Gotowe bibliografie tematyczne / Ionospheric variations

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Gotowa bibliografia na temat „Ionospheric variations”

Autor: Grafiati
Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Ionospheric variations"

1

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 (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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Altadill, D. "On the 18-day quasi-periodic oscillation in the ionosphere." Annales Geophysicae 14, no. 7 (1996): 716–24. http://dx.doi.org/10.1007/s00585-996-0716-0.

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Abstract. The presence and persistence of an 18-day quasi-periodic oscillation in the ionospheric electron density variations were studied. The data of lower ionosphere (radio-wave absorption at equivalent frequency near 1 MHz), middle and upper ionosphere (critical frequencies f0E and f0F2) for the period 1970–1990 have been used in the analysis. Also, solar and geomagnetic activity data (the sunspot numbers Rz and solar radio flux F10.7 cm, and aN index respectively) were used to compare the time variations of the ionospheric with the solar and geomagnetic activity data. Periodogram, complex demodulation, auto- and cross-correlation analysis have been used. It was found that 18-day quasi-periodic oscillation exists and persists in the temporal variations of the ionospheric parameters under study with high level of correlation and mean period of 18–19 days. The time variation of the amplitude of the 18-day quasi-periodic oscillation in the ionosphere seems to be modulated by the long-term solar cycle variations. Such oscillations exist in some solar and geomagnetic parameters and in the planetary wave activity of the middle atmosphere. The high similarities in the amplitude modulation, long-term amplitude variation, period range between the oscillation of investigated parameters and the global activity of oscillation suggests a possible solar influence on the 18-day quasi-periodic oscillation in the ionosphere.
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Danzer, J., S. B. Healy, and I. D. Culverwell. "A simulation study with a new residual ionospheric error model for GPS radio occultation climatologies." Atmospheric Measurement Techniques 8, no. 8 (2015): 3395–404. http://dx.doi.org/10.5194/amt-8-3395-2015.

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Abstract. In this study, a new model was explored which corrects for higher order ionospheric residuals in Global Positioning System (GPS) radio occultation (RO) data. Recently, the theoretical basis of this new "residual ionospheric error model" has been outlined (Healy and Culverwell, 2015). The method was tested in simulations with a one-dimensional model ionosphere. The proposed new model for computing the residual ionospheric error is the product of two factors, one of which expresses its variation from profile to profile and from time to time in terms of measurable quantities (the L1 and L2 bending angles), while the other describes the weak variation with altitude. A simple integral expression for the residual error (Vorob’ev and Krasil’nikova, 1994) has been shown to be in excellent numerical agreement with the exact value, for a simple Chapman layer ionosphere. In this case, the "altitudinal" element of the residual error varies (decreases) by no more than about 25 % between ~10 and ~100 km for physically reasonable Chapman layer parameters. For other simple model ionospheres the integral can be evaluated exactly, and results are in reasonable agreement with those of an equivalent Chapman layer. In this follow-up study the overall objective was to explore the validity of the new residual ionospheric error model for more detailed simulations, based on modeling through a complex three-dimensional ionosphere. The simulation study was set up, simulating day and night GPS RO profiles for the period of a solar cycle with and without an ionosphere. The residual ionospheric error was studied, the new error model was tested, and temporal and spatial variations of the model were investigated. The model performed well in the simulation study, capturing the temporal variability of the ionospheric residual. Although it was not possible, due to high noise of the simulated bending-angle profiles at mid- to high latitudes, to perform a thorough latitudinal investigation of the performance of the model, first positive and encouraging results were found at low latitudes. Furthermore, first application tests of the model on the data showed a reduction in temperature level of the ionospheric residual at 40 km from about −2.2 to −0.2 K.
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Danzer, J., S. B. Healy, and I. D. Culverwell. "A simulation study with a new residual ionospheric error model for GPS radio occultation climatologies." Atmospheric Measurement Techniques Discussions 8, no. 1 (2015): 1151–76. http://dx.doi.org/10.5194/amtd-8-1151-2015.

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Abstract. In this study, a new model was explored, which corrects for higher order ionospheric residuals in global positioning system (GPS) radio occultation (RO) data. Recently, the theoretical basis of this new "residual ionospheric error model" has been outlined (Healy and Culverwell, 2015). The method was tested in simulations with a one-dimensional model ionosphere. The proposed new model for computing the residual ionospheric error is the product of two factors, one of which expresses its variation from profile-to-profile and from time-to-time in terms of measurable quantities (the L1 and L2 bending angles), the other of which describes the weak variation with altitude. A simple integral expression for the residual error (Vorob’ev and Krasil’nikova, 1994) has been shown to be in excellent numerical agreement with the exact value, for a simple Chapman layer ionosphere. In this case, the "altitudinal" element of the residual error varies (decreases) by no more than about 25% between ~10 and ~100 km for physically reasonable Chapman layer parameters. For other simple model ionospheres the integral can be evaluated exactly, and results are in reasonable agreement with those of an equivalent Chapman layer. In this follow-up study the overall objective was to explore the validity of the new residual ionospheric error model for more detailed simulations, based on modelling through a complex three-dimensional ionosphere. The simulation study was set up, simulating day and night GPS RO profiles for the period of a solar cycle with and without an ionosphere. The residual ionospheric error was studied, the new error model was tested, and temporal and spatial variations of the model were investigated. The model performed well in the simulation study, capturing the temporal variability of the ionospheric residual. Although, it was not possible, due to high noise of the simulated bending angle profiles at mid to high latitudes, to perform a thorough latitudinal investigation of the performance of the model, first positive and encouraging results were found at low latitudes. Furthermore, first application tests of the model on the data showed a reduction on temperature level of the ionospheric residual at 40 km from about −2.2 to −0.2 K.
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Håkansson, Martin. "Nadir-Dependent GNSS Code Biases and Their Effect on 2D and 3D Ionosphere Modeling." Remote Sensing 12, no. 6 (2020): 995. http://dx.doi.org/10.3390/rs12060995.

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Recent publications have shown that group delay variations are present in the code observables of the BeiDou system, as well as to a lesser degree in the code observables of the global positioning system (GPS). These variations could potentially affect precise point positioning, integer ambiguity resolution by the Hatch–Melbourne–Wübbena linear combination, and total electron content estimation for ionosphere modeling from global navigation satellite system (GNSS) observations. The latter is an important characteristic of the ionosphere and a prerequisite in some applications of precise positioning. By analyzing the residuals from total electron content estimation, the existence of group delay variations was confirmed by a method independent of the methods previously used. It also provides knowledge of the effects of group delay variations on ionosphere modeling. These biases were confirmed both for two-dimensional ionosphere modeling by the thin shell model, as well as for three-dimensional ionosphere modeling using tomographic inversion. BeiDou group delay variations were prominent and consistent in the residuals for both the two-dimensional and three-dimensional case of ionosphere modeling, while GPS group delay variations were smaller and could not be confirmed due to the accuracy limitations of the ionospheric models. Group delay variations were, to a larger extent, absorbed by the ionospheric model when three-dimensional ionospheric tomography was performed in comparison with two-dimensional modeling.
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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 (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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J. E., Thomas,, George, N. J., Ekanem, A.M, and Akpan, A. E. "IONOSPHERIC PLASMA VARIATIONS AFORE THE EAST OF KURIL ISLANDS EARTHQUAKE OF 13th JANUARY, 2007." Geological Behavior 4, no. 1 (2020): 42–46. http://dx.doi.org/10.26480/gbr.01.2020.42.46.

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Plasma Analyzer (IAP) and Langmuir Probe (ISL) experiments of the DEMETER microsatellite were used to check the state of the ionosphere in the region of the M8.1 East of Kuril Islands earthquake of 13th January, 2007,30 days afore and 10 days after the event using statistical approach. The study strongly revealed that all three investigated ionospheric parameters of electron density, total ion density and electron temperature displayed unfamiliar ionospheric variations eight days before the earthquake in the daytime time half orbit measurement. To this, the electron density, total ion density and electron temperature recorded a variation of 4.09, 5.73 and -2.03 respectively. These irregularities were vetted for untrue signals using the geomagnetic indices of Kp and Dst. It was however realized that the state of the ionosphere was geomagnetically quiet during this day, hence the observed variations were seismogenic.
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Bi, Cheng, Peng Ren, Ting Yin, Zheng Xiang, and Yang Zhang. "Modeling and Forecasting Ionospheric foF2 Variation in the Low Latitude Region during Low and High Solar Activity Years." Remote Sensing 14, no. 21 (2022): 5418. http://dx.doi.org/10.3390/rs14215418.

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Prediction of ionospheric parameters, such as ionospheric F2 layer critical frequency (foF2) at low latitude regions is of significant interest in understanding ionospheric variation effects on high-frequency communication and global navigation satellite system. Currently, deep learning algorithms have made a striking accomplishment in capturing ionospheric variability. In this paper, we use the state-of-the-art hybrid neural network combined with a quantile mechanism to predict foF2 parameter variations under low and high solar activity years (solar cycle-24) and space weather events. The hybrid neural network is composed of a convolutional neural network (CNN) and bidirectional long short-term memory (BiLSTM), in which CNN and BiLSTM networks extracted spatial and temporal features of ionospheric variation, respectively. The proposed method was trained and tested on 5 years (2009–2014) of ionospheric foF2 observation data from Advanced Digital Ionosonde located in Brisbane, Australia (27°53′S, 152°92′E). It is evident from the results that the proposed model performs better than International Reference Ionosphere 2016 (IRI-2016), long short-term memory (LSTM), and BiLSTM ionospheric prediction models. The proposed model extensively captured the variation in ionospheric foF2 feature, and better predicted it under two significant space weather events (29 September 2011 and 22 July 2012).
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Xi, Hui, Hu Jiang, Jiachun An, et al. "Spatial and Temporal Variations of Polar Ionospheric Total Electron Content over Nearly Thirteen Years." Sensors 20, no. 2 (2020): 540. http://dx.doi.org/10.3390/s20020540.

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It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the Weddell Sea anomaly (WSA) as well as geomagnetic storms. In this paper, four different models are utilized to map the ionospheric TEC over the Arctic and Antarctic for about one solar cycle: the polynomial (POLY) model, the generalized trigonometric series function (GTSF) model, the spherical harmonic (SH) model, and the spherical cap harmonic (SCH) model. Compared to other models, the SCH model has the best performance with ±0.8 TECU of residual mean value and 1.5–3.5 TECU of root mean square error. The spatiotemporal distributions and variations of the polar ionospheric TEC are investigated and compared under different ionosphere conditions in the Arctic and Antarctic. The results show that the solar activity significantly affects the TEC variations. During polar days, the ionospheric TEC is more active than it is during polar nights. In polar days over the Antarctic, the maximum value of TEC always appears at night in the Antarctic Peninsula and Weddell Sea area affected by the WSA. In the same year, the ionospheric TEC of the Antarctic has a larger amplitude of annual variation than that of the TEC in the Arctic. In addition, the evolution of the ionization patch during a geomagnetic storm over the Antarctic can be clearly tracked employing the SCH model, which appears to be adequate for mapping the polar TEC, and provides a sound basis for further automatic identification of ionization patches.
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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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Rozprawy doktorskie na temat "Ionospheric variations"

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Thomas, Edwin Christopher. "Phase and amplitude variations in the wave fields of ionospherically reflected radio waves." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/35807.

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The wavefronts of high frequency (HF) radio waves received after reflection from the ionosphere exhibit both spatial non-linearities and temporal variations which limit the performance of large aperture receiving arrays. The objective of this investigation was to measure the phase and amplitude of ionospherically propagated signals in order to relate these parameters to the reflection process. This thesis describes the design and construction of a large aperture multi-element array and its implementation for wavefrot investigations. The hardware and software developed to control the equipment and to record the measurements are described. The procedures required to verify the performance of the experimental system are discussed and results are presented which demonstrate the accuracy of the measurements. The array was utilised for studies of signals received from several transmitters situated throughout Western Europe. The results obtained demonstrate the widely different behaviour of signals received over the various propagation paths and these have been related to the modal content of the received signals. Limited periods existed during which a single ionospheric mode was received and data corresponding to this condition have been compared with those which would be expected if the signal consisted of both a specular component and a cone of diffracted rays. This model is unable to explain the experimental results. Numerical models of the received signal were therefore developed. Results of these and comparisons with experimental results suggest that the measured parameters can be explained by the existence of a specular component with a varying direction of arrival (DOA), plus some contribution from random components. The experimental results indicate that the random or diffracted components normally contribute less than 10% of the received power in a single moded signal.
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Choosakul, Nithiwatthn. "Study on the periodic ionospheric variations after large earthquakes using GPS data." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/126572.

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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(理学)<br>甲第14895号<br>理博第3464号<br>新制||理||1507(附属図書館)<br>27333<br>UT51-2009-M809<br>京都大学大学院理学研究科地球惑星科学専攻<br>(主査)教授 町田 忍, 教授 家森 俊彦, 教授 里村 雄彦<br>学位規則第4条第1項該当
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Shim, JA Soon. "Analysis of Total Electron Content (TEC) Variations in the Low- and Middle-Latitude Ionosphere." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/403.

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Detailed study of the spatial correlations of day-to-day ionospheric TEC variations on a global scale was performed for four 30-day-long periods in 2004 (January, March/April, June/July, September/October) using observations from more than 1000 ground-based GPS receivers. In order to obtain the spatial correlations, initially, the day-to-day variability was calculated by first mapping the observed slant TEC values for each 5-minute GPS ground receiver-satellite pair to the vertical and then differencing it with its corresponding value from the previous day. This resulted in more than 150 million values of day-to-day change in TEC (delta TEC). Next, statistics were performed on the delta TEC values. The study indicates strong correlationsbetween geomagnetic conjugate points, and these correlations are larger at low latitudes than at middle latitudes. Typical correlation lengths, defined as the angular separation at which the correlation coefficient drops to 0.7, were found to be larger at middle latitudes than at low latitudes. The correlation lengths are larger during daytime than during nighttime. The results indicate that the spatial correlation is largely independent of season. These spatial correlations are important for understanding the physical mechanisms that cause ionospheric weather variability and are also relevant to data assimilation. In an effort to better understand the effects of neutral wind and electric field on the TEC variability, a physics-based numerical Ionosphere/Plasmasphere Model (IPM) was used. The model solves the transport equations for the six ions, O+, NO+, O2+, N2+, H+, and He+, on convecting flux tubes that realistically follow the geomagnetic field. Two of the inputs required by the IPM are the thermospheric neutral wind and the low-latitude electric field, which can be given by existing empirical model or externally specified by the user. To study the relative importance of the neutral wind and the electric field for the TEC variations, these two model inputs were externally modified and the resulting variations in TEC were compared. Neutral wind and electric field modifications were introduced at three different local times in order to investigate the effect of different start times of the imposed perturbations on TEC. This study focused on modeled low- and middlelatitude TEC variations in the afternoon and post-sunset at three different longitude sectors for medium solar activity and low geomagnetic activity. The largest changes in TEC were found predominantly in the equatorial anomaly, and a significant longitudinal dependence was observed. The results indicate that the perturbation effect on the TEC at 2100 LT varied nonlinearly with the elapsed time after the imposed neutral wind and electric field perturbations. An important outcome of this study is that daytime neutral wind and/or electric field modifications will lead to essentially identical TEC changes in the 2100 local time sector.
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Jacobi, Christoph, Claudia Unglaub, Gerhard Schmidtke, Robert Schäfer, and Norbert Jakowski. "Delayed response of global ionospheric electron content to EUV variations derived from combined SolACES-SDO/EVE measurements." Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16645.

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The ionospheric response to solar EUV variability during 2011 - 2014 is shown by an EUV proxy based on primary ionization calculations using combined solar spectra from SDO/EVE and SolACES on board the ISS. The daily proxies are compared with global mean TEC analyses. At time scales of the solar rotation and longer, there is a time lag between EUV and TEC variability of about one to two days, indicating dynamical processes in the thermosphere/ionosphere systems. This lag is not seen at shorter time scales. When taking this delay into account the TEC variance at the seasonal and short-term time scale explained by EUV variations increases from 71% to 76%.<br>Die ionosphärische Antwort auf Variationen des solaren EUV im Zeitraum 2011-2014 wird anhand eines Proxys dargestellt, welcher die primäre Ionisation auf der Basis gemessener solare EUV-Spektren beinhaltet. Die täglichen Werte werden mit Analysen des global gemittelten Gesamtelektronengehalts verglichen. Auf Zeitskalen der solaren Rotation und länger findet sich eine Zeitverzögerung zwischen der EUV-Variation und des derjenigen des Gesamtelektronengehalts von ein bis 2 Tagen, welche auf dynamische Prozesse im System Thermosphäre/Ionosphäre hinweist. Die Verzögerung ist auf kurzen Zeitskalen nicht zu sehen. Wenn diese Verzögerung berücksichtigt wird, erhöht sich die durch EUV-Variationen erklärte Varianz des Elektronengehalts von 71% auf 76%.
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Nguyen, Thai Chinh [Verfasser], Harald [Akademischer Betreuer] Schuh, Mahdi [Akademischer Betreuer] Alizadeh, Harald [Gutachter] Schuh, Mahdi [Gutachter] Alizadeh, and Lung-Chih [Gutachter] Tsai. "Use of the East Asia GPS receiving network to observe ionospheric VTEC variations, scintillation and EIA features during the Solar Cycle 24 / Thai Chinh Nguyen ; Gutachter: Harald Schuh, Mahdi Alizadeh, Lung-Chih Tsai ; Harald Schuh, Mahdi Alizadeh." Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1231908394/34.

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Raghuvanshi, Anurag. "Characterization of Airborne Antenna Group Delay as a Function of Arrival Angle and its Impact on Accuracy and Integrity of the Global Positioning System." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1533314646617932.

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Palmer, Jonathan Richard. "Plasma density variations in the aurora." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262167.

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Hui, Debrup. "Altitudinal Variability of Quiet-time Plasma Drifts in the Equatorial Ionosphere." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4536.

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The plasma drifts or electric fields and their structures in the ionosphere affect the accuracy of the present-day space-based systems. For the first time, we have used ionospheric plasma drift data from Jicamarca radar measurements to study the climatology of altitudinal variations of vertical and zonal plasma drifts in low latitudes during daytime. We used data from 1998 to 2014 to derive these climatological values in bimonthly bins from 150 km to 600 km. For the vertical plasma drifts, we observed the drifts increasing with altitudes in the morning and slowly changing to drifts decreasing with altitude in the afternoon hours. The drifts change mostly linearly from E- to F-region altitudes except in the morning hours of May-June when the gradients are very small. The zonal drifts show a highly nonlinear increase in the westward drifts at the lower altitudes and then increase slowly at the higher altitudes. We see a break in the slopes at lower altitudes during the morning hours of March-April and May-June. The E-region zonal drifts, unlike vertical drifts, show a very large variability compared to F-region drifts. We also explored the altitudinal profiles of vertical drifts during late afternoon and evening hours when the electrodynamic properties in the ionosphere change rapidly. For the first time using drifts up to 2000 km, we have shown the drifts increase and decrease below and above the F-region peak before becoming height independent. These structures arise to satisfy the curl-free condition of electric fields in low latitudes. The altitudinal gradients of vertical drifts are balanced by a time derivative of the zonal drifts to satisfy the curl-free condition of electric fields. We have shown how these structures evolve with local time around the dusk sector and change with solar flux. During solar minimum, the peak region can go well below 200 km. The present-day electric field models do not incorporate these gradients, particularly in the evening sectors when they change very rapidly. Very often their results do not match with the observations. Including these gradients along with proper magnetic field models will improve the model results and accuracy of our navigation, communication, and positioning systems.
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Wyllie, Scott John, and scott wyllie@rmit edu au. "Modelling the Temporal Variation of the Ionosphere in a Network-RTK Environment." RMIT University. Mathematical and Geospatial Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080617.161323.

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The Global Positioning System (GPS) has been widely used for precise positioning applications throughout the world. However, there are still some limiting factors that affect the performance of satellite-based positioning techniques, including the ionosphere. The GPS Network-RTK (NRTK) concept has been developed in an attempt to remove the ionospheric bias from user observations within the network. This technique involves the establishment of a series of GNSS reference stations, spread over a wide geographical region. Real time data from each reference station is collected and transferred to a computing facility where the various spatial and temporal errors affecting the GNSS satellite observations are estimated. These corrections are then transmitted to users observations in the field. As part of a Victorian state government initiative to implement a cm-level real time positioning service state-wide, GPSnet is undergoing extensive infrastructure upgrades to meet high user demand. Due to the sparse (+100km) configuration of GPSnet's reference stations, the precise modelling of Victoria's ionosphere will play a key role in providing this service. This thesis aims is to develop a temporal model for the ionospheric bias within a Victorian NRTK scenario. This research has analysed the temporal variability of the ionosphere over Victoria. It is important to quantify the variability of the ionosphere as it is essential that NRTK corrections are delivered sufficiently often with a small enough latency so that they adequately model variations in the ionospheric bias. This will promote the efficient transmission of correctional data to the rover whilst still achieving cm-level accuracy. Temporal analysis of the ionosphere revealed that, during stable ionospheric conditions, Victoria's double differenced ionospheric (DDI) bias remains correlated to within +5cm out to approximately two minutes over baselines of approximately 100km. However, the data revealed that during more disturbed ionospheric conditions this may decrease to one minute. As a preliminary investigation, four global empirical ionospheric models were tested to assess their ability to estimate the DDI bias. Further, three temporal predictive modelling schemes were tested to assess their suitability for providing ionospheric corrections in a NRTK environment. The analysis took place over four seasonal periods during the previous solar maximum in 2001 and 2002. It was found that due to the global nature of their coefficients, the four global empirical models were unable to provide ionospheric corrections to a level sufficient for precise ambiguity resolution within a NRTK environment. Three temporal ionospheric predictive schemes were developed and tested. These included a moving average model, a linear model and an ARIMA (Auto-Regressive Integrated Moving Average) time series analysis. The moving average and ARIMA approaches gave similar performance and out-performed the linear modelling scheme. Both of these approaches were able to predict the DDI to +5cm within a 99% confidence interval, out to an average of approximately two minutes, on average 90% of the time when compared to the actual decorrelation rates of the ionosphere. These results suggest that the moving average scheme, could enhance the implementation of next generation NRTK systems by predicting the DDI bias to latencies that would enable cm-level positioning.
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Liperovskaya, E. V., M. Parrot, V. V. Bogdanov, Claudia-Veronika Meister, M. V. Rodkin, and V. A. Liperovsky. "On long-term variations of foF2 in the mid-latitude ionosphere before strong earthquakes." Universität Potsdam, 2006. http://opus.kobv.de/ubp/volltexte/2007/1501/.

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The statistical analysis of the variations of the dayly-mean frequency of the maximum ionospheric electron density foF2 is performed in connection with the occurrence of (more than 60) earthquakes with magnitudes M > 6.0, depths h < 80 km and distances from the vertical sounding station R < 1000 km. For the study, data of the Tokyo sounding station are used, which were registered every hour in the years 1957-1990. It is shown that, on the average, foF2 decreases before the earthquakes. One day before the shock the decrease amounts to about 5 %. The statistical reliability of this phenomenon is obtained to be better than 0.95. Further, the variations of the occurrence probability of the turbulization of the F-layer (F spread) are investigated for (more than 260) earthquakes with M > 5.5, h < 80 km, R < 1000 km. For the analysis, data of the Japanese station Akita from 1969-1990 are used, which were obtained every hour. It is found that before the earthquakes the occurrence probability of F spread decreases. In the week before the event, the decrease has values of more than 10 %. The statistical reliability of this phenomenon is also larger than 0.95. Examining the seismo-ionospheric effects, here periods of time with weak heliogeomagnetic disturbances are considered, the Wolf number is less than 100 and the index ∑ Kp is smaller than 30.
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Książki na temat "Ionospheric variations"

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Brodscholl, Arnold. Variationen des Erdmagnetfeldes an der GvN-Station, Antarktika: Deren Nutzung für ein elektromagnetisches Induktionsverfahren zur Erkennung zweidimensionaler Leitfähigkeitsanomalien sowie zur Darstellung von Einflüssen ionosphärischer Stromsysteme = Variations of the earthmagnetic field at GVN-Station, Antarctica : applied to the methods of the earthmagnetic deep sounding to detect two-dimensional anomalies of the conductivity and for the demonstration of the influencies [sic] of ionospheric current systems. Alfred-Wegener-Institut für Polar- und Meeresforschung, 1988.

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Brodscholl, Arnold. Variationen des Erdmagnetfeldes an der GvN-Station, Antarktika: Deren Nutzung für ein elektromagnetisches Induktionsverfahren zur Erkennung zweidimensionaler Leitfähigkeitsanomalien sowie zur Darstellung von Einflüssen ionosphärischer Stromsysteme = Variations of the earthmagnetic field at GVN-Station, Antarctica : applied to the methods of the earthmagnetic deep sounding to detect two-dimensional anomalies of the conductivity and for the demonstration of the influencies [sic] of ionospheric current systems. Alfred-Wegener-Institut für Polar- und Meeresforschung, 1988.

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University of Alabama in Huntsville. Center for Space Plasma and Aeronomic Research., University of Alabama in Huntsville. College of Science., and United States. National Aeronautics and Space Administration., eds. Effects of plasmaspheric ion heating due to ionospheric and magnetospheric sources: Final report, grant NAGW-1630, March 1989 - January 1996. National Aeronautics and Space Administration, 1996.

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Effects of plasmaspheric ion heating due to ionospheric and magnetospheric sources: Final report, grant NAGW-1630, March 1989 - January 1996. National Aeronautics and Space Administration, 1996.

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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. National Aeronautics and Space Administration, 1998.

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J. W. Wescott L. R. Brown Wright. Mean Electron Density Variations of the Quiet Ionosphere No. 9 - November 1959; NBS Technical Note 40-9. Creative Media Partners, LLC, 2021.

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J. W. Wescott L. R. Brown Wright. Mean Electron Density Variations of the Quiet Ionosphere No. 8 - October 1959; NBS Technical Note 40-8. Creative Media Partners, LLC, 2021.

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Części książek na temat "Ionospheric variations"

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Zolesi, Bruno, and Ljiljana R. Cander. "Ionospheric Spatial and Temporal Variations." In Ionospheric Prediction and Forecasting. Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-38430-1_4.

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Woods, Thomas N., Francis G. Eparvier, and James P. Mason. "Spectrally Resolved X-Ray and Extreme Ultraviolet Irradiance Variations During Solar Flares." In Ionospheric Space Weather. John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781118929216.ch19.

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Fuller-Rowell, T. J., D. Rees, S. Quegan, R. J. Moffett, and G. J. Bailey. "Simulations of the Seasonal and Universal Time Variations of the High-Latitude Thermosphere and Ionosphere Using a Coupled, Three-Dimensional, Model." In Ionospheric Modelling. Birkhäuser Basel, 1988. http://dx.doi.org/10.1007/978-3-0348-6532-6_2.

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Ivanov-Kholodny, G. S., and A. V. Mikhailov. "Calculation of the Regular Variations of the Mid-Latitude F2-Region." In The Prediction of Ionospheric Conditions. Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-5486-1_4.

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Sibeck, D. G. "The Magnetospheric and Ionospheric Response to Solar Wind Dynamic Pressure Variations." In Geophysical Monograph Series. American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm062p0001.

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D'ujanga, Florence M., Phillip Opio, and Francis Twinomugisha. "Variation of the Total Electron Content with Solar Activity During the Ascending Phase of Solar Cycle 24 Observed at Makerere University, Kampala." In Ionospheric Space Weather. John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781118929216.ch12.

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Patton, D. E., V. L. Peterson, G. H. Stonehocker, and J. W. Wright. "Characteristic Variations in the Antarctic Ionosphere." In Geomagnetism and Aeronomy: Studies in the Ionosphere, Geomagnetism and Atmospheric Radio Noise. American Geophysical Union, 2013. http://dx.doi.org/10.1029/ar004p0047.

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Liu, Dun, Yan Wang, Na Xu, Li Chen, and Huafeng Wang. "An Ionospheric Disturbance Index for SBAS Based on Gradient Variation." In Lecture Notes in Electrical Engineering. Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2580-1_2.

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Mulic, Medzida, and Randa Natras. "Ionosphere TEC Variations Over Bosnia and Herzegovina Using GNSS Data." In Lecture Notes in Geoinformation and Cartography. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56218-6_22.

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Häusler, Kathrin, and Hermann Lühr. "Longitudinal Variations of the Thermospheric Zonal Wind Induced by Nonmigrating Tides as Observed by CHAMP." In Aeronomy of the Earth's Atmosphere and Ionosphere. Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-0326-1_25.

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Streszczenia konferencji na temat "Ionospheric variations"

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Timofeev, V. I., and N. A. Ovchinnikova. "ANALYSIS OF THE INFLUENCE OF FLUCTUATIONS OF ATMOSPHERIC PARAMETERS ON THE PROPAGATION OF SIGNALS FROM GLONASS / GPS SATELLITE RADIO NAVIGATION SYSTEMS." In Aerospace instrumentation and operational technologies. Saint Petersburg State University of Aerospace Instrumentation, 2021. http://dx.doi.org/10.31799/978-5-8088-1554-4-2021-2-244-247.

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The article presents a brief analysis of the influence of variations in the state of the atmosphere (troposphere and ionosphere) on the passage of signals from the GLONASS / GPS satellite radio navigation systems, as well as the conditions for the formation of tropospheric and ionospheric delays in the process of radio signal propagation through the Earth’s atmosphere from navigation satellites to the consumer’s ground equipment.
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Yasyukevich, Anna, and Yury Yasyukevich. "Ionospheric variations during typhoons of autumn 2016." In XXIII International Symposium, Atmospheric and Ocean Optics, Atmospheric Physics, edited by Oleg A. Romanovskii. SPIE, 2017. http://dx.doi.org/10.1117/12.2288759.

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Homam, M. J. "Variations of ionospheric scintillations due to solar activity." In 2014 International Symposium on Antennas & Propagation (ISAP). IEEE, 2014. http://dx.doi.org/10.1109/isanp.2014.7026716.

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Larkina, V. I., and Yu Ya Ruzhin. "Manifestation of "Coast Effect" in Ionospheric Plasma Parameter Variations." In 2007 7th International Symposium on Electromagnetic Compatibility and Electromagnetic Ecology. IEEE, 2007. http://dx.doi.org/10.1109/emceco.2007.4371712.

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Zakharenkova, Irina E., Irk I. Shagimuratov, Iurii V. Cherniak, Andrzej Krankowski, and Nadezhda Yu Tepenitsyna. "Ionospheric variations associated with November 28, 2004 Japanese earthquake." In 2011 XXXth URSI General Assembly and Scientific Symposium. IEEE, 2011. http://dx.doi.org/10.1109/ursigass.2011.6051043.

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Gubicza, Agnes, Richard Kiraly, Pal Bencze, and Antal Banfalvi. "Investigation of cosmic ray variations due to ionospheric irregularities." In 2011 2nd International Conference on Space Technology (ICST). IEEE, 2011. http://dx.doi.org/10.1109/icspt.2011.6064656.

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Dutta, Barsha, Rumajyoti Hazarika, Bitap Raj Kalita, et al. "Ionospheric variations during geomagnetic storms of 7–8 September, 2017." In 2022 URSI Regional Conference on Radio Science (USRI-RCRS). IEEE, 2022. http://dx.doi.org/10.23919/ursi-rcrs56822.2022.10118457.

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Khan, M. Taimur, and Munawar Shah. "Storm Time Ionospheric Variations from GNSS TEC and Swarm Satellites." In 2021 Seventh International Conference on Aerospace Science and Engineering (ICASE). IEEE, 2021. http://dx.doi.org/10.1109/icase54940.2021.9904154.

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Rhazali, Zeti Akma, and Ahmad Faizal Mohd Zain. "Parameterization of ionospheric height variations by antenna pattern synthesis technique." In 2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS). IEEE, 2014. http://dx.doi.org/10.1109/ursigass.2014.6929790.

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Fayyaz, Muhammad, and Najam Abbas Naqvi. "The trends/ variations of Ionospheric parameters (hmF2, foF2) between observatory and International Reference Ionosphere web model values." In 2015 Fourth International Conference on Aerospace Science and Engineering (ICASE). IEEE, 2015. http://dx.doi.org/10.1109/icase.2015.7489521.

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Raporty organizacyjne na temat "Ionospheric variations"

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Jenan, R., T. L. Dammalage, and A. Kealy. The Influences of Solar Activities on TEC Variations of Equatorial Ionosphere over Sri Lanka. Balkan, Black sea and Caspian sea Regional Network for Space Weather Studies, 2020. http://dx.doi.org/10.31401/sungeo.2019.02.05.

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Jenan, R., T. L. Dammalage, and A. Kealy. The Influences of Solar Activities on TEC Variations of Equatorial Ionosphere over Sri Lanka. Balkan, Black sea and Caspian sea Regional Network for Space Weather Studies, 2020. http://dx.doi.org/10.31401/sungeo.2020.02.05.

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Bojilova, Rumiana, and Plamen Mukhtarov. Relationship Between Short-term Variations of Solar Activity and Critical Frequencies of the Ionosphere Represented by FoF2 and MUF3000. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, 2020. http://dx.doi.org/10.7546/crabs.2020.10.11.

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Shellman, C. H. Variability of the Electric Field Strength in the Earth-Ionosphere Waveguide Due to Variations in the Electron Density Profile. Defense Technical Information Center, 1992. http://dx.doi.org/10.21236/ada264808.

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McDonald, Sarah, and Joseph Huba. An Investigation of the Seasonal Variation of Equatorial Electrodynamics and Scintillation Using a Coupled Atmosphere-Ionosphere Model. Defense Technical Information Center, 2009. http://dx.doi.org/10.21236/ada531093.

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BARKHATOV, NIKOLAY, and SERGEY REVUNOV. A software-computational neural network tool for predicting the electromagnetic state of the polar magnetosphere, taking into account the process that simulates its slow loading by the kinetic energy of the solar wind. SIB-Expertise, 2021. http://dx.doi.org/10.12731/er0519.07122021.

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The auroral activity indices AU, AL, AE, introduced into geophysics at the beginning of the space era, although they have certain drawbacks, are still widely used to monitor geomagnetic activity at high latitudes. The AU index reflects the intensity of the eastern electric jet, while the AL index is determined by the intensity of the western electric jet. There are many regression relationships linking the indices of magnetic activity with a wide range of phenomena observed in the Earth's magnetosphere and atmosphere. These relationships determine the importance of monitoring and predicting geomagnetic activity for research in various areas of solar-terrestrial physics. The most dramatic phenomena in the magnetosphere and high-latitude ionosphere occur during periods of magnetospheric substorms, a sensitive indicator of which is the time variation and value of the AL index. Currently, AL index forecasting is carried out by various methods using both dynamic systems and artificial intelligence. Forecasting is based on the close relationship between the state of the magnetosphere and the parameters of the solar wind and the interplanetary magnetic field (IMF). This application proposes an algorithm for describing the process of substorm formation using an instrument in the form of an Elman-type ANN by reconstructing the AL index using the dynamics of the new integral parameter we introduced. The use of an integral parameter at the input of the ANN makes it possible to simulate the structure and intellectual properties of the biological nervous system, since in this way an additional realization of the memory of the prehistory of the modeled process is provided.
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