found to be similar to those previously published for other case studies. The large lead times found for the ionospheric anomalies occurrence may confirm a rather long earthquake preparation period. The possibility of using the relationships obtained for earthquake prediction is finally discussed. Keywords. Ionosphere (Ionospheric disturbances)

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Mannucci, A. J., C. O. Ao, X. Pi i B. A. Iijima. "The impact of large scale ionospheric structure on radio occultation retrievals". Atmospheric Measurement Techniques Discussions 4, nr 3 (4.05.2011): 2525–65. http://dx.doi.org/10.5194/amtd-4-2525-2011.

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Abstract. We study the impact of large-scale ionospheric structure on the accuracy of radio occultation (RO) retrievals of atmospheric parameters such as refractivity and temperature. We use a climatological model of the ionosphere as well as an ionospheric data assimilation model to compare quiet and geomagnetically disturbed conditions. The largest contributor to ionospheric bias is physical separation of the two GPS frequencies as the GPS signal traverses the ionosphere and atmosphere. We analyze this effect in detail using ray-tracing and a full geophysical retrieval system. During quiet conditions, our results are similar to previously published studies. The impact of a major ionospheric storm is analyzed using data from the 30 October 2003 "Halloween" superstorm period. The temperature retrieval bias under disturbed conditions varies from 1 K to 2 K between 20 and 32 km altitude, compared to 0.2–0.3 K during quiet conditions. These results suggest the need for ionospheric monitoring as part of an RO-based climate observation strategy. We find that even during quiet conditions, the magnitude of retrieval bias depends critically on ionospheric conditions, which may explain variations in previously published bias estimates that use a variety of assumptions regarding large scale ionospheric structure. We quantify the impact of spacecraft orbit altitude on the magnitude of bending angle error. Satellites in higher altitude orbits (≧700 km) tend to have lower biases due to the tendency of the residual bending to cancel between the top and bottomside ionosphere. We conclude with remarks on the implications of this study for long-term climate monitoring using RO.

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Rozprawy doktorskie na temat "Ionospheric studies"

Scherliess, Ludger. "Empirical Studies of Ionospheric Electric Fields". DigitalCommons@USU, 1997. https://digitalcommons.usu.edu/etd/6823.

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The first comprehensive study of equatorial- to mid-latitude ionospheric electric fields (plasma drifts) is presented, using extensive incoherent scatter radar measurements from Jicamarca, Arecibo, and Millstone Hill, and F-region ion drift meter data from the polar orbiting DE-2 satellite. Seasonal and solar cycle dependent empirical quiet-time electric field models from equatorial to mid latitudes are developed, which improve and extend existing climatological models. The signatures of electric field perturbations during geomagnetically disturbed periods, associated with changes in the high-latitude currents and the characteristics of storm-time dynamo electric fields driven by enhanced energy deposition into the high-latitude ionosphere, are studied. Analytical empirical models that describe these perturbation drifts are presented. The study provided conclusive evidence for the two basic components of ionospheric disturbance electric fields. It is shown that magnetospheric dynamo electric fields can penetrate with significant amplitudes into the equatorial- to mid-latitude ionosphere, but only for periods up to 1 hour, consistent with results from the Rice Convection Model. The storm-time wind-driven electric fields are proportional to the high-latitude energy input, vary with local time and latitude, and have largest magnitudes during nighttime. These perturbations affect differently the zonal and meridional electric field components. It is shown that equatorial zonal electric fields (vertical drifts) can be disturbed up to 30 hours after large enhancements in the high-latitude currents. These perturbation electric fields are associated with enhanced high-latitude energy deposition taking place predominantly between about 1-12 hours earlier and found to be in good agreement with the Blanc-Richmond disturbance dynamo model. A second class of perturbations occurs around midnight and in the dawn-noon sector with delays of about 18-30 hours between the equatorial- and the high-latitude disturbances , and maximizes during locally quiet geomagnetic times. The latitudinal variation of the meridional disturbance electric fields (zonal drifts) is also presented. It is shown that these perturbation electric fields are predominantly downward/equatorward at all latitudes and due to both prompt penetration and disturbance dynamo electric fields. These results are also generally consistent with predictions from global convection and disturbance dynamo models.

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Abdul, Ahad Awni Edwar. "EISCAT studies of travelling ionospheric disturbances at high-latitudes". Thesis, University of Leicester, 1993. http://hdl.handle.net/2381/35700.

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Travelling Ionospheric Disturbances (T.I.D.s) are perturbations of the plasma in the ionosphere caused by the passage of acoustic gravity waves. These oscillations fall into two distinct classes, labelled large scale (LS) and medium scale (MS), respectively. These TIDs have frequently been observed at high-latitude and their source of generation may be the magnetic activity and/or the weather system within the region. This thesis presents the analysis of TIDs observations taken over a eight year (1981- 1989) period by means of an advanced Incoherent Scatter radars (EISCAT radar system) at F-region high-latitude, employing CP-2 common programme. An eight year synoptic study of TID effects in electron density measured at various heights is presented. A similar investigation of the field aligned ion velocity has also been undertaken. These two data sets have been computed and the wave disturbance in the parameter quantified. Large scale disturbances occured more frequently than those of medium scale and both are observed most frequently during daytime and at the first equinox. There are two dominant azimuths for wave propagation southwest and northeast. A very clear example of wave activity was observed by EISCAT facility on April 25th, 1989 between 0800-1300 UT in the measurements of Ne, Te, Ti, and Vi, extending to hundreds of kilometres height in the ionosphere. The wave trace amplitude shows amplification with height. The relative phase difference between the TID amplitude in Ne/Ne, Te and Ti with Vi has been established. Comparative cases have been presented between the theoretical and the observed values to test Hooke's formula and Hines dispersion relation. It has been noticed that there was no correlation between the three-hourly Kp indices, the hourly AE indices or the international daily sunspot number Ri indices with the average values of the TIDs spectral power. Good correlation was found between the low cloud type occurrence and the MSTIDs main parameters. A method of estimating the horizontal distance of the wave source from the radar position is presented.

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Saito, Akinori. "Studies on the Mid-latitude Ionospheric Electric Field Fluctuations". 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/86238.

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Hosokawa, Keisuke. "Observational Studies on the High-Latitude Ionospheric Plasma Irregularities". 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149076.

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Lunt, Nicholas. "The use of the global positioning system for ionospheric studies". Thesis, Aberystwyth University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415006.

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Hussein, Ahmed A. "Simulation Studies of Parametric Processes Associated with Ionospheric Electromagnetic Radiation". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30733.

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Parametric instability processes are thought to produce Stimulated Electromagnetic Emissions (SEE) during ionospheric heating experiments. The phenomenon is primarily attributed to plasma turbulence excited by the high frequency HF heater in the altitude region where the pump frequency ω₀ is near the plasma upper hybrid frequency ω_uh. In this study, parametric instability processes thought to produce SEE are studied using theoretical and electrostatic Particle-In-Cell PIC simulation models. The simulation plasma is driven with a uniform oscillating electric field directed nearly perpendicular to the background geomagnetic field {B} to consider interactions when ω_uh is near electron cyclotron harmonics nΩ_ce. The pump frequency and amplitude are varied to consider the effects on the simulation electric field power spectrum. In this study, theoretical predictions and numerical simulations are used to study the three-wave decay instability process thought to be responsible for the generation of the down-shifted sidebands, the downshifted peak DP and the downshifted maximum DM. In particular, the lower hybrid decay instability LHDI and the ion cyclotron decay instability ICDI are studied in detail. The theory is used to provide the angular regime, with respect to the direction perpendicular to the magnetic field, at which the sidebands develop as well as the frequency and wavenumber regimes of both the LHDI and the ICDI. The effect of the temperature ratio T_e/T_i for both instabilities is discussed. A comparison between the theoretical predictions, the simulation electric field power spectrum and the experimental observations are presented in this study. Time evolution of both the LHDI and the ICDI is also investigated. The theoretical predictions are also used to investigate the cascading of the LHDI and the ICDI. The spectra show consistencies with the experimental observations. A four-wave parametric decay instability process thought to be responsible for SEE broad up-shifted sideband spectral features is discussed as well. Many theoretical results are presented, in which the effect of stepping the heater frequency closer to the upper hybrid frequency on the angle of maximum growth θ_max, the growth rate γ and on both the frequency and wavenumber regimes of the four-wave process is investigated. The simulation electric field power spectrum showed a large amplitude up-shifted sideband and a much smaller amplitude down-shifted sideband, consistent with the experimental observations. Comparisons between the theoretical predictions, the simulation electric field power spectrum and the experimental observations are discussed in detail. The time evolution of the four-wave process is one important aspect that is also presented in this study. The development of density irregularities, cavities and particle heating is also analyzed and investigated in this study.
Ph. D.

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Atilaw, Tsige Yared. "Characterization of the Multipath Environment of Ionospheric Scintillation Receivers". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16475.

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Includes bibliographical references
Global Navigation Satellite Systems (GNSS) are used to provide information on position, time and velocity all over the world at any time of the day. Currently there are four operational GNSS and one of them is GPS (Global Positioning System) that is developed and maintained by U.S Department of Defence (DoD), which is widely used and accessible all over the world. The accuracy of the output or even the availability of the navigation system depends on current space weather conditions, which can cause random fluctuations of the phase and amplitude of the received signal, called scintillation. Interference of GNSS signals that are reflected and refracted from stationary objects on the ground, with signals that travel along a direct path via the ionosphere to the antenna, cause errors in the measured amplitude and phase. These errors are known as multipath errors and can lead to cycle slip and loss of lock on the satellite or degradation in the accuracy of position determination. High elevation cut off angles used for filtering GNSS signals, usually 15-30°, can reduce non-ionospheric interference due to multipath signals coming from the horizon. Since a fixed-elevation threshold does not take into consideration the surrounding physical environment of each GPS station, it can result in a significant loss of valuable data. Alternatively, if the fixed-elevation threshold is not high enough we run the risk of including multipath data in the analysis. In this project we characterized the multipath environment of the GPS Ionospheric Scintillation and TEC (Total Electron Content) Monitor (GISTM) receivers installed by SANSA (South African National Space Agency) at Gough Island (40:34oS and 9:88° W), Marion Island (46:87° S and 37:86° E), Hermanus (34:42° S and19:22° E) and SANAE IV (71:73° S and 2:2° W) by plotting azimuth-elevation maps of scintillation indices averaged over one year. The azimuth-elevation maps were used to identify objects that regularly scatter signals and cause high scintillation resulting from multipath effects. After identifying the multipath area from the azimuth-elevation map, an azimuth-dependent elevation threshold was developed using the MATLAB curve fitting tool. Using this method we are able to reduce the multi-path errors without losing important data. Using the azimuth-dependent elevation threshold typically gives 5 to 28% more useful data than using a 20° fixed-elevation threshold.

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Angell, Jonathan Price. "Topex dual frequency altimeter studies : ionospheric corrections and ocean surface measurements". Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30618.

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The TOPEX/Poseidon altimetry mission was developed as a NASA/CNES collaboration to provide accurate sea surface height (SSH) measurements. The TOPEX mission's altimeter is the first, and so far only, dual frequency system in space. The use of two frequencies allows a correction to be made for the radar pulse delay imposed by the Earth's ionosphere which would otherwise lead to an underestimation of SSH. Not only does TOPEX/Poseidon provide the most accurate SSH measurements yet from space, it also provides the first ever quasi-global measure of the integrated electron content (IEC) of the ionosphere. This thesis utilises TOPEX/Poseidon data in a combined study of both the oceans and the ionosphere. Firstly a study of the dependence of the IEC on geomagnetic disturbances, and the spatial coherence scale of the IEC is performed by comparison with the International Reference Ionosphere, an empirical ionospheric model. A systematic dependence of IEC with geomagnetic disturbance is found, and the first ever quasi-global maps of IEC spatial coherence distance are produced. This investigation may lead to an improvement in the accuracy of the model, and hence also that of single frequency altimeter systems, which must rely on such empirical models for their correction to the ionospheric delay. Secondly the tropical Pacific Ocean is studied, in particular the characteristics of large scale wave activity in relation to the devastating climatic/oceanic phenomena known as El Nino. Kelvin, Rossby and tropical instability waves are identified, and their interactions and possible mechanisms related to El Nino are investigated. Evidence for both western and eastern boundary reflections are presented, and their significance to the delayed oscillator mechanism is discussed. The study illustrates the necessity for highly accurate SSH measurements.

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Xi, Hong. "Theoretical and Numerical Studies of Frequency Up-shifted Ionospheric Stimulated Radiation". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29279.

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Stimulated electromagnetic emission (SEE) produced by interactions of high-power radio waves with the Earth's ionosphere is currently a topic of significant interest in ionospheric modification physics. SEE is believed to be produced by nonlinear wave-wave interactions involving the electromagnetic and electrostatic plasma waves in the altitude region where the pump wave frequency is near the upper hybrid resonance frequency. The most prominent upshifted feature in the SEE spectrum is the broad upshifted maximum (BUM). In this study, the instability processes thought to be responsible to the BUM spectra in the SEE experiments are discussed and analyzed using theoretical and electrostatic particle-in-cell (PIC) models. From characteristics of this feature, a four-wave parametric decay process has been studied as a viable mechanism for its production. The object is to (1) investigate the early time nonlinear development of the four-wave decay instability by using theoretical and numerical simulation models, (2) study the variation of the four-wave decay instability spectral features for a wide range of plasma and pump wave parameters, and (3) access its possible role in the production of the BUM spectral feature. Results of this investigation show that there is good agreement between predictions of the proposed theoretical model and the numerical simulation experiments. The simulation electric field power spectrum exhibits many of the important features of the experimental observations. The numerical simulation results show that consideration of the full nonlinear development of the four-wave parametric instability is crucial in providing insight into the asymmetric nature of the wave frequency spectrum observed during the experiments. The velocity-space ring-plasma instability, another generation mechanism for the BUM spectra, is studied using a theoretical model. The theoretical calculations show that the growth rate is larger in the region of the upper hybrid wave than that of the electron Bernstein wave. In addition, the effects of various plasma parameters are analyzed and it is predicted that the BUM should be more prominent with a hotter ring, at the direction perpendicular to the magnetic field, or in a closer region of cyclotron harmonic. A detailed comparison of the velocity space ring-plasma instability and the four-wave parametric process is presented where both the differences and the possible relations are discussed.
Ph. D.

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Kero, A. (Antti). "Ionospheric D-region studies by means of active heating experiments and modelling". Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514289163.

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Abstract Powerful radio waves can heat an electron gas via collisions between free electrons and neutral particles. Since the discovery of the Luxembourg effect in 1934, this effect is known to take place in the D-region ionosphere. According to theoretical models, the EISCAT Heating facility is capable of increasing the electron temperature by a factor of 5–10 in the D region, depending mostly on the electron density profile. Various indirect evidence for the existence of the D-region heating effect has been available, including successful modification of ionospheric conductivities and mesospheric chemistry. However, an experimental quantification of the electron temperature at its maximum in the heated D-region ionosphere has been missing. In particular, incoherent scatter (IS) radars should be able to observe directly plasma parameters, such as the electron temperature, although the heated D-region ionosphere is not a trivial target because of low electron density, and hence, small signal-to-noise ratio (SNR). In this thesis, Papers I and III present unique estimates for heated D-region electron temperatures based on IS measurements. It turned out that the theoretical predictions of the electron temperature generally agree with the few existing observations, at least at the altitudes of the maximum heating effect. Quite in contrast, when the D-region heating effect on the cosmic radio noise absorption was verified for the first time by the statistical data analysis presented in Paper II, the absorption enhancements due to heating were found to be an order of magnitude smaller than model results. The reason for this discrepancy remains still as open question, although one possible explanation is provided by the electron-temperature dependent ion chemistry, which was not taken into account in the modelling. The significance of the heating-induced ion chemistry effect in the D-region was investigated in Paper IV. There the heating-induced negative ion formation is proposed as a potential explanation for the observed modulation of Polar Mesosphere Winter Echo (PMWE) power.

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Książki na temat "Ionospheric studies"

United States. National Aeronautics and Space Administration., red. Rocket studies of the lower ionosphere: Final report. [Washington, DC]: National Aeronautics and Space Administration, 1990.

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Collison, Paul Michael. Th e effect of the ionosphere on Merlin observations and radio studies of spiral galaxies. Manchester: University of Manchester, 1994.

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NATO Advanced Research Workshop on Coordinated Studies of the Solar Wind-Magnetosphere-Ionosphere Interaction (1998 Košice, Slovakia). Interball in the ISTP program: Studies of the solar wind-magnetosphere-ionosphere interaction : [proceedings of the NATO Advanced Research Workshop on Coordinated Studies of the Solar Wind-Magnetosphere-Ionosphere Interaction: Interball in the ISTP Program, Košice, Slovakia, September 7-11, 1998]. Dordrecht: Kluwer Academic, 1999.

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Rao, D. R. K. Studies of generation and dev[e]lopment of plasma irregularities in low latitude ionosphere through scintillation of satellite radio beacon: Project completion report, July 1989-March 1994. [Bombay]: Indian Institute of Geomagnetism, 1994.

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Rees, D., J. A. Bittencourt, M. A. Abdu, V. B. Wickwar, R. Schunk, J. A. Bittencourt, M. A. Abdu i V. B. Wickwar. Ionospheric and Thermospheric Studies. Elsevier Science Pub Co, 1992.

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Coordinated studies of magnetospheric/ionospheric coupling and dynamics in the diffuse aurora: Final technical report, NASA grant no. NAG5-5002, 1 May 1993-31 December 1996. [Washington, DC: National Aeronautics and Space Administration, 1998.

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National Aeronautics and Space Administration (NASA) Staff. Rocket Studies of the Lower Ionosphere. Independently Published, 2018.

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A final report for studies of interactive plasma processes in the polar cusp. [Washington, DC: National Aeronautics and Space Administration, 1992.

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Waynick, A. H. Geomagnetism and Aeronomy: Studies in the Ionosphere, Geomagnetism and Atmospheric Radio Noise. Wiley & Sons, Limited, John, 2013.

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First CHAMP Mission Results for Gravity, Magnetic and Atmospheric Studies. Springer, 2012.

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Części książek na temat "Ionospheric studies"

Lühr, Hermann. "Night-time Ionospheric Currents". W First CHAMP Mission Results for Gravity, Magnetic and Atmospheric Studies, 328–38. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-38366-6_48.

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Catherine, J. K., i R. Rajesh. "Total Electron Content in Seismo-Ionospheric Studies". W Encyclopedia of Solid Earth Geophysics, 1–12. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-10475-7_278-1.

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Catherine, J. K., i R. Rajesh. "Total Electron Content in Seismo-ionospheric Studies". W Encyclopedia of Solid Earth Geophysics, 1802–13. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-58631-7_278.

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Jakowski, N., E. Sardon, E. Engler, A. Jungstand i D. Klähn. "About the Use of GPS Measurements for Ionospheric Studies". W GPS Trends in Precise Terrestrial, Airborne, and Spaceborne Applications, 248–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-80133-4_39.

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Pollock, C. J., V. N. Coffey, J. D. England, N. G. Martinez, T. E. Moore i M. L. Adrian. "Thermal Electron Capped Hemisphere Spectrometer (TECHS) for Ionospheric Studies". W Measurement Techniques in Space Plasmas: Particles, 201–7. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm102p0201.

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Penndorf, Rudolf. "The Average Ionospheric Conditions Over the Antarctic". W Geomagnetism and Aeronomy: Studies in the Ionosphere, Geomagnetism and Atmospheric Radio Noise, 1–45. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/ar004p0001.

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Wiltberger, M. "Review of Global Simulation Studies of Effect of Ionospheric Outflow on Magnetosphere-Ionosphere System Dynamics". W Magnetotails in the Solar System, 373–92. Hoboken, NJ: John Wiley & Sons, Inc, 2015. http://dx.doi.org/10.1002/9781118842324.ch22.

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Huang, Jihong, Xingqun Zhan i Rong Yang. "Comprehensive BDS-3 Signal Simulating for Strong Ionospheric Scintillation Studies". W Proceedings of the International Conference on Aerospace System Science and Engineering 2020, 369–86. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-6060-0_26.

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Lognonné, P. "Seismic Waves from Atmospheric Sources and Atmospheric/Ionospheric Signatures of Seismic Waves". W Infrasound Monitoring for Atmospheric Studies, 281–304. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-1-4020-9508-5_10.

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García-Fernández, Miquel, Manuel Hernandez-Pajares, Jose Miguel Juan-Zornoza i Jaume Sanz-Subirana. "An Improvement of Retrieval Techniques for Ionospheric Radio Occultations". W First CHAMP Mission Results for Gravity, Magnetic and Atmospheric Studies, 430–40. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-38366-6_59.

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Streszczenia konferencji na temat "Ionospheric studies"

Huba, Joseph D., i Thomas Goldring. "Propagation studies in a disturbed ionospheric environment". W OE/LASE '90, 14-19 Jan., Los Angeles, CA, redaktorzy Peter B. Ulrich i LeRoy E. Wilson. SPIE, 1990. http://dx.doi.org/10.1117/12.18343.

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Bahari, S. A., M. Abdullah i A. M. Hasbi. "A review of ionospheric studies in Malaysia using GPS". W 2015 International Conference on Space Science and Communication (IconSpace). IEEE, 2015. http://dx.doi.org/10.1109/iconspace.2015.7283751.

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Yu Morton, Dongyang Xu, Mark Carroll, Yu Jiao, Jun Wang, Steve Taylor i Xiaolei Mao. "Multi-constellation and multi-frequency GNSS studies of ionospheric scintillation". W 2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM). IEEE, 2014. http://dx.doi.org/10.1109/usnc-ursi-nrsm.2014.6928060.

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Dyrda, Michal, Andrzej Kulak, Janusz Mlynarczyk i Michal Ostrowski. "Studies of a sudden ionospheric disturbance using the Schumann resonances". W 2015 1st URSI Atlantic Radio Science Conference (URSI AT-RASC). IEEE, 2015. http://dx.doi.org/10.1109/ursi-at-rasc.2015.7303119.

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Vastberg, A. "Ray tracing studies of multipath fading in the ionospheric HF channel". W 7th International Conference on High Frequency Radio Systems and Techniques. IEE, 1997. http://dx.doi.org/10.1049/cp:19970755.

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Dan, Sukabya, Atanu Santra, Somnath Mahato, Chaitali Koley, P. Banerjee i Anindya Bose. "Performance of Low-cost, Dual-frequency GNSS Modules for Ionospheric Studies". W 2022 3rd URSI Atlantic and Asia Pacific Radio Science Meeting (AT-AP-RASC). IEEE, 2022. http://dx.doi.org/10.23919/at-ap-rasc54737.2022.9814390.

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Kathuria, S., B. Grover, P. K. Champati Ray i G. Sharma. "Ionospheric TEC Monitoring Using Ground Based GNSS Observations for Earthquake Precursor Studies". W 79th EAGE Conference and Exhibition 2017. Netherlands: EAGE Publications BV, 2017. http://dx.doi.org/10.3997/2214-4609.201700962.

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Beaudoin, Brian L., Antonio Ting, Steven Gold, Amith H. Narayan, Jayakrishnan A. Karakkad, Gregory S. Nusinovich i Thomas M. Antonsen. "Scaled experimental studies on radio frequency source for megawatt-class ionospheric heaters". W 2018 IEEE International Vacuum Electronics Conference (IVEC). IEEE, 2018. http://dx.doi.org/10.1109/ivec.2018.8391532.

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Ritchie, S. E., i F. Honary. "Case studies of enhanced E-layer formation at high-latitudes following sudden commencement absorption events". W 10th IET International Conference on Ionospheric Radio Systems and Techniques (IRST 2006). IEE, 2006. http://dx.doi.org/10.1049/cp:20060242.

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Wani, M. R., Naseer Iqbal, Sudipta Sasmal i Sandip K. Chakrabarti. "STUDIES OF VLF RADIO WAVES FOR SUDDEN IONOSPHERIC DISTURBANCES (SID) IN KASHMIR REGION". W PROPAGATION EFFECTS OF VERY LOW FREQUENCY RADIO WAVES: Proceedings of the 1st International Conference on Science with Very Low Frequency Radio Waves: Theory and Observations. AIP, 2010. http://dx.doi.org/10.1063/1.3512882.

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Raporty organizacyjne na temat "Ionospheric studies"

Heelis, R. A. Studies of Ionospheric Plasma Electrodynamics. Fort Belvoir, VA: Defense Technical Information Center, styczeń 1999. http://dx.doi.org/10.21236/ada403011.

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Reinisch, Bodo W., Klaus Bibl, Claude G. Dozois, Robert R. gamache i David F. Kitrosser. High Latitude Ionospheric Radio Studies. Fort Belvoir, VA: Defense Technical Information Center, styczeń 1988. http://dx.doi.org/10.21236/ada192270.

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Heelis, R. A. Studies of Global Ionospheric Electrodynamics. Fort Belvoir, VA: Defense Technical Information Center, luty 1993. http://dx.doi.org/10.21236/ada265033.

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Heelis, Roderick A. Studies of Ionospheric Plasma Electrodynamics. Fort Belvoir, VA: Defense Technical Information Center, maj 1997. http://dx.doi.org/10.21236/ada384463.

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Mendillo, Michael. Inter-Hemispheric Studies of Ionospheric Irregularities. Fort Belvoir, VA: Defense Technical Information Center, styczeń 2009. http://dx.doi.org/10.21236/ada531088.

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Basu, Sunanda. Multi-Technique Studies of Ionospheric Plasma Structuring. Fort Belvoir, VA: Defense Technical Information Center, wrzesień 2006. http://dx.doi.org/10.21236/ada612082.

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Kintner, Paul M., i Michael C. Kelley. Studies of Ionospheric Irregularities: Origins and Effects. Fort Belvoir, VA: Defense Technical Information Center, wrzesień 2006. http://dx.doi.org/10.21236/ada613104.

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Kintner, Paul M. Studies of Ionospheric Irregularities: Origins and Effects. Fort Belvoir, VA: Defense Technical Information Center, wrzesień 2009. http://dx.doi.org/10.21236/ada531977.

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Basu, Sunanda. Multi-technique Studies of Ionospheric Plasma Structuring. Fort Belvoir, VA: Defense Technical Information Center, wrzesień 2008. http://dx.doi.org/10.21236/ada533973.

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Kintner, Paul M., i Michael C. Kelley. Studies of Ionospheric Irregularities: Origins and Effects. Fort Belvoir, VA: Defense Technical Information Center, wrzesień 2003. http://dx.doi.org/10.21236/ada628802.

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