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Sample records for order ionospheric effects

  1. First estimates of the second-order ionospheric effect on radio occultation observations

    NASA Astrophysics Data System (ADS)

    Vergados, Panagiotis; Pagiatakis, Spiros D.

    2010-07-01

    This study examines the impact of the second-order ionospheric effect on radio occultation (RO) data products. We propose a new linear combination between dual frequency GPS observables, which retrieves slant total electron content free from the second-order ionospheric effect. Our STEC values differ from those obtained by independent techniques by a maximum of 3 total electron content units (TECU), depending on the geographic location and geomagnetic activity. Additionally, we suggest an alternative method of computing the second-order ionospheric delay in RO experiments, which does not require the use of geomagnetic and ionospheric models. First estimates show that the second-order ionospheric delay for the RO experiments falls within the range [-10, -8] mm, which is of the same order of magnitude with second-order ionospheric delay estimates from ground-based experiments. Finally, as a by-product of our model, we retrieve weighted mean geomagnetic field values, which we compare with theoretical estimates computed by the International Geomagnetic Reference Field-10 (IGRF-10) model. Our estimations agree with the IGRF-10 model between 0.23% and 7.0%.

  2. Distribution and mitigation of higher-order ionospheric effects on precise GNSS processing

    NASA Astrophysics Data System (ADS)

    Hernández-Pajares, Manuel; Aragón-Ángel, Àngela; Defraigne, Pascale; Bergeot, Nicolas; Prieto-Cerdeira, Roberto; García-Rigo, Alberto

    2014-04-01

    Higher-order ionospheric effects (I2+) are one of the main limiting factors in very precise Global Navigation Satellite Systems (GNSS) processing, for applications where millimeter accuracy is demanded. This paper summarizes a comprehensive study of the I2+ effects in range and in GNSS precise products such as receiver position and clock, tropospheric delay, geocenter offset, and GNSS satellite position and clock. All the relevant higher-order contributions are considered: second and third orders, geometric bending, and slant total electron content (dSTEC) bending (i.e., the difference between the STEC for straight and bent paths). Using a realistic simulation with representative solar maximum conditions on GPS signals, both the effects and mitigation errors are analyzed. The usage of the combination of multifrequency L band observations has to be rejected due to its increased noise level. The results of the study show that the main two effects in range are the second-order ionospheric and dSTEC terms, with peak values up to 2 cm. Their combined impacts on the precise GNSS satellite products affects the satellite Z coordinates (up to +1 cm) and satellite clocks (more than ±20 ps). Other precise products are affected at the millimeter level. After correction the impact on all the precise GNSS products is reduced below 5 mm. We finally show that the I2+ impact on a Precise Point Positioning (PPP) user is lower than the current uncertainties of the PPP solutions, after applying consistently the precise products (satellite orbits and clocks) obtained under I2+ correction.

  3. A semi-analytic evaluation of the effect of second-order ionosphere term on GPS positioning

    NASA Astrophysics Data System (ADS)

    Munekane, H.

    2005-05-01

    We developed a method to evaluate the effect of the second-order ionosphere term on GPS positioning. The method is based on the semi-analytic positioning error simulation method developed by Geiger (1988), which assumes the continuous distribution of the GPS satellites and maps the ranging error to the positioning error using the normal equation. We expanded the method to incorporate the satellite positioning error due to the second-order ionospheric term, which is estimated in a similar manner as the site positioning error, assuming the continuous distribution of the ground tracking stations instead of the continuous satellite distribution in the case of the site positioning error estimation. The method is first applied to simulate the positioning errors on three IGS sites (BAHR, COCO, GALA) which were investigated in Kedar et al. (2002) by analyzing the observed GPS data using the GIPSY software with the correction for second-order ionospheric term. We considered three cases, namely, 1) without satellite positioning error, 2) with satellite positioning error, and 3) with satellite positioning error whose spatial average of each component is corrected for. The third case corresponds to the situation where there are other observations available such as SLR and the center of the mass of the GPS satellite network is corrected properly. For the first case, we found that our method reproduced the positioning errors observed at these stations as well as Kedar et al. (2002). For the second case, however, we found that the positioning error is almost canceled. For the third case, we found that the error is reproduced as well as in the first case, though the spatial distribution of the error is different. These results indicate that 1) the semi-analytic method developed in this paper is accurate enough to simulate the position error due to the second-order ionospheric term, and 2) the satellite positioning error due to the second-order ionospheric term may have significant

  4. Higher-order ionosphere modeling for CODE's next reprocessing activities

    NASA Astrophysics Data System (ADS)

    Lutz, S.; Schaer, S.; Meindl, M.; Dach, R.; Steigenberger, P.

    2009-12-01

    CODE (the Center for Orbit Determination in Europe) is a joint venture between the Astronomical Institute of the University of Bern (AIUB, Bern, Switzerland), the Federal Office of Topography (swisstopo, Wabern, Switzerland), the Federal Agency for Cartography and Geodesy (BKG, Frankfurt am Main, Germany), and the Institut für Astronomische und Phsyikalische Geodäsie of the Technische Universität München (IAPG/TUM, Munich, Germany). It acts as one of the global analysis centers of the International GNSS Service (IGS) and participates in the first IGS reprocessing campaign, a full reanalysis of GPS data collected since 1994. For a future reanalyis of the IGS data it is planned to consider not only first-order but also higher-order ionosphere terms in the space geodetic observations. There are several works (e.g. Fritsche et al. 2005), which showed a significant and systematic influence of these effects on the analysis results. The development version of the Bernese Software used at CODE is expanded by the ability to assign additional (scaling) parameters to each considered higher-order ionosphere term. By this, each correction term can be switched on and off on normal-equation level and, moreover, the significance of each correction term may be verified on observation level for different ionosphere conditions.

  5. Low-latitude ionospheric effects on SBAS

    NASA Astrophysics Data System (ADS)

    Arenas, J.; Sardón, E.; Sainz, A.; Ochoa, B.; Magdaleno, S.

    2016-06-01

    Satellite-based augmentation systems (SBAS) provide augmentation to Global Navigation Satellite Systems (GNSS) users in three areas: (1) broadcasting accurate corrections to GNSS satellite ephemeris, (2) providing a real-time empirical ionospheric model in the service area, and (3) providing integrity information in the form of estimates of the confidence of the ephemeris corrections and ionospheric delays. Ionospheric effects on SBAS are twofold: (a) the input data used by the SBAS will be affected by ionospheric effects, and (b) the more perturbed the ionosphere is, the more difficult it will be to provide accurate and reliable ionospheric information to the users. The ionosphere at low latitudes presents larger variability and more intense phenomena than at midlatitudes. Therefore, SBAS providing service to low-latitude regions will be more affected than those at other latitudes. From the different low-latitude ionospheric effects, this paper will focus on those having the largest impact on SBAS, which are total electron content temporal and spatial gradients, ionospheric scintillations, and depletions. This paper will present the impact of these effects on EGNOS (European Global Navigation Overlay System), the European SBAS. Although EGNOS can be considered as a midlatitude SBAS, it has to provide coverage down to rather low latitudes, so sometimes low-latitude ionospheric effects are observed in the EGNOS data. It will be shown how EGNOS performs under nominal conditions and how its performance is degraded when low-latitude ionospheric phenomena occur. Real EGNOS data affected by low-latitude ionospheric phenomena will be used.

  6. Ionospheric scintillation in Brazil: Analyses and Effects on GNSS Positioning

    NASA Astrophysics Data System (ADS)

    Alves, D. B.; Souza, J. S.; Silva, H. D.

    2013-05-01

    Ionosphere has a great influence on GNSS (Global Navigation Satellite System) signals and its behavior depends on several variables: local time, geographic location, seasons and solar activity. Besides, there are ionospheric irregularities that also affect the GNSS signal propagation, as the ionospheric scintillation. The ionospheric scintillation can be described as a fast change in phase and amplitude of GNSS signal, caused by irregularities of electron density. Scintillation can degrade or cause the GNSS signal lost. Due to these described factors, one can say that the ionosphere can cause important effects on GNSS positioning. It can degrade the coordinate accuracy obtained by GNSS positioning methods. In this paper the goal is to evaluate the ionospheric effect, in special the ionospheric scintillation in different regions of Brazil, and its effects on GNSS Point Positioning. In order to evaluate the days where the scintillation was more significant it is used a database (http://200.145.185.118/cigala/index.php) from CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project (http://cigala.galileoic.org/). Using these data it is possible to obtain information about ionospheric scintillation in different GNSS stations in Brazil. It is possible to correlate the data according to time, season and other factors that can contribute to scintillation analysis. In 2013 must occur an intense solar activity, which can intensify the ionospheric effects, and consequently ionospheric scintillation, mainly in Brazil region, where the scintillation index is already intense. Preliminary evaluations, showed larger values of S4 (scintillation index) in Brazil. For example, in October 2012, it was obtained S4 values larger than 1 in several epochs. This causes severe effects in GNSS Positioning. In this paper, the results of GNSS positioning under ionosphere scintillation effects in different regions of Brazil will be presented.

  7. Mitigation of Second-Order Ionospheric Error for Real-Time PPP Users in Europe

    NASA Astrophysics Data System (ADS)

    Abdelazeem, Mohamed

    2016-07-01

    Currently, the international global navigation satellite system (GNSS) real-time service (IGS-RTS) products are used extensively for real-time precise point positioning and ionosphere modeling applications. The major challenge of the dual frequency real-time precise point positioning (RT-PPP) is that the solution requires relatively long time to converge to the centimeter-level accuracy. This relatively long convergence time results essentially from the un-modeled high-order ionospheric errors. To overcome this challenge, a method for the second-order ionospheric delay mitigation, which represents the bulk of the high-order ionospheric errors, is proposed for RT-PPP users in Europe. A real-time regional ionospheric model (RT-RIM) over Europe is developed using the IGS-RTS precise satellite orbit and clock products. GPS observations from a regional network consisting of 60 IGS and EUREF reference stations are processed using the Bernese 5.2 software package in order to extract the real-time vertical total electron content (RT-VTEC). The proposed RT-RIM has spatial and temporal resolution of 1º×1º and 15 minutes, respectively. In order to investigate the effect of the second-order ionospheric delay on the RT-PPP solution, new GPS data sets from another reference stations are used. The examined stations are selected to represent different latitudes. The GPS observations are corrected from the second-order ionospheric errors using the extracted RT-VTEC values. In addition, the IGS-RTS precise orbit and clock products are used to account for the satellite orbit and clock errors, respectively. It is shown that the RT-PPP convergence time and positioning accuracy are improved when the second-order ionospheric delay is accounted for.

  8. Higher-order ionospheric error at Arecibo, Millstone, and Jicamarca

    NASA Astrophysics Data System (ADS)

    Matteo, N. A.; Morton, Y. T.

    2010-12-01

    The ionosphere is a dominant source of Global Positioning System receiver range measurement error. Although dual-frequency receivers can eliminate the first-order ionospheric error, most second- and third-order errors remain in the range measurements. Higher-order ionospheric error is a function of both electron density distribution and the magnetic field vector along the GPS signal propagation path. This paper expands previous efforts by combining incoherent scatter radar (ISR) electron density measurements, the International Reference Ionosphere model, exponential decay extensions of electron densities, the International Geomagnetic Reference Field, and total electron content maps to compute higher-order error at ISRs in Arecibo, Puerto Rico; Jicamarca, Peru; and Millstone Hill, Massachusetts. Diurnal patterns, dependency on signal direction, seasonal variation, and geomagnetic activity dependency are analyzed. Higher-order error is largest at Arecibo with code phase maxima circa 7 cm for low-elevation southern signals. The maximum variation of the error over all angles of arrival is circa 8 cm.

  9. Solar cosmic ray effects in the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Shirochkov, A. V.

    1989-01-01

    The polar cap absorption (PCA) events are the most remarkable geophysical phenomena in the high latitude ionosphere. Their effects are extended on the whole polar region in both hemispheres. The PCA events are caused by the intense fluxes of the solar cosmic rays (SCR) which are generated by the solar proton flares. Entering into the Earth's magnetosphere and ionosphere the SCR fluxes create excessive anomal ionization at the ionospheric heights of 50 to 100 km which exceeds usual undisturbed level of ionization in several orders of magnitude. The PCA events can be considered as catastrophic in relation to the polar ionosphere because all radio systems using ionospheric radio channels ceased to operate during these events. On the other hand the abnormally high level of ionization in the ionospheric D region during the PCA events create excellent opportunities to conduct fruitful aeronomical research for the lower ionosphere. Obvious scientific and practical importance of the PCA events leads to publishing of special PCA catalogues. The ionospheric effects caused by the SCR fluxes were profoundly described in the classical paper (Bailey, 1964). Nevertheless several aspects of this problem were not studied properly. An attempt is made to clarify these questions.

  10. Intercomparison Of Approaches For Modeling Second Order Ionospheric Corrections Using Gnss Measurements

    NASA Astrophysics Data System (ADS)

    Garcia Fernandez, M.; Butala, M.; Komjathy, A.; Desai, S. D.

    2012-12-01

    Correcting GNSS tracking data for the effects of second order ionospheric effects have been shown to cause a southward shift in GNSS-based precise point positioning solutions by as much as 10 mm, depending on the solar cycle conditions. The most commonly used approaches for modeling the higher order ionospheric effect include, (a) the use of global ionosphere maps to determine vertical total electron content (VTEC) and convert to slant TEC (STEC) assuming a thin shell ionosphere, and (b) using the dual-frequency measurements themselves to determine STEC. The latter approach benefits from not requiring ionospheric mapping functions between VTEC and STEC. However, this approach will require calibrations with receiver and transmitter Differential Code Biases (DCBs). We present results from comparisons of the two approaches. For the first approach, we also compare the use of VTEC observations from IONEX maps compared to climatological model-derived VTEC as provided by the International Reference Ionosphere (IRI2012). We consider various metrics to evaluate the relative performance of the different approaches, including station repeatability, GNSS-based reference frame recovery, and post-fit measurement residuals. Overall, the GIM-based approaches tend to provide lower noise in second order ionosphere correction and positioning solutions. The use of IONEX and IRI2012 models of VTEC provide similar results, especially in periods of low solar activity periods. The use of the IRI2012 model provides a convenient approach for operational scenarios by eliminating the dependence on routine updates of the GIMs, and also serves as a useful source of VTEC when IONEX maps may not be readily available.

  11. Ionospheric effects of supernova explosions

    NASA Astrophysics Data System (ADS)

    Edwards, P. J.

    Possible ionospheric effects of supernova explosions are considered, with special attention given to those of SN 1987a. Results are presented on the calculations of anticipated X-ray/UV flare parameters, including the shock temperature, the minimum flare duration, the average photon energy, and the shock-front travel time for a range of stellar radii bracketing SK 202-69, which was identified by White Malin (1987) as the progenitor star for SN 1987a. It is shown that the characteristics of the X-ray/UV flare are strongly influenced by the radius of the shock wave breakout, so that the flare from SN 1987a can be anticipated to have characteristics intermediate between those attributed to compact stars and stars with extended envelopes.

  12. Effects of large-scale magnetic fields in the Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Elphic, R. C.; Russell, C. T.; Brace, L. H.; Hartle, R. E.

    1982-01-01

    Theoretical models of the ionosphere of Venus have been constructed in the past without due consideration of the fact that the ionosphere is sometimes magnetized. This paper examines some differences between the magnetized and unmagnetized dayside Venus ionosphere using the Pioneer Venus Orbiter Langmuir probe and magnetometer data. Particular attention is given to the evaluation of the altitude profiles of the thermal electron heating and comparison of the magnitude of the magnetic force with other forces in the ionosphere. Several examples illustrate how heating profiles are different in the magnetized ionosphere with effective heating below 200 km altitude reduced by orders of magnitude compared to the field-free ionosphere. The force associated with the magnetic field is comparable to other forces in the magnetized ionosphere. The measured plasma density, electron temperature and magnetic field thus suggest that large-scale magnetic fields should be included in future ionosphere models.

  13. Ionospheric effects of solar x-rays

    NASA Astrophysics Data System (ADS)

    Danskin, Donald

    2016-07-01

    The ionospheric absorption of radio waves caused by solar x-ray bursts is measured directly by Riometers from the Canada Riometer Array. The absorption is found to be proportional to the square root of the flux intensity of the X-ray burst with time delays of 18-20 seconds between the peak X-ray emission and absorption in the ionosphere. A detailed analysis showed that some X-ray flares during 2011-2014 are more effective at producing absorption than others. Solar longitude of X-ray burst for several X-class flares shows no consistent pattern of enhancement in the absorption.

  14. Ionospheric effects of the Chelyabinsk meteoroid

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.

    2015-05-01

    Observation results are presented for the lower and upper ionosphere disturbances accompanying the passage and explosion of the Chelyabinsk space body. The effects near the meteoroid's path are investigated from the total electron content variations detected by GPS radio receivers. The ionosphere observations at distances of ˜2000-300 km are based on the ionosonde data and the phase and amplitude measurements for a radio signal at 66.67 kHz on the route from Moscow to Kharkiv. Manifestations are found both of acoustic and gravity waves following the passage and explosion of the space body. Their connection with the passage of the Chelyabinsk meteoroid is discussed.

  15. A review of ionospheric effects on Earth-space propagation

    NASA Technical Reports Server (NTRS)

    Klobuchar, J. A.

    1984-01-01

    A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

  16. Ionospheric Scintillation Effects on GPS

    NASA Astrophysics Data System (ADS)

    Steenburgh, R. A.; Smithtro, C.; Groves, K.

    2007-12-01

    . Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  17. The ionospheric effects of industrial explosions

    NASA Astrophysics Data System (ADS)

    Varshavskii, I. I.; Kalikhman, A. D.

    1984-04-01

    A mathematical model is developed which describes the effect of an industrial explosion on the parameters of a radio signal reflected from the ionosphere. The model predictions are shown to be in good agreement with the observed Doppler shift and angle of arrival of radio signals for actual explosions near Alma-Ata and Sliudianka. Estimates are made of the amplitude and shape of a perturbation wave at the heights of the F layer.

  18. Saturation Effects in the VLF Scattering off Strongly Heated Ionosphere

    NASA Astrophysics Data System (ADS)

    Lehtinen, N. G.; Bell, T. F.; Inan, U. S.

    2011-12-01

    The HAARP ionospheric HF heating facility modifies the conductivity of the lower ionosphere, creating a perturbation in the propagation of VLF transmitter-generated waves. The changes in the VLF amplitude may be detected by ground-based receivers and satellites with VLF instruments. In order to quantify these effects, we introduce a novel computational technique which combines the Stanford FWM (full-wave method) with the method of moments (MoM) to calculate the scattering on localized strong perturbations in stratified media. The Born approximation, which was previously used for similar calculations [Lehtinen et al., 2010], neglects the scattered field inside the perturbation region and therefore becomes invalid when the scattered field is of the order of the incident field, which happens when the perturbation is strong (i.e., the relative change of the conductivity is ~1). On the contrary, the use of MoM allows us to calculate the effects of the total field and thus may be applied to situations with any level of perturbation. This technique is applied to the VLF scattering off ionospheric disturbances created by HF heating. We show how the field measured on the ground and at a satellite deviates from that calculated previously in the Born approximation by demonstrating saturation effects for strong heating.

  19. Effect of the topography on the ionosphere: results from the Mars Express MARSIS experiment.

    NASA Astrophysics Data System (ADS)

    Sánchez-Cano, Beatriz; Witasse, Olivier; Herraiz, Miguel; Radicella, Sandro M.

    2013-04-01

    Active Ionospheric Sounding (AIS) data acquired by the MARSIS instrument on board the Mars Express mission have been used to analyze the effect of the irregular Martian topography on the altitude of the main ionospheric peak. Besides basic parameters, such as heliocentric distance or season, solar activity or solar zenith angle that must be considered when the Martian ionosphere is analyzed, there are other factors that can influence the ionosphere behavior. One of them is the topography. Topography seems to play a role on the Martian ionosphere when regional scale is considered. It has been observed that the main ionospheric peak altitude is higher over large volcanic edifices by as much as 20 km above surrounding areas and lower over impact basins by as much as 15 km below surrounding areas. This behavior, apparently only detected at sub-regional scale, has been found for the most prominent topographic features studied in this work. Correction for the solar zenith angle has been taken into account, in order to remove potential effect due to this parameter. This work examines and evaluates the main variations of the main ionosphere peak altitude found in regions with particular topography. A statistical analysis of the ionosphere deviation over each selected structure is given and special attention is paid to the possible physical mechanisms that can explain this phenomenon. MARSIS data have been downloaded from the ESA planetary science archive and topographic information comes from MOLA instrument on board Mars Global Surveyor mission.

  20. Effects of the different times of sunrise at different altitudes in the ionosphere

    NASA Astrophysics Data System (ADS)

    Verhulst, Tobias; Stankov, Stan

    2016-07-01

    It is well established that the sunrise and sunset periods are of particular importance to ionospheric research and modeling because of the rapid changes in the ionospheric plasma density, temperature, and dynamics. In particular, the sharp increase in the ionisation following sunrise results in a quick increase in the ionospheric peak density, N_mF_2, and a decrease in the peak height, h_mF_2. Changes in plasma temperature, scale height and transport processes add further complexity which makes it difficult to investigate and model the ionospheric behaviour during this transitional period from night to day. One of the aspects contributing to this difficulty is that not all ionospheric altitudes are exposed to the first sunlight of the day at the same time. During sunrise, the upper part of the ionosphere is illuminated prior to the lower part which is still in the dark. The boundary between sunlit and dark regions moves downwards until it reaches the surface of the Earth, which is commonly taken as the moment of sunrise at certain geographical coordinates. This means that the ``traditional'' sunrise does not occur until after the entire ionosphere has been illuminated. During sunset, the same process happens in reverse order. In this presentation, we will address the issue and report on our study of some of the effects of this altitude-dependent time of sunrise on the diurnal variations in the ionospheric characteristics.

  1. The effect of stochastic modeling of ionospheric effect on the various lengths of baseline determination

    NASA Astrophysics Data System (ADS)

    Kwon, J.; Yang, H.

    2006-12-01

    Although GPS provides continuous and accurate position information, there are still some rooms for improvement of its positional accuracy, especially in the medium and long range baseline determination. In general, in case of more than 50 km baseline length, the effect of ionospheric delay is the one causing the largest degradation in positional accuracy. For example, the ionospheric delay in terms of double differenced mode easily reaches 10 cm with baseline length of 101 km. Therefore, many researchers have been tried to mitigate/reduce the effect using various modeling methods. In this paper, the optimal stochastic modeling of the ionospheric delay in terms of baseline length is presented. The data processing has been performed by constructing a Kalman filter with states of positions, ambiguities, and the ionospheric delays in the double differenced mode. Considering the long baseline length, both double differenced GPS phase and code observations are used as observables and LAMBDA has been applied to fix the ambiguities. Here, the ionospheric delay is stochastically modeled by well-known Gaussian, 1st and 3rd order Gauss-Markov process. The parameters required in those models such as correlation distance and time is determined by the least-square adjustment using ionosphere-only observables. Mainly the results and analysis from this study show the effect of stochastic models of the ionospheric delay in terms of the baseline length, models, and parameters used. In the above example with 101 km baseline length, it was found that the positional accuracy with appropriate ionospheric modeling (Gaussian) was about ±2 cm whereas it reaches about ±15 cm with no stochastic modeling. It is expected that the approach in this study contributes to improve positional accuracy, especially in medium and long range baseline determination.

  2. Ionospheric effects to antenna impedance

    NASA Technical Reports Server (NTRS)

    Bethke, K. H.

    1986-01-01

    The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

  3. Ionospheric effects of magnetic storm observed by means of oblique sounding of artificial ionospheric turbulence

    NASA Astrophysics Data System (ADS)

    Uryadov, V. P.; Vertogradov, G. G.; Vertogradov, V. G.; Ponyatov, A. A.

    Results of experimental studies of the influence of the artificial ionospheric turbulence (AIT) on HF propagation are presented. Ionospheric modification and the creation of a scatterer was produced by powerful radio emission of the SURA heating facility (Nizhny Novgorod region). For diagnostics of the AIT were used the Russian chirp sounders network and HF Doppler radar. The reception of scattered signals was carried out in the Rostov-Don on the oblique V-type antenna oriented to the SURA heating facility. It is investigated ionospheric effects of magnetic storm during August 17-22, 2003 accompanied a period of the experiment. It is shown that ionospheric effects of the magnetic storm observed by means of Doppler frequency shift (DFS) measurements signals scattered from artificial small-scale field-aligned irregularities correlate well with the behavior of the southward component Bz of the interplanetary magnetic field and with variations in the geomagnetic field near the Earth surface. It has been found that at heights of the mid-latitude ionospheric F region under undisturbed conditions the electric field and the drift velocity of irregularities correspond to the typical values about 1 mV m-1 and 20 m s-1, respectively. During magnetic storm these values increase up to values of about 8.6 mV m-1 and 186 m s-1, which better correspond to the values typical for the high-latitude ionosphere. It is found that in the magnetically-disturbed period sporadically appearing trains with quasi-periodical modulation of DFS for the scattered signal with a period of ˜ 40-60 s and amplitude reaching 2 Hz were observed. The relation of the quasi-periodical oscillations of the DFS for the scattered signal to the presence of magnetohydrodynamics waves excited during a magnetic storm is considered. It is concluded that use HF Doppler radar for AIT sounding is of interest for diagnostics of wave processes in the ionosphere and magnetosphere. The conditions of formation of the HF

  4. Effects of tropospheric and ionospheric refraction errors in the utilization of GEOS-C altimeter data

    NASA Technical Reports Server (NTRS)

    Goad, C. C.

    1977-01-01

    The effects of tropospheric and ionospheric refraction errors are analyzed for the GEOS-C altimeter project in terms of their resultant effects on C-band orbits and the altimeter measurement itself. Operational procedures using surface meteorological measurements at ground stations and monthly means for ocean surface conditions are assumed, with no corrections made for ionospheric effects. Effects on the orbit height due to tropospheric errors are approximately 15 cm for single pass short arcs (such as for calibration) and 10 cm for global orbits of one revolution. Orbit height errors due to neglect of the ionosphere have an amplitude of approximately 40 cm when the orbits are determined from C-band range data with predominantly daylight tracking. Altimeter measurement errors are approximately 10 cm due to residual tropospheric refraction correction errors. Ionospheric effects on the altimeter range measurement are also on the order of 10 cm during the GEOS-C launch and early operation period.

  5. Ionospheric effects on synthetic aperture radar at VHF

    SciTech Connect

    Fitzgerald, T.J.

    1997-02-01

    Synthetic aperture radars (SAR) operated from airplanes have been used at VHF because of their enhanced foliage and ground penetration compared to radars operated at UHF. A satellite-borne VHF SAR would have considerable utility but in order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. The presence of the ionosphere in the propagation path of the radar will cause a deterioration of the imaging because of dispersion over the bandwidth and group path changes in the imaged area over the collection aperture. In this paper we present calculations of the effects of a deterministic ionosphere on SAR imaging for a radar operated with a 100 MHz bandwidth centered at 250 MHz and over an angular aperture of 23{degrees}. The ionosphere induces a point spread function with an approximate half-width of 150 m in the slant-range direction and of 25 m in the cross-range direction compared to the nominal resolution of 1.5 m in both directions.

  6. Measurements of ionospheric effects on wideband signals at VHF

    SciTech Connect

    Fitzgerald, T.J.

    1998-08-17

    Radars operating at very high frequency (VHF) have enhanced foliage and ground penetration compared to radars operated at higher frequencies. For example, VHF systems operated from airplanes have been used as synthetic aperture radars (SAR); a satellite-borne VHF SAR would have considerable utility. In order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. A satellite-borne radar would likely have to operate at altitudes above the maximum density of the ionosphere; the presence of the ionosphere in the propagation path of the radar will cause a deterioration of the performance because of dispersion over the bandwidth. The author presents measurements of the effects of the ionosphere on radar signals propagated from a source on the surface of the Earth and received by instruments on the FORTE satellite at altitudes of 800 km. The author employs signals with a 90 MHz bandwidth centered at 240 MHz with a continuous digital recording period of 0.6 s.

  7. Ionospheric effects on synthetic aperture radar at 100 MHz to 2 GHz

    NASA Astrophysics Data System (ADS)

    Ishimaru, Akira; Kuga, Yasuo; Liu, Jun; Kim, Yunjin; Freeman, Tony

    1999-01-01

    Recently, there has been increasing interest in the use of spaceborne synthetic aperture radar (SAR) for measuring forest biomass. However, it is noted that conventional SAR using C-band or higher frequencies cannot penetrate into foliage, and therefore the biomass measurements require longer wavelengths, typically P-band (500 MHz). It is also known that the ionosphere is highly dispersive, causing group delay and broadening of pulses. The variance of the refractive index fluctuations due to turbulence is approximately proportional toƒ-4. In addition, the Faraday rotation due to the geomagnetic field in the ionosphere becomes significant. This paper presents an analysis with numerical examples of the following effects in the frequency range from 100 MHz to 2 GHz in order to show the frequency dependence and the effects of total electron content (TEC) of the ionosphere. First, the ionospheric turbulence can reduce the coherent length below the equivalent aperture size, and the azimuthal resolution becomes greater than D/2 where D is the antenna aperture size. Second, the ionospheric dispersion causes a shift of the imagery due to the group velocity. Third, the dispersion also creates broadening of the pulse. In addition, multiple scattering due to ionospheric turbulence gives rise to pulse broadening. Fourth, we consider the Faraday rotation effect and show that the ellipticity change is negligible, but the orientation angle changes significantly at P-band. Numerical examples are shown using typical ionospheric parameters, turbulence spectrum, and TEC values.

  8. Solar Rotational Effects on the Mars Ionosphere

    NASA Astrophysics Data System (ADS)

    Talaat, E. R.; Paxton, L.; Zhu, X.; Yee, J.; Smith, D. C.

    2006-05-01

    In this paper, using opportune periods during the five years of MGS radio occultation observations of the Martian ionosphere, we examine the short-term variability in the ionospheric profile peak densities and peak heights. During solar maximum, strong solar rotational signatures were observed. On Mars, the morphology of the ionosphere is thought to be controlled by photochemical processes (coupled with the neutral atmosphere). In this paper, we will present the observed magnitude of the variabilities the phasing with solar forcing, and quantify the source mechanisms with a 1-D ionospheric model.

  9. Thermospheric storms and related ionospheric effects

    NASA Technical Reports Server (NTRS)

    Chandra, S.; Spencer, N. W.

    1976-01-01

    A comparative study of thermospheric storms for equinox and winter conditions is presented based on neutral-composition measurements from the Aeros-A neutral-atmosphere temperature experiment. The main features of the two storms as inferred from changes in N2, Ar, He, and O are described, and their implications for current theories of thermospheric storms are discussed. On the basis of the study of the F-region critical frequency measured from a chain of ground-based ionospheric stations during the two storm periods, the general characteristics of the ionospheric storms and the traveling ionospheric disturbances are described. It is suggested that the positive and negative phases of ionospheric storms are different manifestations of thermospheric storms.

  10. Bounding higher-order ionosphere errors for the dual-frequency GPS user

    NASA Astrophysics Data System (ADS)

    Datta-Barua, S.; Walter, T.; Blanch, J.; Enge, P.

    2008-10-01

    Civil signals at L2 and L5 frequencies herald a new phase of Global Positioning System (GPS) performance. Dual-frequency users typically assume a first-order approximation of the ionosphere index of refraction, combining the GPS observables to eliminate most of the ranging delay, on the order of meters, introduced into the pseudoranges. This paper estimates the higher-order group and phase errors that occur from assuming the ordinary first-order dual-frequency ionosphere model using data from the Federal Aviation Administration's Wide Area Augmentation System (WAAS) network on a solar maximum quiet day and an extremely stormy day postsolar maximum. We find that during active periods, when ionospheric storms may introduce slant range delays at L1 as high as 100 m, the higher-order group errors in the L1-L2 or L1-L5 dual-frequency combination can be tens of centimeters. The group and phase errors are no longer equal and opposite, so these errors accumulate in carrier smoothing of the dual-frequency code observable. We show the errors in the carrier-smoothed code are due to higher-order group errors and, to a lesser extent, to higher-order phase rate errors. For many applications, this residual error is sufficiently small as to be neglected. However, such errors can impact geodetic applications as well as the error budgets of GPS Augmentation Systems providing Category III precision approach.

  11. Investigation of the seismo-ionospheric effects on the base of GPS/GLONASS measurements

    NASA Astrophysics Data System (ADS)

    Zakharenkova, I.; Cherniak, Iu.; Shagimuratov, I.; Suslova, O.

    2012-04-01

    During last years the monitoring of the ionospheric effects of different origin is carried out mainly with use of Global Navigating Satellite Systems (GPS / GLONASS). By means of measurements of the signals temporal delays it is possible to do the mapping of total electron content (TEC) in a column of unit cross section through the Earth's ionosphere and investigate its temporal evolution depended on the variations of electron concentration (NmF2) in the F2 ionospheric region. In the given report we present results of analysis of spatial-temporal variability of the ionosphere during the earthquake preparation phase for several major earthquakes which took place in Japan. It was revealed that for considered events mainly positive TEC anomalies appeared 1-5 days prior to the earthquake. The enhancement of electron concentration reached the value of 30-70% relative to the quiet geomagnetic conditions. In order to analyze the revealed effects in more details it was additionally involved data of GPS TEC values over GPS stations located at different distances from earthquake epicenters and data of vertical sounding of the ionosphere (NICT database). The hourly values of critical frequency of ionospheric F2 and Es layers were obtained from manually scaled ionograms recorded at Japanese ionospheric sounding stations Wakkanai, Kokubunji and Yamagawa. Acknowledgments. We acknowledge the IGS community for providing GPS permanent data and WDC for Ionosphere, Tokyo, National Institute of Information and Communications Technology (NICT) for providing ionosonde data. This work was supported by Russian Federation President grant MK-2058.2011.5.

  12. Effects of UGTs on the ionosphere

    NASA Astrophysics Data System (ADS)

    Argo, P. E.; Fitzgerald, T. J.

    The processes that propagate local effects of underground nuclear tests from the ground into the upper atmosphere, and produce a detectable signal in the ionosphere are described. Initially, the blast wave from a underground test (UGT) radially expands, until it reaches the surface of the earth. The wave is both reflected and transmitted at this sharp discontinuity in propagation media. Tne reflected wave combines with the incident wave to form an 'Airy surface,' at which very strong ripping forces tear the earth apart. This broken region is called the 'spat zone,' and is launched into ballistic motion. The resultant ground motion launches an acoustical wave into the atmosphere. This acoustic wave, with overpressures of a few tenths of one percent, propagates upwards at the speed of sound. Assuming purely linear propagation, the path of the acoustic energy can be tracked using raytracing models. Most of the wave energy, which is radiated nearly vertically, tends to propagate into the upper atmosphere, while wave energy radiated at angles greater than about 30 degrees to the vertical will be reflected back to earth and is probably what is seen by most infrasonde measurements.

  13. Ionospheric Geo-effectiveness of Magnetic Clouds

    NASA Astrophysics Data System (ADS)

    Bronder, T. J.; Knipp, D. J.; Lynch, B.; Zurbuchen, T.; McHarg, M. G.; Chun, F. K.

    2002-12-01

    We present an analysis of the geo-effectiveness of magnetic clouds and the disturbed solar wind surrounding them. Estimates of the ionospheric Joule heating rates based on two ground magnetic indices and estimates of auroral zone particle heating from polar satellites will be combined to provide a summary of the total geomagnetic heating during magnetic cloud passage. Preliminary estimates suggest that intervals of magnetic cloud passage experience about 50 percent greater heating rates than intervals associated with the more general class of interplanetary coronal mass ejection. Heating rates for magnetic clouds are about four times greater than heating rates estimated for intervals of background slow solar wind flow. Preliminary work also indicates that magnetic clouds lying in the ecliptic plane (leading or trailing fields oriented N-S or S-N) have heating rates about 50 percent greater than clouds with leading or trailing fields perpendicular to the ecliptic plane. We will provide hourly heating profiles for more than 50 magnetic clouds passing the earth during the rise and peak of solar cycle 23.

  14. Ionospheric criticial frequencies and solar cycle effects

    NASA Astrophysics Data System (ADS)

    Kilcik, Ali; Ozguc, Atila; Rozelot, Jean Pierre; Yiǧit, Erdal; Elias, Ana; Donmez, Burcin; Yurchyshyn, Vasyl

    2016-07-01

    The long term solar activity dependencies of ionospheric F1 and F2 regions critical frequencies (foF1 and foF2) are investigated observationally for the last four solar cycles (1976-2015). We here show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency (foF1) peaks at the same time with small SG numbers, while the foF2 reaches its maximum at the same time with the large SG numbers especially during the solar cycle 23. Thus, we may conclude that the sensitivities of ionospheric F1 and F2 region critical frequencies to sunspot group (SG) numbers are associated with different physical processes that are yet to be investigated in detail. Such new results provide further evidence that the two ionospheric regions have different responses to the solar activity. We also analyzed short term oscillatory behavior of ionospheric critical frequencies and found some solar signatures.

  15. Method for Canceling Ionospheric Doppler Effect

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1982-01-01

    Unified transponder system with hydrogen-maser oscillators at both stations can compensate for both motional and ionospheric components of Doppler shift. Appropriate choices of frequency shift in output of mixer m3. System exploits proportionality between dispersive component of frequency shift and reciprocal of frequency to achieve cancellation of dispersive component at output.

  16. Effect of Ionosphere on Geostationary Communication Satellite Signals

    NASA Astrophysics Data System (ADS)

    Erdem, Esra; Arikan, Feza; Gulgonul, Senol

    2016-07-01

    Geostationary orbit (GEO) communications satellites allow radio, television, and telephone transmissions to be sent live anywhere in the world. They are extremely important in daily life and also for military applications. Since, satellite communication is an expensive technology addressing crowd of people, it is critical to improve the performance of this technology. GEO satellites are at 35,786 kilometres from Earth's surface situated directly over the equator. A satellite in a geostationary orbit (GEO) appears to stand still in the sky, in a fixed position with respect to an observer on the earth, because the satellite's orbital period is the same as the rotation rate of the Earth. The advantage of this orbit is that ground antennas can be fixed to point towards to satellite without their having to track the satellite's motion. Radio frequency ranges used in satellite communications are C, X, Ku, Ka and even EHG and V-band. Satellite signals are disturbed by atmospheric effects on the path between the satellite and the receiver antenna. These effects are mostly rain, cloud and gaseous attenuation. It is expected that ionosphere has a minor effect on the satellite signals when the ionosphere is quiet. But there are anomalies and perturbations on the structure of ionosphere with respect to geomagnetic field and solar activity and these conditions may cause further affects on the satellite signals. In this study IONOLAB-RAY algorithm is adopted to examine the effect of ionosphere on satellite signals. IONOLAB-RAY is developed to calculate propagation path and characteristics of high frequency signals. The algorithm does not have any frequency limitation and models the plasmasphere up to 20,200 km altitude, so that propagation between a GEO satellite and antenna on Earth can be simulated. The algorithm models inhomogeneous, anisotropic and time dependent structure of the ionosphere with a 3-D spherical grid geometry and calculates physical parameters of the

  17. Effects of Saturn's magnetospheric dynamics on Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Edberg, N. J. T.; Andrews, D. J.; Bertucci, C.; Gurnett, D. A.; Holmberg, M. K. G.; Jackman, C. M.; Kurth, W. S.; Menietti, J. D.; Opgenoorth, H. J.; Shebanits, O.; Vigren, E.; Wahlund, J.-E.

    2015-10-01

    We use the Cassini Radio and Plasma Wave Science/Langmuir probe measurements of the electron density from the first 110 flybys of Titan to study how Saturn's magnetosphere influences Titan's ionosphere. The data is first corrected for biased sampling due to varying solar zenith angle and solar energy flux (solar cycle effects). We then present results showing that the electron density in Titan's ionosphere, in the altitude range 1600-2400 km, is increased by about a factor of 2.5 when Titan is located on the nightside of Saturn (Saturn local time (SLT) 21-03 h) compared to when on the dayside (SLT 09-15 h). For lower altitudes (1100-1600 km) the main dividing factor for the ionospheric density is the ambient magnetospheric conditions. When Titan is located in the magnetospheric current sheet, the electron density in Titan's ionosphere is about a factor of 1.4 higher compared to when Titan is located in the magnetospheric lobes. The factor of 1.4 increase in between sheet and lobe flybys is interpreted as an effect of increased particle impact ionization from ˜200 eV sheet electrons. The factor of 2.5 increase in electron density between flybys on Saturn's nightside and dayside is suggested to be an effect of the pressure balance between thermal plus magnetic pressure in Titan's ionosphere against the dynamic pressure and energetic particle pressure in Saturn's magnetosphere.

  18. Ionospheric Effects of Underground Nuclear Explosions

    NASA Astrophysics Data System (ADS)

    Park, J.; von Frese, R. R.; G-Brzezinska, D. A.; Morton, Y.

    2010-12-01

    Telemetry from the Russian INTERCOSMOS 24 satellite recorded ELF and VLF electromagnetic disturbances in the outer ionosphere from an underground nuclear explosion that was detonated at Novaya Zemlya Island on 24 October 1994. The IC24 satellite observations were obtained at about 900 km altitude within a few degrees of ground zero. The disturbances were interpreted for magnetohydrodynamic excitation of the ionosphere’s E layer by the acoustic wave. Electrons are accelerated along the magnetic force lines to amplify longitudinal currents and magnetic disturbances that may be measured by magnetometers at ground-based observatories and on-board satellites. The underground nuclear test near P’unggye, North Korea on 25 May 2009 provides a further significant opportunity for studying the utility of ionospheric disturbances for characterizing ground zero. Of the seismic, infrasound, hydroacoustic, and radionuclide detection elements of the International Monitoring System (IMS) established by the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), only the first two elements detected this event. However, the event also appears to have been recorded as a direct traveling ionospheric disturbance (TID) in the slant total electron content (TEC) observations derived from a network of the Global Navigation Satellite System (GNSS) measurements. The TID was observed to distances of at least 600 km from the explosion site propagating with a speed of about 281m/s. Thus, the global distributions and temporal variations of the TEC, may provide important information to help detect and characterize clandestine underground nuclear explosions.

  19. Ionospheric Effects from the superbolid exploded over the Chelyabinsk area

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yuri; Smirnov, Vladimir; Kuznetsov, Vladimir; Smirnova, Elena

    The Chelyabinsk meteorite fall is undoubtedly the most documented in history. Its passage through the atmosphere was recorded by video and photographers, visual observers, infrasonic microphones, seismographs on the ground, and by satellites in orbit. The data of transionospheric sounding by signals from the GPS cluster satellites carried out in the zone of explosion of the Chelyabinsk meteoroid have been analyzed. The analysis has shown that the explosion had a very weak effect on the ionosphere. The observed ionospheric disturbances were asymmetric with respect to the explosion epicenter. The signals obtained were compared both in shape and in amplitude with the known surface explosions for which the diagnostics of the ionospheric effects had been made by radio techniques. Ionospheric effects in the form of acoustic-gravity waves (AGW) produced by 500-600 tons TNT explosions on the ground are detected with confidence both by vertical sounding and by GPS techniques. This allows us to suggest that the reported equivalent of the meteoroid explosion was obviously overestimated. The experiments on the injection of barium vapor (3.3 kg) carried out under similar conditions in the terminator zone revealed the response of the ionosphere in variations of the critical frequencies of the layer at a distance of 1500-2000 km (AGW with a period of 5-10 min). The absence of such ionospheric effects in the remote zone at 1500-1700 km from the epicenter of the bolide explosion in the case under discussion also makes us feel doubtful about the estimated explosion equivalent.

  20. Maps of average ionospheric vorticity ordered by relationship with the open-closed magnetic field line boundary

    NASA Astrophysics Data System (ADS)

    Chisham, Gareth

    2015-04-01

    Spatiotemporal variations of ionospheric vorticity are a measure of the dynamical coupling of the magnetosphere to the ionosphere via magnetic field-aligned currents (FACs). Indeed, ionospheric vorticity measurements have often been used as proxy measurements for FACs. Previously, we have determined statistical models of ionospheric vorticity using 6 years of ionospheric convection velocity measurements made by the SuperDARN HF radar network in the northern hemisphere ionosphere and shown that the spatial variation of these probability distributions is well organised according to the well-established large-scale FAC structure in the polar ionosphere. However, to date, these statistical models have been parameterised solely by the state of the interplanetary magnetic field (IMF), and as such do not account for the range of polar cap sizes that occur for a single IMF state. This leads to a distortion of the shape of the resulting statistical maps that makes features in the statistical variations appear smoother than those in instantaneous/short-time averaged measurements. This is because the averaging process does not consider the variable size of the polar cap, by which spatial features in the ionospheric vorticity variation are ordered. Using open-closed magnetic field line boundary measurements determined from FUV imager data from the IMAGE spacecraft, we investigate the parameterisation of the statistical ionospheric vorticity models with polar cap size in addition to the state of the IMF. The results of this analysis have implications for other statistical models determined in this way, such as those for FACs and ionospheric convection.

  1. Irregularities in ionospheric plasma clouds: their evolution and effect on radio communication. Technical report

    SciTech Connect

    Vesecky, J.F.; Chamberlain, J.W.; Cornwall, J.M.; Hammer, D.A.; Perkins, F.W.

    1980-09-01

    Both satellite radio communications, which travel through the Earth's ionosphere, and high frequency (HF) sky wave circuits, which use the ionosphere as a refracting medium, can be strongly affected by radio wave scintillation. High altitude nuclear explosions cause scintillation (by strongly disturbing the ionosphere) and thus severely degrade satellite radio communications over a large region. Since further atmospheric nuclear tests are banned, a thorough understanding of the physics involved in both the disturbed ionosphere and its interaction with radio waves is necessary in order to design radio communications systems which will operate satisfactorily in a nuclear environment. During the 1980 JASON Summer Study we addressed some aspects of the evolution of ionospheric irregularities following a high altitude nuclear explosion--the radio wave propagation theory being apparently well understood for the satellite link case. In particular, we have worked on irregularity evolution at late times (approx. hours) after an explosion and the impact of early time irregularity structure on late time evolution. We also raise the question of scintillation effects on HF sky wave communications.

  2. Numerical modeling of the ionospheric effects of substorms

    NASA Astrophysics Data System (ADS)

    Klimenko, M. V.; Klimenko, V. V.

    2008-12-01

    The investigations of the substorm are carried out already many years. In spite of that, the single-valued answers on many questions which arise at the researchers of the substorm till now are not given. To such questions it is possible to concern the questions about the mechanism of occurrence of the substorm and on the influence of the substorm on the Earth's ionosphere. At modeling of the ionospheric effects of substorms it is important to know the following. How does the potential drop through polar caps change at initial stages of the substorm development - stepwise or smoothly? What is the duration of these changes? What and how does occur with the potential drop in the further during development of the substorm down to its termination? How does the time course of intensity of the field aligned currents of the first zone change before the substorm beginning, during substorm and after its termination? Is there a time delay of changes of the field aligned currents of the second zone relative to changes of the field aligned currents of the first zone or potential drop through polar caps? If the delay exists, what is it? How does the high-energy particle precipitation in the auroral zones and polar caps change during the substorm? Is it necessary to set at the modeling of the substorm effects the Substorm Current Wedge? If it is necessary, how make it correctly? On these questions we do not have the single-valued answers. But we shall like very strongly for them to have. We have carried out the modeling researches of the substorm influence on the ionosphere in various statements of the problem. The investigations were spent on the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere, added by the new block of calculation of electric fields in the Earth's ionosphere. In our investigations we have given the particular attention: to electrodynamics of the ionosphere; to changes of the global distributions of foF2, TEC and ion composition of

  3. Stochastic Modeling Considering Ionospheric Scintillation Effects on GNSS Relative and Point Positioning

    NASA Astrophysics Data System (ADS)

    Silva, H. A.; Camargo, P. D.; Monico, J. F.; Aquino, M.; Marques, H. A.; de Franceschi, G.

    2008-12-01

    Nowadays, Global Navigation Satellite Systems (GNSS), especially the Global Positioning System (GPS), represent one of the most used techniques for geodetic positioning. The functional models related with the GNSS observables are better understood than the stochastic models, considering that the development of the latter is more complex. Usually, the stochastic models are used in a simplified form, as the standard models, which assume that all the GNSS observables are statistically independent and have the same variance. However, the stochastic models may be investigated in more detail, considering for example, the effects of ionospheric scintillation. The high latitudes regions experiment strong influence of the ionospheric effects, in particular ionospheric scintillation. Considering the availability of specially designed GNSS receivers that provide ionospheric scintillation parameters, these effects can be mitigated through improved stochastic models. This paper presents the methodology and results from GPS relative and point positioning considering ionospheric scintillation in the stochastic modeling. Two programs have been developed to obtain the results from relative and point positioning: "GPSeq" (currently under development at the FCT/UNESP Sao Paulo State University - Brazil) and "pp_sc" (developed in a collaborative project between FCT/UNESP and Nottingham University - UK). The point positioning approach can be realized considering an epoch by epoch solution and the relative positioning using a Kalman Filter and the LAMBDA method to solve the Double Differences ambiguities. Both programs have the option to estimate the ionospheric residuals as one stochastic process using the white noise or random walk correlation models. In both cases it is also possible to use the L1/L2 ion-free linear combination. The stochastic modeling considering ionospheric scintillation has been implemented based in the models of Conker et al. (2003), following the approach

  4. Ionospheric modelling for navigation

    NASA Astrophysics Data System (ADS)

    Aragon Angel, M. A.

    Signals transmitted to and from satellites for communication and navigation purposes must pass through the ionosphere Ionospheric irregularities most common at equatorial latitudes although they could occur anywhere can have a major impact on system performance and reliability and commercial navigation service satellite-based providers need to account for their effects For a GNSS single-frequency receiver the Slant Total Electron Content STEC must be known by the user through broadcast corrections In this context there are several sets of broadcast parameters that can be defined to take into account this ionospheric term The chosen model to generate the ionospheric correction coefficients for the present study is the NeQuick model although with a number of adaptations intended to improve effective ionospheric effect modelling performances The aim of this study is to describe a possible adaptation to the NeQuick model for real time purposes and suitable for single frequency users Therefore it will be necessary to determine the performance of this modified NeQuick model in correcting the ionospheric delay In order to generate the ionospheric corrections for single frequency receivers using the NeQuick model a certain approach should be followed to adapt the performance of NeQuick since this model was originally developed to provide TEC using averaged monthly information of the solar activity and not daily one Thus to use NeQuick for real time applications as an ionospheric broadcasted model such as Klobuchar solar daily information at the user point

  5. Ionospheric effects of the extreme solar activity of February 1986

    NASA Technical Reports Server (NTRS)

    Boska, J.; Pancheva, D.

    1989-01-01

    During February 1986, near the minimum of the 11 year Solar sunspot cycle, after a long period of totally quiet solar activity (R sub z = 0 on most days in January) a period of a suddenly enhanced solar activity occurred in the minimum between solar cycles 21 and 22. Two proton flares were observed during this period. A few other flares, various phenomena accompanying proton flares, an extremely severe geomagnetic storm and strong disturbances in the Earth's ionosphere were observed in this period of enhanced solar activity. Two active regions appeared on the solar disc. The flares in both active regions were associated with enhancement of solar high energy proton flux which started on 4 February of 0900 UT. Associated with the flares, the magnetic storm with sudden commencement had its onset on 6 February 1312 UT and attained its maximum on 8 February (Kp = 9). The sudden enhancement in solar activity in February 1986 was accompanied by strong disturbances in the Earth's ionosphere, SIDs and ionospheric storm. These events and their effects on the ionosphere are discussed.

  6. Effects of ionizing energetic electrons and plasma transport in the ionosphere during the initial phase of the December 2006 magnetic storm

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.; Huang, C.-M.; Dmitriev, A. V.; Kunitsyn, V. E.; Andreeva, E. S.; Nesterov, I. A.; Klimenko, M. V.; Klimenko, V. V.; Tumanova, Yu. S.

    2016-06-01

    The initial phase of a major geomagnetic storm on 14 December 2006 was selected in order to investigate the ionizing effect of energetic electrons in the ionosphere. The global network of GPS receivers was used to analyze the total electron content (TEC). A strong positive ionospheric storm of ~20 TEC units (TECU) with ~6 h duration was observed on the dayside during the interval of northward interplanetary magnetic field. At the same time, the NOAA/POES satellites observed long-lasting intense fluxes of >30 keV electrons in the topside ionosphere at middle and low latitudes, including a near-equatorial forbidden zone outside of the South Atlantic Anomaly (SAA). We found that the TEC increases overlapped well with the enhancements of energetic electrons. Modeling of the ionospheric response by using a Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere, based on the standard mechanisms of plasma transport, could only partially explain the ionospheric response and was unable to predict the long-duration increase of TEC. For the energetic electrons, we estimated the ionizing effect of ~45 TECU and ~23 TECU in the topside ionosphere, respectively, inside and outside of SAA. The ionizing effect contributed from 50% to 100% of TEC increases and provided the long duration and wide latitudinal extension of the positive ionospheric storm. This finding is a very important argument in supporting significant ionizing effect of energetic electrons in the storm time ionosphere both at middle and low latitudes.

  7. IMF-By effect on the mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Jin, Hidekatsu

    The primary factor that controls ionospheric total electron content (TEC) variations is solar UV/EUV radiations through the ionization of the thermospheric neutral particles and through the modification of the thermosphere. Changes in temperature and composition of the neutral atmosphere and the atmospheric circulation greatly affect the ionospheric electron density. Because such a relationship between the solar spectral irradiance and the ionospheric TEC is highly complex, we applied an artificial neural network (ANN) technique that has a great capability of function approximation of complex systems to model solar irradiance effects on TEC. Three solar proxies, F_{10.7}, SOHO_SEM_{26-34} EUV emission index, and MgII_c-w-r were chosen as input parameters to the ANN-TEC model. Another channel of energy flow from the sun to the earth’s ionosphere is the solar wind. The am index and several solar wind magnetosphere coupling functions were chosen as additional inputs to the ANN to model the effects of magnetic disturbances. Somewhat minor but interesting effects on TEC variations emerged when the major effects of solar irradiance and magnetic disturbances were removed. We analyzed the time series of the residual error in TEC prediction by using a wavelet transformation, which revealed a periodic increase in error approximately every 27 days in the summer. Possible origins of the error are (1) insufficient modeling of the solar activity effect, (2) lunar tidal forcing, (3) coupling with planetary waves in the lower atmosphere, and (4) solar wind effects. Examinations refused the first three possibilities. We investigated solar wind parameters that are not concerned in geomagnetic disturbances. The 27-day periodic error during the summer disappeared when the IMF-By component and the solar wind velocity were included in the input space of the ANN. Possible explanation of the IMF-By effect is discussed in terms of changes in the thermospheric general circulation pattern.

  8. Stormtime Ionospheric Outflow Effects in Global Multi-Fluid MHD

    NASA Astrophysics Data System (ADS)

    Garcia-Sage, K.; Moore, T. E.; Eccles, V.; Merkin, V. G.; Welling, D. T.; Schunk, R. W.; Barakat, A. R.

    2015-12-01

    We present work detailing the effects of ionospheric outflow in the magnetosphere during the Sept 27- Oct 4, 2002 and Oct 22- Oct 29, 2002 GEM storms. The Multi-Fluid LFM global MHD code is driven by OMNI solar wind and IMF data and by outflow from the Generalized Polar Wind (GPW) model. The GPW input results in a realistic and dynamic, although not self-consistent, outflow of O+, H+, and He+ from the ionosphere. The validity of this outflow and its entry into the magnetosphere is tested through comparisons to Cluster and geosynchronous spacecraft observations. We show the access of these various populations to the magnetosphere, and we examine their effects on plasma sheet structure and storm time dynamics.

  9. Ionospheric storm effects at subauroral latitudes: A case study

    SciTech Connect

    Proelss, G.W. ); Brace, L.H.; Mayr, H.G. ); Carignan, G.R.; Killeen, T.L. ); Klobuchar, J.A. )

    1991-02-01

    An attempt is made to classify ionospheric storm effects at subauroral latitudes according to their presumed origin. The storm of December 7/8, 1982, serves as an example. It is investigated using ionosonde, electron content, and DE 2 satellite data. The following effects are distinguished: (1) positive storm effects caused by traveling atmospheric disturbances, (2) positive storm effects caused by changes in the large-scale thermospheric wind circulation, (3) positive storm effects caused by the expansion of the polar ionization enhancement, (4) negative storm effects caused by perturbations of the neutral gas composition, and (5) negative storm effects caused by the equatorward displacement of the trough region.

  10. Ionospheric storm effects at subauroral latitudes - A case study

    NASA Technical Reports Server (NTRS)

    Proelss, G. W.; Brace, L. H.; Mayr, H. G.; Carignan, G. R.; Killeen, T. L.

    1991-01-01

    An attempt is made to classify ionospheric storm effects at subauroral latitudes according to their presumed origin. The storm of December 7/8, 1982, serves as an example. It is investigated using ionosonde, electron content, and DE 2 satellite data. The following effects are distinguished: (1) positive storm effects caused by traveling atmospheric disturbances, (2) positive storm effects caused by changes in the large-scale thermospheric wind circulation, (3) positive storm effects caused by the expansion of the polar ionization enhancement, (4) negative storm effects caused by perturbations of the neutral gas composition, and (5) negative storm effects caused by the equatorward displacement of the trough region.

  11. The Effect of Ionospheric Models on Electromagnetic Pulse Locations

    SciTech Connect

    Fenimore, Edward E.; Triplett, Laurie A.

    2014-07-01

    Locations of electromagnetic pulses (EMPs) determined by time-of-arrival (TOA) often have outliers with significantly larger errors than expected. In the past, these errors were thought to arise from high order terms in the Appleton-Hartree equation. We simulated 1000 events randomly spread around the Earth into a constellation of 22 GPS satellites. We used four different ionospheres: “simple” where the time delay goes as the inverse of the frequency-squared, “full Appleton-Hartree”, the “BobRD integrals” and a full raytracing code. The simple and full Appleton-Hartree ionospheres do not show outliers whereas the BobRD and raytracing do. This strongly suggests that the cause of the outliers is not additional terms in the Appleton-Hartree equation, but rather is due to the additional path length due to refraction. A method to fix the outliers is suggested based on fitting a time to the delays calculated at the 5 GPS frequencies with BobRD and simple ionospheres. The difference in time is used as a correction to the TOAs.

  12. Influence of geomagnetic storms of September 26-30, 2011, on the ionosphere and HF radiowave propagation. I. Ionospheric effects

    NASA Astrophysics Data System (ADS)

    Klimenko, M. V.; Klimenko, V. V.; Bessarab, F. S.; Ratovsky, K. G.; Zakharenkova, I. E.; Nosikov, I. A.; Stepanov, A. E.; Kotova, D. S.; Vorobjev, V. G.; Yagodkina, O. I.

    2015-11-01

    Geomagnetic storm ionospheric effects observed at different latitudes and longitudes on September 26 and 28-30, 2011, are interpreted with the GSM TIP model. It has been justified that the results of this model can subsequently be used to calculate the HF radiowave ray tracing under quiet conditions and for the selected dates in September 2011. The model calculations are compared with observations of the ionospheric parameters performed by different radiophysical methods. The presented results confirm the classical mechanisms by which positive and negative ionospheric storms are formed during the main phase of a geomagnetic storm. At high latitudes, the electron density is mainly disturbed due to changes in the neutral composition of the thermosphere, resulting in an increase in the chemical loss rates, and the electromagnetic drift, which results in a substantial reconstruction of the high-latitude ionosphere owing to the horizontal plasma transfer. During the storm recovery phase at midlatitudes, electron density positive disturbances are formed in the daytime due to an increase in the n(O)/ n(N2) ratio; at the same time, negative effects in the electron density are formed at night as a result of plasma tube devastation. Comparison with the observations indicates that the presented model calculation results can be used to describe a medium for solving problems of radiowave propagation in the ionosphere during the storm main phase on September 26 and during the recovery phase on September 28-30, 2011.

  13. Improved Ionospheric Correction for DGPS by taking into account the Horizontal Gradient Effect over the Equatorial Region

    NASA Astrophysics Data System (ADS)

    Nagarajoo, Karthigesu

    Improved Ionospheric Correction for DGPS by taking into account the Horizontal Gradient Effect over the Equatorial Region K Nagarajoo Universiti Tun Hussein Onn Malaysia 86400 Parit Raja Johor Darul Takzim Email: karthi@uthm.edu.my DGPS is a system where the range error at a reference station will be eliminated from the range measurement at the user, which `view' the same satellite, presuming that the satellite's path to both the reference station and the user experience common errors due to the ionosphere, clock errors, multipath etc. In this assumption, the error due to the ionospheric refraction is assumed to be the same for the two closely spaced paths (such as a baseline length between reference station and the user is 10km) and thus the presence of ionospheric horizontal gradient is ignored. If a user's path is exposed to a drastically large ionosphere gradient (i.e., over the equatorial region), the large difference of ionosphere delays between the reference station and the user can result in significant position error for the user. Apart from that, the difference in the elevation angle at the reference and the user that `view' the same satellite to get the range measurement does also introduce some millimetre to centimetre of range difference. The neglect of the effect due to the presence of an ionospheric horizontal gradient and the elevation angle's difference (at both ends of the baseline) will cause a significant amount of error in the final DGPS user positioning. In this work, those two effects have been investigated in order to obtain a more accurate ionospheric correction for DGPS and have been found to be roughly comparable showing that they are both important. By performing ray-tracing calculations (using Jones 3-D Ray Tracing program) with and without a linear horizontal ionosphere gradient, the effects of elevation angle and horizontal gradient have been separated and a final positioning improvement of about 8cm has been shown at the user of a

  14. Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Fontheim, E. G.; Ong, R. S. B.; Roble, R. G.; Mayr, H. G.; Hoegy, W. H.; Ionson, J. A.; Baron, M. J.; Wickwar, V. B.; Vondrak, R. R.

    1978-01-01

    By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.

  15. Methods of alleviation of ionospheric scintillation effects on digital communications

    NASA Technical Reports Server (NTRS)

    Massey, J. L.

    1974-01-01

    The degradation of the performance of digital communication systems because of ionospheric scintillation effects can be reduced either by diversity techniques or by coding. The effectiveness of traditional space-diversity, frequency-diversity and time-diversity techniques is reviewed and design considerations isolated. Time-diversity signaling is then treated as an extremely simple form of coding. More advanced coding methods, such as diffuse threshold decoding and burst-trapping decoding, which appear attractive in combatting scintillation effects are discussed and design considerations noted. Finally, adaptive coding techniques appropriate when the general state of the channel is known are discussed.

  16. Effects of the equatorial ionosphere on L-band Earth-space transmissions

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.; Flock, Warren L.

    1993-01-01

    Ionosphere scintillation can effect satellite telecommunication up to Ku-band. Nighttime scintillation can be attributed to large-scale inhomogeneity in the F-region of the ionosphere predominantly between heights of 200 and 600 km. Daytime scintillation has been attributed to sporadic E. It can be thought of as occurring in three belts: equatorial, high-latitude, and mid-latitude, in order of severity. Equatorial scintillation occurs between magnetic latitudes +/- 25 degrees, peaking near +/- 10 degrees. It commonly starts abruptly near 2000 local time and dies out shortly after midnight. There is a strong solar cycle dependence and a seasonal preference for the equinoxes, particularly the vernal one. Equatorial scintillation occurs more frequently on magnetically quiet than on magnetically disturbed days in most longitudes. At the peak of the sunspot cycle scintillation depths as great as 20 dB were observed at L-band.

  17. The effect of large-scale tropospheric storms on the ionospheres of giant planets

    NASA Astrophysics Data System (ADS)

    Matcheva, Katia

    2015-11-01

    It is well recognized that large-scale storms in the Earth troposphere can leave observable signatures in the structure of the ionosphere in terms of local electron density distribution. Terrestrial numerical models indicate that thunderstorms can change the electron density by more than an order of magnitude (Shao et al. 2012). The atmospheres of Jupiter and Saturn are riddled by atmospheric storms of all scales. Lightning has been successfully detected in optical images in the tropospheres of both planets. Our work presents a theoretical study of the dynamical and electromagnetic effects of large thunderstorms on the vertical plasma distribution in the ionospheres of Jupiter and Saturn and compares the predicted signatures with the available electron density profiles from the Galileo and the Cassini missions.

  18. Examination of Prompt Effects of Solar X-ray Flares on Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Eccles, J. V.

    2007-12-01

    Photons from solar X-ray flares arrive at the Earth only eight minutes after emission. The short wavelength region of the solar spectrum is effective in modifying the ionization of the dayside upper atmosphere. For periods like the 2003 Halloween Solar events, the solar flares enhanced the E and D regions significantly over the quiet time background ionosphere. The effects of these enhancements on HF and VLF signal propagation and absorption are well understood and widely known. We present studies of the space weather impacts of sustained, elevated solar x-ray and EUV levels of the background spectrum during solar active times related to the changes in the dayside conductivities. We show that not only the dayside conductivities sustain at an order of magnitude higher values than background levels, but the Pedersen-to-Hall conductivity ratio increases by a factor of 2 to 3 during high solar X-ray periods when compared to quiet periods. The effects of prompt changes of the dayside conductivities associated with a solar flare event on the dynamo electric fields and ionospheric currents are then systematically examined by using a model of the low-latitude ionospheric electrodynamics.

  19. Effects of ionospheric turbulence on SPS pilot signal

    NASA Technical Reports Server (NTRS)

    Clynch, J. R.

    1981-01-01

    The spatial variation of the electron density was studied by monitoring the differential Doppler on radio beacons aboard the Navy navigation satellites. The radio frequency heater was used to deposit energy in the F-region ionosphere with the heating frequency above peak plasma frequency. The effects of the solar power satellite power beam on the pilot signal were simulated. It was found that a small depletion was formed in the beam and that there was turbulence in the elctron density up the magnetic field line from the beam. It is suggested that the depletion will not seriously affect the power or pilot beams of the solar power satellite.

  20. Effects of solar flares on the ionosphere of Mars.

    PubMed

    Mendillo, Michael; Withers, Paul; Hinson, David; Rishbeth, Henry; Reinisch, Bodo

    2006-02-24

    All planetary atmospheres respond to the enhanced x-rays and ultraviolet (UV) light emitted from the Sun during a flare. Yet only on Earth are observations so continuous that the consequences of these essentially unpredictable events can be measured reliably. Here, we report observations of solar flares, causing up to 200% enhancements to the ionosphere of Mars, as recorded by the Mars Global Surveyor in April 2001. Modeling the altitude dependence of these effects requires that relative enhancements in the soft x-ray fluxes far exceed those in the UV. PMID:16497929

  1. Studing Solar Flare Effects on Ionosphere Using AWESOME Receiver

    NASA Astrophysics Data System (ADS)

    Mustafa, Famil; Babayev, Elchin; Alekperov, Ilgar

    2015-08-01

    Ground based observations of Extremely Low Frequency (ELF) / Very Low Frequency (VLF) (300 Hz 30 kHz) waves are considered as an important remote sensing tool for the investigation of the ionosphere and the magnetosphere. VLF waves find their origin in various natural and artificial phenomena; the natural sources include thunderstorms, lightning and associated phenomena. Sub-ionospheric VLF transmissions propagating inside the Earth-ionosphere wave-guide is also being widely used for investigating sudden ionospheric perturbations (SIDs) in lower part of the ionosphere.

  2. Ion effects on ionospheric electron resonance phenomena

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1974-01-01

    Ion effects are often observed on topside-sounder stimulated electron plasma wave phenomena. A commonly observed effect is a spur, appearing after a time delay corresponding to the proton gyro period, attached to the low frequency side of an electron plasma resonance. The spurs are often observed on the resonances at the electron plasma frequency f sub N, the harmonics nf sub H of the electron cyclotron frequency f sub H (n = 2, 3, 4, ...), and occasionally on the upper hybrid frequency. The spurs on the f sub N resonance are usually quite small unless the f sub N resonance overlaps with an nf sub H resonance; very large spurs are observed during such overlap conditions. Proton spurs are only observed on the nf sub H resonances when the electron plasma waves associated with these resonances are susceptible to the Harris instability and when the electromagnetic z wave can be initiated by the sounderpulse. This instability is the result of a sounder stimulated anisotropic electron velocity distribution. The observations suggest that energy is fed into the nf sub H longitudinal plasma wave from the z wave via wave-mode coupling. The magnitude of the nf sub H spurs for large n is much greater than for small n.

  3. Very low frequency and ELF effects in the upper ionosphere caused by large-scale acoustic waves in the lower ionosphere observed from AUREOL-3 satellite

    NASA Astrophysics Data System (ADS)

    Galperin, Y. I.; Gladyshev, V. A.; Jorjio, N. V.; Kovrazhkin, R. A.; Lissakov, Y. V.; Maslov, V. D.; Nikolaenko, L. M.; Sagdeev, R. Z.; Molchanov, O. A.; Mogilevsky, M. M.

    The active MASSA experiment studied the effects generated in the upper atmosphere and in the magnetosphere by a large-scale acoustic wave from a chemical explosion reaching ionospheric altitudes. The AUREOL-3 satellite crossed the corresponding magnetic force tubes by the time of the development of the electromagnetic processes expected in the lower ionosphere E-region above the explosion. Measurements reveal electromagnetic effects in the ionospheric and magnetospheric plasmas. Effects include nearly electrostatic ELF and VLF noises in the magnetic force tube based on the E-layer ionosphere above the explosion. Their area expands with a velocity of 0.6 km/sec, i.e., as of an acoustic wave in the lower ionosphere. An intense MHD wave is detected at L = 1.31, equatorwards from the explosion L-shell (L = 1.5).

  4. Modeling the Earth-ionosphere cavity. Effects of hypothetical earthquake precursors over the Schumann resonance

    NASA Astrophysics Data System (ADS)

    Toledo-Redondo, Sergio; Salinas, Alfonso; Fornieles, Jesús; Portí, Jorge

    2013-04-01

    Schumann resonances (SR) are global phenomena which occur within the Earth-ionosphere cavity. They are the result of waves propagating several turns around the Earth. Due to the dimensions of the cavity, SR belong to the ELF spectra. The main source of excitation is lightning, and several natural processes do modify the geometry of the cavity and its parameters, like for instance seismo-electromagnetic activity, atmospheric aerosols, solar radiation, etc. Therefore, SR are a promising tool for monitoring (and even forecasting) these natural events. Although several measurements seem to confirm the link between electromagnetic activity and earthquake precursors, the physical mechanisms which produce them are still not clear, and several possibilities have been proposed, like for instance piezoelectric effects on the rocks in the lithosphere, emanation of ionizing gasses like radon, or acoustic gravity waves modifying the properties of the ionosphere in the earthquake preparation zone. However, further measurements combined with analytical models and/or numerical simulations are required in order to better understand the seismo-electromagnetic activity. In this work, the whole Earth-ionosphere electromagnetic cavity has been modeled with 10 km accuracy, by means of Transmission-Line Modeling (TLM) method. Since Schumann resonance parameters depend primarily on the geometry of such cavity, electromagnetic changes produced by earthquake precursors can modify the properties of SR. There is not much quantitative information available about the changes produced by the precursors, either in the lithosphere, atmosphere, or ionosphere. Therefore, different models of the precursors are proposed and their consequences over the SR are evaluated. The so-called Chi-Chi earthquake is employed as a case of study.

  5. Broadband Electron Precipitation in Global MHD Simulation and its Effect on the Ionosphere

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Lotko, W.; Brambles, O. J.; Wiltberger, M. J.

    2010-12-01

    A broadband electron (BBE) precipitation model is implemented and analyzed in the MI coupling module of the Lyon-Fedder-Mobarry MHD simulation. Both number flux and energy flux of precipitating BBEs are regulated by MHD variables calculated near the low-altitude boundary of the LFM simulation. An empirical relation deduced from results of Keiling et al. (2003) is used to relate the AC Poynting flux to the energy flux precipitating BBEs in the simulation. We are investigating two different ways of regulating the number flux of BBE precipitation, one using an empirical relation between AC Poynting flux and number flux (Strangeway, unpublished) and another by constraining the intensity and cut-off energy of a fixed-pitch angle distribution of BBEs in terms of MHD simulation variables. The contributions to ionospheric conductance from BBE precipitation are evaluated using empirical relations derived by Robinson et al. (1987). The BBE-induced-conductance is added to the “standard” auroral contribution to conductance derived from monoenergetic and diffuse electron precipitation in the existing LFM precipitation model. The simulation is driven by ideal SW/IMF conditions with Vsw=400 km/s, Nsw=5/cc and Bz=-5 nT. The simulated time-average AC Poynting flux pattern resembles statistical patterns from Polar data (Keiling et al. 2003), and the simulated statistical pattern of BBE number flux resembles the statistical maps derived from DMSP data (Newell et al. 2009) on the nightside with a similar dawn-dusk asymmetry. The ionospheric Pedersen and Hall conductances are enhanced about 20% by the BBE precipitation. The number flux produced by BBEs is the same order of magnitude as that of monoenergetic and diffuse electrons. We thus expect BBE precipitation to have a moderate effect on the E-region ionosphere and a more significant influence on the density distribution of the F-region ionosphere.

  6. Effects of geographic-geomagnetic pole offset on ionospheric outflow: Can the ionosphere wag the magnetospheric tail?

    NASA Astrophysics Data System (ADS)

    Barakat, Abdallah R.; Eccles, J. Vincent; Schunk, Robert W.

    2015-10-01

    The generalized polar wind model was used to simulate the polar ionosphere during the September/October 2002 storm. The solar terminator moved across the polar caps in a diurnal oscillation during this equinox period. The main conclusions of this study are the following: (1) the terminator oscillation generates a diurnal oscillation in the total hemispheric fluxes of the polar wind from the ionosphere into the magnetosphere; (2) the diurnal oscillation of outflow in the Northern Hemisphere is 12 h out of phase with the Southern Hemisphere; (3) the H+ outflow flux is near its limiting value, so the oscillation is larger than the nonperiodic contributions (e.g., geomagnetic activity); and (4) the O+ flux is less than its limiting value, hence the diurnal oscillation is comparable to the non-periodic effects. The simulation suggests that the hemispherical asymmetry and periodicity of the total ion outflow could "wag the magnetospheric tail" and perhaps contribute to substorm triggering.

  7. Foreword: Ionospheric effects on communication and related systems (IES)

    NASA Astrophysics Data System (ADS)

    Goodman, John M.; Klobuchar, John A.; Soicher, Haim

    1988-07-01

    The special section contained in this issue of Radio Science is the second of two which have been developed from papers presented at the 1987 symposium on the Effect of the Ionosphere on Communication, Navigation, and Surveillance Systems (IES 1987). This technical conference was jointly sponsored by the Naval Research Laboratory (NRL), the Office of Naval Research (ONR), the Air Force Geophysics Laboratory (AFGL), and the Army Communications-Electronics Command (USACECOM). The symposium was held in Springfield, Virginia on May 5-7, 1987 in cooperation with the Defense Nuclear Agency (DNA), the Naval Ocean Systems Center (NOSC), the Institute for Telecommunication Sciences (ITS), and the Voice of America (VOA). See the May-June 1988 issue of Radio Science for a more complete foreword (Radio Sci., 23, 209, 1988).

  8. Ionospheric physics

    SciTech Connect

    Sojka, J.J. )

    1991-01-01

    Advances in all areas of ionospheric research are reviewed for the 1987-1990 time period. Consideration is given to the equatorial ionosphere, the midlatitude ionosphere and plasmasphere, the auroral ionosphere, the polar ionosphere and polar wind, ionospheric electrodynamic inputs, plasma waves and irregularities, active experiments, ionospheric forecasting, and coupling the ionosphere with other regions.

  9. Investigation of ionospheric effects on SAR Interferometry (InSAR): A case study of Hong Kong

    NASA Astrophysics Data System (ADS)

    Zhu, Wu; Ding, Xiao-Li; Jung, Hyung-Sup; Zhang, Qin; Zhang, Bo-Chen; Qu, Wei

    2016-08-01

    Synthetic Aperture Radar Interferometry (InSAR) has demonstrated its potential for high-density spatial mapping of ground displacement associated with earthquakes, volcanoes, and other geologic processes. However, this technique may be affected by the ionosphere, which can result in the distortions of Synthetic Aperture Radar (SAR) images, phases, and polarization. Moreover, ionospheric effect has become and is becoming further significant with the increasing interest in low-frequency SAR systems, limiting the further development of InSAR technique. Although some research has been carried out, thorough analysis of ionospheric influence on true SAR imagery is still limited. Based on this background, this study performs a thorough investigation of ionospheric effect on InSAR through processing L-band ALOS-1/PALSAR-1 images and dual-frequency Global Positioning System (GPS) data over Hong Kong, where the phenomenon of ionospheric irregularities often occurs. The result shows that the small-scale ionospheric irregularities can cause the azimuth pixel shifts and phase advance errors on interferograms. Meanwhile, it is found that these two effects result in the stripe-shaped features in InSAR images. The direction of the stripe-shaped effects keep approximately constant in space for our InSAR dataset. Moreover, the GPS-derived rate of total electron content change index (ROTI), an index to reflect the level of ionospheric disturbances, may be a useful indicator for predicting the ionospheric effect for SAR images. This finding can help us evaluate the quality of SAR images when considering the ionospheric effect.

  10. Effective recombination coefficients in the high-latitude lower ionosphere from solar eclipse observations

    NASA Astrophysics Data System (ADS)

    Cherniakov, Sergey

    2016-07-01

    The photochemistry of processes in the lower ionosphere is rather difficult and up to the end is not developed: it is necessary to specify photochemical schemes, there is big uncertainty in coefficients of separate reactions and concentration of small neutral components. Therefore introduction of the effective coefficients determining the total speed of several reactions was widely adopted when modeling the lower ionosphere, especially the D-region. Experimental opportunities of obtaining of effective recombination coefficients are rather limited. One of the methods allows to define effective recombination coefficients is based on the phenomenon of a solar eclipse and the changes of electron concentration in the ionosphere connected with it. During a solar eclipse there is a short-term and controlled change of solar ionizing radiation intensity that allows to research photochemical processes at known input parameters. The time delay between the eclipse maximum (the sunlight minimum) and the electron concentration minimum at the chosen height during the "short night" is defined as the "sluggishness" [Appleton E.V., 1953] and "relaxation time" [Mitra A., 1974]. The received time delay from observations at the considered ionosphere height with the known electron concentration value gives possibility to calculate the effective recombination coefficient for this height. During solar eclipses on 1 August 2008, on 1 June 2011 and on 20 March 2015 at the partial reflection facility of the observatory "Tumanny" (69° N, 35.7 E) observations of the lower ionosphere behavior were made. On the basis of the obtained data the electron concentration profiles at the heights of the lower ionosphere were received. Calculation of relaxation times allowed to define effective recombination coefficients at some heights of D region of the ionosphere. Appleton, E. V. A note on the "sluggishness" of the ionosphere // J. Atmos. Terr. Phys. - 1953. - Vol. 3, N 5. - P. 282-284. Mitra, A. P

  11. The Search for Ionospheric Effects at 150 MHz with PAPER

    NASA Astrophysics Data System (ADS)

    Gugliucci, Nicole E.; Bradley, R.; PAPER Collaboration

    2012-01-01

    PAPER (the Precision Array to Probe the Epoch of Reionization) is a telescope designed to detect the redshifted hydrogen signal from the early universe. The hydrogen is at a redshift of approximately 6-14, bringing the spin-flip transition of neutral hydrogen from 1.4 GHz to a regime between 100 and 230 GHz. PAPER has a test site with 32 antennas in the Radio Quiet Zone of Green Bank, West Virginia, and a 64-antenna array at the Square Kilometer Array candidate site in the Karoo, South Africa. Astronomical observations at such low frequencies are made more challenging by the refractive properties of the ionosphere. We present the angular shifts in bright source positions (Cyg A, Cas A, Vir A, and Tau A) as probes of the variations in the total electron content (TEC) along the lines of sight between the sources and the 32-element array in Green Bank. With an integration time of 10 seconds, we can probe for the small fluctuations, using the visibilities, that may be the most difficult to calibrate in upcoming experiments and observations. More sensitive probes of longer timescales are also done by imaging the sky with both the 32 and 64-element arrays. Here again, the bright source position stability is used as an indicator of the TEC stability. The wideband nature of the PAPER instrument enables it to probe the effects of a varying TEC over a nearly 100 MHz bandwidth. We compare these measurements to more traditional methods of probing the ionosphere, such as GPS satellites, and we discuss the implications that these measurements will have on experiments aimed at detecting the epoch of reionization.

  12. Lightning Interaction with the Lower Ionosphere: Effects of Mesospheric Ions and Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Marshall, R. A.; Inan, U. S.

    2011-12-01

    The interaction between the lightning electromagnetic pulse (EMP) and quasi-electrostatic (QE) fields and the D-region ionosphere has been observed optically in the past 20 years through sprites, elves, and gigantic jets. Very-low-frequency (VLF) measurements have been used to measure direct ionospheric modification, which may comprise electron density changes and/or heating. In the same time period, a number of models have been used to study the lightning-ionosphere interaction. Here, we present new time-domain 2D and 3D models of the lightning-ionosphere interaction, including EMP and QE effects. These spherical-coordinate models include effects of Earth's magnetic field; effects of mesospheric and ionospheric electron and ion densities; and responses to arbitrary lightning amplitudes, waveforms, and orientations. In this paper, we use the new models to investigate the response of the ionosphere under varying conditions. First, we focus on the effects of different mesospheric ion density profiles. Mesospheric ions, for which measurements are nearly nonexistent, serve to reduce the amplitude of the electromagnetic pulse as it propagates towards the ionosphere; high ion densities will reduce the wave electric field enough that it does not exceed the breakdown field in the ionosphere. We demonstrate the relationship between the lightning parameters, ion density profile, and observed elve intensity, and show that elves are suppressed when the ion density is high. Second, we investigate the effects of the geomagnetic field magnitude and orientation on wave propagation in and through the ionosphere. We compare these simulation results with known global lightning distributions and compare to the observed whistler distributions onboard satellites.

  13. Space Weather Topics at Ionospheric Effects Symposium 2008

    NASA Astrophysics Data System (ADS)

    Goodman, John

    2008-08-01

    The ionosphere has captured the interest of scientists and communications specialists for many years. Research has been intrinsically applications oriented since Guglielmo Marconi identified an ionized region within the upper atmosphere that acted like a high-altitude mirror reflecting radio waves so that long-distance communication could be achieved. His successful transatlantic radio transmissions early in the twentieth century heralded the beginning of an era of wireless communications. Eager to capitalize on this, civilian and military industries sponsored research to better understand the ionosphere. These endeavors established that the ionosphere exhibits considerable variability, with significant changes associated with ionospheric storms that are driven by solar disturbances. This variability, now termed space weather, also introduces changes in radio propagation conditions that can disrupt various radio systems, such as high-frequency and satellite communications, the Global Positioning System, radar, and specialized surveillance methods.

  14. Long-duration positive ionospheric storm during the December 2006 geomagnetic storm: Ionizing effect of forbidden electrons

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.; Huang, C.-M.; Tsai, L.-C.; Dmitriev, A. V.; Ratovsky, K. G.

    2015-11-01

    The magnetosphere-ionosphere coupling at low latitudes was studied during the major geomagnetic storm on 14-16 December 2006. Data from NOAA/POES satellites were used to identify the enhancements of forbidden energetic electrons (FEE). Global Ionospheric Maps and COSMIC/FORMOSAT-3 radio occultation measurements were used for studying positive ionospheric storm phases. We found that long-lasting positive ionospheric storms were concomitant with FEE enhancements. We discussed relative contributions of the FEE ionizing effect as well as other general mechanisms to the positive ionospheric storm at different phases of the geomagnetic storm.

  15. Effects of X-ray flares on the aeronomy of Mars: Simultaneous measurements of ionospheric effects of X-ray flares on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Haider, Syed A.; Machado Santos, Angela; Abdu, Mangalathayil A.; Batista, Inez S.; Shah, Siddhi Y.; Thirupathaiah, P.

    2016-07-01

    MIRI: Validation and Testing Requirements We have studied X-ray aeronomy in the ionospheric E region of Mars during six X-ray flares that occurred on 28 March and 6 April, 2001; 17,18 March and 21 April, 2003 and 19 February, 2005 respectively. These flares were responded by the corresponding electron density profiles of Mars Global Surveyor (MGS). The time series of photoionization rate, photoelectron impact ionization rate, photoelectron flux, ion density, electron density and total Electron Content (TEC) are predicted for each flare day. The estimated production rate, flux and densities are increased by 1-2 orders of magnitude due to effects of these flares in the E region ionosphere of Mars. The normalized estimated TEC are compared with the normalized measured TEC of MGS profiles. At the peak flare time the normalized estimated and normalized measured TEC were enhanced by a factor of 5-10 and 2 respectively. The effects of these flares were also registered in the D region equatorial ionosphere of Earth at Fortaleza observatory. The flares of 6 April, 2001, 17 March and 21 April, 2003 also produced electron density enhancement in the E region ionosphere of Earth at College AK and Cachoeira Paulista observatories. The minimum frequency fmin, recorded in ionogram, increased by 100% (due to D region absorption) while the foE increased by 20%, in the Earth's ionosphere.

  16. The High-Latitude Ionosphere and Its Effects on Radio Propagation

    NASA Astrophysics Data System (ADS)

    Moses, Ronald W., Jr.

    2004-05-01

    The ionosphere is indeed the place where Earth and space come together. Correspondingly, the ionosphere is subject to the details and complexities of both Earth and space. If one is to develop a logical understanding of even a limited portion of the ionosphere, that knowledge will be constructed on a foundation of many facts of nature. Awareness of those facts will in turn be supported by a vast historical array of scientific effort to ascertain the fundamentals of Earth and space that combine to form the ionosphere as we know it. Fortunately for us, R. D. Hunsucker and J. K. Hargreaves have written a book that goes from the Earth up and comes from the Sun down to arrive at a remarkably detailed physical description of the ionosphere and its impact on human activities, especially radio-frequency (RF) communications. The High-Latitude Ionosphere and its Effects on Radio Propagation is a bit of a misnomer, because the book covers many more topics than its title suggests. The authors set the stage by developing a detailed picture of the density, temperature, chemical, neutral, and charge states of the atmosphere-ionosphere system. Basic models of the ionization and recombination processes are presented with supporting mathematics and graphical examples. Concepts such as the Chapman production function are introduced and applied, whereby ionizing solar radiation produces electron-ion pairs. One can then grasp how the so-called D, E, and F layers of the ionosphere are related to the ionization of specific molecular species. Along the way, the authors are careful to introduce the extensive nomenclature of ionospheric descriptors. There is a comfortable relationship of prose, mathematics, and graphical material. Reading this book is a pleasure for the scientifically curious mind.

  17. Effects of Atmospheric Variability on Ionospheric Manifestations of Earthquakes and Tsunamis

    NASA Astrophysics Data System (ADS)

    Godin, O. A.; Zabotin, N. A.; Zabotina, L.

    2014-12-01

    There is a large and increasing number of ground-based and satellite-borne instruments, which reliably reveal ionospheric manifestations of natural hazards such as large earthquakes, strong tsunamis, and powerful tornadoes. As the focus shifts from detecting the ionospheric features associated with the natural hazards to characterizing the hazards for the purposes of improving early warning systems and contributing to disaster recovery, it becomes imperative to relate quantitatively characteristics of the observed ionospheric disturbances and the underlying natural hazard. The relation between perturbations at the ground level and their ionospheric manifestations is strongly affected by parameters of the intervening atmosphere. In this paper, we employ the ray theory to model propagation of acoustic gravity waves in three-dimensionally inhomogeneous atmosphere. Huygens' wavefront-tracing and Hamiltonian ray-tracing algorithms are used to simulate wave propagation from an earthquake hypocenter through the earth's crust and ocean to the upper atmosphere as well as the generation of atmospheric waves by seismic surface waves and tsunamis. We quantify the influence of temperature stratification and winds, including their seasonal variability, and air viscosity and thermal conductivity on the geometry and amplitude of ionospheric disturbances. Modeling results are verified by comparing observations of the velocity fluctuations at altitudes of 150-160 km by a coastal Dynasonde HF radar system with theoretical predictions of ionospheric manifestations of background infragravity waves in the ocean. Dynasonde radar systems are shown to be a promising means for monitoring acoustic-gravity wave activity and observing ionospheric perturbations due to earthquakes and tsunamis. The effects will be discussed of background ionospheric disturbances and uncertainty in atmospheric parameters on the feasibility and accuracy of retrieval of open-ocean tsunami heights from observations

  18. HF Radar Observations of Space Weather Effects in the Low and Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Menk, F. W.

    2015-12-01

    The ionosphere is dynamically coupled to the magnetosphere and hence diurnal and seasonal processes in the ionosphere are strongly influenced by space weather effects. These may vary the electron density distribution and cause changes in the reflection and absorption of HF radio signals. Other consequences include the formation of enhanced convective flows and irregularity features which may contribute to Doppler clutter. While there has been much discussion on the ionospheric signatures of magnetic storms at high latitudes, this presentation focuses on effects detected using mid- and low-latitude HF radars which examine field lines mapping to the vicinity of the ring current. Characteristic features include travelling ionospheric disturbances, high velocity flows and sustained irregular and quasi-sinusoidal 5 - 20 mHz waves recorded near the plasmapause. Such observations provide new insight on complex M-I coupling dynamics.

  19. Stochastic modelling considering ionospheric scintillation effects on GNSS relative and point positioning

    NASA Astrophysics Data System (ADS)

    da Silva, Heloísa Alves; de Oliveira Camargo, Paulo; Galera Monico, João Francisco; Aquino, Marcio; Marques, Haroldo Antonio; de Franceschi, Giorgiana; Dodson, Alan

    2010-05-01

    Global Navigation Satellite Systems (GNSS), in particular the Global Positioning System (GPS), have been widely used for high accuracy geodetic positioning. The Least Squares functional models related to the GNSS observables have been more extensively studied than the corresponding stochastic models, given that the development of the latter is significantly more complex. As a result, a simplified stochastic model is often used in GNSS positioning, which assumes that all the GNSS observables are statistically independent and of the same quality, i.e. a similar variance is assigned indiscriminately to all of the measurements. However, the definition of the stochastic model may be approached from a more detailed perspective, considering specific effects affecting each observable individually, as for example the effects of ionospheric scintillation. These effects relate to phase and amplitude fluctuations in the satellites signals that occur due to diffraction on electron density irregularities in the ionosphere and are particularly relevant at equatorial and high latitude regions, especially during periods of high solar activity. As a consequence, degraded measurement quality and poorer positioning accuracy may result. This paper takes advantage of the availability of specially designed GNSS receivers that provide parameters indicating the level of phase and amplitude scintillation on the signals, which therefore can be used to mitigate these effects through suitable improvements in the least squares stochastic model. The stochastic model considering ionospheric scintillation effects has been implemented following the approach described in Aquino et al. (2009), which is based on the computation of weights derived from the scintillation sensitive receiver tacking models of Conker et al. (2003). The methodology and algorithms to account for these effects in the stochastic model are described and results of experiments where GPS data were processed in both a relative and

  20. Solar Flare Effects on the Thermosphere and Ionosphere

    NASA Astrophysics Data System (ADS)

    Solomon, S.; Qian, L.; Rodgers, E.; Bailey, S.

    The Solar Extreme-ultraviolet Experiment SEE on the TIMED satellite and by the X-ray Photometer System XPS on the SORCE satellite provide the first comprehensive irradiance measurements of the complete solar spectrum during large solar flares However the soft X-ray portion of these observations are performed using silicon photodiodes coated with metallic filters to provide photometric measurements with multiple band passes which leads to complexities in obtaining spectral information A new analysis technique developed specifically for flare conditions is used to infer flare spectra in this region These are combined with spectrographic measurements in the extreme ultraviolet and far ultraviolet and applied to the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model TIE-GCM The electron content neutral density and airglow response to large flares during the declining phase of solar cycle 23 are calculated using this model and compared to several measurement sets obtaining good agreement This supports both the validity of the solar X-ray analysis and the modeling methodology showing that although flare-driven effects in the upper atmosphere are significant they are shorter and of much smaller magnitude than geomagnetic disturbances

  1. Ionospheric refraction effects on orbit determination using the orbit determination error analysis system

    NASA Technical Reports Server (NTRS)

    Yee, C. P.; Kelbel, D. A.; Lee, T.; Dunham, J. B.; Mistretta, G. D.

    1990-01-01

    The influence of ionospheric refraction on orbit determination was studied through the use of the Orbit Determination Error Analysis System (ODEAS). The results of a study of the orbital state estimate errors due to the ionospheric refraction corrections, particularly for measurements involving spacecraft-to-spacecraft tracking links, are presented. In current operational practice at the Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF), the ionospheric refraction effects on the tracking measurements are modeled in the Goddard Trajectory Determination System (GTDS) using the Bent ionospheric model. While GTDS has the capability of incorporating the ionospheric refraction effects for measurements involving ground-to-spacecraft tracking links, such as those generated by the Ground Spaceflight Tracking and Data Network (GSTDN), it does not have the capability to incorporate the refraction effects for spacecraft-to-spacecraft tracking links for measurements generated by the Tracking and Data Relay Satellite System (TDRSS). The lack of this particular capability in GTDS raised some concern about the achievable accuracy of the estimated orbit for certain classes of spacecraft missions that require high-precision orbits. Using an enhanced research version of GTDS, some efforts have already been made to assess the importance of the spacecraft-to-spacecraft ionospheric refraction corrections in an orbit determination process. While these studies were performed using simulated data or real tracking data in definitive orbit determination modes, the study results presented here were obtained by means of covariance analysis simulating the weighted least-squares method used in orbit determination.

  2. Meteorological effects of ionospheric disturbances from vertical radio sounding data

    NASA Astrophysics Data System (ADS)

    Chernigovskaya, M. A.; Shpynev, B. G.; Ratovsky, K. G.

    2015-12-01

    We studied ionospheric disturbances caused by the wave-like processes in the middle atmosphere. The ionospheric data were obtained from continuous measurements with the DPS-4 vertical sounding ionosondes in Irkutsk and Norilsk over 2008-2010. The ionospheric disturbances were considered as deviations of the F2 layer peak density variations from the daily average values. We also used ECMWF ERA-Interim reanalysis data for the middle atmosphere dynamics analysis, and the Aura MLS data on the atmospheric temperature at the stratosphere and upper mesosphere heights obtained within the above period. The analysis allowed us to reveal periods of middle-scale wave motions in the stratosphere and lower mesosphere during winter seasons in the Northern Hemisphere. The wave motions observed in the study were associated with the jet streams at the stratosphere/lower mesosphere heights localized mainly between 50 and 80°N. The middle-scale waves in the stratosphere were compared with ionospheric disturbances over two ionosonde stations in Irkutsk and Norilsk. A noticeable increase in the wave activity was found at the F2 layer heights during the periods of stratospheric wave activity. For both stations, the maximal variability in the ionosphere F2 layer parameters was observed in winter with the minimal variability observed in summer. The summer-winter difference was more pronounced in the case of the high-latitude ionosonde in Norilsk.

  3. Modeling the pre-earthquake electrostatic effect on the F region ionosphere

    NASA Astrophysics Data System (ADS)

    Kim, V. P.; Liu, J. Y.; Hegai, V. V.

    2012-12-01

    This paper presents the results of modeling the ionospheric effect of the seismogenic electrostatic field (SEF) seen at the earth's surface as a perturbation of the vertical atmospheric electrostatic field in the earthquake preparation zone. The SEF distribution at ionospheric altitudes is obtained as an analytical solution of the continuity equation for the electric current density. It is shown that at night, the horizontally large scale SEF can efficiently penetrate into the ionosphere and produce noticeable changes in the horizontal distribution of the F region electron density. The results suggest that the seismogenic electrostatic field could be a possible source for the ionospheric variations observed over Taiwan before the strong Chi Chi earthquake of September 21, 1999.

  4. Effects of the equatorial ionosphere anomaly on the interhemispheric circulation in the thermosphere

    NASA Astrophysics Data System (ADS)

    Qian, Liying; Burns, Alan G.; Wang, Wenbin; Solomon, Stanley C.; Zhang, Yongliang; Hsu, V.

    2016-03-01

    We investigate the interhemispheric circulation at the solstices, in order to understand why O/N2 is larger in the northern hemisphere winter than in the southern hemisphere winter. Our studies reveal that the equatorial ionosphere anomaly (EIA) significantly impacts the summer-to-winter wind through plasma-neutral collisional heating, which changes the summer-to-winter pressure gradient, and ion drag. Consequently, the wind is suppressed in the summer hemisphere as it encounters the EIA but accelerates after it passes the EIA in the winter hemisphere. The wind then converges due to an opposing pressure gradient driven by Joule heating in auroral regions and produces large O/N2 at subauroral latitudes. This EIA effect is stronger near the December solstice than near the June solstice because the ionospheric annual asymmetry creates greater meridional wind convergence near the December solstice, which in turn produces larger O/N2 in the northern hemisphere winter than in the southern hemisphere winter.

  5. Ionospheric Effects of Strong El Nino Southern Oscillation Conditions

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; England, S.; Forbes, J. M.; Nguyen, V.; Lieberman, R. S.; Maute, A. I.; Greer, K.

    2015-12-01

    The current prediction for the occurrence of a very strong positive phase in the El Nino Southern Oscillation (ENSO) in late 2015 has implications for weather around the entire planet. Furthermore, recent investigations show that ENSO-related changes in tropospheric water vapor and rainfall drive extraordinary changes in the temperature and wind structure in the middle atmosphere, through the modification of the spectrum of atmospheric tides. Given that several components of the tidal spectrum can propagate into the thermosphere, ENSO-related changes at altitudes above the mesopause and into the ionosphere may be expected. We will show the ionospheric and thermospheric variations expected for El Niño and La Niña conditions. These efforts are enabled in part by modeling capabilities developed for the upcoming NASA Ionospheric Connection Explorer mission.

  6. Effects of Soft Electron Precipitation on the Coupled Magnetosphere-Ionosphere-Thermosphere

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Lotko, W.; Brambles, O.; Wiltberger, M. J.; Wang, W.; Schmitt, P. J.; Lyon, J.

    2011-12-01

    Global simulations play an important role in understanding the coupled magnetosphere-ionosphere-thermosphere (MIT) system. The MIT interaction involves both electrodynamic and plasma transport processes, and it is influenced by precipitating particles that deposit both thermal and kinetic energy from the magnetosphere in the ionosphere-thermosphere. Currently, global simulation codes do not include soft electron precipitation, which can significantly influence the thermospheric and ionospheric structure. In this study, two types of causally specified soft electron precipitation, direct-entry cusp and broadband electron precipitation, are implemented in the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model. The direct entry cusp electron precipitation is modeled by specifying the electron thermal flux and temperature in a dynamically determined cusp area. The broadband electron precipitation is regulated by the downward Alfvenic Poynting flux based on empirical relations from Polar and FAST satellite data. Simulation results show that while both types of soft electron precipitation have only minor effects on the ionospheric conductance, they can significantly modify the plasma distribution in the F-region ionosphere and the neutral density in the thermosphere.

  7. Precise Point Positioning with Ionosphere Estimation and application of Regional Ionospheric Maps

    NASA Astrophysics Data System (ADS)

    Galera Monico, J. F.; Marques, H. A.; Rocha, G. D. D. C.

    2015-12-01

    The ionosphere is one of most difficult source of errors to be modelled in the GPS positioning, mainly when applying data collected by single frequency receivers. Considering Precise Point Positioning (PPP) with single frequency data the options available include, for example, the use of Klobuchar model or applying Global Ionosphere Maps (GIM). The GIM contains Vertical Electron Content (VTEC) values that are commonly estimated considering a global network with poor covering in certain regions. For this reason Regional Ionosphere Maps (RIM) have been developed considering local GNSS network, for instance, the La Plata Ionospheric Model (LPIM) developed inside the context of SIRGAS (Geocentric Reference System for Americas). The South American RIM are produced with data from nearly 50 GPS ground receivers and considering these maps are generated for each hour with spatial resolution of one degree it is expected to provide better accuracy in GPS positioning for such region. Another possibility to correct for ionosphere effects in the PPP is to apply the ionosphere estimation technique based on Kalman filter. In this case, the ionosphere can be treated as a stochastic process and a good initial guess is necessary what can be obtained from an ionospheric map. In this paper we present the methodology involved with ionosphere estimation by using Kalman filter and also the application of global and regional ionospheric maps in the PPP as first guess. The ionosphere estimation strategy was implemented in the house software called RT_PPP that is capable of accomplishing PPP either for single or dual frequency data. GPS data from Brazilian station near equatorial region were processed and results with regional maps were compared with those by using global maps. Improvements of the order 15% were observed. In case of ionosphere estimation, the estimated coordinates were compared with ionosphere free solution and after PPP convergence the results reached centimeter accuracy.

  8. Physics of planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Bauer, S. J.

    1973-01-01

    The fundamental physical and chemical processes in an idealized planetary ionosphere are considered as a general abstraction, with actual planetary ionospheres representing special cases. After describing the structure of the neutral atmospheres (the barosphere, the thermosphere, and the exosphere) and noting the principal ionizing radiations responsible for the formation of planetary ionospheres, a detailed study is made of the thermal structure of these ionospheres and of the chemical processes and plasma-transport processes occurring in them. The features of equilibrium and realistic models of planetary ionospheres are discussed, and an attempt is made to determine the extent of these ionospheres. Considering the ionosphere as a plasma, a plasma kinetic approach is developed for determining the effects of interactions between individual particles and waves in this plasma. The use of remote-sensing radio techniques and direct measurement or in situ techniques is discussed. Finally, the observed properties of the ionospheres of the Earth, Mars, Venus, and Jupiter are reviewed.

  9. Ionospheric effects observed during the BIME (Brazilian Ionospheric Modification Experiments) campaign over Fernando de Noronha and Fortaleza

    NASA Astrophysics Data System (ADS)

    Abdu, M. A.; Sobral, J. H. A.; Kantor, I. J.; Ramirez, R.; Alves, P. R. G.

    1983-03-01

    Two scanning 6300A photometers, an HF ionosonde and a VHF electronic polarimeter were operated. Special soundings were carried out also by the ionosonde. Observations with these instruments were taken during all the four rocket chemical release experiments, namely, the explosive chemical releases to create electron hole and the metallic vapor release experiments carried out in an attempt to initiate plasma bubble formation in the evening equatorial ionosphere. The photometers detected immediate effects from the chemical release experiments, namely, significant enhancements in the 6300A emission following the detonations and their subsequent decays. They did not, however, detect plasma bubble developments as an after effect of the chemical release experiments. The ionosonde and polarimeter did observe plasma bubble and spread F irregularity developments and their eastward motions shortly following the chemical release, in all the four experiments.

  10. Solar Flare and IMF Sector Structure Effects in the Lower Ionosphere

    NASA Technical Reports Server (NTRS)

    Lastovicka, J.

    1984-01-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  11. Solar flare and IMF sector structure effects in the lower ionosphere

    SciTech Connect

    Lastovicka, J.

    1984-05-01

    About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.

  12. Investigation of the Ionospheric Fluctuations Caused by Space Weather Effects Using GNSS TEC Measurements

    NASA Astrophysics Data System (ADS)

    Shagimuratov, Irk; Krankowski, Andrzej; Cherniak, Iurii; Ephishov, Ivan; Zakharenkova, Irina; Yakimova, Galina

    2013-04-01

    It is known that GPS radio signals passing through the ionosphere suffer varying degrees of rapid variations of their amplitude and phase - signal scintillations. The scintillations are caused by the presence of wide range of scale size irregularities in the ionosphere. It is very important to estimate scintillation and phase fluctuation effects on GNSS navigation system (GPS/GLONASS) performance and consequently on the precession of the obtained position. Effects of the ionospheric irregularities on the GPS signals can be evaluated by measurements of the differential phase time rate of dual frequency GPS signals. GPS observations carried out at the Arctic IGS (International GNSS Service) stations were used to study the development of TEC fluctuations in the high latitude ionosphere. Standard GPS measurements with 30s sampling rate allow the detection of middle- and large-scale ionospheric irregularities. For detection of ionospheric fluctuations the rate of TEC (ROT, in the unit of TECU/min) at 1 min interval was used. The temporal occurrence of TEC fluctuations is clearly observed in time variations in the dual frequency carrier phase along satellite passes. As a measure of the fluctuation activity level the Rate of TEC Index (ROTI) based on standard deviation of ROT was also used. ROTI was estimated in 10-minute interval. These techniques and IGS data were used to study the occurrence of TEC fluctuations at the northern latitude ionosphere for selected geomagnetic storms occurred at the end of 23rd and beginning of new 24th solar cycles. Results demonstrate that fluctuation activity of GPS signals in the high latitude ionosphere is depended on geomagnetic conditions. Intensity of fluctuations essentially increases during geomagnetic storms. The strongest TEC fluctuations occurred as short time rate of TEC enhancements of a factor of 2-5 relative to the quiet time. During geomagnetic disturbed conditions strong phase fluctuations can register at latitudes low

  13. Electric fields and conductivity in the nighttime E-region - A new magnetosphere-ionosphere-atmosphere coupling effect

    NASA Technical Reports Server (NTRS)

    Banks, P. M.; Yasuhara, F.

    1978-01-01

    Calculations have been made of the effects of intense poleward-directed electric fields upon the nighttime ionospheric E-region. The results show the Pedersen and Hall conductivities are substantially changed, thereby decreasing the ionospheric electrical load seen by magnetospheric sources. It appears that relatively large electric fields can exist in the absence of accompanying large field-aligned currents, as long as the underlying ionosphere remains in darkness and/or energetic particle precipitation is absent.

  14. Effects of the 20 March 2015 total solar eclipse on the ionosphere-thermosphere system

    NASA Astrophysics Data System (ADS)

    Grandin, Maxime; Marchaudon, Aurelie; Aikio, Anita; Blelly, Pierre-Louis; Kozlovsky, Alexander; Pitout, Frederic; Ulich, Thomas; Lester, Mark; Miller, Ethan; Yeoman, Tim

    2015-04-01

    A total solar eclipse is a spectacular natural phenomenon whose consequences over the underlying ionosphere and thermosphere remain complex and not fully explained. On 20 March 2015, a total solar eclipse lasting almost 2 hours passed over the Atlantic Ocean, then over Svalbard. These specific regions are extremely interesting as they are covered by several ground-based instruments: SuperDARN radars, EISCAT Svalbard radar (ESR), magnetometers, and imaging instruments. We take advantage of this excellent instrumental configuration coupled with results from detailed ionosphere models to study the dynamic consequences of this eclipse on the underlying ionosphere and thermosphere. In particular, we run specific scanning modes on the SuperDARN radars in order to identify a possible generation of Atmospheric Gravity Waves (AGW) caused by the eclipse. We present the observations of the different instruments and compare them with initial simulations made with the TRANSCAR ionosphere model. As this eclipse is first located on closed field lines, we also investigate the possible exchange of energy and particle fluxes with the opposite sunlit hemisphere by running the interhemispheric version of our ionosphere model.

  15. Ionospheric Effects Prior to the Napa Earthquake of August 24, 2014

    NASA Astrophysics Data System (ADS)

    Kelley, M. C.; Swartz, W. E.; Komjathy, A.; Mannucci, A. J.; Shume, E. B.; Heki, K.; Fraser-Smith, A. C.; McCready, M. A.

    2014-12-01

    Recently, evidence that the ionosphere reacts in a reliable, reproducible manner before major earthquakes has been increasing. Fraser-Smith (1990) reported ULF magnetic field fluctuations prior to the Loma Prieta quake. Although not an ionospheric measurement, such magnetic fields before a quake are part of our explanation for the ionospheric effect. Heki (2011) and Heki and Enomoto (2013) reported in great detail the devastating March 11, 2011 Tohoku-Oki earthquake in which numerous GPS satellite/ground-station pairs showed apparent changes, both increases and decreases, starting 40 minutes before the event. We say "apparent" since our theory is that electric fields associated with stresses before an earthquake map through the ionosphere at the speed of light and raise or lower the main ionosphere. Both effects have been detected. Heki's results for four quakes exceeding M = 7 are shown in Figure 4 of Heki (2011). Based on the inserted curve of Heki's Figure 4 relating the size of the ionospheric effect to the quake's magnitude, we were not optimistic about detecting an effect for the 6.0 Napa quake. However, it occurred at night, when the well-known shielding effect of the ionospheric D and lower E regions for EM fields becomes very small. When this special session with a later abstract deadline was announced, JPL researchers were asked to examine GPS data from California stations. Based on their data, the plot shown (left panel) combined with a similar plot for the Tohoku-Oki earthquake (right panel, based on Heki's data) was produced. Both panels show fluctuations of STEC (Slant Total Electron Content) before the quake times (indicated by asterisks showing the positions of ionospheric penetration points (IPP) at the respective quake times). Although alternative explanations for the TEC fluctuations cannot be ruled out entirely, these results suggest that a patent-pending system able to predict an earthquake some 30 minutes before an event by using satellites

  16. Ppp Analisys with GPS and Glonass Integration in Periods Under Ionospheric Scintillation Effects

    NASA Astrophysics Data System (ADS)

    Marques, H. A. S.

    2015-12-01

    The GNSS is widely used nowadays either for geodetic positioning or scientific purposes. The GNSS currently includes GPS, GLONASS, Galileo among other emerging systems. The GPS and GLONASS are currently operational with a full satellite constellation. The GPS is still the most used nowadays and both GPS and GLONASS are under a modernization process. The geodetic positioning by using data from multi-constellation can provide better accuracy in positioning and also more reliability. The PPP is benefited once the satellite geometry is crucial in this method, mainly for kinematic scenarios. The satellite geometry can change suddenly for data collected in urban areas or in conditions of strong atmospheric effects such as Ionospheric Scintillation (IS) that causes weakening of signals with cycle slips and even loss of lock. The IS is caused by small irregularities in the ionosphere layer and is characterized by rapid change in amplitude and phase of the signal being stronger in equatorial and high latitudes regions. In this work the PPP is evaluated with GPS and GLONASS data collected by monitoring receivers from Brazilian CIGALA/CALIBRA network under IS conditions. The PPP processing was accomplished by using the GPSPPP software provided by Natural Resources Canadian (NRCAN). The IS effects were analyzed taking account the S4 and PHI60 indices. Considering periods with moderate IS effects, the use of only GPS data in the PPP presented several peaks in the coordinate time series due to cycle slips and loos of lock. In cycle slip conditions the ambiguity parameter are reinitialized by GPSPPP and considering loss of lock few satellites can be available in some epochs affecting the positioning geometry and consequently decreasing accuracy. In such situations, the PPP using GPS and GLONASS data presented improvements in positioning accuracy of the order to 70% in height component when compared with PPP using only GPS data. Analyses of GDOP and ambiguities parameters were

  17. The worldwide ionospheric data base

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    1989-01-01

    The worldwide ionospheric data base is scattered over the entire globe. Different data sets are held at different institutions in the U.S., U.S.S.R., Australia, Europe, and Asia. The World Data Centers on the different continents archive and distribute part of the huge data base; the scope and cross section of the individual data holdings depend on the regional and special interest of the center. An attempt is made to pull together all the strings that point toward different ionospheric data holdings. Requesters are provided with the information about what is available and where to get it. An attempt is also made to evaluate the reliability and compatibility of the different data sets based on the consensus in the ionospheric research community. The status and accuracy of the standard ionospheric models are also discussed because they may facilitate first order assessment of ionospheric effects. This is a first step toward an ionospheric data directory within the framework of NSSDC's master directory.

  18. Ionospheric effects in active retrodirective array and mitigating system design

    NASA Technical Reports Server (NTRS)

    Nandi, A. K.; Tomita, C. Y.

    1980-01-01

    The operation of an active retrodirective array (ARA) in an ionospheric environment (that is either stationary or slowly-varying) was examined. The restrictions imposed on the pilot signal structure as a result of such operation were analyzed. A 3 tone pilot beam system was defined which first estimates the total electron content along paths of interest and then utilizes this information to aid the phase conjugator so that correct beam pointing can be achieved.

  19. Local and long-distance effects of meteor showers in the low ionosphere

    NASA Astrophysics Data System (ADS)

    Vilas Boas, J. W. S.; Paes Leme, N. M.; Rizzo Piazza, L.; da Costa, A. M.; Macedo Moura, M. S. S.

    1986-07-01

    The effect of the Geminids and alpha Scorpiids meteor showers in the lower ionosphere have been observed using two different methods. Low ionosphere group heights, measured by a VLF ionosonde located in southern Brazil, indicated significant anomalous lowering of the effective reflection height which was in good correlation with the transit of the alpha Scorpiids stream. The diurnal VLF phase variations over two long-distance propagation paths showed significant phase deviations from the average during the transits of the showers' radiants. Geomagnetic activity during the periods concerned was low and the results obtained using the two different techniques confirm the occurrence of changes in the physical conditions of the low ionosphere produced by meteor showers on local, as well as on long-distance, scales.

  20. Anomalous electron heating effects on the E region ionosphere in TIEGCM

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Wang, Wenbin; Oppenheim, Meers; Dimant, Yakov; Wiltberger, Michael; Merkin, Slava

    2016-03-01

    We have recently implemented a new module that includes both the anomalous electron heating and the electron-neutral cooling rate correction associated with the Farley-Buneman Instability (FBI) in the thermosphere-ionosphere electrodynamics global circulation model (TIEGCM). This implementation provides, for the first time, a modeling capability to describe macroscopic effects of the FBI on the ionosphere and thermosphere in the context of a first-principle, self-consistent model. The added heating sources primarily operate between 100 and 130 km altitude, and their magnitudes often exceed auroral precipitation heating in the TIEGCM. The induced changes in E region electron temperature in the auroral oval and polar cap by the FBI are remarkable with a maximum Te approaching 2200 K. This is about 4 times larger than the TIEGCM run without FBI heating. This investigation demonstrates how researchers can add the important effects of the FBI to magnetosphere-ionosphere-thermosphere models and simulators.

  1. Mitigation of Ionospheric Effects on DGPS and WADGPS Operations

    NASA Astrophysics Data System (ADS)

    Skone, S.

    2007-12-01

    Under high levels of ionospheric activity, significant degradations in differential GPS (DGPS) and wide area DGPS (WADGPS) positioning accuracies can occur. DGPS and WADGPS methods are employed for many applications and millions of users. Examples include marine DGPS services, land applications (such as transportation monitoring, fleet management and emergency response) and commercial aviation. In previous studies for the North American sector, DGPS and WADGPS positioning errors were observed to increase by factors of 10-30 under increased ionospheric activity. In particular, gradients of up to 50 ppm are associated with a feature known as storm enhanced density (SED). This feature is a localized enhancement of total electron content (TEC) extending northwest through the mid-latitudes. Positioning errors of 20 m or more have persisted for hours during such events. Specific WADGPS services include the Satellite-Based Augmentation Systems (SBAS) WAAS and EGNOS. The WAAS has been designed for commercial aviation in the United States; EGNOS operates in a similar manner for the European sector. In this presentation, DGPS, WAAS and EGNOS capabilities are assessed under severe ionosphere events. The horizontal and vertical positioning accuracies are determined throughout North America and Europe during such events using available data from existing GPS networks (IGS and CORS). All DGPS baselines of length 100-200 km are processed; one station of the baseline is designated as reference and the other as remote user. Differential corrections are computed for the reference and applied at the remote user location. DGPS positioning solutions are generated for hundreds of baselines simultaneously in this manner to derive full spatial statistics of positioning accuracies. WADGPS positioning solutions are also generated for the same set of remote user stations using archived WAAS and EGNOS messages, and computing and applying localized corrections. An extensive study is conducted

  2. Speed-dependent collision effects on radar back-scattering from the ionosphere

    NASA Technical Reports Server (NTRS)

    Theimer, O.

    1981-01-01

    A computer code to accurately compute the fluctuation spectrum for linearly speed dependent collision frequencies was developed. The effect of ignoring the speed dependence on the estimates of ionospheric parameters was determined. It is shown that disagreements between the rocket and the incoherent scatter estimates could be partially resolved if the correct speed dependence of the i-n collision frequency is not ignored. This problem is also relevant to the study of ionospheric irregularities in the auroral E-region and their effects on the radio communication with satellites.

  3. The effect of moving cold fronts over Central Europe to the variability of the ionosphere

    NASA Astrophysics Data System (ADS)

    Potuznikova, Katerina; Koucka Knizova, Petra; Boska, Josef; Sindelarova, Tereza; Mosna, Zbysek

    2015-04-01

    Cold fronts represent well known source of atmospheric waves, (especially short and medium scale AGW - acoustic gravity waves), that are able to propagate up to the ionospheric heights. In our study we focus on the effects of the transitions of cold front over the region of Central Europe on the variations of the ionosphere. We concentrate on periods of low solar and geomagnetic activity. Neutral atmosphere data are compared with the wave-like oscillations in the E and F layer. Our tropospheric data comprise synoptic maps on of 500 hPa and 850 hPa geopotential heights. Within ionospheric data we search for variability that is linked to the tropospheric disturbances. The ionospheric parameters (electron concentration and corresponding height) we analyse by the wavelet transform method. The Modern HF digisonde DPS-4 D (Digisonde Portable Sounder), which is in operation at the Pruhonice observatory (49.59 N; 14.33 E) of the Institute of Atmospheric Physics, Prague (IAP) since 2004, represents an excellent source of the ionospheric data for Central Europe. Pruhonice digisonde usually operates in standard mode - one ionogram and electron density profie N(h) each 15 minutes. Besides that, data from several european stations of the digisonde world network (data from Juliusruhe, Chilton, Brusel, Roma and Tortosa digisonde stations) are included in the study.

  4. Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Murphy, Tara; Bell, Martin E.; Kaplan, David L.; Lenc, Emil; Offringa, André R.; Hurley-Walker, Natasha; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Kasper, J. C.; Kratzenberg, E.; Lonsdale, C. J.; Lynch, M. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2015-11-01

    Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 h of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-time-scale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10-20 arcsec) at 154 MHz are small enough that search radii of 1-2 arcmin should be sufficient for cross-matching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1-3 per cent for the various nights. For sources fainter than ˜1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz.

  5. Ionospheric Asymmetry Evaluation using Tomography to Assess the Effectiveness of Radio Occultation Data Inversion

    NASA Astrophysics Data System (ADS)

    Shaikh, M. M.; Notarpietro, R.; Yin, P.; Nava, B.

    2013-12-01

    The Multi-Instrument Data Analysis System (MIDAS) algorithm is based on the oceanographic imaging techniques first applied to do the imaging of 2D slices of the ionosphere. The first version of MIDAS (version 1.0) was able to deal with any line-integral data such as GPS-ground or GPS-LEO differential-phase data or inverted ionograms. The current version extends tomography into four dimensional (lat, long, height and time) spatial-temporal mapping that combines all observations simultaneously in a single inversion with the minimum of a priori assumptions about the form of the ionospheric electron-concentration distribution. This work is an attempt to investigate the Radio Occultation (RO) data assimilation into MIDAS by assessing the ionospheric asymmetry and its impact on RO data inversion, when the Onion-peeling algorithm is used. Ionospheric RO data from COSMIC mission, specifically data collected during 24 September 2011 storm over mid-latitudes, has been used for the data assimilation. Using output electron density data from Midas (with/without RO assimilation) and ideal RO geometries, we tried to assess ionospheric asymmetry. It has been observed that the level of asymmetry was significantly increased when the storm was active. This was due to the increased ionization, which in turn produced large gradients along occulted ray path in the ionosphere. The presence of larger gradients was better observed when Midas was used with RO assimilated data. A very good correlation has been found between the evaluated asymmetry and errors related to the inversion products, when the inversion is performed considering standard techniques based on the assumption of spherical symmetry of the ionosphere. Errors are evaluated considering the peak electron density (NmF2) estimate and the Vertical TEC (VTEC) evaluation. This work highlights the importance of having a tool which should be able to state the effectiveness of Radio Occultation data inversion considering standard

  6. Ionospheric effects of the Mt. Kirishima volcanic eruption as seen from subionospheric VLF observations

    NASA Astrophysics Data System (ADS)

    Rozhnoi, A.; Hayakawa, M.; Solovieva, M.; Hobara, Y.; Fedun, V.

    2014-01-01

    Data from the Pacific network of VLF receivers have been used to study the response of the lower ionosphere to the January 2011 Mt. Kirishima (South Japan) volcanic eruption. A major explosive eruption occurred on January 27, which was preceded by several small eruptions. Perturbations of nighttime subionospheric VLF signals have been detected on the day of the first small eruption on January 18 (UT) with the maximum observed about 1.5 h after the eruption. The nighttime signal remained disturbed during the subsequent pre-eruptive and eruptive activity of Mt. Kirishima. The daytime perturbations were not observed. The frequency of the maximum spectral amplitude was found to be in the range of periods of 6-30 min, which corresponds to the periods of internal gravity waves. These results suggest that the observed VLF ionospheric effects can possibly be produced by the penetration of gravity waves caused by the volcanic activity into the ionosphere.

  7. Effects of a Weak Planetary Field on a Model Venus Ionosphere

    NASA Astrophysics Data System (ADS)

    Luhmann, Janet G.; Ma, Yingjuan; Villarreal, Michaela

    2014-05-01

    There are a number of attributes of the near-Venus space environment and upper atmosphere that remain mysterious, including occasional large polar magnetic field stuctures seen on VEX and nightside ionospheric holes seen on PVO. We have been exploring the consequences of a weak global dipole magnetic field of Venus using results of BATS-R-US MHD simulations. An advantage of these models is that they include the effects on a realistic ionosphere. We compare some of the weak magnetosphere's ionospheric properties with the typical unmagnetized ionsphere case. The results show the differences can be quite subtle for dipole fields less than ~10 nT at the equator, as might be expected. Nevertheless the dipole fields do produce distinctive details, especially in the upper regions.

  8. VLF Radio Observations and Modeling of the Ionospheric Effects of SGR 1550-5418

    NASA Astrophysics Data System (ADS)

    Carlson, B. E.; Lehtinen, N. G.; Cohen, M.; Fishman, G. J.; Kouveliotou, C.; van der Horst, A.; Chaplan, V.; Inan, U. S.

    2010-12-01

    Cosmic gamma-ray bursts ionize the upper atmosphere, affecting sub-ionospheric propagation of very-low-frequency (VLF) radio waves. Perturbations of VLF radio signals can therefore be used to study gamma-ray burst effects on the ionosphere. We present observations of VLF radio signal perturbations coincident with bursts observed by the Fermi satellite to be produced by soft gamma-ray repeater (SGR) 1550-5418 on January 22, 2009. Massive VLF signal amplitude perturbations as large as 15 dB are seen coincident with the gamma-ray events. Models of gamma-ray ionization and chemical recovery of the upper atmosphere are then used to drive simulations of VLF radio propagation. Simulation results are compared to the observed radio data and to Fermi gamma-ray observations and are used to constrain the properties of the ionosphere and the gamma-ray events.

  9. Calculation of ionospheric effects due to acoustic radiation from an underground nuclear explosion

    NASA Astrophysics Data System (ADS)

    Rudenko, G. V.; Uralov, A. M.

    1995-03-01

    Within the framework of the ionospheric detection of underground nuclear tests, we have developed analytic computing technique for the acoustic effect of a confined nuclear explosion on upper layers of the Earth's atmosphere. The relationship is obtained, which relates the nuclear test parameters (depth, explosion yield, and mechanical properties of the rock) to the vertical displacement of the ionosphere produced by the shock wave over the explosion's epicenter. It is also shown that most of the acoustic energy produced by a confined underground nuclear explosion escapes upward, with only a small fraction being captured by the atmospheric waveguide.

  10. Magnetic field-aligned coupling effects on ionospheric plasma structure

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.; Vickrey, J. F.

    1990-01-01

    This paper presents a mathematical description of the electrical coupling and dynamics of plasma structure in the E and F regions. The scale size dependence of the electric field coupling along the magnetic field is examined for a realistic background ionosphere and atmosphere. It is shown that, while normalized potentials map reciprocally between two altitudes, the potential disturbance caused by a fixed amplitude plasma density perturbation does not. The magnitude of electrostatic potential created by structured ionization is also shown to be strongly dependent on the altitude of the structure. The role of diffusion parallel to the magnetic field in the redistribution and decay of plasma structure is illustrated.

  11. Possible effects of ionospheric beating for the formation of Pc1 pearl structures based on 6-year ground observations in Canada, Russia and Japan

    NASA Astrophysics Data System (ADS)

    Jun, C. W.; Shiokawa, K.; Connors, M. G.; Schofield, I.; Poddelsky, I.; Shevtsov, B.

    2014-12-01

    We investigate pearl structures (amplitude modulation) of Pc1 pulsations simultaneously observed at Athabasca (ATH, 54.7N, 246.7E, L=4.3) in Canada, Magadan (MGD, 60.1N, 150.7E, L=2.6) in Russia, and Moshiri (MOS, 44.4N, 142.3E, L=1.5) in Japan. From a 6-year period of ground observations, from 2008 to 2013, we selected 150 events at longitudinally separated stations (ATH and MGD, group 1), 782 at latitudinally separated stations (MGD and MOS, group 2), all with high coherence of Pc1 waveforms (r > 0.5). As a result, we found that the peak occurrence rates of simultaneous Pc1 events were at 12-18 UT in group1, when ATH was in the morning sector and MGD in the midnight sector. In group 2, the peak was at 18-21 UT, with MGD and MOS in the morning sector. Using cross-correlation analysis, we confirmed the similarity of Pc1 pearl structures at different stations during Pc1 event timing. 82 % of Pc1 events in group 1 were less than 40 % of similarity of Pc1 pearl structures. In addition, 18 % of Pc1 events in group 1, which are over than 40 % of similarity of Pc1 pearl structures, were concentrated at 10-18 UT. According to polarization angle distribution in group 1, 57 % of Pc1 events occurred between ATH and MGD. Most of those events had high similarity of Pc1 amplitude envelopes. We investigated the relationship between the similarity of Pc1 pearl structures and geomagnetic activities (AE and SYM-H indices). The AE index seemed suddenly to start decreasing before the Pc1 onset and increasing after 80 min. The variation of SYM-H index was increasing 2 hours before Pc1 onset. From our statistical analysis, we suggest that the beating process in the ionosphere could be the dominant generation mechanism of Pc1 pearl structures in the ionosphere. It seems that the ionospheric duct in dawn sector of the ionosphere is well-defined during Pc1 pulsation propagating from ionospheric sources to stations. In order to understand the beating process in the ionosphere more clearly

  12. The effects on the ionosphere of inertia in the high latitude neutral thermosphere

    NASA Technical Reports Server (NTRS)

    Burns, Alan; Killeen, Timothy

    1993-01-01

    High-latitude ionospheric currents, plasma temperatures, densities, and composition are all affected by the time-dependent response of the neutral thermosphere to ion drag and Joule heating through a variety of complex feedback processes. These processes can best be studied numerically using the appropriate nonlinear numerical modeling techniques in conjunction with experimental case studies. In particular, the basic physics of these processes can be understood using a model, and these concepts can then be applied to more complex realistic situations by developing the appropriate simulations of real events. Finally, these model results can be compared with satellite-derived data from the thermosphere. We used numerical simulations from the National Center of Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) and data from the Dynamic Explorer 2 (DE 2) satellite to study the time-dependent effects of the inertia of the neutral thermosphere on ionospheric currents, plasma temperatures, densities, and composition. One particular case of these inertial effects is the so-called 'fly-wheel effect'. This effect occurs when the neutral gas, that has been spun-up by the large ionospheric winds associated with a geomagnetic storm, moves faster than the ions in the period after the end of the main phase of the storm. In these circumstances, the neutral gas can drag the ions along with them. It is this last effect, which is described in the next section, that we have studied under this grant.

  13. Effects of Solar Activity Variation on the Low Latitude Topside Nighttime Ionosphere

    NASA Astrophysics Data System (ADS)

    Min, K. W.; Kim, H.; Park, J.; Park, S.; Lee, J.; Lee, E.

    2006-05-01

    We investigate the effects of solar activity variation on the topside nighttime ionosphere of the low latitude region using the DMSP F15 data taken at 840 km altitude as well as the KOMPSAT-1 data taken at 685 km altitude. The change of the ionospheric parameters shows a good correlation with F 10.7 variations, in accordance with 27-day solar rotations. The correlation is especially good when a time delay of 1 to 2 days is incorporated and when the F 10.7 variation is large. Vertical drift velocities and the oxygen ion fractions, observed by DMSP F15, are also seen to have good correlations with F 10.7 with similar time delays. We suspect the delayed correlation of the ionospheric response is closely related to the neutral density changes affected by the solar activity as it has been reported that changes in the solar soft X-rays and the neutral density are well correlated with a delay of approximately 1.5 days. We also compare the ionospheric response for the solar maximum period with that of the declining phase using the data for the period 2000 through 2004 during which average F 10.7 varied from over 200 to around 100. The density does not seem to saturate at high F 10.7 values even during the solar maximum phase, in contrast to the daytime ionospheric response reported previously. The density during the low solar activity cycle is observed to be lower than that of the high solar activity for the same F 10.7 values, implying the long term dependence of the ionosphere in addition to the prompt response of 1 to 2 days.

  14. Ionospheric effects of the missile destruction on 9 December 2009

    NASA Astrophysics Data System (ADS)

    Kozlovsky, Alexander; Shalimov, Sergey; Lukianova, Renata; Lester, Mark

    2014-05-01

    We report on ionosonde and meteor radar observations made in Sodankylä Geophysical Observatory (SGO, 67°22'N, 26°38'E, Finland) on 9 December 2009, during a test launch of the Russian solid propellant military missile. Due to a technical problem, the missile was self-destroyed around 07 UT at an ionospheric height (near 200 km altitude) over the Kola Peninsula (Russia), at a distance about 500 km to east from the observatory. Products of the explosion were spread into a large area and reached the region of SGO meteor radar observations in about 2 h (around 09 UT). After about 3 h (around 10 UT), a sporadic E layer presumably composed of the remains including long-lived metallic (aluminum and its oxides) ions, was observed near the zenith of the SGO ionosonde. We discuss possible mechanisms accounting for transport of the remains. (1) Since the event occurred during a long-lasting period of extremely low solar and magnetic activity, the ionospheric electric field was unlikely to play a substantial role in the transport of the remains and sporadic E layer formation. (2) The horizontal transport of the remains cannot be explained by the neutral winds based on empirical models. (3) Theoretical estimations suggest that the observed transport could be due to thermospheric turbulence.

  15. The ionospheric storm effects at low latitudes and equatorial regions during the 2015 St. Patrick's Day storm

    NASA Astrophysics Data System (ADS)

    Kuai, Jiawei; Liu, Libo

    2016-04-01

    Ionospheric storms manifest an extreme state of the ionosphere caused by geomagnetic storms, and the complicated ionospheric storm effects are always a research focus for the ionospheric community. The geomagnetic storm occurring on 17-20 March 2015, which is characterized by the minimum SYM-H value -233 nT, is an extremely event of space weather in the current 24th solar cycle. In this report, multiple observations including GPS total electron content (TEC), ionospheric parameters from ionosondes, and magnetometer data are used to investigate the profound ionospheric disturbances at low latitudes and equatorial regions during this geomagnetic storm. Through observation and analysis, the disturbed electric fields, which comprise penetration electric fields (PEFs) and disturbance dynamo electric fields (DDEFs), are closely related to the ionospheric storm effects at low latitudes and equatorial regions during this event. The decisive role of electrodynamics at equatorial regions are focused in view of these observations to understand the complete process of the low-latitude and equatorial ionospheric response during the great geomagnetic storm.

  16. Effect of Solar Eclipse of March 20, 2015 on the Ionosphere

    NASA Astrophysics Data System (ADS)

    Ippolito, Alessandro; Settimi, Alessandro; Sabbagh, Dario; Scotto, Carlo; Sgrigna, Vittorio

    2016-04-01

    The effect on the ionosphere of solar eclipse of March 20, 2015 on different ionospheric layers has been studied, using the vertical ionospheric soundings from the ionosondes of Rome, Gibilmanna and San Vito dei Normanni. The response of the critical frequencies foF1 and foF2 have been investigated during the solar eclipse. The DuCharme and Petrie's formulation used to estimate foF1 has been corrected taking into account the decreased solar irradiance. This effect has been modeled by a Solar Obscuration Factor (SOF) and comparison with experimental values has been performed. A further study on the occurrence of the Sporadic E layer during the eclipse is here presented. As reported in literature, sporadic E layer appears during the eclipse, if the ionograms for 3 days before and 3 days after are analysed. When a wider set of days before and after the eclipse event are taken into account this phenomenon does not appear so clear. The behaviour of a regional adaptive and assimilative 3D ionospheric model has been tested as well, assimilating plasma frequency profiles fp(h). The study of the model behaviour in such particular condition has let us introduce corrections to F1 and E region modeling, improving its performances.

  17. Impacts of Space Weather Effects on the Ionospheric Vertical Total Electron Content

    NASA Astrophysics Data System (ADS)

    Hinrichs, Johannes; Bothmer, Volker; Mrotzek, Niclas; Venzmer, Malte; Erdogan, Eren; Dettmering, Denise; Limberger, Marco; Schmidt, Michael; Seitz, Florian; Börger, Klaus; Brandert, Sylvia; Görres, Barbara; Kersten, Wilhelm F.

    2016-04-01

    Space weather effects on the terrestrial ionospheric vertical total electron content (VTEC) are caused by solar EUV- and X-Ray emissions, solar wind streams and coronal mass ejections (CMEs), amongst other processes. They can lead to major disturbances of telecommunication and navigation systems. Accurately predicting the global VTEC distribution is thus of utmost importance for our societal infrastructure. Here we present results obtained within the German space situational awareness project OPTIMAP (OPerational Tool for Ionosphere Mapping And Prediction) through analyzing the solar effects on the global and regional distribution as well as on the temporal variation of the ionospheric VTEC. For the state-of-the-art analysis in the OPTIMAP project, key data from the GOES, SDO, ACE, SOHO, Proba2 and STEREO missions are analysed together with ground based parameters such as the F10.7 index. The ionospheric data are taken from global VTEC-maps provided by the International GNSS Service (IGS). The results will be used as input for the development of an improved operational VTEC forecast service providing forecasts up to five days in advance.

  18. Tropical cyclone effects on the equatorial ionosphere: First result from the Indian sector

    NASA Astrophysics Data System (ADS)

    Guha, Anirban; Paul, Bapan; Chakraborty, Monti; De, Barin Kumar

    2016-06-01

    Ionospheric response to the effects of tropical cyclone (TC) "Mahasen" in 2013 and Hudhud in 2014 is studied on the equatorial ionosphere over the Indian sector for the first time using Global Positioning System-derived total electron content (TEC) data. We observed an anomalous decrease of 3.8 TEC unit (1 TECU = 1016 el m-2) in vertical TEC (VTEC) value from the monthly mean for TC Mahasen and 2.1 TECU for TC Hudhud on the day of the landfall. We have also observed similar VTEC depletion of 1.5, 1.9, and 2.1 TECU for three different receivers on the landfall day for TC Vongfong over Japan. This anomalous decrease is observed over a wide zone around the trajectory of the cyclone during the active cyclonic storm stage. This observed anomaly might be the result of combined effect of TC-inspired gravity waves, ejection of neutral particles from the terminator of a TC, and lightning electric fields which redistribute the chemical constituents of the ionosphere by increasing the number of neutral particles at different ionospheric heights, thus decreasing the TEC over the satellite-receiver path.

  19. Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

    NASA Technical Reports Server (NTRS)

    Singh, N.; Schunk, R. W.; Sojka, J. J.

    1982-01-01

    The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

  20. Interplanetary magnetic field effects on high latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1985-01-01

    Relations between the electric field and the electric current in the ionosphere can be established on the basis of a system of mathematical and physical equations provided by the equations of current continuity and Ohm's law. For this reason, much of the synthesis of electric field and plasma velocity data in the F-region is made with the aid of similar data sets derived from field-aligned current and horizontal current measurements. During the past decade, the development of a self-consistent picture of the distribution and behavior of these measurements has proceeded almost in parallel. The present paper is concerned with the picture as it applies to the electric field and plasma drift velocity and its dependence on the interplanetary magnetic field. Attention is given to the southward interplanetary magnetic field and the northward interplanetary magnetic field.

  1. Cyclotron resonance effects on stochastic acceleration of light ionospheric ions

    NASA Astrophysics Data System (ADS)

    Singh, N.; Schunk, R. W.; Sojka, J. J.

    1982-09-01

    The production of energetic ions with conical pitch angle distributions along the auroral field lines is a subject of considerable current interest. There are several theoretical treatments showing the acceleration (heating) of the ions by ion cyclotron waves. The quasi-linear theory predicts no acceleration when the ions are nonresonant. In the present investigation, it is demonstrated that the cyclotron resonances are not crucial for the transverse acceleration of ions by ion cyclotron waves. It is found that transverse energization of ionospheric ions, such as He(+), He(++), O(++), and O(+), is possible by an Electrostatic Hydrogen Cyclotron (EHC) wave even in the absence of cyclotron resonance. The mechanism of acceleration is the nonresonant stochastic heating. However, when there are resonant ions both the total energy gain and the number of accelerated ions increase with increasing parallel wave number.

  2. Effect of enhanced x-ray flux on the ionosphere over Cyprus during solar flares

    NASA Astrophysics Data System (ADS)

    Mostafa, Md. Golam; Haralambous, Haris

    2015-06-01

    In this work we study the effect of solar flares on the ionosphere over Cyprus. Solar flares are impulsive solar activity events usually coupled with Coronal Mass Ejection (CME). The arrival and the subsequent impact of solar flares on geospace, following an eruption on the Sun's surface is almost immediate (around 9 min) whereas the impact of CMEs is rather delayed (2-3 days) as the former is based on X-ray radiation whereas the latter phenomenon is related with particles and magnetic fields travelling at lower speeds via the Solar Wind. The penetration of X-rays down to the Dregion following such an event enhances the electron density. This increase can be monitored by ionosondes, which measure the electron density up to the maximum electron density NmF2. The significance of this increase lies on the increase of signal absorption causing limited window of operating frequencies for HF communications. In this study the effect of enhanced X-ray flux on the ionosphere over Cyprus during solar flares has been investigated. To establish the correlation and extent of impact on different layers, data of X-ray intensity from Geostationary Operational Environmental Satellite (GOES) and ionospheric characteristics (D & F layer) over Nicosia station (35° N, 33° E) were examined for all solar flares during the period 2011-2014. The analysis revealed a positive and good correlation between frequency of minimum reflection, fmin and X-ray intensity for D layer demonstrating that X-rays play a dominant role in the ionization of lower ionosphere. Hence, X-ray flux can be used as a good proxy for studying the solar flare effects on lower ionosphere. The correlation coefficient between maximum electron density of F layer, NmF2 and X-ray intensity was found to be poor.

  3. Effects of an atmospheric gravity wave on the midlatitude ionospheric F layer

    SciTech Connect

    Millward, G.H.; Moffett, R.J.; Quegan, S.; Fuller-Rowell, T.J. |

    1993-11-01

    A modeling study of the atmospheric response to a single short burst of enhanced ion convection at high latitudes, undertaken using the Sheffield/University College London/Space Environment Laboratory coupled ionosphere/thermosphere model, has revealed a large-scale atmospheric gravity wave (AGW) moving equatorward from a source in the dawn sector auroral zone. The wave propagates to midlatitude, perturbing the ionosphere and creating a traveling ionospheric disturbance. Analysis of the interaction between the thermosphere and ionosphere during the passage of the AGW at midlatitudes is undertaken and reveals a complex height-dependent response. At lower altitudes the field-aligned velocity of the ions follows closely the field-aligned wind. Above the F peak, diffusion processes become important and the field-aligned ion velocity shows fluctuations which exceded those in the wind. Changes in N{sub m}F{sub 2} and h{sub m} F{sub 2}, during the interaction, are due to redistribution of plasma alone with changes in production and loss insignificant. As the F layer is lifted by the positive surge in the gravity wave, N{sub m}F{sub 2} decreases, due to a divergence in the ion flux, itself caused by the combination of a divergent neutral wind and an increase in the effects of diffusion with altitude. The slab thickness also increases. Subsequently, the opposite happens as h{sub m}F{sub 2} falls below its equilibrium value. 14 refs., 9 figs., 1 tab.

  4. Review of radio-frequency, non-linear effects on the ionosphere

    NASA Astrophysics Data System (ADS)

    Gordon, William E.; Duncan, Lewis M.

    1988-06-01

    The nonlinear effects of powerful radio waves on the ionosphere are reviewed. The history of such effects beginning in the early 1930s are retold, highlighting important events up to the late 1960s. A phenomenological treatment is then given to ohmic heating, parametric instabilities, self-focusing, and kilometric-scale irregularities, meter-scale irregularities, and a collection of recently discovered effects. The benefits that international cooperation would provide for this research are discussed, giving a list of future research challenges.

  5. Ionospheric effects of the magnetic storm on 18-22 August 2003 according to the data of HF sounding of the artificial ionospheric turbulence

    NASA Astrophysics Data System (ADS)

    Uryadov, V. P.; Vertogradov, G. G.; Vertogradov, V. G.; Ponyatov, A. A.; Frolov, V. L.

    2004-07-01

    The results of the experimental studies of the influence on the HF signals characteristics of the artificial ionospheric turbulence (AIT) created by the impact on the ionosphere of the powerful radioemission of the heating facilities SURA (Nizhny Novgorod region of Russia) are presented. The measurements were conducted on 18-22 August 2003 in the evening time (1600-2000 UT) at the linearly frequency modulated (LFM) sounding paths: Khabarovsk-Rostov on Don, Irkutsk-Rostov on Don, and Inskip (England)-Rostov on Don and also at the Moscow-Rostov on Don path by the reception of signals of the RVM precise time stations. It was found that at the presence of a strong sporadic E layer at the Irkutsk-SURA path, there appeared the conditions for the SW signal propagation through the upper ionosphere at the frequencies exceeding the maximum usable frequency of the standard hop-like propagation through the F region. The presence of these signals was detected by descending of radio waves from F region altitudes to the Rostov-on-Don reception point due to their scatter at artificial small-scale magnetically oriented irregularities. Using the measurements of the Doppler shift of the frequency of the signals scattered at AIT, ionospheric effects of the magnetic storm occurred in the period of the experiment were studied. It is shown that during the magnetic storm the electric field and irregularity drift velocity at F region heights over the SURA facility reached values of ~8.6 mV m-1 and 186 m s-1, respectively, that is, the values typical for the high-latitude ionosphere. The relation of the quasiperiodic oscillations of the Doppler frequency of the scattered signal to propagation of magnetohydrodynamics waves excited during a magnetic storm is considered.

  6. Ionospheric research opportunity

    NASA Astrophysics Data System (ADS)

    Rickel, Dwight

    1985-05-01

    Ground-based explosions have been exploited successfully in the past as a relatively controlled source for producing ionospheric disturbances. On June 25, the Defense Nuclear Agency will conduct a high explosives test on the northern section of the White Sands Missile Range. Approximately 4,800 tons of ammonium nitrate and fuel oil (ANFO) will be detonated at ground level, producing an acoustic shock wave with a surface pressure change of approximately 20 mbar at a 6 km range. This shock front will have sufficient strength to propagate into the ionosphere with at least a 10% change in the ambient pressure across the disturbance front in the lower F region. Such an ionospheric perturbation will give ionospheric researchers an excellent opportunity to investigate acoustic propagation at ionospheric heights, shock dissipation effect, the ion-neutral coupling process, acoustic-gravity wave (traveling ionospheric disturbance) generation mechanisms, and associated RF phenomena.

  7. The flywheel effect: Ionospheric currents after a geomagnetic storm

    SciTech Connect

    Deng, W.; Killeen, T.L.; Burns, A.G. ); Roble, R.G. )

    1991-10-01

    In the period following a geomagnetic storm the high-latitude, magnetospheric-driven convection pattern is normally weak. However, the neutral circulation, set up by ion-neutral momentum coupling during the main phase of the storm, may continue for several hours after the storm has ended. This persistent neutral circulation has the potential to drive Hall currents for some hours. In this paper the authors investigate these flywheel' currents by simulating a storm which occurred on the 23rd of November 1982 using the National Center for Atmospheric Research Thermosphere Ionosphere General Circulation Model (NCAR-TIGCM). The resulting high-latitude, height-integrated Hall currents are dominated by the neutral-wind-driven component for several hours after the end of main phase of the storm. The direction of these currents is reversed from normal. Analysis of the neutral and ion components of this current system indicates that the neutral component may drive as much as 80% of the high-latitude current system immediately after the storm has ended, and may continue to dominate this system for 4 to 5 hours.

  8. Optimization of satellite coverage in observing cause and effect changes in the ionosphere, magnetosphere, and solar wind. Master's thesis

    SciTech Connect

    Loveless, M.J.

    1993-06-01

    Disturbances in the ionosphere sometimes cause adverse effects to communications systems, power grids, etc. on the earth. Currently, very little, if any, lead time is given to warn of an impending problem. If a forecast could be made of ionospheric occurrences, some lead time may be given to appropriate agencies and equipment may be saved. Most changes that occur in the ionosphere are a result of interaction of energy, currents, etc. between the magnetosphere and/or solar wind. Before a forecast can be made, however, improvement of ionospheric models currently in use need to be made. The models currently depict features in various regions of the ionosphere but not always where these features are actually observed. So an improvement to the model is needed to create an accurate baseline condition, or in other words an accurate depiction of the current ionosphere. Models could be improved by inputting real-time data from the ionosphere into the model. This data would come from satellites and/or ground-based stations.

  9. Stratospheric Sudden Warming Effects on the Ionospheric Migrating Tides during 2008-2010 observed by FORMOSAT-3/COSMIC

    NASA Astrophysics Data System (ADS)

    Lin, J.; Lin, C.; Chang, L. C.; Liu, H.; Chen, W.; Chen, C.; Liu, J. G.

    2013-12-01

    In this paper, ionospheric electron densities obtained from radio occultation soundings of FORMOSAT-3/COSMIC are decomposed into their various constituent tidal components for studying the stratospheric sudden warming (SSW) effects on the ionosphere during 2008-2010. The tidal analysis indicates that the amplitudes of the zonal mean and major migrating tidal components (DW1, SW2 and TW3) decrease around the time of the SSW, with phase/time shifts in the daily time of maximum around EIA and middle latitudes. Meanwhile consistent enhancements of the SW2 and nonmigrating SW1 tides are seen after the stratospheric temperature increase. In addition to the amplitude changes of the tidal components, well matched phase shifts of the ionospheric migrating tides and the stratospheric temperatures are found for the three SSW events, suggesting a good indicator of the ionospheric response. Although the conditions of the planetary waves and the mean winds in the middle atmosphere region during the 2008-2010 SSW events may be different, similar variations of the ionospheric tidal components and their associated phase shifts are found. Futher, these ionospheric responses will be compared with realistic simulations of Thermosphere-Ionosphere-Mesophere-Electrodynamics General Circulation Model (TIME-GCM) by nudging Modern-Era Retrospective analysis for Research and Applications (MERRA) data.

  10. On differences of magnetic storm effects on ionosphere above neighbouring locations

    NASA Astrophysics Data System (ADS)

    Buresova, Dalia; Bosco Habarulema, John; Thobeka Katamzi, ama; Lastovicka, Jan; Chum, Jaroslav; Sindelarova, Tereza; Mosna, Zbysek; Urbar, Jaroslav; Kouba, Daniel

    2016-04-01

    The paper is focused on cases of different ionospheric reaction above a few neighbouring European and South African locations to disturbances induced by CIR/HSS-related storms. Most of storms involved in the analysis occurred within the 23rd and 24th solar cycle. We analysed variability of the F2 layer critical frequency foF2, peak height hmF2 and GPS TEC values for the entire storm period. Both positive and negative deviations of foF2, hmF2 and TEC have been obtained independently on season. Observed differences in ionospheric effects (mainly in positive effects) for the individual events and neighbouring locations are well pronounced both in foF2 and hmF2. We considered an impact of several factors (e.g. intensity of geomagnetic storm, local geomagnetic situation, and season, difference between geographic and geomagnetic coordinates etc.) with aim to identify the "main players".

  11. Magnetic zenith effect in the ionospheric modification by an X-mode HF heater wave

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Haggstrom, I.; Rietveld, M. T.; Yeoman, T. K.

    2013-12-01

    We report experimental results aimed at an investigation of the magnetic zenith effect in the high latitude ionosphere F region from ionospheric modification by powerful HF heater wave with X-polarization. The ionospheric modification was produced by the HF heating facility at Tromsø (Norway) using the phased array with a narrow beam with of 6 degrees. Effective radiated power was varied between 450 and 1000 MW. The HF pump wave radiated in different directions relative to the magnetic field from 90 degrees (vertical) to 78 degrees (magnetic zenith) at frequencies near or above the ordinary-mode critical frequency. The response of the ionosphere plasma to the HF pump wave impact was checked by the UHF incoherent scatter radar located in the immediate vicinity of the HF heater. UHF radar was probing the plasma parameters, such as electron density and temperature (Ne and Te), HF-induced plasma and ion lines in the altitude range from 90 to 600 km. It was running in a scanning mode when UHF radar look angles were changed from 74 to 90 degrees by 1 or 2 degree step. It was clearly demonstrated that the strongest heater-induced effects took place in the magnetic field-aligned direction when HF pointing was also to the magnetic zenith. It was found that strong Ne enhancement of up to 80 % along magnetic field (artificial density ducts) were excited only under HF pumping towards magnetic zenith. The width of the artificial ducts comes to only 2 degrees. The Ne increases were accompanied by the Te enhancements of up to about 50 %. Less pronounced Te increases were also observed in the directions of 84 and 90 degrees. Strong Ne enhancements can be accompanied by excitation of strong HF-induced plasma and ion lines. Thus experimental results obtained points to the strong magnetic zenith effect due to self-focusing powerful HF radio wave with X-mode polarization.

  12. The spectral effect of the ionospheric irregularities on the scintillation of transionospheric signals

    SciTech Connect

    Lyle, R.; Kuo, S.P.; Huang, J.

    1995-12-31

    The effect of the spectral width {Delta}k of the ionospheric density irregularity an scintillation of the transionospheric signal is examined. The results show that the Scinti1lation Index S{sub 4} depends strongly on {Delta}/k which can enhance or reduce S{sub 4} value depending on the wave length of the irregularity. However, a 10% spectral width reduces S{sub 4} to a negligibly small value almost independent of the scale length of the irregularity.

  13. Effect of finite blob size on the current convective instability in the auroral ionosphere. Memorandum report

    SciTech Connect

    Huba, J.D.; Chaturvedi, P.K.

    1986-04-11

    It has been suggested that the current convective instability may be responsible for the structuring, i.e., generation of density irregularities, of density enhancements (known as blobs) in the auroral ionosphere. However, previous theories have neglected the finite extent of the blob along the geomagnetic field. In this paper, a nonlocal theory of the current convective instability is developed, which considers the finite extent of an ionospheric blob parallel to the geomagnetic field. It was found that the growth rate of the instability can be substantially reduced in the finite-sized blob case from the value obtained in the local approximation for an infinitely long blob. For auroral ionosphere parameters, the reduction in the growth rate for medium scale irregularities (1-10 km) can be one to two orders of magnitude for the typical observed values of blob sizes (approx. a few hundred km). Thus, it appears that the current convective instability is not a viable mechanism to generate scintillation causing irregularities, i.e., 1-10 km irregularities.

  14. Effect of interhemispheric currents on equivalent ionospheric currents in two hemispheres: Simulation results

    NASA Astrophysics Data System (ADS)

    Lyatskaya, Sonya; Lyatsky, Wladislaw; Zesta, Eftyhia

    2016-02-01

    In this research, we used numerical simulation to study the effect of interhemispheric field-aligned currents (IHCs), going between two conjugate ionospheres in two hemispheres, on the equivalent ionospheric currents (EICs). We computed the maps of these EICs in two hemispheres during summer-winter conditions, when the effect of the IHCs is especially significant. The main results may be summarized as follows. (1) In winter hemisphere, the IHCs may significantly exceed and be a substitute for the local R1 currents, and they may strongly affect the magnitude, location, and direction of the EICs in the nightside winter auroral ionosphere. (2) While in summer polar cap the EICs tend to flow sunward, and in winter polar cap the EICs turn toward dawn due to the effect of the IHCs. (3) The well-known reversal in the direction of the EICs in the vicinity of the midnight meridian, in winter hemisphere, is observed not at the polar caps boundary (as usually expected) but equatorward of this boundary in the region of the IHCs location. (4) The IHCs in winter hemisphere may be, in fact, not only a substitute for the R1 currents but also the major source of the Westward Auroral Electrojet, observed in both hemispheres during substorm activity.

  15. Effects of the Ionosphere on Passive Microwave Remote Sensing of Ocean Salinity from Space

    NASA Technical Reports Server (NTRS)

    LeVine, D. M.; Abaham, Saji; Hildebrand, Peter H. (Technical Monitor)

    2001-01-01

    Among the remote sensing applications currently being considered from space is the measurement of sea surface salinity. The salinity of the open ocean is important for understanding ocean circulation and for modeling energy exchange with the atmosphere. Passive microwave remote sensors operating near 1.4 GHz (L-band) could provide data needed to fill the gap in current coverage and to complement in situ arrays being planned to provide subsurface profiles in the future. However, the dynamic range of the salinity signal in the open ocean is relatively small and propagation effects along the path from surface to sensor must be taken into account. In particular, Faraday rotation and even attenuation/emission in the ionosphere can be important sources of error. The purpose or this work is to estimate the magnitude of these effects in the context of a future remote sensing system in space to measure salinity in L-band. Data will be presented as a function of time location and solar activity using IRI-95 to model the ionosphere. The ionosphere presents two potential sources of error for the measurement of salinity: Rotation of the polarization vector (Faraday rotation) and attenuation/emission. Estimates of the effect of these two phenomena on passive remote sensing over the oceans at L-band (1.4 GHz) are presented.

  16. HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.

    2014-12-01

    In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.

  17. Implementation of Inductive Magnetosphere-Ionosphere Coupling and its Effects on Global MHD Magnetospheric Simulations

    NASA Astrophysics Data System (ADS)

    Xi, S.; Lotko, W.; Zhang, B.; Brambles, O.; Wiltberger, M. J.; Lyon, J.; Merkin, V. G.

    2010-12-01

    In global modeling, magnetosphere-ionosphere (MI) coupling physically connects a global magnetospheric (GM) model and a global ionospheric-thermospheric (GIT) model. The field-aligned current from the GM model and the conductance distributions from the GIT model are used in a Poisson equation derived from the ionospheric Ohm's law combined with current continuity to determine the electrostatic potential in the ionosphere. In current GM models, this electrostatic potential is mapped to the inner boundary of the GM simulation to determine electrostatic boundary conditions on the electric field and MHD velocity there. Inductive effects and the finite Alfven transit time between the low-altitude GM boundary and the high-altitude GIT boundary (MI gap region) are neglected in this formulation of MI coupling. Using fields and currents derived from Lyon-Fedder-Mobarry GM simulations, and conductance distributions derived from its standalone empirical conductance model in the MI coupling Poisson equation, we have computed the fast Fourier transform of the electrostatic field at the low-altitude LFM simulation boundary as described above, and the FFT of the inductive electric field at the boundary under the assumption that μ 0 Σ P vA ≤ 1, where Σ P is the ionospheric Pedersen conductance and vA is the smallest value of the Alfven speed in the MI gap region. In this regime, the complete electric field at the low-altitude simulation boundary includes the usual mapped electrostatic field with an inductive addition for which the finite Alfven transit time and the diversion of field-aligned into polarization currents in the gap region are negligible (Lotko, 2004). By comparing the boundary-averaged spectra of the electrostatic and so-determined inductive fields, we confirm that the purely electrostatic formulation of MI coupling is valid when the MHD state varies on times scales exceeding about 200 s. For faster MHD time variations, the inductive electric field is shown to

  18. Modeling the ionospheric impact of tsunami-driven gravity waves with SAMI3: Conjugate effects

    NASA Astrophysics Data System (ADS)

    Huba, J. D.; Drob, D. P.; Wu, T.-W.; Makela, J. J.

    2015-07-01

    The Naval Research Laboratory first-principles ionosphere model SAMI3 is used to study the ionospheric effects associated with tsunami-driven gravity waves. Specifically, the Tohoku-Oki tsunami of 11 March 2011 is modeled. It is shown that gravity wave-induced variations in the neutral wind lead to plasma velocity variations both perpendicular and parallel to the geomagnetic field. Moreover, the electric field induced by the neutral wind perturbations can map to the conjugate hemisphere. Thus, electron density variations can be generated in both hemispheres which impact the total electron content (TEC) and 6300 Šairglow emission. It is found that the TEC exhibits variations of ≲ ±0.1 total electron content unit (1 TECU = 1016 el m-2) and the 6300 Šairglow emission variation is up to ˜±2.5% relative to the unperturbed background airglow.

  19. The 20 March 2015 total solar eclipse: effects in the high-latitude lower ionosphere

    NASA Astrophysics Data System (ADS)

    Cherniakov, Sergey; Tereshchenko, Valentina; Ogloblina, Olga; Vasiliev, Evgeny; Gomonov, Alexander

    2016-07-01

    The medium-wave facility of partial reflections of the Polar Geophysical Institute (observatory "Tumanny", 69 N, 35.7 E) has observed behavior of the lower high-latitude ionosphere during the 20 March 2015 total solar eclipse. There were several effects during the eclipse. Generally on the heights of the lower ionosphere the "short night" effect had shown, but at some heights local enhanced electron concentration were revealed and the behavior of the electron concentration had the wave-like form. It had seen also at the behavior of the total electron content of the lower ionosphere. The periods and behavior of the wave are considered. It can be explained by influence of acoustic-gravity waves which originated after cooling of the atmosphere by the lunar shadow during its supersonic movement along the earth surface. The periods and behavior of waves during the eclipse were also received using riometer data at the observatory "Tumanny" and the magnetometer at the observatory "Loparskaya" (68.63 N, 33.38 E).

  20. Ionospheric effects of rocket exhaust products (HEAO-C, Skylab and SPS-HLLV)

    SciTech Connect

    Zinn, J; Sutherland, D; Stone, S N; Duncan, L M; Behnke, R

    1980-10-01

    This paper reviews the current state of our understanding of the problem of ionospheric F-layer depletions produced by chemical effects of the exhaust gases from large rockets, with particular emphasis on the Heavy Lift Launch Vehicles (HLLV) proposed for use in the construction of solar power satellites. The currently planned HLLV flight profile calls for main second-stage propulsion confined to altitudes below 124 km, and a brief orbit-circularization maneuver at apogee. The second-stage engines deposit 9 x 10/sup 31/ H/sub 2/O and H/sub 2/ molecules between 56 and 124 km. Model computations show that they diffuse gradually into the ionospheric F region, where they lead to weak but widespread and persistent depletions of ionization and continuous production of H atoms. The orbit-circularization burn deposits 9 x 10/sup 29/ exhaust molecules at about 480-km altitude. These react rapidly with the F2 region 0/sup +/ ions, leading to a substantial (factor-of-three) reduction in plasma density, which extends over a 1000- by 2000-km region and persists for four to five hours. Also described are experimental airglow and incoherent-scatter radar measurements performed in conjunction with the 1979 launch of satellite HEAO-C, together with prelaunch and post-launch computations of the ionospheric effects. Several improvements in the model have been driven by the experimental observations. The computer model is described in some detail.

  1. Partial order of quantum effects

    NASA Astrophysics Data System (ADS)

    Lahti, Pekka J.; Ma̧czynski, Maciej J.

    1995-04-01

    The set of effects is not a lattice with respect to its natural order. Projection operators do have the greatest lower bounds (and the least upper bounds) in that set, but there are also other (incomparable) effects which share this property. However, the coexistence, the commutativity, and the regularity of a pair of effects are not sufficient for the existence of their infima and suprema. The structure of the range of an observable (as a normalized POV measure) can vary from that of a commutative Boolean to a noncommutative non-Boolean subset of effects.

  2. The effects of neutral inertia on ionospheric currents in the high-latitude thermosphere following a geomagnetic storm

    SciTech Connect

    Deng, W.; Killeen, T.L.; Burns, A.G. ); Roble, R.G. ); Slavin, J.A.; Wharton, L.E. )

    1993-05-01

    The authors extend previous work with a National Center for Atmospheric Research (NCAR) thermosphere/ionosphere general circulation model (TIGCM), to study dynamo effects in the high latitude thermosphere. Ionospheric convection can drive neutral currents in much the same pattern by means of ion drag reactions. It has been observed that ion currents established during magnetic storms can induce neutral currents which persist for hours after the end of the storm. Model results have shown that such currents can account for up to 80 percent of the Hall currents in the period immediately following storms. Here this previous work is extended and compared with experimental observations. The authors simulate time dependent Hall currents, field-aligned currents, and electrical power fluxes coupling the magnetosphere and ionosphere. They discuss their results in terms of a loaded magnetosphere, which accounts for the fact that the neutral currents can also induce currents and electric fields in the ionosphere.

  3. Effects of magnetospheric precipitation and ionospheric conductivity on the ground magnetic signatures of traveling convection vortices

    NASA Astrophysics Data System (ADS)

    Zhu, L.; Schunk, R. W.; Sojka, J. J.

    1999-04-01

    By using an improved TCV model (Zhu et al., 1997), a quantitative study of the effects of magnetospheric precipitation and ionospheric background conductivity on the ground magnetic signatures of traveling convection vortices (TCVs) has been conducted. In this study the localized conductivity enhancement associated with the TCVs is present and the ratio of the Hall and Pedersen conductances vary both spatially and temporally according to the hardness of the TCV precipitation. It is found that a strong conductivity enhancement associated with hard TCV precipitation can significantly distort the TCV current closure in the ionosphere and lead to ground magnetic disturbance patterns with strong asymmetry in E-W direction. The asymmetry of the ground magnetic patterns is characterized by a stronger magnetic disturbance on the side of the upward field-aligned currents (clockwise convection cell) and a possible rotation of the whole magnetic patterns. Specifically, the modeling results predict that when the characteristic energy of the TCV precipitation is below 500 eV, the asymmetry of the ground magnetic patterns is minimal (less than 1%) and may not be detectable. When the characteristic energy of the precipitation is about 7 keV, the asymmetry of the magnetic patterns can be well above 30%. It is also found that a low ionospheric background conductivity favors the appearance of strong asymmetry in the ground magnetic patterns of the TCVs, while a high ionospheric background conductivity favors the appearance of strong ground magnetic disturbances but with less asymmetry. We concluded that the most favorable condition for the appearance of strong asymmetry in the TCV ground magnetic signatures is the condition of winter, solar minimum, and hard precipitation.

  4. A re-analysis of the atmospheric and ionospheric effects of the Flixborough explosion

    NASA Astrophysics Data System (ADS)

    Krasnov, V. M.; Drobzheva, Ya. V.; Venart, J. E. S.; Lastovicka, J.

    2003-07-01

    The ionospheric record of the 1974 cyclohexane vapour cloud explosion (VCE) accident near Flixborough is re-examined in light of a new theory used to describe the acoustic field in the atmosphere and ionosphere caused by explosions on the ground. The reconstructed oblique Doppler sounding records from six radio traces agree remarkably well with experimental results when a ground source explosion yield of 283+/-38tons of TNT is utilized. This result, when compared to the detonation of large hydrocarbon fuel-drop-air clouds, suggests that only 14+/-2tons of cyclohexane was involved in the explosion. Additionally the time of the explosion determined from the model, 15:52:08+/-6, agrees, within the mutual uncertainty, with that determined seismically, 15:52:15.5+/-2 UT. The precision in the value of the yield and accuracy of the time of the explosion validates the model used to describe the propagation of acoustic waves by taking into account expansion, absorption, and non-linear and inhomogeneous effects in the atmosphere and ionosphere.

  5. Thermospheric tidal effects on the ionospheric midlatitude summer nighttime anomaly using SAMI3 and TIEGCM

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Lin, C. H.; Chang, L. C.; Huba, J. D.; Lin, J. T.; Saito, A.; Liu, J. Y.

    2013-06-01

    This paper is the first study to employ a three-dimensional physics-based ionosphere model, SAMI3, coupled with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) and Global Scale Wave Model to simulate the mesospheric and lower thermospheric tidal effects on the development of midlatitude summer nighttime anomaly (MSNA). Using this coupled model, the diurnal variation of MSNA electron densities at 300 km altitude is simulated on both June solstice (day of year (DOY) 167) and December solstice (DOY 350) in 2007. Results show successful reproduction of the southern hemisphere MSNA structure including the eastward drift feature of the southern MSNA, which is not reproduced by the default SAMI3 runs using the neutral winds provided by the empirical Horizontal Wind Model 93 neutral wind model. A linear least squares algorithm for extracting tidal components is utilized to examine the major tidal component affecting the variation of southern MSNA. Results show that the standing diurnal oscillation component dominates the vertical neutral wind manifesting as a diurnal eastward wave-1 drift of the southern MSNA in the local time frame. We also find that the stationary planetary wave-1 component of vertical neutral wind can cause diurnal variation of the summer nighttime electron density enhancement around the midlatitude ionosphere.

  6. Testing Ionospheric Faraday Rotation Corrections in CASA

    NASA Astrophysics Data System (ADS)

    Kooi, Jason E.; Moellenbrock, George

    2015-04-01

    The Earth’s ionosphere introduces direction- and time-dependent effects over a range of physical and temporal scales and so is a major source for unmodeled phase offsets for low frequency radioastronomical observations. Ionospheric effects are often the limiting factor to making sensitive radioastronomical measurements to probe the solar corona or coronal mass ejections at low frequencies (< 5 GHz). It has become common practice to use global ionospheric models derived from the Global Positioning System (GPS) to provide a means of externally calibrating low frequency data. We have developed a new calibration algorithm in the Common Astronomy Software Applications (CASA) package. CASA, which was developed to meet the data post-processing needs of next generation telescopes such as the Karl G. Jansky Very Large Array (VLA), did not previously have the capability to mitigate ionospheric effects. This algorithm uses GPS-based global ionosphere maps to mitigate the first and second order ionospheric effects (dispersion delay and Faraday rotation, respectively). We investigated several data centers as potential sources for global ionospheric models and chose the International Global Navigation Satellite System Service data product because data from other sources are generally too sparse to use without additional interpolation schemes. This implementation of ionospheric corrections in CASA has been tested on several sets of VLA observations and all of them showed a significant reduction of the dispersion delay. In order to rigorously test CASA’s ability to mitigate ionospheric Faraday rotation, we made VLA full-polarization observations of the standard VLA phase calibrators J0359+5057 and J0423+4150 in August 2014, using L band (1 - 2 GHz), S band (2 - 4 GHz), and C band (4 - 6 GHz) frequencies in the D array configuration. The observations were 4 hours in duration, beginning near local sunrise. In this paper, we give a general description of how these corrections are

  7. Ionospheric effects on a wide-bandwidth, polarimetric, space-based, synthetic-aperture radar

    NASA Astrophysics Data System (ADS)

    Brock, B. C.

    1993-01-01

    The earth's ionosphere consists of an ionized plasma which will interact with any electromagnetic wave propagating through it. The interaction is particularly strong at vhf and uhf frequencies but decreases for higher microwave frequencies. These interaction effects and their relationship to the operation of a wide-bandwidth, synthetic-aperture, space-based radar are examined. Emphasis is placed on the dispersion effects and the polarimetric effects. Results show that high-resolution (wide-bandwidth) and high-quality coherent polarimetrics will be very difficult to achieve below 1 GHz.

  8. Ionospheric effects in uncalibrated phase delay estimation and ambiguity-fixed PPP based on raw observable model

    NASA Astrophysics Data System (ADS)

    Gu, Shengfeng; Shi, Chuang; Lou, Yidong; Liu, Jingnan

    2015-05-01

    Zero-difference (ZD) ambiguity resolution (AR) reveals the potential to further improve the performance of precise point positioning (PPP). Traditionally, PPP AR is achieved by Melbourne-Wübbena and ionosphere-free combinations in which the ionosphere effect are removed. To exploit the ionosphere characteristics, PPP AR with L1 and L2 raw observable has also been developed recently. In this study, we apply this new approach in uncalibrated phase delay (UPD) generation and ZD AR and compare it with the traditional model. The raw observable processing strategy treats each ionosphere delay as an unknown parameter. In this manner, both a priori ionosphere correction model and its spatio-temporal correlation can be employed as constraints to improve the ambiguity resolution. However, theoretical analysis indicates that for the wide-lane (WL) UPD retrieved from L1/L2 ambiguities to benefit from this raw observable approach, high precision ionosphere correction of better than 0.7 total electron content unit (TECU) is essential. This conclusion is then confirmed with over 1 year data collected at about 360 stations. Firstly, both global and regional ionosphere model were generated and evaluated, the results of which demonstrated that, for large-scale ionosphere modeling, only an accuracy of 3.9 TECU can be achieved on average for the vertical delays, and this accuracy can be improved to about 0.64 TECU when dense network is involved. Based on these ionosphere products, WL/narrow-lane (NL) UPDs are then extracted with the raw observable model. The NL ambiguity reveals a better stability and consistency compared to traditional approach. Nonetheless, the WL ambiguity can be hardly improved even constrained with the high spatio-temporal resolution ionospheric corrections. By applying both these approaches in PPP-RTK, it is interesting to find that the traditional model is more efficient in AR as evidenced by the shorter time to first fix, while the three

  9. The ionospheric effect of Total solar eclipse of 22 July 2009 in the equatorial anomaly region

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Singh, R.; Singh, A. K.

    2012-12-01

    Response of the D and E and F-region of the ionosphere to the total solar eclipse of 22 July 2009 at low latitude, Varanasi (geomagnetic lat = 140 55'N, longitude = 1540 E, dip. angle = 37.30) was investigated using multi-instrument. The solar eclipse started at 05:30:04.4 hrs IST and lasted up to 07:27 hrs IST with totally from 6.25 IST to 6.27 IST in the morning hours at Varanasi. Here we have analyzed narrowband (Amplitude and phase of transmitted signal) as well as broadband (entire VLF signal spectrum) VLF data to find any significant changes in amplitude and/or phase of the signals from various transmitters across the world and any variation from the normal diurnal behavior in ionospheric parameters such as electron density, VLF reflection height. The changes in D-region ionospheric VLF reflection heights and electron density during eclipse have been estimated from tweek analysis. The reflection height increased from ~90 km from the first occurrence of tweek to about 93-94 km at the totality and then decreased to ~89 km at the end of the eclipse. Observations suggest that about 30-40% obscuration of solar disc can lead to the tweeks occurrence which otherwise occur only in the nighttime. A significant increase of 3 dB in the strength of the amplitude of VLF signal of 22.2 kHz transmitted from JJI-Japan is observed around the time of the total solar eclipse (TSE) as compared to a normal day. The modeled electron density height profile of the lower ionosphere depicts linear variation in the electron density with respect to solar radiation as observed by tweek analysis also. We have also used GPS based TEC measurement along with the VHF scintillation to study effect of total solar eclipse. To observe the variability of TEC at Varanasi we have used the VTEC of some selected PRNs and quiet mean VTEC of the same PRN. The percentage change in VTEC (DTEC) compared to quiet mean for each PRN is also plotted to observe the effect. There is considerable reduction in

  10. New Ionospheric Interaction Experiments

    NASA Astrophysics Data System (ADS)

    Sheerin, J. P.

    2004-11-01

    Current upgrades to both the HF transmitter and diagnostic capabilities at the HAARP facility near Gakona, AK will permit a new generation ionospheric interaction experiments. We explore some of the new phenomena accessible with significantly increased ERP. Large-scale long-lived density structures induced by the HF pump in the ionospheric plasma are investigated. Long-lived density structures which convect with the ambient ionosphere, may serve as tracers for ionospheric flows and fields. Recent advances in HF and VHF radar diagnostics available for HAARP experiments, permit plasma wave detection and monitoring. We survey the mode structures expected with the next generation of high intensity experiments. Together with existing complementary diagnostics such as stimulated HF emissions and optical effects, these data will provide unprecedented views of highly nonlinear phenomena induced by high intensity RF radiation in the ionosphere.

  11. The energetics of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Roboz, A.; Nagy, A. F.

    1994-02-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  12. Large-Scale Ionospheric Effects Related to Electron-Gyro Harmonics: What We Have Learned from HAARP.

    NASA Astrophysics Data System (ADS)

    Watkins, B. J.; Fallen, C. T.; Secan, J. A.

    2014-12-01

    The HAARP ionospheric modification facility has unique capabilities that enable a wide range of HF frequencies with transmit powers ranging from very low to very high values. We will review a range of experiment results that illustrate large-scale ionospheric effects when the HF frequencies used are close to electron gyro-harmoncs and we focus mainly on the 3rd and 4th harmonics. The data are primarily from the UHF diagnosticc radar and total electron content (TEC) observations through the heated topside ionosphere. Radar data for HF frequencies just above and just below gyro harmoncs show significant differences in radar scatter cross-section that suggest differing plasma processes, and this effect is HF power dependent with some effects only observable with full HF power. For the production of artificial ionization in the E-region when the HF frequency is near gyro-harmoncs the results differ significantly for relatively small (50 kHz) variations in the HF frequency. We show how slow FM scans in conjunction with gyro-harmonic effects are effective in producing artificial ionization in the lower ionosphere.In the topside ionosphere enhanced density and upward fluxes have been observed and these may act as effective ducts for the propagation of VLF waves upward into the magneosphere. Experimental techniques have been developed that may be used to continuously maintain these effects in the topside ionossphere.

  13. Ionosphere Waves Service - A demonstration

    NASA Astrophysics Data System (ADS)

    Crespon, François

    2013-04-01

    In the frame of the FP7 POPDAT project the Ionosphere Waves Service was developed by ionosphere experts to answer several questions: How make the old ionosphere missions more valuable? How provide scientific community with a new insight on wave processes that take place in the ionosphere? The answer is a unique data mining service accessing a collection of topical catalogues that characterize a huge number of Atmospheric Gravity Waves, Travelling Ionosphere Disturbances and Whistlers events. The Ionosphere Waves Service regroups databases of specific events extracted by experts from a ten of ionosphere missions which end users can access by applying specific searches and by using statistical analysis modules for their domain of interest. The scientific applications covered by the IWS are relative to earthquake precursors, ionosphere climatology, geomagnetic storms, troposphere-ionosphere energy transfer, and trans-ionosphere link perturbations. In this presentation we propose to detail the service design, the hardware and software architecture, and the service functions. The service interface and capabilities will be the focus of a demonstration in order to help potential end-users for their first access to the Ionosphere Waves Service portal. This work is made with the support of FP7 grant # 263240.

  14. Ionospheric effects during first 2 hours after the "Chelyabinsk" meteorite impact

    NASA Astrophysics Data System (ADS)

    Berngardt, Oleg; Kurkin, Vladimir; Zherebtsov, Gelii; Grigorieva, Svetlana; Kusonski, Oleg

    In this paper, we analyzed the ionospheric effects within the 100-1500 km ranges from the Chelyabinsk meteorite explosion site from the ISTP SB RAS EKB radar data, and from the IG UB RAS PARUS ionosonde data. Both instruments are located at the Arti Observatory, approximately 200 km north of the supposed explosion location. The ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. Essential effects, however, were observed at more than 100-200 km from the explosion site, and farther, up to 1500 km. Almost simultaneously with the explosion and for 3 minutes (03:20-03:23 UT), there was a motion away from the radar 400 km southwest of the latter (and approximately 200 km west of the explosion site) at the E-layer height with the characteristic velocities 200 m/s and high spectral width. A short delay of the detected effect at a significant distance from the explosion site also testifies to the hypothesis of a large short-living irregularity formations at the heights of the lower E-layer, with the transversal size of several hundreds of kilometers. The first disturbance in the F-layer was observed 15 minutes after the explosion, and it propagated away from the radar almost radially. The radial disturbances were observed up to about 80-100 minutes. The main disturbances in the F-layer were nearly radial waves with the center close to the explosion site. Analyzing the experimental data allowed us to determine the equivalent ionospheric velocities for individual travel mode. The work was done under financial support of RFBR grant #14-05-00514-a.

  15. Environmental assessment for the Satellite Power System: concept development and evaluation program - effects of ionospheric heating on telecommunications

    SciTech Connect

    Not Available

    1980-08-01

    The microwave power beam that is associated with the operation of the Satellite Power System (SPS) will provide a continuous source of power density into the earth's ionosphere. As currently conceptualized, the power density at the center of the beam would be 23 mW/cm/sup 2/. This power density may be of sufficient magnitude to give rise to changes in the structure of the ionosphere and to increases in the electron temperature in the ionosphere. The work described in this report was undertaken to assess the degree to which the ionosphere and ionospheric-dependent telecommunication systems would be impacted by the passage of the Satellite Power System microwave power beam. The program of study utilized resources from Government, industry, and universities in order to conduct theoretical and experimental investigations that relate to the operational scenario surrounding the Satellite Power System concept. The results of the numerous investigations that were undertaken are summarized in this document and areas in which further study is required are pointed out.

  16. Preface to the Special Issue on Thunderstorm Effects in the Atmosphere-Ionosphere System

    NASA Astrophysics Data System (ADS)

    Gordillo-Vázquez, F. J.; Luque, A.

    2013-11-01

    The first summer school of the "Thunderstorm Effects in the Atmosphere-Ionosphere System" (TEA-IS) funded by the European Science Foundation through its Research Network Programme took place in Torremolinos (Spain) on June 17-22, 2012. The meeting gathered almost 100 scientists with different backgrounds (plasma physics, electrical and signal engineering, geophysics, space physics and computational science) coming from 20 countries, both from inside and outside TEA-IS member countries. We very briefly comment here on the five review papers included in this Special Issue of Surveys in Geophysics devoted to the 2012 TEA-IS summer school.

  17. A case study of ionospheric storm effects in the Chinese sector during the October 2013 geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Mao, Tian; Sun, Lingfeng; Hu, Lianhuan; Wang, Yungang; Wang, Zhijun

    2015-11-01

    In this study, we investigate the ionospheric storm effects in the Chinese sector during 2 October 2013 geomagnetic storm. The TEC map over China sector (1° × 1°) and eight ionosondes data along the longitude of 110°E are used to show significant positive ionospheric phases (enhancements in TEC and ionospheric peak electron density NmF2) in the high-middle latitude region and the negative effects at the low latitude and equatorial region during the storm. A wave structure with periods about 1-2 h and horizontal speed about 680 m/s, propagating from the high latitudes to the low latitudes is observed in electron densities within the height region from 200 to 400 km, which is caused by the combined effects of neutral wind and the large-scale traveling disturbances (LSTIDs). In the low latitude regions, compared with those in the quiet day, the ionospheric peak heights of the F2 layer (hmF2) in the storm day obviously increase accompanying a notably decrease in TEC and NmF2, which might be as a result of the eastward prompt penetration electric field (PPEF) evidenced by the two magnetometers and the subsequent westward disturbance dynamo electric fields (DDEF). The storm-time TEC enhancement mainly occurs in the topside ionosphere, as revealed from the topside TEC, bottomside TEC and GPS TEC.

  18. Prompt and delayed effects of solar disturbances in magnetosphere-ionosphere system on March 4-7, 2012

    NASA Astrophysics Data System (ADS)

    Romanova, Elena; Kurkin, Vladimir; Zolotukhina, Nina; Polekh, Nelya

    We analyze prompt and delayed effects of five X-class solar flares observed on March 4-7, 2012 at Siberian and Far Eastern ionospheric stations. The flares were associated with intensification of solar cosmic rays and Earth-directed coronal mass ejections. The prompt effects were caused by EUV, X-rays and relativistic particles. They were observed as increase in the daytime lowest frequency reflected from the ionosphere from 1.5-2 MHz to 4-8 MHz and the disappearance of reflections (complete blackout) from the high-latitude ionosphere. Delayed effects were caused by heliospheric inhomogeneity created by four interacting coronal mass ejections. The inhomogeneity enveloped the Earth’s magnetosphere during 80 hours and triggered two (moderate and strong) magnetic storms accompanied by ionospheric storms. Because of the strong variability of the solar wind and the interplanetary magnetic field in the inhomogeneity, the magnetospheric and ionospheric storms had specific features discussed in our report. The work was supported by the Russian Foundation for Basic Research (grant 13-05-91159 and 13-05-00733) and RF President Grant of Public Support for RF Leading Scientific Schools (NSh-2942.2014.5).

  19. Mitigating ionospheric scintillation effects by integrating coding and interleaving

    NASA Astrophysics Data System (ADS)

    Ng, Wai-Hung

    Since conventional interleaving cannot be effectively integrated into coded high data rate communications systems operating in slow and deep fading environments, a new adaptive approach to overcome the problem has been derived. This technique would enable the communications system to delete burst errors as well as to correct random errors. Therefore, it could minimize the effects of various interferences including jamming, antenna switching, and deep fading occurring in nuclear scintillation. In this paper, this new technique is introduced, and the performance of this new approach is illustrated.

  20. Solar Illumination of the Polar Ionosphere and Its Effects on Cold Ion Outflow.

    NASA Astrophysics Data System (ADS)

    Maes, L.; Maggiolo, R.; Haaland, S.; Li, K.; Andre, M.; Eriksson, A. I.

    2015-12-01

    Solar illumination is the most important form of energy driving the outflow of cold ionospheric ions in the polar regions, called the polar wind. Due to the offset of the magnetic poles from the rotation axis and Earth's rotational and orbital motion, the part of the magnetic polar cap being illuminated and the part being in the dark, will vary throughout the day and the seasons. Therefore the outflowing ion flux from the whole polar cap will vary accordingly. Moreover, the offset in the Northern hemisphere is different from the one in the Southern hemisphere. Thus the flux from both polar caps will also be different. With a very simple model we will explore the effects of this on the outflowing flux, which will affect the atmospheric erosion as well as the supply of ionospheric ions to the plasma sheet. In recent observations with the Cluster satellites, the heavier O⁺ ions have been shown to be affected more strongly by solar illumination than H⁺ ions. So this may lead to an alteration of the mass density in the plasma sheet on a periodic basis. This study will also look for signatures of the effects predicted by this model in data of cold ion outflow. The Cluster extensive data set from André et al. [2015] seems best suited for this. It uses the technique detecting the wake formed behind a charged spacecraft in a low density and low energy plasma environment. This technique will generally only observe ions with an energy too low to overcome the spacecraft potential (i.e. ~< 40 eV). The measurements are made in the magnetospheric lobes, up to altitudes of 20 RE, between 2001 and 2010. This long period of observations creates the possibility to study the seasonal variation of cold ion outflow from the polar ionosphere and look for possible differences between both hemispheres.

  1. Investigations into the properties, conditions, and effects of the ionosphere. Final report 4 Dec 86-31 Dec 89

    SciTech Connect

    Fremouw, E.J.; Reinisch, B.W.; Szuszczewica, E.P.

    1990-01-15

    The contractor and its subcontractors supported GL/AFSC research in ionospheric physics and its systems effects. Support was provided in the following six categories; laboratory measurements; field measurements, aircraft measurements; rocket, satellite, and Shuttle measurements; analytical and theoretical investigations; and engineering analysis. This report summarizes results on 15 specific topics. These topics included ionospheric characteristics central to operation of HF systems, such as OTH radars; engineering studies of meteor/scatter communication links; effects on transionospheric radio propagation controlled by the total electron content (path integral of electron density) of the ionosphere and its fine structure (which produces radiowave scintillation); optical and ultraviolet effects of the aurora and airglow, as well as laboratory uv studies; and feasibility studies on modifying radio blackout and measuring electron density in the D region..

  2. Geomagnetic activity effect on the global ionosphere during the 2007-2009 deep solar minimum

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing

    2014-05-01

    In this paper the significant effect of weaker geomagnetic activity during the 2007-2009 deep solar minimum on ionospheric variability on the shorter-term time scales of several days was highlighted via investigating the response of daily mean global electron content (GEC, the global area integral of total electron content derived from ground-based GPS measurements) to geomagnetic activity index Ap. Based on a case during the deep solar minimum, the effect of the recurrent weaker geomagnetic disturbances on the ionosphere was evident. Statistical analyses indicate that the effect of weaker geomagnetic activity on GEC variations on shorter-term time scales was significant during 2007-2009 even under relatively quiet geomagnetic activity condition; daily mean GEC was positively correlated with geomagnetic activity. However, GEC variations on shorter-term time scales were poorly correlated with geomagnetic activity during the solar cycle descending phase of 2003-2005 except under strong geomagnetic disturbance condition. Statistically, the effects of solar EUV irradiance, geomagnetic activity, and other factors (e.g., meteorological sources) on GEC variations on shorter-term time scales were basically equivalent during the 2007-2009 solar minimum.

  3. Effect of double layers on magnetosphere-ionosphere coupling

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Hudson, Mary K.

    1987-01-01

    The Earth's auroral zone contains dynamic processes occurring on scales from the length of an auroral zone field line which characterizes Alfven wave propagation to the scale of microscopic processes which occur over a few Debye lengths. These processes interact in a time-dependent fashion since the current carried by the Alfven waves can excite microscopic turbulence which can in turn provide dissipation of the Alfven wave energy. This review will first describe the dynamic aspects of auroral current structures with emphasis on consequences for models of microscopic turbulence. A number of models of microscopic turbulence will be introduced into a large-scale model of Alfven wave propagation to determine the effect of various models on the overall structure of auroral currents. In particular, the effects of a double layer electric field which scales with the plasma temperature and Debye length is compared with the effect of anomalous resistivity due to electrostatic ion cyclotron turbulence in which the electric field scales with the magnetic field strength. It is found that the double layer model is less diffusive than in the resistive model leading to the possibility of narrow, intense current structures.

  4. Ionospheric irregularity physics modelling

    SciTech Connect

    Ossakow, S.L.; Keskinen, M.J.; Zalesak, S.T.

    1982-01-01

    Theoretical and numerical simulation techniques have been employed to study ionospheric F region plasma cloud striation phenomena, equatorial spread F phenomena, and high latitude diffuse auroral F region irregularity phenomena. Each of these phenomena can cause scintillation effects. The results and ideas from these studies are state-of-the-art, agree well with experimental observations, and have induced experimentalists to look for theoretically predicted results. One conclusion that can be drawn from these studies is that ionospheric irregularity phenomena can be modelled from a first principles physics point of view. Theoretical and numerical simulation results from the aforementioned ionospheric irregularity areas will be presented.

  5. Modeling the effects of ionospheric oxygen outflow on bursty magnetotail flows

    NASA Astrophysics Data System (ADS)

    Garcia-Sage, K.; Moore, T. E.; Pembroke, A.; Merkin, V. G.; Hughes, W. J.

    2015-10-01

    Using a global multifluid MHD model, we demonstrate the effects of magnetospheric O+ on bursty magnetotail flows. We carry out two simulations without ionospheric outflow to use as baseline, one driven by real solar wind data and one driven by idealized solar wind. Solar wind data from 1 October 2001 are used as a storm time solar wind driver. During this event, the plasma sheet was observed to be rich in O+, making the event of interest for a model analysis of the effects of ionospheric origin O+ on magnetospheric dynamics. We carry out outflow comparison simulations for both the realistic and idealized solar wind drivers using a simple empirical model that places auroral outflow in regions where downward propagating Poynting flux and electron precipitation are present, combined with a low-flux thermal energy O+ outflow over the entire polar region. We demonstrate the effects of O+ on magnetotail structure and the occurrence rate and strength of bursty, fast earthward flows. The addition of O+ to the magnetotail stretches the tail and increases the velocity of bursty earthward flows. This increase is shown to be produced by reconnection events in an extended current sheet created by tail stretching.

  6. The effects of ionospheric outflow on ICME and SIR driven sawtooth events

    NASA Astrophysics Data System (ADS)

    Brambles, O. J.; Lotko, W.; Zhang, B.; Ouellette, J.; Lyon, J.; Wiltberger, M.

    2013-10-01

    Magnetosphere sawtooth oscillations have been observed during interplanetary coronal mass ejection (ICME) events, when the solar wind conditions are relatively steady, and during periods when the interplanetary magnetic field (IMF) fluctuates between northward and southward, as during interplanetary stream interaction regions (SIR). The impact of ionospheric outflow on the ICME-driven 18 April 2002 and SIR-driven 24 October 2002 sawtooth events is investigated using a multifluid adaptation of the Lyon-Fedder-Mobarry global simulation. The mechanisms that generate the sawtooth oscillations are investigated by comparing a baseline simulation without outflow and a simulation that includes an O+ outflow model. The ionospheric outflow is regulated by a statistical relationship between Alfvénic Poynting flux and O+ ion outflow flux. In the baseline simulation for the 18 April 2002 ICME-driven event, one substorm is observed that is generated by the southward turning of the IMF, after which the magnetosphere-ionosphere system settles into a quasi-steady convection mode. When outflow is included, quasi-periodic substorms are observed suggesting that the sawtooth oscillations are generated internally by the effects of the O+ ions. In contrast, during the 24 October 2002 SIR-driven event, quasi-periodic substorms are generated regardless of whether outflow is included or not. For this event, the generation and triggering of the substorms is controlled by the external driving of the solar wind. For both events, when outflow is included, the signatures of the substorms are more intense and are more noticeable across a wider range of local times than in the baseline simulations.

  7. Study of potential ionospheric effects on space-based radars. Report for 7 July 1987-28 February 1988

    SciTech Connect

    Fremouw, E.J.; Secan, J.A.

    1988-02-28

    The Air Force and the Navy have considered development of space-based radars for purposes of defense surveillance. System configurations considered include sufficiently low frequencies and grazing angles and sufficiently large apertures (synthetic or otherwise) to require consideration of the effects of the ionosphere on the radar propagation path. Toward this end, the Air Force Geophysics Laboratory hosted a Workshop in which engineering organizations responsible for system design were brought together with research organizations active in identifying and characterizing ionospheric effects to assess the need for and state of relevant knowledge. This report summarizes an assessment of the suitability and limitations of information presented at the Workshop and available from related studies. Dispersive phase, Ionosphere, Radar clutter, Radiowave scintillation, Space-based radar, Synthetic-aperture radar, TEC, Defense surveillance, Total electron content.

  8. Effects of the ionosphere and solar activity on radio occultation signals: Application to CHAllenging Minisatellite Payload satellite observations

    NASA Astrophysics Data System (ADS)

    Pavelyev, A. G.; Liou, Y. A.; Wickert, J.; Schmidt, T.; Pavelyev, A. A.; Liu, S. F.

    2007-06-01

    We analyze the ionospheric effect on the phase and amplitude of radio occultation (RO) signal. The introduced theoretical model predicts a correlation between the phase acceleration and intensity variations of RO signal and opens a way to locate layered structures in the propagation medium, in particular, in trans-ionospheric satellite-to-satellite links. For considered CHAllenging Minisatellite Payload (CHAMP) RO events, the locations of the inclined plasma layers in the lower ionosphere are estimated, and the electron density distribution is retrieved. By analysis of the CHAMP RO data, we reveal the dependence of the intensity variations of RO signal on sharp changes in the DST index and on the local time. Maps of the seasonal, geographical, and temporal distributions of the CHAMP RO events with amplitude scintillations, having high S4 index values, and observed during the years 2001-2004 indicate dependence on solar activity. As follows from this analysis, the GPS signals in the trans-ionospheric links can be used for investigating the location and parameters of inclined plasma layers and monitoring the influence of solar activity on the ionosphere with global coverage.

  9. Utilization of ionosonde data to analyze the latitudinal penetration of ionospheric storm effects

    SciTech Connect

    Forbes, J.M.; Codrescu, M.; Hall, T.J.

    1988-03-01

    Increased emphasis is placed on global coupling between the magnetosphere, ionosphere, and thermosphere systems, particularly with regard to the penetration of dynamic, chemical, and electrodynamic effects from high to low latitudes during magnetically disturbed periods. An emerging potential exists for latitudinal and longitudinal chains of ionosondes to contribute uniquely to this thrust in ways complementary to the capabilities and shortcomings of other groundbased sensors and satellites. Here is illustrated a methodology to realize the fullest potential of such ionosonde data. Hourly values are fit in latitude using Legendre polynominals, and variations from quiet time values are displayed in latitude - U.T. coordinates using a color graphics method which provides an illuminating illustration of the penetration of ionospheric disturbances in latitude and their dependence on Kp, storm time, and local time. Observed effects are interpreted in terms of plausible electric field, neutral wind, and neutral composition changes during the storm period. Besides reflecting the anticipated southward flows and equatorward extensions in conjunction with magnetically disturbed conditions, the 24-hour average meridional winds exhibit a northward return flow after the magnetic disturbance has relaxed.

  10. Counterbalancing for Serial Order Carryover Effects in Experimental Condition Orders

    ERIC Educational Resources Information Center

    Brooks, Joseph L.

    2012-01-01

    Reactions of neural, psychological, and social systems are rarely, if ever, independent of previous inputs and states. The potential for serial order carryover effects from one condition to the next in a sequence of experimental trials makes counterbalancing of condition order an essential part of experimental design. Here, a method is proposed…

  11. Magnetic field effects on the accuracy of ionospheric mirror models for geolocation

    NASA Astrophysics Data System (ADS)

    Dao, Eugene V.; McNamara, Leo F.; Colman, Jonah J.

    2016-04-01

    The geolocation of an uncooperative HF emitter is based on observations of the azimuth and elevation (angle of arrival; AoA) of its signals as they arrive at a surveillance site, along with a model of the propagation medium. The simplest propagation model that provides an estimate of the location of the emitter is based on the use of a horizontal mirror placed at the appropriate altitude. If there are large-scale horizontal ionospheric gradients or traveling ionospheric disturbances present, tilts derived from a suitable ionosonde or from the AoA of convenient known emitters (check targets) may be applied to the mirror before geolocation is performed. However, the methodology of this approach to geolocation completely ignores the Earth's magnetic field, producing errors that can reach 25% of range for a short range (less than 100 km) low-latitude target. The errors are generally smaller at midlatitudes. This paper investigates and characterizes these errors in terms of wave polarization, magnetic dip, circuit length, and azimuth relative to the direction of the magnetic field. The magnetic field also affects the procedure of using tilts derived from check-target AoA because the field effects can masquerade as tilts of unknown magnitude.

  12. Ionospheric effects of the solar eclipse of September 23, 1987, around the equatorial anomaly crest region

    SciTech Connect

    Kang Cheng; Yinnnien Huang; Senwen Chen )

    1992-01-01

    The ionospheric responses to the solar eclipse of September 23, 1987, in the equatorial anomaly crest region have been investigated by using ionospheric vertical sounding, VLF propagation delay time, and differential Doppler shift data observed at Chungli, which is located near the northern equatorial anomaly crest region. It has been found that temporal variations of the F{sub 1} layer and D region are mainly controlled by local solar radiation. Quantitative analysis of the variations of the F{sub 1} layer critical frequency, F{sub o} F{sub 1}, shows that electrons are removed from the F{sub 1} layer through ionic recombination. However, the temporal variations of f{sub o}F{sub 2} and electron density above 200 km show that the variations o the F{sub 2} layer around the equatorial anomaly region are controlled not by local solar radiation but by solar radiation at the equator. The fountain effect plays an important role even during the solar eclipse. The VLF propagation time delay is controlled by the variations of average path obscuration. Atmospheric gravity waves produced by the moving bow wave front of the solar eclipse are found with a period around 17-23 min and wavelength about 293 km.

  13. Use of the index of TEC vertical variation disturbance in studying ionospheric effects of the Chelyabinsk meteorite

    NASA Astrophysics Data System (ADS)

    Voeykov, S. V.; Berngardt, O. I.; Shestakov, N. V.

    2016-03-01

    The results of an analysis of the ionospheric effects accompanying fall of the Chelyabinsk meteorite on February 15, 2013 are presented using a method of calculating the index of the disturbance of total electron content vertical variations ( Wtec) according to data from the GPS receiver network. A substantial increase (by a factor of 2-3) in the Wtec index with a duration of ~1.5 h was observed in the studied region after the main height explosion accompanying the meteorite fall at 0320 UT. The ionospheric response in Wtec was most significant statistically registered at the radio rays "receiver-satellite" for the GPS located southward from the place of explosion.

  14. Realtime Monitoring of Traveling Ionospheric Disturbances Caused by Tsunamis

    NASA Astrophysics Data System (ADS)

    McBride, P. J.; Crowley, G.; Reynolds, A.; Azeem, I.; Makela, J. J.; Vadas, S.

    2014-12-01

    The ocean-ionosphere coupling associated with tsunamis was predicted as early as the 1970s and had been observed previously by various radio frequency techniques, including arrays of ground-based Global Positioning System (GPS) receivers. Much work is still needed in order to fully understand the coupling mechanism and allow for the development of effective tsunami detection/warning systems. These challenges include the need for additional observations of the tsunami ionospheric signature to provide new scientific insight into the geophysical source phenomenology and wave propagation physics, and to better constrain the conditions under which ocean-atmospheric coupling is effective. One of the ionospheric signatures of tsunamis is a Traveling Ionospheric Disturbance (TID). ASTRA has developed a realtime TID Mapping System based on HF radio sounding. We will provide examples of TIDs associated with various tsunamis, including the propagation characteristics of the TIDs. We are deploying an expanded ground-based observation network using strategically placed optical imaging systems together with ASTRA's TID Mapping Systems, to obtain new information about the ionospheric waves associated with tsunamis. We will also use a published and validated gravity wave ray trace model to perform studies of the propagation of tsunami-generated gravity waves through the atmosphere and into the thermosphere/ionosphere system. This work will also enhance our understanding of upward coupling caused by all gravity wave sources in the lower atmosphere (not just tsunamis) and how this coupling can generate ionospheric irregularities that affect navigation, communications and surveillance systems.

  15. Estimation of Ionospheric Conductivity Based on the Measurements by Superdarn

    NASA Astrophysics Data System (ADS)

    Lee, Eun-Ah; An, Byung-Ho; Yi, Yu

    2002-06-01

    The ionosphere plays an important role in the electrodynamics of space environment. In particular, the information on the ionospheric conductivity distribution is indispensable in understanding the electrodynamics of the magnetosphere and ionosphere coupling study. To meet such a requirement, several attempts have been made to estimate the conductivity distribution over the polar ionosphere. As one of such attempts we compare the ionospheric plasma convection patterns obtained from the Super Dual Auroral Radar Network (SuperDARN), from which the electric field distribution is estimated, and the simultaneously measured ground magnetic disturbance. Specifically, the electric field measured from the Goose Bay and Stokkseyri radars and magnetic disturbance data obtained from the west coast chain of Greenland are compared. In order to estimate ionospheric conductivity distribution with these information, the overhead infinite sheet current approximation is employed. As expected, the Hall conductance, height-integrated conductivity, shows a wide enhancement along the center of the auroral electrojet. However, Pedersen conductance shows negative values over a wide portion of the auroral oval region, a physically unacceptable situation. To alleviate this problem, the effect of the field-aligned current is taken into account. As a result, the region with negative Pedersen conductance disappears significantly, suggesting that the effect of the field-aligned current should be taken into account, when one wants to estimate ionospheric conductance based on ground magnetic disturbance and electric field measurements by radars.

  16. Birth Order: Reconciling Conflicting Effects.

    ERIC Educational Resources Information Center

    Zajonc, Robert B.; Mullally, Patricia R.

    1997-01-01

    Introduces the confluence model as a theory specifying the process by which the intellectual environment modifies intellectual development. Using this model, explores the contradiction between prediction of secular trends in test scores by trends in aggregate birth order and the lack of prediction of individual test scores by birth order using…

  17. Climatology of GNSS ionospheric scintillation at high latitudes

    NASA Astrophysics Data System (ADS)

    Spogli, L.; Alfonsi, L.; de Franceschi, G.; Romano, V.; Aquino, M.; Dodson, A.; Mitchell, C. N.

    2009-12-01

    Under perturbed conditions caused by intense solar wind magnetosphere coupling, the ionosphere may become highly turbulent and irregularities, typically enhancements or depletions of the electron density embedded in the ambient ionosphere, can form. Such irregularities cause diffraction effects, mainly due to the random fluctuations of the refractive index of the ionosphere, on the satellites signals passing through them and consequent perturbations may cause GNSS navigation errors and outages, abruptly corrupting its performance. Due to the morphology of the geomagnetic field, whose lines are almost vertical at high latitude, polar areas are characterized by the presence of significant ionospheric irregularities having scale sizes ranging from hundreds of kilometers down to a few centimeters and with highly dynamic structures. The understanding of the effect of such phenomena is important, not only in preparation for the next solar cycle (24), whose maximum is expected in 2012, but also for a deeper comprehension of the dynamics of the high-latitude ionosphere. We analyze the fluctuations in the carrier frequency of the radio waves received on the ground, commonly referred to as ionospheric amplitude and phase scintillations, to investigate the physical processes causing them. The phase scintillations on GNSS signals are likely caused by ionospheric irregularities of scale size of hundreds of meters to few kilometers. The amplitude scintillations on GNSS signals are caused by ionospheric irregularities of scale size smaller than the Fresnel radius, which is of the order of hundreds of meters for GNSS signals, typically embedded into the patches. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Institute of Engineering Surveying and Space Geodesy (IESSG) of the University of Nottingham manage the same kind of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers over the European high and mid latitude regions and over Antarctica. The

  18. Ordered delinquency: the "effects" of birth order on delinquency.

    PubMed

    Cundiff, Patrick R

    2013-08-01

    Juvenile delinquency has long been associated with birth order in popular culture. While images of the middle child acting out for attention or the rebellious youngest child readily spring to mind, little research has attempted to explain why. Drawing from Adlerian birth order theory and Sulloway's born-to-rebel hypothesis, I examine the relationship between birth order and a variety of delinquent outcomes during adolescence. Following some recent research on birth order and intelligence, I use new methods that allow for the examination of between-individual and within-family differences to better address the potential spurious relationship. My findings suggest that contrary to popular belief, the relationship between birth order and delinquency is spurious. Specifically, I find that birth order effects on delinquency are spurious and largely products of the analytic methods used in previous tests of the relationship. The implications of this finding are discussed. PMID:23719623

  19. The investigation of man-made modifications of the ionosphere. [effects of detonations and rocket exhaust

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Darosa, A. V.; Price, K. M.

    1980-01-01

    Topics covered include: (1) the application of ionosphere modifications models to the simulation of results obtained when rocket-borne explosives were detonated in the ionosphere; (2) the problem of hypersonic vapor releases from orbiting vehicles; (3) measuring the electron content reduction resulting from the firing of a Centaur rocket in the ionosphere; and (4) the preliminary design of the critical frequency tracker which displays the value of electron concentration at the peak of the F 2 region, in real time.

  20. The effects on the ionosphere of inertia in the high latitude neutral thermosphere. Final report, April 1989-April 1993

    SciTech Connect

    Burns, A.; Killeen, T.

    1993-02-01

    High-latitude ionospheric currents, plasma temperatures, densities, and composition are all affected by the time-dependent response of the neutral thermosphere to ion drag and Joule heating through a variety of complex feedback processes. These processes can best be studied numerically using the appropriate nonlinear numerical modeling techniques in conjunction with experimental case studies. In particular, the basic physics of these processes can be understood using a model, and these concepts can then be applied to more complex realistic situations by developing the appropriate simulations of real events. Finally, these model results can be compared with satellite-derived data from the thermosphere. We used numerical simulations from the National Center of Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) and data from the Dynamic Explorer 2 (DE 2) satellite to study the time-dependent effects of the inertia of the neutral thermosphere on ionospheric currents, plasma temperatures, densities, and composition. One particular case of these inertial effects is the so-called 'fly-wheel effect'. This effect occurs when the neutral gas, that has been spun-up by the large ionospheric winds associated with a geomagnetic storm, moves faster than the ions in the period after the end of the main phase of the storm. In these circumstances, the neutral gas can drag the ions along with them. It is this last effect, which is described in the next section, that has been studied under this grant.

  1. Magnetosphere-ionosphere coupling currents in JupiterÂ’s middle magnetosphere: dependence on the effective ionospheric Pedersen conductivity and iogenic plasma mass outflow rate

    NASA Astrophysics Data System (ADS)

    Nichols, J. D.; Cowley, S. W. H.

    2003-07-01

    The amplitude and spatial distribution of the coupling currents that flow between Jupiter’s ionosphere and middle magnetosphere, which enforce partial corotation on outward-flowing iogenic plasma, depend on the values of the effective Pedersen conductivity of the jovian ionosphere and the mass outflow rate of iogenic plasma. The values of these parameters are, however, very uncertain. Here we determine how the solutions for the plasma angular velocity and current components depend on these parameters over wide ranges. We consider two models of the poloidal magnetospheric magnetic field, namely the planetary dipole alone, and an empirical current sheet field based on Voyager data. Following work by Hill (2001), we obtain a complete normalized analytic solution for the dipole field, which shows in compact form how the plasma angular velocity and current components scale in space and in amplitude with the system parameters in this case. We then obtain an approximate analytic solution in similar form for a current sheet field in which the equatorial field strength varies with radial distance as a power law. A key feature of the model is that the current sheet field lines map to a narrow latitudinal strip in the ionosphere, at approx 15° co-latitude. The approximate current sheet solutions are compared with the results of numerical integrations using the full field model, for which a power law applies beyond approx 20 RJ, and are found to agree very well within their regime of applicability. A major distinction between the solutions for the dipole field and the current sheet concerns the behaviour of the field-aligned current. In the dipole model the direction of the current reverses at moderate equatorial distances, and the current system wholly closes if the model is extended to infinity in the equatorial plane and to the pole in the ionosphere. In the approximate current sheet model, however, the field-aligned current is unidirectional, flowing consistently from

  2. Effect of HF Emission of the topside sounder transmitter aboard the COSMOS-1809 satellite on the ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Baranets, N. V.; Gladyshev, V. A.; Afonin, V. V.

    The experiment on investigation of effect of the HF emission (300 W) by the dipole antenna on the ionospheric plasma was carried out onboard the COSMOS-1809 satellite (1987). The sounder accelerated particles (SAP) at the electron cyclotron harmonics n x omegace and in the frequency region of antenna resonance were detected by the charged particle spectrometer.

  3. Multi-GNSS for Ionospheric Scintillation Studies

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2015-12-01

    GNSS have been widely used for ionospheric monitoring. We anticipate over 160 GNSS satellites broadcasting 400 signals by 2023, nearly double the number today. With their well-defined signal structures, high spatial density and spectral diversity, GNSS offers low cost and distributed passive sensing of ionosphere effects. There are, however, many challenges to utilize GNSS resources to characterize and forecast ionospheric scintillation. Originally intended for navigation purposes, GNSS receivers are designed to filter out nuisance effects due to ionosphere effects. GNSS measurements are plagued with errors from multipath, oscillator jitters, processing artifacts, and neutral atmosphere effects. Strong scintillation events are often characterized by turbulent structures in ionosphere, causing simultaneous deep amplitude fading and abrupt carrier phase changes. The combined weak signal and high carrier dynamics imposes conflicting requirements for GNSS receiver design. Therefore, GNSS receivers often experience cycle slips and loss of lock of signals during strong scintillation events. High quality, raw GNSS signals bearing space weather signatures and robust receiver algorithms designed to capture these signatures are needed in order for GNSS to be a reliable and useful agent for scintillation monitoring and forecasting. Our event-driven, reconfigurable data collection system is designed to achieve this purpose. To date, our global network has collected ~150TB of raw GNSS data during space weather events. A suite of novel receiver processing algorithms has been developed by exploitating GNSS spatial, frequency, temporal, and constellation diversity to process signals experiencing challenging scintillation impact. The algorithms and data have advanced our understanding of scintillation impact on GNSS, lead to more robust receiver technologies, and enabled high spatial and temporal resolution depiction of ionosphere responses to solar and geomagnetic conditions. This

  4. Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

    NASA Astrophysics Data System (ADS)

    Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

    2013-04-01

    In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a

  5. Meteor showers effects in the low terrestrial ionosphere detected at VLF ionosonde and long distance propagation paths

    NASA Astrophysics Data System (ADS)

    Vilas-Boas, J. W. S.; Paesleme, N. M.; Piazza, L. R.; Macedomoura, M. S. S.

    1984-08-01

    The effect of Geminids and eta Aquarids meteor showers in the lower ionosphere were observed using two different methods. Low ionosphere group heights measured by a very low frequency ionosonde located south of Brazil indicated an anomalous lowering of the effective reflection height and presented night-time 5 sigma deviation in good correlation with Eta Aquarids stream transit. The group reflection coefficients present a very pronounced variation reaching values 3 sigma below the normal values. Diurnal very low frequency phase variations in two long-distance propagation paths present night-time 7 sigma and 4 sigma phase deviations from the average during the Eta Aquarids shower transit. The Geminids shower effect in the lower ionosphere was detected in two different long distance very low frequency propagation paths: NAA, Culter, U.S.A. - Atibaia, S.P., Brazil presented 5 sigma phase deviation and ARG, Argentina - Atibaia, S.P., Brasil presented 3.5 sigma phase deviation from the average. The geomagnetic activity in the periods covered by this investigation was low and the results obtained are a confirmation through two different techniques of changes in the physical conditions of the low ionosphere by meteor shower.

  6. On the utilization of ionosonde data to analyze the latitudinal penetration of ionospheric storm effects

    SciTech Connect

    Forbes, J.M.; Codrescu, M.; Hall, T.J.

    1988-03-01

    Upper atmosphere science is placing increased emphasis on global coupling between the magnetosphere, ionosphere, and thermosphere systems, particularly with regard to the penetration of dynamic, chemical, and electrodynamic effects from high to low latitudes during magnetically disturbed periods. An emerging potential exists for latitudinal and longitudinal chains of ionosondes to contribute uniquely to this thrust in ways complementary to the capabilities and shortcomings of other groundbased sensors and satellites. Here we illustrate a methodology whereby the fullest potential of such ionosonde data can be realized. Data from a chain of stations close to the -165/sup 0/ magnetic meridian and separated by about 5/sup 0/ in magnetic latitude are used to study the relationships between magnetic activity, hmF2, foF2, and inferred meridional winds during 17--28 April, 1979. Hourly values are fit in latitude using Legendre polynomials, and variations from quiet-time values are displayed in latitude-U.T. coordinates using a color graphics method which provides an illuminating illustration of the penetration of ionospheric disturbances in latitude and their dependence on Kp, storm time, and local time. Observed effects are interpreted in terms of plausible electric field, neutral wind, and neutral composition changes during the storm period. For instance, net depletions in foF2 occur over the entire disturbed interval down to about 25/sup 0/--30/sup 0/ latitude, apparently due to such increased N/sub 2/ densities that the resulting enhanced plasma loss rates overcompensate and ''positive'' storm effects whereby southward winds elevate the F-layer peak to altitudes of reduced chemical loss.

  7. Source, propagation, and effects of lightning in the Earth-ionosphere system

    NASA Astrophysics Data System (ADS)

    Hutchins, Michael L.

    The capabilities of the World Wide Lightning Location Network (WWLLN) are expanded to enable research of the source, propagation, and effects of lightning in the Earth-ionosphere system. The main expansion of the network capability is the measurement of the very low frequency radiated energy from lightning; the radiated stroke energy is one to one related to the canonical peak current measurements of other ground based networks. Stroke energy is used to develop a model of the network relative detection efficiency; this internal model rates the coverage capabilities of the network compared to the networks best regional coverage. The last dataset developed and discussed is the clustering of the lightning locations into both flashes and the active lightning regions of thunderstorms. These three capabilities of the network allow tracing the effects of lightning and thunderstorms from their source, to a proxy for the global electric circuit and to the magnetosphere. The source of lightning is investigated in two regimes: within thunderstorms and between thunderstorms. Within thunderstorms the time between flashes is found to be proportional to the resulting flash energy for differing thunderstorms, regions, and seasons. Between thunderstorms the lightning energy is shown to differ between land and ocean, with oceanic thunderstorms producing stronger and fewer strokes. The propagation of the radiated energy is measured using the lightning as a probe of attenuation along the different propagation paths. Attenuation is seen to have an asymmetry with magnetic azimuth: eastward moving waves are attenuated less than westward moving waves. The attenuation asymmetry is complimentary to the observed asymmetry in whistler and radio energy emitted through the ionosphere into the magnetosphere. Thunderstorm clusters are used to estimate the total upward current contribution of thunderstorms to the global electric circuit. It is shown that WWLLN can provide one of the first

  8. Modification of the lower ionospheric conductivity by thunderstorm electrostatic fields

    NASA Astrophysics Data System (ADS)

    Salem, Mohammad A.; Liu, Ningyu; Rassoul, Hamid K.

    2016-01-01

    This paper reports a modeling study of the modifications of the nighttime lower ionospheric conductivity by electrostatic fields produced by underlying thunderstorms. The model used combines Ohm's law with a simplified lower ionospheric ion chemistry model to self-consistently calculate the steady state nighttime conductivity above a thunderstorm. The results indicate that although the electron density is generally increased, the lower ionospheric conductivity can be reduced by up to 1-2 orders of magnitude because electron mobility is significantly reduced due to the electron heating effect. For a typical ionospheric density profile, the resulting changes in the reflection heights of extremely low frequency and very low frequency waves are 5 and 2 km, respectively.

  9. Ionosphere research

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A report is presented on on-going research projects in ionospheric studies. The topics discussed are planetary atmospheres, E and F region, D region, mass spectrometer measurements, direct measurements and atmospheric reactions.

  10. Ionospheric research

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Data from research on ionospheric D, E, and F, regions are reported. Wave propagation, mass spectrometer measurements, and atmospheric reactions of HO2 with NO and NO2 and NH2 with NO and O2 are summarized.

  11. Simulation study of ionospheric response to the annular eclipse on May 21, 2012

    NASA Astrophysics Data System (ADS)

    Shinagawa, H.; Miyoshi, Y.; Jin, H.; Matsumura, M.; Fujiwara, H.; Tsugawa, T.; Kubo, Y.; Murata, T.

    2012-12-01

    It is widely accepted that the ionosphere varies significantly during a solar eclipse. Previous ionospheric observations have indicated that reduction in solar EUV and X-ray radiation results in significant decrease of electron densities. In addition, some studies have suggested that neutral wind variations and neutral composition changes caused by local cooling of the neutral atmosphere indirectly affect the ionosphere. However, effects of the atmospheric processes on the ionospheric variations have not been fully understood. The annular solar eclipse on May 21, 2012 passed over Japan provided us with a good opportunity for studying the ionospheric variations during a solar eclipse. A number of ionospheric data have been obtained at various observatories in Japan. In order to quantitatively study variations in the ionosphere and atmosphere during the solar eclipse, we used the whole atmosphere-ionosphere coupled model (GAIA), and compared the simulation results with the observed data of the ionosphere. The results indicate that electron density decrease is primarily caused by reduction in solar EUV/X-ray radiation, but that neutral atmospheric variations driven by cooling of the atmosphere during the solar eclipse also play an important role in the electron density variations.

  12. Thunderstorm coupling to the magnetosphere and associated ionospheric effects. Semiannual Report, 1 November 1991-30 April 1992

    SciTech Connect

    Inan, U.S.

    1992-01-01

    This project deals with the coupling of electromagnetic energy released during a thunderstorm to the magnetosphere and the ionosphere. Both the effects of an individual lightning event as well the aggregate of all the lightning events during a thunderstorm are considered. Energy in the very low frequency (VLF) band can play a variety of roles in the magnetospheric and ionospheric physics: generation of plasmaspheric hiss believed to be responsible for the slot region in the radiation belts, generation of lower hybrid waves that can heat ions in the auroral and subauroral regions, precipitation of energetic electrons, ionospheric heating etc. While these phenomena have been identified, and characterized to some extent, the influence and role of thunderstorm energy on the magnetosphere and ionosphere at a global scale is not known. Only recently, simultaneous high resolution (temporal and spatial) data sets from ground based lightning detectors and space and ground based VLF detectors have become available, and thus it has become possible to raise a question of the kind mentioned above and try to answer it quantitatively. Work on the correlation between individual lightning discharges in a thunderstorm as detected by the lightning network and the whistlers observed on the DE-1 satellite continued during this period. Results are summarized.

  13. The effect of including field-aligned potentials in the coupling between Jupiter's thermosphere, ionosphere, and magnetosphere

    NASA Astrophysics Data System (ADS)

    Ray, L. C.; Achilleos, N. A.; Yates, J. N.

    2015-08-01

    Jupiter's magnetosphere-ionosphere-thermosphere system drives the brightest, steadiest aurora in our solar system. This emission is the result of an electrical current system, which couples the magnetosphere to the planetary atmosphere in an attempt to enforce the corotation of the middle magnetospheric plasma. Field-aligned currents transfer angular momentum from the atmosphere to the magnetosphere. In the equatorial plane, the field-aligned currents diverge into radially outward currents, which exert a torque on the plasma due to the J × B forces. Equatorward ionospheric currents exert an opposite torque on the ionosphere, which interacts with the thermosphere via ion-neutral collisions. The upward field-aligned currents result in auroral electron precipitation, depositing energy into the high-latitude atmosphere. This energy input is a possible candidate for explaining the large thermospheric temperature measured by the Galileo probe at equatorial latitudes; however, previous atmospheric circulation models have shown that the bulk of the energy is transported poleward, rather than equatorward. We present numerical results of Jupiter's coupled magnetosphere-ionosphere-thermosphere system including, for the first time, field-aligned potentials. The model is compared with three previously published works. We find that the rotational decoupling of the magnetospheric and thermospheric angular velocities in the presence of field-aligned potentials tempers the thermospheric response to the outward transport of magnetospheric plasma, but this is a secondary effect to variations in the Pedersen conductance.

  14. F region ionosphere effects on the mapping accuracy of SuperDARN HF radar echoes

    NASA Astrophysics Data System (ADS)

    Chen, X.-C.; Lorentzen, D. A.; Moen, J. I.; Oksavik, K.; Baddeley, L. J.; Lester, M.

    2016-05-01

    Structured particle precipitation in the cusp is an important source for the generation of F region ionospheric irregularities. The equatorward boundaries of broad Doppler spectral width in Super Dual Auroral Radar Network (SuperDARN) data and the concurrent OI 630.0 nm auroral emission are good empirical proxies for the dayside open-closed field line boundary. However, SuperDARN currently employs a simple virtual model to determine the location of its echoes, instead of a direct calculation of the radio wave path. The varying ionospheric conditions could influence the final mapping accuracy of SuperDARN echoes. A statistical comparison of the offsets between the SuperDARN Finland radar spectral width boundary (SWB) and the OI 630.0 nm auroral emission boundary (AEB) from a meridian-scanning photometer (MSP) on Svalbard is performed in this paper. By restricting the location of the 630.0 nm data to be near local zenith where the MSP has the highest spatial resolution, the optical mapping errors were significantly reduced. The variation of the SWB-AEB offset confirms that there is a close relationship between the mapping accuracy of the HF radar echoes and solar activity. The asymmetric variation of the SWB-AEB offset versus magnetic local time suggests that the intake of high-density solar extreme ultraviolet ionized plasma from postnoon at subauroral latitudes could result in a stronger refraction of the HF radar signals in the noon sector, while changing the HF radar operating frequency also has a refraction effect that contributes to the final location of the HF radar echoes.

  15. F-region ionosphere effects on the mapping accuracy of SuperDARN HF radar echoes

    NASA Astrophysics Data System (ADS)

    Chen, Xiangcai; Lorentzen, Dag; Moen, Jøran; Oksavik, Kjellmar; Baddeley, Lisa; Lester, Mark

    2016-04-01

    Structured particle precipitation in the cusp is an important source for the generation of F -region ionospheric irregularities. The equatorward boundaries of broad Doppler spectral width in Super Dual Auroral Radar Network (SuperDARN) data and the concurrent OI 630.0 nm auroral emission are good empirical proxies for the dayside open-closed field line boundary (OCB). However, SuperDARN currently employs a simple virtual model to determine the location of its echoes, instead of a direct calculation of the radio wave path. The varying ionospheric conditions could influence the final mapping accuracy of SuperDARN echoes. A statistical comparison of the offsets between the SuperDARN Finland radar spectral width boundary (SWB) and the OI 630.0 nm auroral emission boundary (AEB) from a meridian-scanning photometer (MSP) in Longyearbyen from December 1995 to January 2014 in wintertime is performed. By restricting the location of the OI 630.0 nm data to be near local zenith, where the MSP has the highest spatial resolution, the mapping errors were significantly reduced for the AEB. The variation of the SWB - AEB offset confirms that there is a close relationship between the mapping accuracy of the HF radar echoes and solar activity. The asymmetric variation of the SWB - AEB offset versus magnetic local time suggests that the intake of high density solar extreme ultraviolet ionized plasma from post-noon at sub-auroral latitudes could result in a stronger refraction of the HF radar signals in the noon sector. The changing HF radar operating frequency also has a refraction effect that contributes to the final location of the HF radar echoes.

  16. A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

    SciTech Connect

    Rodriguez, J.V.; Inan, U.S. ); Li, Y.Q.; Holzworth, R.H. ); Smith, A.J. , Cambridge ); Orville, R.E. ); Rosenberg, T.J. )

    1992-01-01

    Simultaneous ground-based observations of narrowband and broadband VLF radio waves and of cloud-to-ground lightning were made at widely spaced locations during the 1987 Wave-Induced Particle Precipitation (WIPP) campaign, conducted from Wallops Island, Virginia. Based on these observations, the first case study has been made of the relationships among located cloud-to-ground (CG) lightning flashes, whistlers, and associated ionospheric effects during a substorm particle injection event. This event took place 2 days after the strongest geomagnetic storm of 1987, during a reintensification in geomagnetic activity that did not affect the high rate of whistlers observed at Faraday Station, Antarctica. At the time of the injection event, several intense nighttime thunderstorms were located over Long Island and the coast of New England, between 400 km northwest and 600 km north of the region geomagnetically conjugate to Faraday. About two thirds of the CG flashes that were detected in these thunderstorms during the hour following the injection event onset were found to be causatively associated with whistlers received at Faraday. During the same period the amplitude of the 24.0-kHz signal from the NAA transmitter in Cutler, Maine, propagating over the thunderstorm centers toward Wallops Island was repeatedly perturbed in a manner characteristic of previously reported VLF signatures of transient and localized ionization enhancements at D region altitudes. Though such enhancements may have been caused by whistler-induced bursts electron precipitation from the magnetosphere, the data in this case are insufficient to establish a clear connection between the NAA amplitude perturbations and the Faraday Station whistlers. In view of the proximity of the NAA great circle path to the storm center, having the lower ionosphere by intense radiation from lightning may also have played a role in the observed VLF perturbations.

  17. A case study of ionospheric storm effects during long-lasting southward IMF Bz-driven geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Liu, Libo; Nakamura, Takuji; Zhao, Biqiang; Ning, Baiqi; Yoshikawa, A.

    2014-09-01

    Multiple instrumental observations including GPS total electron content (TEC), foF2 and hmF2 from ionosondes, vertical ion drift measurements from Communication/Navigation Outage Forecasting System, magnetometer data, and far ultraviolet airglow measured by Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14-17 July 2012 geomagnetic storm event, which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h below -10 nT. In the East Asian/Australian sector, latitudinal profile of TEC variations in the main phase were characterized by three bands of increments and separated by weak depressions in the equatorial ionospheric anomaly (EIA) crest regions, which were caused by the combined effects of disturbance dynamo electric fields (DDEF) and equatorward neutral winds. In the recovery phase, strong inhibition of EIA occurred and the summer crest of EIA disappeared on 16 July due to the combined effects of intrusion of neutral composition disturbance zone as shown by the TIMED/GUVI O/N2 measurements and long-lasting daytime westward DDEF inferred from the equatorial electrojet observations. The transit time of DDEF over the dip equator from westward to eastward is around 2200 LT. In the American longitude, the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase, preceded by storm-enhanced density plume in the initial phase. In addition, multiple short-lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field (IMF) Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset.

  18. Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)

    NASA Technical Reports Server (NTRS)

    Radomski, M. S.; Doll, C. E.

    1991-01-01

    This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions

  19. Whole Atmosphere-Ionosphere Coupled Model (GAIA) for Space Weather Research

    NASA Astrophysics Data System (ADS)

    Shinagawa, H.; Jin, H.; Miyoshi, Y.; Fujiwara, H.; Tanaka, T.; Fujita, S.; Terada, K.; Murata, K. T.

    2011-12-01

    Space near the Earth, called geospace, is a highly complex system, consisting of the solar wind, the magnetosphere, the ionosphere, and the neutral atmosphere. Those regions have different physical characteristics with different temporal and spatial scales. In particular, the magnetosphere, the ionosphere, and the neutral atmosphere are strongly coupled with each other, and interaction between the regions is nonlinear and extremely complicated. Even within each region, there are strong interactions between physical processes with different temporal and spatial scales. Furthermore, the geospace environment significantly varies as electromagnetic energy and particles from the sun vary. In order to quantitatively understand such a complicated system, it is necessary to model the entire region by including all fundamental processes self-consistently. Various types of global numerical models of geospace have been constructed and used to study space weather disturbances in many institutions in the world. At the National Institute of Information and Communications Technology (NICT) of Japan, a real-time solar wind model, magnetosphere model, and ionosphere-thermosphere model have been developed and used for daily space weather forecast. In addition to the effect of geospace disturbance on the upper atmosphere, recent observations of the ionosphere and the thermosphere have revealed that atmospheric waves generated in the lower atmosphere significantly influence the upper atmosphere, the ionosphere, and possibly the magnetosphere. In order to quantitatively study the effects of the lower atmosphere on the ionosphere, we have developed an atmosphere-ionosphere coupled model, which includes the whole neutral atmosphere and the ionosphere. The model is called GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy). Using GAIA, relationship between the ionosphere and the atmosphere is being studied. We plan to incorporate magnetospheric inputs to the polar

  20. Ionospheric refraction correction in radio astronomy

    NASA Astrophysics Data System (ADS)

    Chai, Yan; Han, Wen-Jun

    1986-10-01

    Using Snell's law in polar coordinates, the ionospheric refraction effects on the declination and right ascension determination are discussed in this paper. A ray tracing method is also given. With the ionospheric data observed in Beijing, the correction of ionospheric refraction is estimated and some useful conclusions are drawn.

  1. Ionosphere of Mars as seen by Mars Express. Effect of crustal fields

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Andrews, D.; Witasse, O.; Barabash, S.

    2015-10-01

    The Martian ionosphere is studied using the local electron number densities and total electron content (TEC) derived from the observations onboard Mars Express. The data are complemented by the ASPER A-3 observations which provide us with the information about upward/downward velocity of the low-energy ions and electron precipitation. We consider 5 years of Mars Express observations at different solar cycle intervals. Different factors which influence the ionosphere dynamics are analyzed. The focus is made on a role of the crustal magnetic field on the Martian ionosphere.

  2. A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

    NASA Technical Reports Server (NTRS)

    Rodriguez, J. V.; Inan, U. S.; Li, Y. Q.; Holzworth, R. H.; Smith, A. J.; Orville, R. E.; Rosenberg, T. J.

    1992-01-01

    The relationships among cloud-to-ground (CG) lightning, sferics, whistlers, VLF amplitude perturbations, and other ionospheric phenomena occurring during substorm events were investigated using data from simultaneous ground-based observations of narrow-band and broad-band VLF radio waves and of CG lightning made during the 1987 Wave-Induced Particle Precipitation campaign conducted from Wallops Island (Virginia). Results suggest that the data collected on ionospheric phenomena during this event may represent new evidence of direct coupling of lightning energy to the lower ionosphere, either in conjunction with or in the absence of gyroresonant interactions between whistler mode waves and electrons in the magnetosphere.

  3. Empirical model of ionospheric storm effects on the F2 layer peak height associated with changes of peak electron density

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.

    2012-02-01

    An empirical model of storm-time behavior of the ionospheric peak height hmF2 associated with changes of peak electron density NmF2 is inferred from the topside true-height profiles provided by ISIS 1, ISIS 2, IK-19, and Cosmos-1809 satellites for the period of 1969-1987. The topside-derived quiet-time models of the ionospheric peak height hqF2 and peak electron density NqF2 are used as a frame of reference. To harmonize the model with storm and substorm effects induced by large-scale traveling ionospheric disturbances (LSTIDs), constraints are applied to the topside data, excluding their changes deviating above LSTID extreme limits. The degree of disturbance is estimated by the ionospheric weather W index; then, the least squares fitting is applied to the median of log(hm/hq) versus log(Nm/Nq). Anticorrelation between instant changes of hmF2 and NmF2 has a particular seasonal-magnetic latitude structure varying with solar activity that is used for the buildup of the analytical model. The model allows the deduction of the instantaneous hmF2 associated with the assessment or forecast of the respective NmF2. The model is validated with the data of five ground-based ionosondes during severe space weather storms at times of high solar activity (2000) and low solar activity (2006), and results agree reasonably well with the peak parameters derived from an ionogram. The model is incorporated into the coupled International Reference Ionosphere-Plasmasphere (IRI-Plas) code, used in the assimilative mode as the three-dimensional (3-D) interpolator of the GPS-derived total electron content, TECgps.

  4. Lunar tidal effects in the electrodynamics of the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Tracy, Brian D.

    We used extensive measurements made by the Jicamarca Unattended Long-Term Investigations of the Ionosphere and Atmosphere (JULIA) and Incoherent Scatter Radar (ISR) systems at Jicamarca, Peru during geomagnetic quiet conditions to determine the climatologies of lunar tidal effects on equatorial vertical plasma drifts. We use, for the first time, the expectation maximization (EM) algorithm to derive the amplitudes and phases of the semimonthly and monthly lunar tidal perturbations. Our results indicate, as expected, lunar tidal effects can significantly modulate the equatorial plasma drifts. The local time and seasonal dependent phase progression has been studied in much more detail than previously and has shown to have significant variations from the average value. The semimonthly drift amplitudes are largest during December solstice and smallest during June solstice during the day, and almost season independent at night. The monthly lunar tidal amplitudes are season independent during the day, while nighttime monthly amplitudes are largest and smallest in December solstice and autumnal equinox, respectively. The monthly and semimonthly amplitudes decrease from early morning to afternoon and evening to morning with moderate to large increases near dusk and dawn. We also examined these perturbation drifts during periods of sudden stratospheric warmings (SSWs). Our results show, for the first time, the enhancements of the lunar semimonthly tidal effects associated with SSWs to occur at night, as well as during the day. Our results also indicate during SSWs, monthly tidal effects are not enhanced as strongly as the semimonthly effects.

  5. High Resolution Reconstruction of the Ionosphere for SAR Applications

    NASA Astrophysics Data System (ADS)

    Minkwitz, David; Gerzen, Tatjana; Hoque, Mainul

    2014-05-01

    Caused by ionosphere's strong impact on radio signal propagation, high resolution and highly accurate reconstructions of the ionosphere's electron density distribution are demanded for a large number of applications, e.g. to contribute to the mitigation of ionospheric effects on Synthetic Aperture Radar (SAR) measurements. As a new generation of remote sensing satellites the TanDEM-L radar mission is planned to improve the understanding and modelling ability of global environmental processes and ecosystem change. TanDEM-L will operate in L-band with a wavelength of approximately 24 cm enabling a stronger penetration capability compared to X-band (3 cm) or C-band (5 cm). But accompanied by the lower frequency of the TanDEM-L signals the influence of the ionosphere will increase. In particular small scale irregularities of the ionosphere might lead to electron density variations within the synthetic aperture length of the TanDEM-L satellite and in turn might result into blurring and azimuth pixel shifts. Hence the quality of the radar image worsens if the ionospheric effects are not mitigated. The Helmholtz Alliance project "Remote Sensing and Earth System Dynamics" (EDA) aims in the preparation of the HGF centres and the science community for the utilisation and integration of the TanDEM-L products into the study of the Earth's system. One significant point thereby is to cope with the mentioned ionospheric effects. Therefore different strategies towards achieving this objective are pursued: the mitigation of the ionospheric effects based on the radar data itself, the mitigation based on external information like global Total Electron Content (TEC) maps or reconstructions of the ionosphere and the combination of external information and radar data. In this presentation we describe the geostatistical approach chosen to analyse the behaviour of the ionosphere and to provide a high resolution 3D electron density reconstruction. As first step the horizontal structure of

  6. Experimental investigation of the ionospheric hysteresis effect on the threshold excitation level of the Stimulated Electromagnetic Emission (SEE) during heating at the second electron gyro-harmonic frequency

    NASA Astrophysics Data System (ADS)

    Samimi, A.; Scales, W.; Cruz, M.; Isham, B.; Bernhardt, P. A.

    2012-12-01

    Recent experimental observations of the stimulated electromagnetic emission (SEE) spectrum during heating at the second electron gyro-harmonic show structures ordered by ion gyro-frequency. The proposed generation mechanism considers parametric decay of a pump upper hybrid/electron Bernstein (UH/EB) wave into another UH/EB and a group of neutralized ion Bernstein waves. The presumption of the proposed mechanism is that the pump electromagnetic wave is converted into the UH/EB wave. This conversion process generates field aligned irregularity which exhibits hysteresis effect. The predicted ionospheric hysteresis effect is studied during the PARS 2012 at HAARP. The preliminary results are presented for the first time. Also, experimental study of the effects of 1) the transmitter beam angle and 2) the transmitter frequency offset relative to the second electron gyro-harmonic frequency on the ion gyro-harmonic structures in the SEE spectrum are provided. The aforementioned observations are compared to the predictions of the analytical model. Possible connection of the SEE spectral features and artificially generated ionospheric descending layer is also discussed

  7. HF ground scatter from the polar cap: Ionospheric propagation and ground surface effects

    NASA Astrophysics Data System (ADS)

    Ponomarenko, P. V.; St. Maurice, J.-P.; Hussey, G. C.; Koustov, A. V.

    2010-10-01

    In addition to being scattered by the ionospheric field-aligned irregularities, HF radar signals can be reflected by the ionosphere toward the Earth and then scattered back to the radar by the rugged ground surface. These ground scatter (GS) echoes are responsible for a substantial part of the returns observed by HF radars making up the Super Dual Auroral Radar Network (SuperDARN). While a GS component is conventionally used in studying ionosphere dynamics (e.g., traveling ionospheric disturbances, ULF waves), its potential in monitoring the state of the scattering surface remains largely unexploited. To fill this gap, we investigated diurnal and seasonal variation of the ground echo occurrence and location from a poleward-looking SuperDARN radar at Rankin Inlet, Canada. Using colocated ionosonde information, we have shown that seasonal and diurnal changes in the high-latitude ionosphere periodically modulate the overall echo occurrence rate and spatial coverage. In addition, characteristics of GS from a particular geographic location are strongly affected by the state of the underlying ground surface. We have shown that (1) ice sheets rarely produce detectable backscatter, (2) mountain ranges are the major source of GS as they can produce echoes at all seasons of the year, and (3) sea surface becomes a significant source of GS once the Arctic sea ice has melted away. Finally, we discuss how the obtained results can expand SuperDARN abilities in monitoring both the ionosphere and ground surface.

  8. Low-latitude ionospheric effects of energetic electrons during a recurrent magnetic storm

    NASA Astrophysics Data System (ADS)

    Suvorova, A. V.; Huang, C.-M.; Matsumoto, H.; Dmitriev, A. V.; Kunitsyn, V. E.; Andreeva, E. S.; Nesterov, I. A.; Tsai, L.-C.

    2014-11-01

    We study a magnetosphere-ionosphere coupling at low latitudes during a moderate (corotating interaction regions/high-speed solar wind streams-driven) geomagnetic storm on 22 July 2009. Recently, it has been shown that during major (coronal mass ejection-driven) storms, quasi-trapped >30 keV electrons largely enhance below the radiation belt in the forbidden zone and produce an additional ionization in the topside ionosphere. In this work, we examine a case of the recurrent storm when the magnetosphere-ionosphere coupling through the quasi-trapped electrons also may take place. Data from NOAA/Polar-orbiting Operational Environmental Satellite and Japanese Greenhouse gases Observing Satellite were used to identify the forbidden electron enhancement (FEE). We find a positive vertical gradient of the electron fluxes that indicates to the radiation belt as a source of FEE. Using global ionospheric maps, radiotomography reconstructions from beacon data and COSMIC/FORMOSAT-3 radio occultation measurements, we have observed an unusually large area in the nighttime ionosphere with increased total electron content (TEC) and prominent elevation of the F layer at low latitudes that coincides with FEEs spatially and temporarily. Ionizing particles are considered as an addition source of ionization along with generally accepted mechanisms for storm time TEC increase (a positive ionospheric storm). We discuss relative contributions of the FEE and disturbance dynamo electric field in the TEC increases during the storm recovery phase.

  9. foF2 seismo-ionospheric effect analysis: actual data and numerical simulations

    NASA Astrophysics Data System (ADS)

    Liperovskaya, E. V.; Biagi, P.-F.; Meister, C.-V.; Rodkin, M. V.

    2008-12-01

    On the background of seasonal and helio-geomagnetic disturbances, disturbances of the ionization density near noon connected to earthquakes are investigated. The study is performed for some tens of earthquakes with magnitudes M>5 and depths h<70 km, which occur at distances from the vertical sounding stations "Tokyo", "Akita", and "Yamagawa" not larger than R=exp(M)+150 km. The analysis is performed using data registered by the three sounding stations every hour during 30 years. Especially methods of the statistical analysis are applied to search for regularities in the lithospheric-ionospheric links before and after earthquakes. The growth of the mean ionization density N at the F-layer electron density maximum Fof2 five-three days before earthquakes, and the decrease of N approaching the eruption and during a few days after the earthquake is investigated in dependence on both the magnitude of the earthquake M and the ionization density N near the F-layer maximum. It is found that some days before earthquakes the decrease of the ionization density ΔN is proportional to the values of M and N. After the earthquakes, ΔN depends much weaker on the magnitude M, and it is not influenced by the ionization density N. The variations of the ionization density three days before earthquakes do not depend on N and M (within the same order of approximation).

  10. Effects of convection electric field on upwelling and escape of ionospheric O(+)

    NASA Technical Reports Server (NTRS)

    Cladis, J. B.; Chiu, Yam T.; Peterson, William K.

    1992-01-01

    A Monte Carlo code is used to explore the full effects of the convection electric field on distributions of upflowing O(+) ions from the cusp/cleft ionosphere. Trajectories of individual ions/neutrals are computed as they undergo multiple charge-exchange collisions. In the ion state, the trajectories are computed in realistic models of the magnetic field and the convection, corotation, and ambipolar electric fields. The effects of ion-ion collisions are included, and the trajectories are computed with and without simultaneous stochastic heating perpendicular to the magnetic field by a realistic model of broadband, low frequency waves. In the neutral state, ballistic trajectories in the gravitational field are computed. The initial conditions of the ions, in addition to ambipolar electric field and the number densities and temperatures of O(+), H(+), and electrons as a function of height in the cusp/cleft region were obtained from the results of Gombosi and Killeen (1987), who used a hydrodynamic code to simulate the time-dependent frictional-heating effects in a magnetic tube during its motion though the convection throat. The distribution of the ion fluxes as a function of height are constructed from the case histories.

  11. Common origin of positive ionospheric storms at middle latitudes and the geomagnetic activity effect at low latitudes

    SciTech Connect

    Proelss, G.W. )

    1993-04-01

    The author looks for a correlation between two different atmospheric effects. They are a positive atmospheric storm (an anomalous increase in the F2 region ionization density), observed at middle latitudes, and the geomagnetic activity effect (the anomalous changes of temperature and gas density seen in the thermosphere), observed at low latitudes. A temporal correlation is sought to test the argument that both of these effects are the result of travelling atmospheric disturbances (TAD). A TAD is a pulselike atmospheric wave thought to be generated by substorm activity, and to propagate with high velocity (600 m/s) from polar latitudes toward equatorial latitudes. The author looks at data from five separate events correlating magnetic, ionospheric, and neutral atmospheric measurements. The conclusion is that there is a positive correlation between magnetic substorm activity at high latitudes, and positive ionospheric storms at middle latitudes and geomagnetic activity at low latitudes. The time correlations are consistent with high propagation speeds between these events. The author also presents arguments which indicate that the middle latitude positive ionospheric storms are not the result of electric field effects.

  12. Statistical Analysis of the Ionosphere based on Singular Value Decomposition

    NASA Astrophysics Data System (ADS)

    Demir, Uygar; Arikan, Feza; Necat Deviren, M.; Toker, Cenk

    2016-07-01

    Ionosphere is made up of a spatio-temporally varying trend structure and secondary variations due to solar, geomagnetic, gravitational and seismic activities. Hence, it is important to monitor the ionosphere and acquire up-to-date information about its state in order both to better understand the physical phenomena that cause the variability and also to predict the effect of the ionosphere on HF and satellite communications, and satellite-based positioning systems. To charaterise the behaviour of the ionosphere, we propose to apply Singular Value Decomposition (SVD) to Total Electron Content (TEC) maps obtained from the TNPGN-Active (Turkish National Permanent GPS Network) CORS network. TNPGN-Active network consists of 146 GNSS receivers spread over Turkey. IONOLAB-TEC values estimated from each station are spatio-temporally interpolated using a Universal Kriging based algorithm with linear trend, namely IONOLAB-MAP, with very high spatial resolution. It is observed that the dominant singular value of TEC maps is an indicator of the trend structure of the ionosphere. The diurnal, seasonal and annual variability of the most dominant value is the representation of solar effect on ionosphere in midlatitude range. Secondary and smaller singular values are indicators of secondary variation which can have significance especially during geomagnetic storms or seismic disturbances. The dominant singular values are related to the physical basis vectors where ionosphere can be fully reconstructed using these vectors. Therefore, the proposed method can be used both for the monitoring of the current state of a region and also for the prediction and tracking of future states of ionosphere using singular values and singular basis vectors. This study is supported by by TUBITAK 115E915 and Joint TUBITAK 114E092 and AS CR14/001 projects.

  13. Effects of plasmaspheric ion heating due to ionospheric and magnetospheric sources

    NASA Technical Reports Server (NTRS)

    Comfort, Richard H.

    1996-01-01

    In an initial study, the He(+) observations from the Retarding Ion Mass Spectrometer on Dynamics Explorer 1 (RIMS/DE 1) was examined for more than 120 transits of the plasmasphere in the fall of 1981. The He(+) to H(+) ratio was determined as it varied spatially over portions of the DE 1 orbit, and its variation with solar and magnetic activities and with local time, focusing specifically on the inner plasmasphere. These variations were compared along the L = 2 field line with calculations made by the Field Line Interhemispheric Plasma (FLIP) code. In a recently submitted paper, the He(+) to H(+) density ratio was examined for all the available data from 1981 to 1984 from the RIMS on DE 1. There are two basic characteristics of the ratio: one is that the ratio decreases with radial distance in the plasmasphere, and the other is the strong dependence of the density ratio on solar activity. In addition to the He(+)/H(+) ratio research, a phenomenon has been studied in the topside ionosphere which relates to the thermal coupling of the ionosphere to the plasmasphere. There is little or no correlation with magnetic and solar activity here. Another study has been directed toward the relation of plasma properties to the density gradients forming the plasmapause. The study has followed a two-pronged approach. First, the observations have been analyzed to determine what happens to the plasma properties across these boundary layers (density gradients). Second, comparisons were made with FLIP model calculations to determine how well the model is able to treat these conditions. Among the significant lessons learned in these studies are two that bear directly on the direction of future investigations in this area. First, composition cannot be viewed independently of thermal structure. Second, solar and magnetic activity effects are real; but the causal relationship between activity and effects is frequently quite complicated because several different processes appear to be

  14. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Cole, K. D.

    1993-03-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  15. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Cole, Keith D.

    1993-01-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  16. Radiotomography and HF ray tracing of the artificially disturbed ionosphere above the Sura heating facility

    NASA Astrophysics Data System (ADS)

    Andreeva, E. S.; Frolov, V. L.; Kunitsyn, V. E.; Kryukovskii, A. S.; Lukin, D. S.; Nazarenko, M. O.; Padokhin, A. M.

    2016-06-01

    We present the results of the radiotomographic imaging of the artificial ionospheric disturbances obtained in the recent experiments on the modification of the midlatitude ionosphere by powerful HF radiowaves carried out at the Sura heater. Radio transmissions from low orbital PARUS beacon satellites recorded at the specially installed network of three receiving sites were used for the remote sensing of the heated ionosphere. We discuss the possibility to generate acoustic-gravity waves (AGWs) with special regimes of ionospheric heating (with the square wave modulation of the effective radiated power at the frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere at ionospheric heights during several hours) and present radiotomographic images of the spatial structure of the disturbed volume of the ionosphere corresponding to the directivity pattern of the heater, as well as the spatial structure of the wave-like disturbances, which are possibly heating-induced AGWs, diverging from the heated area of the ionosphere. We also studied the HF propagation of the pumping wave through the reconstructed disturbed ionosphere above the Sura heater, showing the presence of heater-created, field-aligned irregularities that effectively serve as "artificial radio windows."

  17. Implications of Ionospheric Scintillation for GNSS Users in Northern Europe

    NASA Astrophysics Data System (ADS)

    Aquino, Marcio; Moore, Terry; Dodson, Alan; Waugh, Sam; Souter, Jock; Rodrigues, Fabiano S.

    2005-05-01

    Extensive ionospheric scintillation and Total Electron Content (TEC) data were collected by the Institute of Engineering Surveying and Space Geodesy (IESSG) in Northern Europe during years of great impact of the solar maximum on GNSS users (2001 2003). The ionospheric TEC is responsible for range errors due to its time delay effect on transionospheric signals. Electron density irregularities in the ionosphere, occurring frequently during these years, are responsible for (phase and amplitude) fluctuations on GNSS signals, known as ionospheric scintillation. Since June 2001 four GPS Ionospheric Scintillation and TEC Monitor receivers (the NovAtel/AJ Systems GSV4004) have been deployed at stations in the UK and Norway, forming a Northern European network, covering geographic latitudes from 53° to 70° N approximately. These receivers compute and record GPS phase and amplitude scintillation parameters, as well as TEC and TEC variations. The project involved setting up the network and developing automated archiving and data analysis strategies, aiming to study the impact of scintillation on DGPS and EGNOS users, and on different GPS receiver technologies. In order to characterise scintillation and TEC variations over Northern Europe, as well as investigate correlation with geomagnetic activity, long-term statistical analyses were also produced. This paper summarises our findings, providing an overview of the potential implications of ionospheric scintillation for the GNSS user in Northern Europe.

  18. Space weather effects on the low latitude D-region ionosphere during solar minimum

    NASA Astrophysics Data System (ADS)

    Kumar, Abhikesh; Kumar, Sushil

    2014-12-01

    The effects of the solar flares and the geomagnetic storms (disturbance storm time ( Dst) < -50 nT) during December 2006 to 2008, a period during the unprecedented solar minimum of solar cycles 23 and 24, have been examined on sub-ionospheric very low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 kHz), VTX (18.2 kHz), and NLK (24.8 kHz) transmitters monitored at Suva (18.2° S, 178.4° E), Fiji. Apart from the higher class solar flares (C to X), a solar flare of class B8.5 also produced enhancements both on the amplitude and phase. The amplitude enhancements in NLK, NPM, and NWC signals as a function of peak solar flare X-ray flux in decibel (dB; relative to 1 μW/m2) shows that the relationship curve is steeper and quite linear between the flare power levels of 0 to 15 dB; below 0 dB, the curve gets less steep and flattens towards -5 dB flare power level, while it also gets less steep above 15 dB and almost flattens above 20 dB. In general, the level of amplitude enhancement for NLK signal is higher than that for NPM and NWC signals for all solar flares. The enhancement in the amplitude and phase of VLF signals by solar flares is due to the increase in the D-region electron density by the solar flare-produced extra ionization. The modeling of VLF perturbations produced by B8.5 and C1.5 classes of solar flares on 29 January 2007 using LWPC (Long Wave Propagation Capability) V2.1 codes show that reflection height ( H') was reduced by 0.6 and 1.2 km and the exponential sharpness factor ( β) was raised by 0.010 and 0.005 km-1, respectively. Out of seven storms with Dst < -50 nT, only the intense storm of 14 to 16 December 2006 with a minimum Dst of -145 nT has shown a clear reduction in the signal strength of NWC and NPM sub-ionospheric signals due to storm-induced reduction in the D-region electron density.

  19. Ionospheric Data Assimilation

    NASA Astrophysics Data System (ADS)

    Schunk, R.; Scherliess, L.; Sojka, J.; Thompson, D.

    2003-04-01

    Ionospheric weather disturbances can have detrimental effects on a variety of civilian and military systems and operations. They can affect over-the-horizon (OTH) radars, HF communications, surveying and navigation systems, surveillance, spacecraft charging, power grids, pipelines, and the FAA's Wide-Area Augmentation System (WAAS). In an effort to mitigate the adverse effects of the ionosphere on these systems/operations, there is a strong emphasis on developing specification and forecast models. One of the models under development is the Global Assimilation of Ionospheric Measurements (GAIM) model. GAIM uses a physics-based ionosphere-plasmasphere-polar wind model and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. Some of the data that are assimilated include in situ electron density measurements from the DMSP satellites, bottomside electron density profiles from the Air Force network of digisondes, GPS-TEC data from a network of more than 100 stations, and occultation data. GAIM provides specifications and forecasts on a spatial grid that can be global, regional, or local (25 x 25 km). The primary GAIM output is in the form of 3-dimensional electron density distributions from 90 km to the geosynchronous altitude (35,000 km). GAIM also provides auxiliary parameters (N_mF_2, h_mF_2, N_mE, h_mE, slant and vertical TEC) and global distributions of the self-consistent ionospheric drivers (neutral winds and densities, magnetospheric and dynamo electric fields, and particle precipitation patterns). In its specification mode, GAIM provides quantitative estimates for the accuracy of the reconstructed ionospheric densities. An outline of the GAIM model will be presented and then the presentation will focus on data issues, including the availability of real-time data sources, data quality problems, and the need to have realistic errors attached to all of the real-time data.

  20. Perturbation effect of the electronic induction drag on the orbital elements of a charged satellite moving in an ionosphere

    NASA Astrophysics Data System (ADS)

    Li, Lin-Sen

    The influence of the electronic induction drag on the variation of the orbital elements of a charged satellite moving in a magnetic-field-free ionosphere are studied. The theoretical result show that the induction drag results in both the secular and periodic variations of the semi-major axis, however the eccentricity, the argument of perigee and the mean longitude of epoch exhibits no secular variation, but only periodic variation. The inclination and the ascending node remain no variation. As example, the secular effect of the induction drag on the orbital semi-major axis at a supposed satellite is calculated. It can be shown that the semi-major axis is contracted due to the induction drag, if this satellite carries many charges in an ionosphere.

  1. Ensemble Ionospheric Total Electron Content Forecasting during Storms

    NASA Astrophysics Data System (ADS)

    Chartier, A.; Mitchell, C. N.; Lu, G.; Anderson, J. L.; Collins, N.; Hoar, T. J.; Bust, G. S.; Matsuo, T.

    2014-12-01

    Earth's ionosphere presents a threat to human activities such as satellite positioning and timing, radio communications and surveillance. Nowcasts and forecasts of the ionosphere could help mitigate these damaging effects. Recent advances in the field of ionospheric imaging, as well as new storm-time ionospheric forecasting results are presented here. The approach combines globally distributed GPS Total Electron Content (TEC) measurements with an ensemble of coupled thermosphere-ionosphere models in order to produce short-term forecasts during a storm. One-hour forecast accuracy is much better than a climatological model run. Using this ensemble approach, it is possible to infer the neutral O/N2 ratio from TEC measurements so that subsequent TEC forecasts are improved. A review of ionospheric physics and data assimilation will also be given. The term data assimilation refers to a group of techniques designed to estimate atmospheric or oceanic states. In practice, data assimilation techniques seek to improve modeled estimates of the atmospheric state by incorporating observations. The relationship between data assimilation and forecasting is explored with reference to the physics of the thermosphere-ionosphere system. The work presented here uses the Data Assimilation Research Testbed (DART), which is an ensemble Kalman filter data assimilation framework. This is combined with a version of the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) that has been modified to accept more detailed solar and geomagnetic driver specifications. Future directions of work include the inference of Solar and geomagnetic drivers from the data assimilation process as well as coupling with lower-atmospheric models.

  2. Radio Tomography of Ionospheric Structures (probably) due to Underground-Surface-Atmosphere-Ionosphere Coupling

    NASA Astrophysics Data System (ADS)

    Kunitsyn, V.; Nesterov, I.; Andreeva, E.; Rekenthaler, D. A.

    2012-12-01

    . The single-point measurements (by ionosondes or by isolated receivers) are not amenable to unambiguous interpretation; based on these data, it is impossible to distinguish the contribution of USAI coupling from the ionospheric effects induced by the "ordinary" impacts (the Sun, the solar wind, geomagnetic perturbations, galactic cosmic rays, etc.). In order to localize sources of the ionospheric disturbances, the geophysicist needs information on the spatial structure and dynamics of the ionospheric perturbations. This information (2D-4D RT images) is optimally provided by RT methods. We present examples of the ionospheric disturbances caused by EQs as well as the ionospheric precursors of these EQs in the form of specific ionospheric irregularities: AGW- and soliton-like wave disturbances, which we identified using RT methods. Based on the results of the RT studies in the Alaska and Taiwan regions, we have detected several dozen AGW-related precursors of EQs. These data allow us to attempt to locate the source of these perturbations. We discuss the possibilities and prospects of further research aimed at identifying and analyzing precursors of EQs and establishing the mechanisms of USAI coupling. We are grateful to Northwest Research Associates, Inc., and Dr. L.-C.Tsai for providing raw RT data for Alaska and Taiwan.

  3. Refractive index effects on the scatter volume location and Doppler velocity estimates of ionospheric HF backscatter echoes

    NASA Astrophysics Data System (ADS)

    Ponomarenko, P. V.; St-Maurice, J.-P.; Waters, C. L.; Gillies, R. G.; Koustov, A. V.

    2009-11-01

    Ionospheric E×B plasma drift velocities derived from the Super Dual Auroral Radar Network (SuperDARN) Doppler data exhibit systematically smaller (by 20-30%) magnitudes than those measured by the Defence Meteorological Satellites Program (DMSP) satellites. A part of the disagreement was previously attributed to the change in the E/B ratio due to the altitude difference between the satellite orbit and the location of the effective scatter volume for the radar signals. Another important factor arises from the free-space propagation assumption used in converting the measured Doppler frequency shift into the line-of-sight velocity. In this work, we have applied numerical ray-tracing to identify the location of the effective scattering volume of the ionosphere and to estimate the ionospheric refractive index. The simulations show that the major contribution to the radar echoes should be provided by the Pedersen and/or escaping rays that are scattered in the vicinity of the F-layer maximum. This conclusion is supported by a statistical analysis of the experimental elevation angle data, which have a signature consistent with scattering from the F-region peak. A detailed analysis of the simulations has allowed us to propose a simple velocity correction procedure, which we have successfully tested against the SuperDARN/DMSP comparison data set.

  4. A case study of Ionospheric storm effects during long-lasting southward IMF Bz driven geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Liu, J., Sr.

    2014-12-01

    Multiple instrumental observations including GPS TEC, foF2 and hmF2 from ionosondes, vertical ion drift measurements from C/NOFS, magnetometer data and far-ultraviolet airglow measured by TIMED/GUVI are used to investigate the profound ionospheric disturbances at mid- and low-latitudes during the 14-17 July 2012 geomagnetic storm event, which was featured by prolonged southward interplanetary geomagnetic field component for about 30 hours below -10 nT. In the East Asian/Australian sector, latitudinal profile of TEC variations in the main phase were characterized by three bands of increments and separated by weak depressions in the Equatorial Ionospheric Anomaly (EIA) crest regions, which were caused by the combined effects of disturbance dynamo electric fields (DDEF) and equatorward neutral winds. In the recovery phase, strong inhibition of EIA occurred and the summer crest of EIA disappeared on 16 July due to the combined effects of intrusion of neutral composition disturbance zone as shown by the TIME/GUVI O/N2 measurements and long-lasting daytime westward DDEF inferred from the equatorial electric electrojet (EEJ) observations. The transit time of DDEF over the dip equator from westward to eastward is around 2200 LT. In the American longitude, the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase, preceded by storm enhanced density (SED) plume in the initial phase. In addition, multiple short-lived prompt penetration electric fields (PPEF) appeared during stable southward IMF Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset.

  5. GPS Monitoring of Ionospheric TEC Over the Area of Thessaliniki in Order to Detect Disturbances Related to the Local Tectonic Activity

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Arambelos, D.; Asteriadis, G.; Pikridas, Ch.; Spatalas, S.

    2004-04-01

    Atmospheric and underground explosions as well as shallow earthquakes producing strong vertical ground displacement, are known to produce pressure waves (e.g. Calais and Minster 1995) that propagates at infrasonic speeds in the atmosphere. At ionospheric altitudes these waves are coupled to ionospheric gravity waves and induce variations in the ionospheric electron density. On the other hand local lithospheric density variations, produced by the local tectonic activity during the earthquake preparation period, affect the local gravity field and consequently the overlying atmospheric and ionospheric density. This fact is reflected in the presence of exalting on atmospheric tide parameters (e.g. Arabelos et al. 2003, Contadakis et al. 2004) and on LF radio signals (Biagi et al. 2003). That is the lithospheric near surface tectonic activity results in local pre-, co- and post-seismic disturbances on the ionospheric Total Electronic Content. There for a program for the monitoring of TEC over the area of Thessaloniki in relation with the local seismic activity was initiated, using the data of the GPS permanent station of the Department of Surveying and Geodesy, University of Thessaloniki. In this paper the organizing of the observations and the method of analysis are presented and the first results of the observed ionospheric TEC variations in relation with the weak local seismic activity are being discussed.

  6. Effects of a “day-time” substorm on the ionosphere and radio propagation

    NASA Astrophysics Data System (ADS)

    Blagoveshchensky, D.; Kalishin, A.; MacDougall, J.

    2009-11-01

    Propagation mechanisms of lateral (non-great-circle) signals on a high-latitude HF radio path during magnetospheric substorms that occurred in the day-time have been considered. The path is equipped with oblique ionospheric sounding (OIS) from Murmansk to St. Petersburg. The OIS method gives the possibility to determine propagation modes, MOF (maximum observed frequency) values, signal delays, etc. Data of the CUTLASS radar, the IMAGE magnetometer system, the Finnish riometer chain, and the Tromso ionosonde were also used for the analysis. The main results are the following: (1) the lateral signal propagation takes place, as a rule, if the path midpoint is located near the irregularity region that moves sharply from high to low latitudes. The lateral signal propagation appearing during day-time is a new effect. (2) Formation of dense field-aligned irregularities during a substorm leads to decreasing F2MOF values on radio paths. These results can be useful for problems of radiolocation, HF communications and navigation.

  7. The simulation of electromagnetically driven strong Langmuir turbulence effect on the backscatter radiation from ionosphere

    NASA Astrophysics Data System (ADS)

    Kochetov, Andrey

    2016-07-01

    Numerical simulations of the dynamics of electromagnetic fields in a smoothly inhomogeneous nonlinear plasma layer in frameworks of the nonlinear Schrödinger equation with boundary conditions responsible for the pumping of the field in the layer by an incident wave and the inverse radiation losses supplemented the volume field dissipation due to the electromagnetic excitation of Langmuir turbulence are carried out. The effects of the threshold of non-linearity and it's evolution, of the threshold and saturation levels of dissipation in the vicinity of the wave reflection point on the features of the dynamics of reflection and absorption indexes are investigated. We consider the hard drive damping depending on the local field amplitude and hysteresis losses with different in several times "on" and "off" absorption thresholds as well. The dependence of the thresholds of the steady-state, periodic and chaotic regimes of plasma-wave interaction on the scenario of turbulence evolution is demonstrated. The results are compared with the experimental observations of Langmuir stage ionospheric modification.

  8. Time and Order Effects on Causal Learning

    ERIC Educational Resources Information Center

    Alvarado, Angelica; Jara, Elvia; Vila, Javier; Rosas, Juan M.

    2006-01-01

    Five experiments were conducted to explore trial order and retention interval effects upon causal predictive judgments. Experiment 1 found that participants show a strong effect of trial order when a stimulus was sequentially paired with two different outcomes compared to a condition where both outcomes were presented intermixed. Experiment 2…

  9. Using Lightning Waveforms To Probe Thunderstorm's Electromagnetic Effects On The Ionospheric D-Layer

    NASA Astrophysics Data System (ADS)

    Shao, X.; Lay, E. H.; Jacobson, A. R.

    2011-12-01

    Previous studies indicated that ionospheric D-layer could be disturbed by electromagnetic activities of the underling thunderstorms, either due to impulsive EM radiation (EMP) produced by intense ground strokes or due to removal of charges by lightning flashes (quasi-static electrical, QE). More recent study by the authors showed that the dominant fluctuations in the D-layer could be attributed to the effects of atmospheric gravity wave (AGW) that was originated by the storm. With time-domain, near-range (100s km), multi-station, and broadband VLF/LF observations from the Los Alamos Sferic Array (LASA), high spatial and temporal resolution detection of the D-layer behavior became feasible. Especially, the simultaneous multi-station measurements provide a chance of probing the D-layer from different directions and at different distances from the effecting storm. Together with the measurement, we also developed a time-domain VLF/LF propagation model, which takes the D-layer electron profile as the dominant parameter. In this study, we compare the measured return stroke waveforms with the model simulation and find the best match between the two, and to retrieve the corresponding D-layer electron profile. Our analysis indicated that additional and static ionization occurred directly above some storms, possibly due to the QE effect (or rather a static electrical effect, SE). In the range of a few hundred km, the altitude of the D-layer was found to continuously descending as one approaching toward the storm, suggesting an EMP effect that occurred nearly continuously.

  10. Tsunami Ionospheric warning and Ionospheric seismology

    NASA Astrophysics Data System (ADS)

    Lognonne, Philippe; Rolland, Lucie; Rakoto, Virgile; Coisson, Pierdavide; Occhipinti, Giovanni; Larmat, Carene; Walwer, Damien; Astafyeva, Elvira; Hebert, Helene; Okal, Emile; Makela, Jonathan

    2014-05-01

    The last decade demonstrated that seismic waves and tsunamis are coupled to the ionosphere. Observations of Total Electron Content (TEC) and airglow perturbations of unique quality and amplitude were made during the Tohoku, 2011 giant Japan quake, and observations of much lower tsunamis down to a few cm in sea uplift are now routinely done, including for the Kuril 2006, Samoa 2009, Chili 2010, Haida Gwai 2012 tsunamis. This new branch of seismology is now mature enough to tackle the new challenge associated to the inversion of these data, with either the goal to provide from these data maps or profile of the earth surface vertical displacement (and therefore crucial information for tsunami warning system) or inversion, with ground and ionospheric data set, of the various parameters (atmospheric sound speed, viscosity, collision frequencies) controlling the coupling between the surface, lower atmosphere and the ionosphere. We first present the state of the art in the modeling of the tsunami-atmospheric coupling, including in terms of slight perturbation in the tsunami phase and group velocity and dependance of the coupling strength with local time, ocean depth and season. We then show the confrontation of modelled signals with observations. For tsunami, this is made with the different type of measurement having proven ionospheric tsunami detection over the last 5 years (ground and space GPS, Airglow), while we focus on GPS and GOCE observation for seismic waves. These observation systems allowed to track the propagation of the signal from the ground (with GPS and seismometers) to the neutral atmosphere (with infrasound sensors and GOCE drag measurement) to the ionosphere (with GPS TEC and airglow among other ionospheric sounding techniques). Modelling with different techniques (normal modes, spectral element methods, finite differences) are used and shown. While the fits of the waveform are generally very good, we analyse the differences and draw direction of future

  11. Evidence and effects of the sunrise enhancement of the equatorial vertical plasma drift in the F region ionosphere

    NASA Astrophysics Data System (ADS)

    Zhang, Ruilong; Liu, Libo; Le, Huijun; Chen, Yiding

    2016-05-01

    Recent studies based on the satellite observations demonstrated that the equatorial vertical plasma drift can also enhance near sunrise in a way similar to the prereversal enhancement. However, it is not clear whether the signature of this sunrise enhancement appears in observations with other sounding techniques. In this work, we explore the Jicamarca (12°S, 283.2°E) incoherent scatter radar measurements to present the evidence of sunrise enhancement in vertical plasma drift on 12 May and 10 June 2004, which are under magnetically quiet and solar minimum conditions. The effects of the sunrise enhancement on the ionosphere are, for the first time, investigated by analyzing the ionograms recorded by the Digisonde Portable Sounder at Jicamarca and conducting the Theoretical Ionospheric Model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences. The observations showed that, during the sunrise enhancement, the F2 layer peak height is lifted remarkably, and the F2 layer peak density and bottomside electron density tend to decrease compared to the days without sunrise enhancements. The simulations indicated that the sunrise enhancement drift can lift the equatorial ionosphere to higher heights and distort the equatorial electron density profiles. What is more, the simulations display an F3 layer in the equatorial F region during the sunrise enhancement, and a new F2 layer develops at lower altitudes under the jointed control of the usual photochemical and dynamical processes.

  12. Modeling ionospheric electron precipitation due to wave particle scattering in the magnetosphere and the feedback effect on the magnetospheric dynamics

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Jordanova, V.; Ridley, A. J.; Albert, J.; Horne, R. B.; Jeffery, C. A.

    2015-12-01

    Electron precipitation down to the atmosphere caused by wave-particle scattering in the magnetosphere contribute significantly to the enhancement of auroral ionospheric conductivity. Global MHD models that are incapable of capturing kinetic physics in the inner magnetosphere usually adopt MHD parameters to specify the precipitation flux to estimate auroral conductivity, hence losing self-consistency in the global circulation of the magnetosphere-ionosphere system. In this study we improve the coupling structure in global models by connecting the physics-based (wave-particle scattering) electron precipitation with the ionospheric electrodynamics and investigate the feedback effect on the magnetospheric dynamics. We use BATS-R-US coupled with a kinetic ring current model RAM-SCB that solves pitch angle dependent particle distributions to study the global circulation dynamics during the Jan 25-26, 2013 storm event. Following tail injections, we found enhanced precipitation number and energy fluxes of tens of keV electrons being scattered into loss cone due to interactions with enhanced chorus and hiss waves in the magnetosphere. This results in a more profound auroral conductance and larger electric field imposing on the plasma transport in the magnetosphere. We also compared our results with previous methods in specifying the auroral conductance, such as empirical relation used in Ridley et al. (2004). It is found that our physics-based method develops a larger convection electric field in the near-Earth region and therefore leads to a more intense ring current.

  13. Effect of interplanetary magnetic field on ionosphere over the magnetic equator

    NASA Technical Reports Server (NTRS)

    Rastogi, R. G.; Patel, V. L.

    1975-01-01

    Large and quick changes of the latitude of the interplanetary magnetic field from its southward to northward direction are shown to be associated with the disappearance of the Es-q layer (Knecht, 1959) at the equatorial ionosphere during the daytime or with the reversal of E region horizontal and F region vertical electron drifts during both night and day. This phenomenon is suggested as the imposition of an electric field in the ionosphere in a direction opposite to that of the Sq electric field. The resultant electrostatic field on the equatorial ionosphere would be decreased or even reversed from its normal direction, resulting in the reduction of electron drift velocity. When the normal Sq field is over-compensated by the magnetospheric electric field, the electron drifts are reversed and the irregularities in the E region due to the cross-field instabilities are inhibited, resulting in the sudden disappearance of the Es-q layers.

  14. Ionospheric range-rate effects in satellite-to-satellite tracking

    NASA Technical Reports Server (NTRS)

    Lipofsky, J. R.; Bent, R. B.; Llewellyn, S. K.; Schmid, P. E.

    1977-01-01

    Investigation of ionospheric range and range-rate corrections in satellite-to-satellite tracking were investigated. Major problems were cited and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information, as a simple median model cannot possibly account for the complex interaction of the many variables. The findings provide a basis from which the residual errors can be estimated after ionospheric modeling is incorporated in the reduction. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits.

  15. Effect of Precipitating Electrons on Ring Current Energy Content, Ionospheric Conductance, and Thermospheric Properties

    NASA Astrophysics Data System (ADS)

    Chen, M.; Lemon, C. L.; Walterscheid, R. L.; Yoo, B.; Hecht, J. H.; Shprits, Y.; Orlova, K.; Schulz, M.; Evans, J. S.

    2014-12-01

    We investigate how scattering of electrons by waves in the plasma sheet and plasmasphere affects precipitating energy flux distributions during magnetic storms, how the precipitating electrons modify the ionospheric Hall and Pederson conductivity and electric potential, how these processes feedback on magnetospheric particle transport and redistribute the ring current, and how the ionization and energy deposition of precipitating electrons affects thermospheric winds and temperature. Our main approach is to couple simulation models: (1) the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere, (2) the B3c transport model for electron-proton-hydrogen atom aurora in the ionosphere, and (3) the Thermosphere-Ionsphere-Electrodynamics General Circulation Model (TIEGCM) of the ionosphere and thermosphere. Realistic descriptions of electron pitch-angle diffusion by whistler chorus in the plasma sheet/magnetotail and hiss in the plasmasphere are included in the RCM-E. We use parameterized rates of electron pitch-angle scattering with whistler chorus of Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time. To study how the precipitating electron energy flux distributions affect ionospheric conductivity and ionospheric electric potential patterns, we have performed a one-way coupling of the RCM-E and ionospheric B3c model. The simulated precipitating electron flux distributions are used to specify the energy flux and particle heating due to precipitating auroral electrons for TIEGCM simulations of the neutral atmosphere. We simulate a storm event and compare simulated quantities with in situ observations.

  16. The Effects of Neutral Inertia on Ionospheric Currents in the High-Latitude Thermosphere Following a Geomagnetic Storm

    NASA Technical Reports Server (NTRS)

    Deng, W.; Killeen, T. L.; Burns, A. G.; Roble, R. G.; Slavin, J. A.; Wharton, L. E.

    1993-01-01

    Results of an experimental and theoretical investigation into the effects of the time dependent neutral wind flywheel on high-latitude ionospheric electrodynamics are presented. The results extend our previous work which used the National Center for Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) to theoretically simulate flywheel effects in the aftermath of a geomagnetic storm. The previous results indicated that the neutral circulation, set up by ion-neutral momentum coupling in the main phase of a geomagnetic storm, is maintained for several hours after the main phase has ended and may dominate height-integrated Hall currents and field-aligned currents for up to 4-5 hours. We extend the work of Deng et al. to include comparisons between the calculated time-dependent ionospheric Hall current system in the storm-time recovery period and that measured by instruments on board the Dynamics Explorer 2 (DE 2) satellite. Also, comparisons are made between calculated field-aligned currents and those derived from DE 2 magnetometer measurements. These calculations also allow us to calculate the power transfer rate (sometimes called the Poynting flux) between the magnetosphere and ionosphere. The following conclusions have been drawn: (1) Neutral winds can contribute significantly to the horizontal ionospheric current system in the period immediately following the main phase of a geomagnetic storm, especially over the magnetic polar cap and in regions of ion drift shear. (2) Neutral winds drive Hall currents that flow in the opposite direction to those driven by ion drifts. (3) The overall morphology of the calculated field-aligned current system agrees with previously published observations for the interplanetary magnetic field (IMF) B(sub Z) southward conditions, although the region I and region 2 currents are smeared by the TI(ICM model grid resolution. (4) Neutral winds can make significant contributions to the field-aligned current

  17. Ionospheric effects of the acoustic wave above the epicenter of an industrial explosion

    SciTech Connect

    Drobzhev, V.I.; Zheleznyakov, E.V.; Idrisov, I.K.; Kaliev, M.Z.; Kazakov, V.V.; Krasnov, V.M.; Pelenitsyn, G.M.; Savel'ev, V.L.

    1988-06-01

    Results obtained during two industrial explosions are compared. The appearance of identical minute pulsations in the geomagnetic field is determined. The efficiency of ionospheric action of ground-based explosions with the energy of several hundred tons of TNT is confirmed, together with the dependence of duration of the ionospheric response upon the explosion energy. Dopplergrams are used to reconstruct the time profile of neutral gas velocity in the acoustic perturbation at the reflection point of the probing radio wave at a height of /approximately/200 km.

  18. Ionospheric mapping functions based on electron density fields

    NASA Astrophysics Data System (ADS)

    Zus, Florian; Deng, Zhiguo; Heise, Stefan; Wickert, Jens

    2016-04-01

    We developed an ionospheric Mapping Function (MF) for the Global Navigation Satellite System (GNSS) which is based on the electron density field of the International Reference Ionosphere (IRI). The station specific MF utilizes a look-up table which contains a set of ray-traced ionospheric delays. Hence, unlike the simple MFs that are currently in use, the developed MF depends on the time, location, elevation and azimuth angle. Ray-bending is taken into account, which implies that the MF depends on the carrier frequency as well. This frequency dependency of the MF can be readily used to examine higher-order ionospheric effects due to ray-bending. We compare the proposed MF with the so-called single layer model MF and find significant differences in particular around the equatorial anomaly. In so-far as the proposed MF is based on a realistic electron density field (IRI) our comparison shows the potential error of the single-layer model MF in practice. We conclude that the developed MF concept might be valuable in the GNSS Total Electron Content estimation. The frequency dependency of the MF can be used to mitigate higher-order ionospheric effects.

  19. Analysis of FORTE data to extract ionospheric parameters

    NASA Astrophysics Data System (ADS)

    Roussel-Dupré, Robert A.; Jacobson, Abram R.; Triplett, Laurie A.

    2001-01-01

    The ionospheric transfer function is derived for a spherically symmetric ionosphere with an arbitrary radial electron density profile in the limit where the radio frequencies of interest ω are much larger than the plasma frequency ωpe. An expansion of the transfer function to second order in the parameter X (= ω2pe/ω2) is carried out. In this limit the dispersive properties of the ionosphere are manifested as a frequency-dependent time of arrival that includes quadratic, cubic, and quartic terms in 1/ω. The coefficients of these terms are related to the total electron content (TEC) along the slant path from transmitter to receiver, the product of TEC and the longitudinal magnetic field strength along the slant path, and refractive bending and higher-order electron density profile effects, respectively. By fitting the time of arrival versus frequency of a transionospheric signal to a polynomial in 1/ω it is possible to extract the TEC, the longitudinal magnetic field strength, the peak electron density, and an effective thickness for the ionosphere. This exercise was carried out for a number of transionospheric pulses measured in the VHF by the FORTE satellite receiver and generated by the Los Alamos Portable Pulser. The results are compared with predictions derived from the International Reference Ionosphere and the United States Geological Survey geomagnetic field model.

  20. Fluctuations in the Venusian Ionosphere and Their Effect on Venus Express Lightning Detection Rates

    NASA Astrophysics Data System (ADS)

    Hart, R. A.; Russell, C. T.; Zhang, T.

    2015-12-01

    Venus Express completed its nearly 9 year campaign at Earth's sister planet in late 2014. During this period the onboard fluxgate magnetometer collected data up to 64 Hz in frequency near periapsis. This is the expected frequency range for lightning-generated whistler-mode waves at Venus, between the local electron (~100 Hz) and ion gyrofrequencies (~1 Hz). These waves are right-hand circularly polarized and are guided by the local magnetic field. When the Venusian ionopause is low enough to reside in the collisional region, the interplanetary magnetic field can get carried down with the ions and magnetize the lower ionosphere. As the field travels towards terminator it gains a radial component, enabling whistlers to reach higher altitudes and be detected by the spacecraft. The mission covered almost an entire solar cycle and frequently observed a magnetized ionosphere during the solar minimum phase when the ionosphere was weak due to reduced incident EUV. In addition, the detection rate of whistler-mode signals varied with the solar cycle. Here, we examine the changes in the ionospheric properties associated with the evolution of the solar cycle and the rate of detection of these lightning-generated signals.

  1. Solar Cycle Effects on Equatorial Electrojet Strength and Low Latitude Ionospheric Variability (P10)

    NASA Astrophysics Data System (ADS)

    Veenadhari, B.; Alex, S.

    2006-11-01

    veena_iig@yahoo.co.in The most obvious indicators of the activity of a solar cycle are sunspots, flares, plages, and soon. These are intimately linked to the solar magnetic fields, heliospheric processes which exhibit complex but systematic variations. The changes in geomagnetic activity, as observed in the ground magnetic records follow systematic correspondence with the solar activity conditions. Thus the transient variations in the magnetic field get modified by differing solar conditions. Also the solar cycle influences the Earth causing changes in geomagnetic activity, the magnetosphere and the ionosphere. Daily variations in the ground magnetic field are produced by different current systems in the earth’s space environment flowing in the ionosphere and magnetosphere which has a strong dependence on latitude and longitude of the location. The north-south (Horizontal) configuration of the earth’s magnetic field over the equator is responsible for the narrow band of current system over the equatorial latitudes and is called the Equatorial electrojet (EEJ) and is a primary driver for Equatorial Ionization anomaly (EIA). Equatorial electric fields and plasma drifts play the fundamental roles on the morphology of the low latitude ionosphere and strongly vary during geomagnetically quiet and disturbed periods. Quantitative study is done to illustrate the development process of EEJ and its influence on ionospheric parameters. An attempt is also made to examine and discuss the response of the equatorial electrojet parameters to the fast varying conditions of solar wind and interplanetary parameters.

  2. Electron densities and temperatures in the Venus ionosphere Effects of solar EUV, solar wind pressure and magnetic field

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Russell, C. T.; Brace, L. H.

    1985-01-01

    The Venus ionosphere is influenced by variations in both solar EUV flux and solar wind conditions. On the dayside the location of the topside of the ionosphere, the ionopause, is controlled by solar wind dynamic pressure. Within the dayside ionosphere, however, electron density is affected mainly by solar EUV variations, and is relatively unaffected by solar wind variations and associated magnetic fields induced within the ionosphere. The existence of a substantial nightside ionosphere of Venus is thought to be due to the rapid nightward transport of dayside ionospheric plasma across the terminator. Typical solar wind conditions do not strongly affect this transport and consequently have little direct influence on nightside ionospheric conditions, except on occasions of extremely high solar wind dynamic pressure. However, both nightside electron density and temperature are affected by the presence of magnetic field, as in the case of ionospheric holes.

  3. UHF Radar observations at HAARP with HF pump frequencies near electron gyro-harmonics and associated ionospheric effects

    NASA Astrophysics Data System (ADS)

    Watkins, Brenton; Fallen, Christopher; Secan, James

    Results for HF modification experiments at the HAARP facility in Alaska are presented for experiments with the HF pump frequency near third and fourth electron gyro-harmonics. A UHF diagnostic radar with range resolution of 600 m was used to determine time-dependent altitudes of scattering from plasma turbulence during heating experiments. Experiments were conducted with multiple HF frequencies stepped by 20 kHz above and below the gyro-harmonic values. During times of HF heating the HAARP facility has sufficient power to enhance large-scale ionospheric densities in the lower ionosphere (about 150-200 km altitude) and also in the topside ionosphere (above about 350 km). In the lower ionosphere, time-dependent decreases of the altitude of radar scatter result from electron density enhancements. The effects are substantially different even for relatively small frequency steps of 20 kHz. In all cases the time-varying altitude decrease of radar scatter stops about 5-10 km below the gyro-harmonic altitude that is frequency dependent; we infer that electron density enhancements stop at this altitude where the radar signals stop decreasing with altitude. Experiments with corresponding total electron content (TEC) data show that for HF interaction altitudes above about 170 km there is substantial topside electron density increases due to upward electron thermal conduction. For lower altitudes of HF interaction the majority of the thermal energy is transferred to the neutral gas and no significant topside density increases are observed. By selecting an appropriate HF frequency a little greater than the gyro-harmonic value we have demonstrated that the ionospheric response to HF heating is a self-oscillating mode where the HF interaction altitude moves up and down with a period of several minutes. If the interaction region is above about 170 km this also produces a continuously enhanced topside electron density and upward plasma flux. Experiments using an FM scan with the HF

  4. Effect of high-latitude ionospheric convection on Sun-aligned polar caps

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Zhu, L.; Crain, D. J.; Schunk, R. W.

    1994-01-01

    A coupled magnetospheric-ionospheric (M-I) magnetohydrodynamic (MHD) model has been used to simulate the formation of Sun-aligned polar cap arcs for a variety of interplanetary magnetic field (IMF) dependent polar cap convection fields. The formation process involves launching an Alfven shear wave from the magnetosphere to the ionosphere where the ionospheric conductance can react self-consistently to changes in the upward currents. We assume that the initial Alfven shear wave is the result of solar wind-magnetosphere interactions. The simulations show how the E region density is affected by the changes in the electron precipitation that are associated with the upward currents. These changes in conductance lead to both a modified Alfven wave reflection at the ionosphere and the generation of secondary Alfven waves in the ionosphere. The ensuing bouncing of the Alfven waves between the ionosphere and magnetosphere is followed until an asymptotic solution is obtained. At the magnetosphere the Alfven waves reflect at a fixed boundary. The coupled M-I Sun-aligned polar cap arc model of Zhu et al.(1993a) is used to carry out the simulations. This study focuses on the dependence of the polar cap arc formation on the background (global) convection pattern. Since the polar cap arcs occur for northward and strong B(sub y) IMF conditions, a variety of background convection patterns can exist when the arcs are present. The study shows that polar cap arcs can be formed for all these convection patterns; however, the arc features are dramatically different for the different patterns. For weak sunward convection a relatively confined single pair of current sheets is associated with the imposed Alfven shear wave structure. However, when the electric field exceeds a threshold, the arc structure intensifies, and the conductance increases as does the local Joule heating rate. These increases are faster than a linear dependence on the background electric field strength. Furthermore

  5. Multi-PLL with two-stage fusion to mitigate ionospheric scintillation effects on GPS receivers

    NASA Astrophysics Data System (ADS)

    Xu, Rui; Liu, Zhizhao; Chen, Wu

    2015-07-01

    Ionospheric scintillation poses a great threat to the reliability and accuracy of Global Positioning System (GPS) in various applications. It can increase tracking errors of the phase-locked loop (PLL) in a GPS receiver and even cause the PLL loss of lock under severe scintillations. To mitigate the effect of scintillation on GPS receivers, especially to reduce the occurrence of loss of lock, a multi-PLL with two-stage fusion (i.e., tracking fusion and output fusion) is proposed in this paper. This algorithm integrates several parallel sub-PLLs with different loop parameters into one channel to track one GPS satellite's signal. Every sub-PLL has its own discriminator, loop filter, carrier numerical controlled oscillator, and a tracking fusion (i.e., the first stage fusion). The tracking fusion of each sub-PLL integrates the Doppler frequency measurements from all other sub-PLLs to detect the state of its own sub-PLL and feeds back reliable Doppler frequency measurements. Simultaneously, the tracking fusion outputs the Doppler frequency measurements to the second stage fusion (i.e., output fusion), which integrates the outputs from all tracking fusions to provide continuous and accurate Doppler frequency measurements for the following positioning/navigation estimator. Performances of the proposed algorithm are tested using real-world GPS data with different levels of scintillations and compared with results from single-PLLs. For three real-world scintillation cases (S4 = 0.26-1.1, σϕ = 0.05-1.49 rad, and average C/N0 = 41.2-45.7 dB Hz), the multi-PLL algorithm performs more robustly than the single-PLLs and is able to keep tracking in all scintillation cases.

  6. The "SABEIS" Project: Warning systems based on earthquake and tsunamis-induced ionospheric effects.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Bouza, Marta; Sánchez-Dulcet, Francisco; Herraiz, Miguel; Rodríguez-Caderot, Gracia; Altadill, David; Blanch, Estefania; Santoyo, Miguel Angel

    2016-04-01

    The study of a possible lithosphere-atmosphere-ionosphere coupling (LAI) is mainly focused on the analysis and comprehension of atmospheric and ionospheric anomalies caused by extreme lithospheric events. In this context, earthquakes are considered as possible sources of atmosphere-ionosphere anomalies. The goal of the two-year long project SABEIS (Sistemas de Alerta Basados en Efectos de terremotos y tsunamis en la IonoSfera) granted by the Spanish Ministry of Economy and Competitiveness, is to analyze the disturbances caused by earthquakes and tsunamis and their possible contribution to warning systems. These topics are receiving increased attention in the scientific community and their correct understanding can meaningfully contribute to the protection of people and economic assets in areas subject to seismic threat. The project is based on the analysis of Total Electron Content (TEC) obtained from signals of Global Navigation Satellite Systems (GNSS) and anomalies of the ionospheric F2 layer observed in ionograms. This methodology was partially applied in a previous study of the Mw6.1 earthquake in Greece occurred on January 26, 2014. In that case two TEC disturbances were detected the days prior the earthquake. The first one, four days before, was registered by the majority of the stations analyzed over Europe and after studying its temporal variation, was considered unrelated to the earthquake. The second one occurred the day before the earthquake. This anomaly appeared only at stations close to the epicenter and their temporal proximity to the earthquake point to a possible connection with the earthquake preparation process. In the SABEIS project possible anomalies caused by earthquakes in Mexico and Peru with magnitude ranging from 5.5 to 8.2, will be studied. If the results confirm the influence of seismic events on the ionosphere, the possibility of incorporating this type of analysis in a seismic alert network for the Gulf of Cadiz (southern Iberian

  7. The effect of gravity and pressure in the electrodynamics of the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Eccles, J. Vincent

    2004-05-01

    The source of the plasma drift structure in the low-latitude ionosphere during magnetically quiet times is generally understood. Nearly all the quiet time electric field structure has been attributed to divergences in the neutral wind current dynamo. However, there are other current drivers active in the low latitude ionosphere: a gravity-driven current (g × B drift of O+) and a gradient-pressure current (∇P × B drift of e and O+). The gravity-driven current is important in the development of the Rayleigh-Taylor instability and equatorial spread F (ESF) but is ignored in global dynamo electric field models. The gradient pressure and gravity terms in the ionosphere momentum equation normally oppose each other. This paper examines the magnitude of the large-scale electric fields generated by divergences in these lesser currents in a coupled ionosphere-electrodynamics model. The low-latitude electric fields generated by the neutral wind dynamo are altered only slightly by these additional terms. The resulting vertical electric fields (zonal plasma drifts) do not change significantly but the vertical plasma drifts are affected by ˜10 to 15 m/s in the hours before sunrise and after sunset. These low-latitude plasma drift differences are due entirely to the inclusion of the gravity-driven current. The gravity current term produces a downward drift after sunset, which reduces the evening prereversal enhancement. Additionally, the positive vertical drift before sunrise is sometimes large enough to cause a predawn vertical enhancement. The gradient pressure terms can be ignored for large and medium scale ionosphere features.

  8. Calculating Second-Order Effects in MOSFET's

    NASA Technical Reports Server (NTRS)

    Benumof, Reuben; Zoutendyk, John A.; Coss, James R.

    1990-01-01

    Collection of mathematical models includes second-order effects in n-channel, enhancement-mode, metal-oxide-semiconductor field-effect transistors (MOSFET's). When dimensions of circuit elements relatively large, effects neglected safely. However, as very-large-scale integration of microelectronic circuits leads to MOSFET's shorter or narrower than 2 micrometer, effects become significant in design and operation. Such computer programs as widely-used "Simulation Program With Integrated Circuit Emphasis, Version 2" (SPICE 2) include many of these effects. In second-order models of n-channel, enhancement-mode MOSFET, first-order gate-depletion region diminished by triangular-cross-section deletions on end and augmented by circular-wedge-cross-section bulges on sides.

  9. Initial results from the operation of two argon ion generators in the auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Erlandson, R. E.; Cahill, L. J., Jr.; Pollock, C. J.; Arnoldy, R. L.; Scales, W. A.

    1987-01-01

    Two argon ion generators have been lofted by sounding rockets in order to investigate ion beam dynamics and beam effects on the ionosphere, and auroral electrodynamics during rocket passage over auroral arcs. The ion generators were on a subpayload that was separated from the main payload early in the flight. The main payload conducted the diagnostic measurements during ion beam operations. Evidence of heating of the ionosphere around the subpayload during each ion beam emission is noted.

  10. Study of the mid-latitude ionospheric response to geomagnetic storms in the European region

    NASA Astrophysics Data System (ADS)

    Berényi, Kitti Alexandra; Barta, Veronika; Kis, Arpad

    2016-07-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere through different physical and atmospheric processes. The phenomena that can be regarded as a result of these processes, generally is named as "ionospheric storm". The processes depend on altitude, segment of the day, the geomagnetic latitude and longitude, strength of solar activity and the type of the geomagnetic storm. We examine the data of ground-based radio wave ionosphere sounding measurements of European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory) in order to determine how and to what extent a geomagnetic disturbance of a certain strength affects the mid-latitude ionospheric regions in winter and in summer. For our analysis we used disturbed time periods between November 2012 and June 2015. Our results show significant changing of the ionospheric F2 layer parameters on strongly disturbed days compared to quiet ones. We show that the critical frequencies (foF2) increase compared to their quiet day value when the ionospheric storm was positive. On the other hand, the critical frequencies become lower, when the storm was negative. In our analysis we determined the magnitude of these changes on the chosen days. For a more complete analysis we compare also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. The results present the evolution of an ionospheric storm over a geographic meridian. Furthermore, we compared the two type of geomagnetic storms, namely the CME caused geomagnetic storm - the so-called Sudden impulse (Si) storms- and the HSS (High Speed Solar Wind Streams) caused geomagnetic storms -the so-called Gradual storms (Gs)- impact on the ionospheric F2-layer (foF2 parameter). The results show a significant difference between the effect of Si and of the Gs storms on the ionospheric F2-layer.

  11. Magnetic Field Measurement on the C/NOFS Satellite: Geomagnetic Storm Effects in the Low Latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Le, Guan; Pfaff, Rob; Kepko, Larry; Rowland, Doug; Bromund, Ken; Freudenreich, Henry; Martin, Steve; Liebrecht, C.; Maus, S.

    2010-01-01

    The Vector Electric Field Investigation (VEFI) suite onboard the Communications/Navigation Outage Forecasting System (C/NOFS) spacecraft includes a sensitive fluxgate magnetometer to measure DC and ULF magnetic fields in the low latitude ionosphere. The instrument includes a DC vector measurement at 1 sample/sec with a range of +/- 45,000 nT whose primary objective is to provide direct measurements of both V x B and E x B that are more accurate than those obtained using a simple magnetic field model. These data can also be used for scientific research to provide information of large-scale ionospheric and magnetospheric current systems, which, when analyzed in conjunction with the C/NOFS DC electric field measurements, promise to advance our understanding of the electrodynamics of the low latitude ionosphere. In this study, we use the magnetic field data to study the temporal and local time variations of the ring currents during geomagnetic storms. We first compare the in situ measurements with the POMME (the POtsdam Magnetic Model of the Earth) model in order to provide an in-flight "calibration" of the data as well as compute magnetic field residuals essential for revealing large scale external current systems. We then compare the magnetic field residuals observed both during quiet times and during geomagnetic storms at the same geographic locations to deduce the magnetic field signatures of the ring current. As will be shown, the low inclination of the C/NOFS satellite provides a unique opportunity to study the evolution of the ring current as a function of local time, which is particularly insightful during periods of magnetic storms. This paper will present the initial results of this study.

  12. Monitoring the ionospheric positioning error with a GNSS dense network

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Lejeune, Sandrine; Warnant, René

    2010-05-01

    Local variability in the ionospheric Total Electron Content (TEC) can seriously affect the accuracy of GNSS real-time applications. In relative positioning, users have to compute the vector (called baseline) linking their receiver to a reference station for which the position is accurately known. As long as the ionosphere remains quiet (i.e. a background ionosphere with no local disturbance), the accuracy of relative positioning using phase measurements is of a few cm. The SoDIPE-RTK software developed at the Royal Meteorological Institute of Belgium allows to compute the part of the positioning error only due to the ionosphere (referred later as "ionospheric error") for a given baseline. In practice, baselines considered in this paper are not larger than 40km in order to ensure a successful ambiguity resolution process for both L1 and L2 carriers. More precisely, data analysed in the frame of this work are baselines belonging to the Belgian GPS dense network called Active Geodetic Network (AGN). SoDIPE-RTK has been applied on the whole network during typical ionospheric conditions: quiet, active and stormy. Active conditions refer to disturbed ionosphere due to the occurrence of Traveling Ionospheric Disturbances (TID's) while stormy conditions are relative to extremely disturbed plasma during the occurrence of powerful geomagnetic storms. From this dataset, we extract some descriptive statistics like average, standard deviation, extrema... of the ionospheric error. As expected, this term is centimeter-level during quiet conditions while maximum values are reached during stormy conditions. For a 10km baseline, one can observe ionospheric errors of about 15cm during the occurrence of a winter medium-scale TID (MSTID) and up to 1m during geomagnetic storms. Moreover, the availability of a dense network allows to study the influence of baseline orientation on ionospheric error magnitude. We have analysed two specific cases of moving ionospheric structures: a winter

  13. Full 3-D TLM simulations of the Earth-ionosphere cavity: Effect of conductivity on the Schumann resonances

    NASA Astrophysics Data System (ADS)

    Toledo-Redondo, S.; Salinas, A.; Fornieles, J.; Portí, J.; Lichtenegger, H. I. M.

    2016-06-01

    Schumann resonances can be found in planetary atmospheres, inside the cavity formed by the conducting surface of the planet and the lower ionosphere. They are a powerful tool to investigate both the electric processes that occur in the atmosphere and the characteristics of the surface and the lower ionosphere. Results from a full 3-D model of the Earth-ionosphere electromagnetic cavity based on the Transmission-Line Modeling (TLM) method are presented. A Cartesian scheme with homogeneous cell size of 10 km is used to minimize numerical dispersion present in spherical schemes. Time and frequency domain results have been obtained to study the resonance phenomenon. The effect of conductivity on the Schumann resonances in the cavity is investigated by means of numerical simulations, studying the transition from resonant to nonresonant response and setting the conductivity limit for the resonances to develop inside the cavity. It is found that the transition from resonant to nonresonant behavior occurs for conductivity values above roughly 10-9 S/m. For large losses in the cavity, the resonances are damped, but, in addition, the peak frequencies change according to the local distance to the source and with the particular electromagnetic field component. These spatial variations present steep variations around each mode's nodal position, covering distances around 1/4 of the mode wavelength, the higher modes being more sensitive to this effect than the lower ones. The dependence of the measured frequency on the distance to the source and particular component of the electric field offers information on the source generating these resonances.

  14. The ionospheric signature of flux transfer events

    SciTech Connect

    Southwood, D.J. )

    1987-04-01

    The author examines the motion of an isolated flux tube connecting the interplanetary and terrestrial magnetic field that has been created by reconnection at the dayside magnetopause. Such tubes should create a distinct localized flow pattern at their feet in the ionosphere. Observational effects are discussed. It is argued that the delay time of the order of a minute or more corresponding to the time for propagation of information from the reconnection site to the ionosphere is important and could control the creation of flux transfer events. It is predicted that magnetic pulsations in the Pc 5 frequency band are likely to be set up on closed flux tubes immediately neighboring the newly connected tubes.

  15. HIGHER ORDER HARD EDGE END FIELD EFFECTS.

    SciTech Connect

    BERG,J.S.

    2004-09-14

    In most cases, nonlinearities from magnets must be properly included in tracking and analysis to properly compute quantities of interest, in particular chromatic properties and dynamic aperture. One source of nonlinearities in magnets that is often important and cannot be avoided is the nonlinearity arising at the end of a magnet due to the longitudinal variation of the field at the end of the magnet. Part of this effect is independent of the longitudinal of the end. It is lowest order in the body field of the magnet, and is the result of taking a limit as the length over which the field at the end varies approaches zero. This is referred to as a ''hard edge'' end field. This effect has been computed previously to lowest order in the transverse variables. This paper describes a method to compute this effect to arbitrary order in the transverse variables, under certain constraints.

  16. A multiple receiver - multiple transmitter VLF high-order differential analysis evaluation network for near real-time detection and discrimination of seismic-ionospheric precursor phenomena

    NASA Astrophysics Data System (ADS)

    Skeberis, Christos; Zaharis, Zaharias; Xenos, Thomas; Spatalas, Spyridon; Stratakis, Dimitrios; Maggipinto, Tommaso; Biagi, Pier francesco

    2016-04-01

    This study provides an evaluation of the application of high-order differential analysis on VLF signals on a multiple-receiver multiple-transmitter network. This application provides a method for near-real-time detection of disturbances that can be attributed to seismic-ionospheric precursor phenomena and can discriminate disturbances that could be classified as false positives and thus should be attributed to other geomagnetic influences. VLF data acquired in Thessaloniki, Greece (40.59N, 22,78E) Herakleion, Greece (35.31N, 25.10E), Nicosia, Cyprus (35.17N, 33.35E), Italy (42.42N, 13.08E) and transmitted by the VLF station in Tavolara, Italy (ICV station 40.923N, 9.731E) and the station in Keflavik, Iceland (ICE 64.02N, 22.57W) from January 2015 to January 2016 were used for the purpose of this paper. The receivers have been developed by Elettronika Srl and are part of the International Network for Frontier Research on Earthquake Precursors (INFREP). The process applied for this study has been further developed and is based on differential analysis. The signals undergo transformation using an enhanced version of the Hilbert Huang Transform, and relevant spectra are produced. On the product of this process, differential analysis is applied. Finally, the method produces the correlation coefficient of signals that are on the same path over an earthquake epicenter in order to highlight disturbances, and on the opposite can make comparisons with unrelated transmitted signals of different paths to eliminate disturbances that are not localized to the area of interest. This improvement provides a simple method of noise cancellation to signals that would otherwise be considered as false positives. A further evaluation of the method is provided with the presentation and discussion of sample results. The method seems to be a robust tool of analysis of VLF signals and also an automatic detection tool with built-in noise cancellation of outside disturbances.

  17. On diurnal dependence and spatial scales of seismo-ionospheric effects in the E-layer

    NASA Astrophysics Data System (ADS)

    Liperovskaya, E. V.; Meister, C.-V.; Hoffmann, D. H. H.; Silina, A. S.

    In the present work, disturbances of the fbEs -frequency of the sporadic E-layer of the ionosphere are investigated in connection with earthquakes. The fbEs -frequency is proportional to the square root of the maximum ionisation density of the sporadic E-layer. In this work, it is shown that two days before a seismic shock with magnitude M > 5.5 , and during the shock, an increase of the fbEs -frequency is obtained around midnight at distances from the epicentre R < expM + 100 km in the case that the focus of the shock was situated at depths smaller than 60 km. Data obtained by the three ionospheric sounding stations "Kokubunji", "Akita" and "Yamagawa" are analysed, which were recorded during a total time of 42 years. The superimposed epoches method is applied for a few tens of earthquakes.

  18. A new global ionospheric model

    NASA Technical Reports Server (NTRS)

    Yip, K. W.; Vonroos, O. H.

    1975-01-01

    A new global ionospheric model was successfully implemented. The daytime portion of this model provides one-way ionospheric range corrections that compare favorably with those derived from the Mariner Venus/Mercury S- and X-band dual frequency Doppler data. For elevation angles, gamma higher than 30 deg and solar zenith angle less than 80 deg, this model provides calibrations accurate to a few centimeters. The calibrations provided by the nighttime model are also very reasonable. It is interesting to note that the daytime ionospheric calibrations derived from the current calibration scheme, DIEN/TIEN, are fairly close to those given by the new global model, especially in the temporal variations and thus the Doppler effects. The comparison between the nighttime model and DIEN/TIEN was based on the one-way ionospheric range corrections for three passes near the Mariner 9 encounter with Mars in 1971. They can differ by over 30%.

  19. The Effects of Magnetic Anomalies Discovered at Mars on the Structure of the Martian Ionosphere and the Solar Wind Interaction as Follows from Radio Occultation Experiments

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Acuna, M. H.; Connerney, J. E. P.; Cloutier, P.; Kliore, A. J.; Breus, T. K.; Krymskii, A. M.; Bauer, S. J.

    1999-01-01

    The electron density distribution in the ionosphere of nonmagnetic (or weakly magnetized) planet depends not only on the solar ultraviolet intensity, but also on the nature of the SW interaction with this planet. Two scenarios previously have been developed based on the observations of the bow shock crossings and on the electron density distribution within the ionosphere. According to one of them Mars has an intrinsic magnetosphere produced by a dipole magnetic field and the Martian ionosphere is protected from the SW flow except during "overpressure conditions, when the planetary magnetic field can not balance the SW dynamic pressure. In the second scenario the Martian intrinsic magnetic dipole field is so weak that Mars has mainly an induced magnetosphere and a Venus-like SW/ionosphere interaction. Today the possible existence of a sufficiently strong global magnetic field that participates in the SW/Mars interaction can no longer be supported. The results obtained by the Mars-Global-Surveyor (MGS) space-craft show the existence of highly variable, but also very localized magnetic fields of crustal origin at Mars as high as 400-1500 nT. The absence of the large-scale global magnetic field at Mars makes it similar to Venus, except for possible effects of the magnetic anomalies associated with the remnant crustal magnetization. However the previous results on the Martian ionosphere obtained mainly by the radio occultation methods show that there appears to be a permanent existence of a global horizontal magnetic field in the Martian ionosphere. Moreover the global induced magnetic field in the Venus ionosphere is not typical at the solar zenith angles explored by the radio occultation methods. Additional information is contained in the original extended abstract.

  20. Comparison of Ionospheric and Thermospheric Effects During Two High Speed Stream Events

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Tsurutani, B.; Mannucci, A. J.; Paxton, L.; Mlynczak, M. G.; Hunt, L. A.; Echer, E.

    2013-12-01

    We analyze two CIR-HSS events during ascending phase of the current solar cycle. The first event occurred on 8-12 May 2012 and was characterized by a large CIR and intense High Intensity Long Duration Continuous Auroral Activity (HILDCAA). Long-duration moderate geomagnetic storm (Dst ~ -50 nT) occurred during this event. The second event on 29 April - 4 May 2011 had a large CIR and extended HSS, but weaker geomagnetic activity. We focus on understanding differences and similarities of the magnetosphere-ionosphere-thermosphere coupling during these two events. We will use a suite of ground-based and satellite measurements to create a comprehensive picture of the events. Evolution of the polar cap convection pattern is analyzed based on SuperDARN data. DMSP/SSUSI far ultraviolet measurements provide information on airglow intensity and characteristics of the F-region of the dusktime ionosphere. The GPS total electron content (TEC) database and JPL's Global Ionospheric Maps (GIM) are used to study vertical TEC (VTEC) for different local times and latitude ranges. We discuss dynamics of VTEC above individual ground GPS sites with respect to local time and latitude ranges. We analyze the TIMED/SABER zonal flux of nitric oxide (NO) infrared cooling radiation and auroral heating throughout the events. Global dynamics of the column density ratio ΣO/N2 is studied based on TIMED/GUVI measurements. Our results will advance understanding of the ionosphere-thermosphere response to external forcing and help future forecasting efforts.

  1. General overview of the solar activity effects on the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Danilov, A. D.

    1989-01-01

    Solar activity influences the ionospheric D region. That influence manifests itself both in the form of various solar induced disturbances and in the form of the D region dependence on solar activity parameters (UV-flux, interplanetary magnetic field, solar wind etc.) in quiet conditions. Relationship between solar activity and meteorological control of the D region behavior is considered in detail and examples of strong variations of aeronomical parameters due to solar or meteorological events are given.

  2. Investigation of seismo-ionospheric effects associated with Elazig and Van earthquakes in Turkey

    NASA Astrophysics Data System (ADS)

    Shagimuratov, I.; Cherniak, Iu.; Zakharenkova, I.; Tepenitsyna, N.; Yakimova, G.

    2012-04-01

    This report presents the specific features of TEC (total electron content of the ionosphere) behavior associated with earthquakes 08 March 2010 (Elazıg, Mw 6.1) and devastating earthquake with M 7.3, occurred on 23 October 2011 in Van. For this purpose we used both the GPS TEC data from the nearest to the epicenter GPS-IGS stations and constructed TEC maps over Europe. The favorable circumstance for this analysis was the quiet geomagnetic situation during the period previous to the earthquakes (the sum of Kp didn't exceed 5 for first and less than 15 for second case). The typical anomaly was found out one week prior to Elazıg earthquake and three days prior to Van earthquake as the day-time significant increase of TEC at the nearest stations up to the value of 50% relative to the background condition. To estimate the spatial dimensions of seismo-ionospheric anomaly the differential mapping method was used. Anomalous TEC enhancement was registered since 10 UT and reached the maximal value of 45-55% at 18-20 UT. So, the seismo-ionospheric anomaly was found out as the cloud-shaped increase of total electron content of the ionosphere, it had a well-defined local character and it was situated in the immediate vicinity of the earthquake epicenter area. Acknowledgments. The authors are grateful to the IGS community for providing GPS permanent data and to the USGS Earthquake Hazards Program for the detailed earthquake information. The research leading to these results has received funding from the European Union Sevenths Framework Program (FP7/20017-2013) under grant agreement No. 263502 - PRE-EARTHQUAKES project.

  3. Ionospheric effects at low latitudes during the March 22, 1979, geomagnetic storm

    SciTech Connect

    Fesen, C.G. ); Crowley, G.; Roble, R.G. )

    1989-05-01

    This paper investigates the response of the equatorial ionosphere to the neutral atmosphere perturbations produced by the magnetic storm of March 22, 1979. A numerical model of the equatorial ionosphere is used to calculate the maximum electron densities and F layer heights associated with a storm-perturbed neutral atmosphere and circulation model. Possible electric field perturbations due to the storm are ignored. The neutral atmosphere and dynamics are simulated by the National Center for Atmospheric Research thermospheric general circulation model (TGCM) for the storm day of March 22, 1979, and the preceding quiet day. The most striking feature of the TGCM storm day simulations is the presence of waves in the neutral composition, wind, and temperature fields which propagate from high latitudes to the equator. The TGCM-calculated fields for the two days are input into a low-latitude ionosphere model which calculates n{sub max} and h{sub max} between {plus minus}20{degree}dip latitude. The calculated nighttime 6300-{angstrom} airglow emission and the altitude profiles of electron concentration are also highly perturbed by the storm. Examination of ionosonde data for March 22, 1979, shows remarkable agreement between the measured and predicted changes in f{sub 0}F{sub 2} and h{sub max} near 140{degree}W. Poorer agreement near 70{degree}W may be due to the neglect of electric field perturbations and the approximations inherent in the modeling. The results of these simulations indicate that the major factor influencing the storm time ionospheric behavior in this case is the neutral wind.

  4. Magnetosphere--Ionosphere Coupling: Effects of Plasma Alfven Wave Relative Motion

    NASA Astrophysics Data System (ADS)

    Christiansen, P. J.; Dum, C. T.

    1989-06-01

    The introduction of relative perpendicular motion between a flux-tube supporting shear Alfven wave activity and the background plasma is studied in the context of the coupling of a wave generating region with a distant ionosphere. The results of a representative simulation, using an extended version of the code developed by Lysak & Dum (J. geophys. Res. 88, 365 (1983)), are used as a basis for interpreting some aspects of recent satellite observations.

  5. Magnetosphere-ionosphere coupling: effects of plasma Alfvén wave relative motion.

    NASA Astrophysics Data System (ADS)

    Christiansen, P. J.; Dum, C. T.

    The introduction of relative perpendicular motion between a flux-tube supporting shear Alfvén wave activity and the background plasma is studied in the context of the coupling of a wave generating region with a distant ionosphere. The results of a representative simulation, using an extended version of the code developed by Lysak & Dum, are used as a basis for interpreting some aspects of recent satellite observations.

  6. A review of vertical coupling in the Atmosphere-Ionosphere system: Effects of waves, sudden stratospheric warmings, space weather, and of solar activity

    NASA Astrophysics Data System (ADS)

    Yiğit, Erdal; Koucká Knížová, Petra; Georgieva, Katya; Ward, William

    2016-04-01

    This brief introductory review of some recent developments in atmosphere-ionosphere science is written for the "Vertical Coupling Special Issue" that is motivated by the 5th IAGA/ICMA/SCOSTEP Workshop on Vertical Coupling in the Atmosphere-Ionosphere System. Basic processes of vertical coupling in the atmosphere-ionosphere system are discussed, focusing on the effects of internal waves, such as gravity waves and solar tides, sudden stratospheric warmings (SSWs), and of solar activity on the structure of the atmosphere. Internal waves play a crucial role in the current state and evolution of the upper atmosphere-ionosphere system. SSW effects extend into the upper atmosphere, producing changes in the thermospheric circulation and ionospheric disturbances. Sun, the dominant energy source for the atmosphere, directly impacts the upper atmosphere and modulates wave-induced coupling. The emphasis is laid on the most recent developments in the field, while giving credits to older works where necessary. Various international activities in atmospheric vertical coupling, such as SCOSTEP's ROSMIC project, and a brief contextual discussion of the papers published in the special issue are presented.

  7. Magnetosphere-ionosphere mapping at Jupiter: Quantifying the effects of using different internal field models

    NASA Astrophysics Data System (ADS)

    Vogt, Marissa F.; Bunce, Emma J.; Kivelson, Margaret G.; Khurana, Krishan K.; Walker, Raymond J.; Radioti, Aikaterini; Bonfond, Bertrand; Grodent, Denis

    2015-04-01

    The lack of global field models accurate beyond the inner magnetosphere (<30 RJ) makes it difficult to relate Jupiter's polar auroral features to magnetospheric source regions. We recently developed a model that maps Jupiter's equatorial magnetosphere to the ionosphere using a flux equivalence calculation that requires equal flux at the equatorial and ionospheric ends of flux tubes. This approach is more accurate than tracing field lines in a global field model but only if it is based on an accurate model of Jupiter's internal field. At present there are three widely used internal field models—Voyager Io Pioneer 4 (VIP4), the Grodent Anomaly Model (GAM), and VIP Anomaly Longitude (VIPAL). The purpose of this study is to quantify how the choice of an internal field model affects the mapping of various auroral features using the flux equivalence calculation. We find that different internal field models can shift the ionospheric mapping of points in the equatorial plane by several degrees and shift the magnetospheric mapping to the equator by ~30 RJ radially and by less than 1 h in local time. These shifts are consistent with differences in how well each model maps the Ganymede footprint, underscoring the need for more accurate Jovian internal field models. We discuss differences in the mapping of specific auroral features and the size and location of the open/closed field line boundary. Understanding these differences is important for the continued analysis of Hubble Space Telescope images and in planning for Juno's arrival at Jupiter in 2016.

  8. Effects of Energetic Solar Emissions on the Earth-Ionosphere Cavity of Schumann Resonances

    NASA Astrophysics Data System (ADS)

    Sátori, Gabriella; Williams, Earle; Price, Colin; Boldi, Robert; Koloskov, Alexander; Yampolski, Yuri; Guha, Anirban; Barta, Veronika

    2016-07-01

    Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower ionosphere (Schumann in Z Naturforsch A 7:6627-6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth's SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth-ionosphere cavity.

  9. Effects of Energetic Solar Emissions on the Earth-Ionosphere Cavity of Schumann Resonances

    NASA Astrophysics Data System (ADS)

    Sátori, Gabriella; Williams, Earle; Price, Colin; Boldi, Robert; Koloskov, Alexander; Yampolski, Yuri; Guha, Anirban; Barta, Veronika

    2016-03-01

    Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower ionosphere (Schumann in Z Naturforsch A 7:6627-6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth's SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth-ionosphere cavity.

  10. Ionospheric and Thermospheric Effects During the Initial Radiative Phase of the Bastille Day Event

    NASA Astrophysics Data System (ADS)

    Meier, R. R.; Drob, D. P.; Nicholas, A. C.; Bishop, J.; Picone, J. M.; Thonnard, S. E.; Dymond, K. F.; Budzien, S. A.; Lean, J.; Mariska, J. T.; Huba, J. D.; Joyce, G.; Warren, H. P.; Judge, D. L.

    2001-05-01

    Increases in the solar EUV and X-ray irradiance during a solar flare can produce enhanced ionization and heating in the terrestrial ionosphere. The resulting energetic photoelectrons in turn cause increases in the far ultraviolet (FUV) dayglow (100 - 150 nm). Enhancements of some 50 per cent had previously been detected in OGO-4 nadir-viewing data [C B Opal, Space Research XIII, 797, 1973]. Similar enhancements have now been seen in the FUV limb-viewing dayglow observations from the ARGOS satellite during the Bastille Day flare (July 14, 2000). Because extinction of the FUV dayglow by O2 prevents seeing below 140 km tangent altitude on the limb, increases in the dayglow above that altitude must be caused by the component of the flare spectral irradiance which is deposited there, namely at wavelengths greater than 20 nm. This conclusion is corroborated by the observation of the flare at 30.3 nm made by the SEM instrument on the SOHO satellite. We study this solar-ionospheric connection using a modified version of the NRL solar spectrum as input to the SAMI2 ionospheric model, and also calculate thermospheric heating rates for this event.

  11. An effect of the ionospheric Alfvén resonator on multiband Pc1 pulsations

    NASA Astrophysics Data System (ADS)

    Prikner, K.; Mursula, K.; Kangas, J.; Kerttula, R.; Feygin, F.

    2004-02-01

    . On 2 December 1999, the magnetometer stations in northern Finland registered structured Pc1 activity simultaneously in three distinct frequency bands. Using simultaneous EISCAT radar measurements of the high-latitude ionosphere, we have studied the ionospheric resonator properties during this multiband Pc1 event. The frequencies of the three structured Pc1 bands were found to closely correspond to the second, third and fourth harmonic of the calculated fundamental frequency of the ionospheric Alfvén resonator (IAR). In addition, those frequencies of the three pearl bands that were closest to the exact IAR harmonics were found to have the strongest intensities. The results demonstrate that the resonator can have an important role on ground-based Pc1 activity over a notably large frequency range, favoring transmission of waves with frequencies close to the resonator's eigenfrequencies. Since the frequencies of all three bands correspond to the maximum rather than the minimum of the transmission coefficient, the traditional bouncing wave packet model needs to be revised.

  12. Ionosphere-reflected propagation

    NASA Technical Reports Server (NTRS)

    Reddy, B. M.

    1979-01-01

    The predictability of those ionospheric parameters relevant to ionosphere-reflected communications is considered along with their optimum utilization. Several excellent original articles and review papers which have been published from time to time dealing with the long term and short term forecasting of ionospheric parameters, radio systems, and modelling needs for ionospheric communications, are covered.

  13. Development of an ionosphere-atmosphere coupled model for space weather forecast

    NASA Astrophysics Data System (ADS)

    Shinagawa, Hiroyuki; Jin, Hidekatsu; Miyoshi, Yasunobu; Fujiwara, Hitoshi; Fujita, Shigeru; Tanaka, Takashi; Terada, Naoki; Terada, Kaori

    The solar-terrestrial system consists of the solar atmosphere, the solar wind, the magneto-sphere, the ionosphere, and the neutral atmosphere. Those regions have different physical characteristics with different temporal and spatial scales. In particular, the magnetosphere, the ionosphere, and the neutral atmosphere are strongly coupled with each other, and inter-action between the regions is nonlinear and extremely complicated. Even within each region, there are strong interactions between different physical processes. Furthermore, the geospace environment significantly varies as electromagnetic energy and particles from the sun vary. In order to quantitatively understand such a complicated system, it is necessary to model the entire region by including all fundamental processes self-consistently. Various types of global numerical models of the geospace have been constructed by many institutions in the world, and used to study and predict geospace disturbances. At the National Institute of Information and Communications Technology (NICT), real-time solar wind, magnetosphere, and ionosphere-thermosphere models have been developed and used for daily space weather forecast. However, recent observations of the ionosphere and the thermosphere have revealed that atmospheric waves generated in the lower atmosphere significantly influence the upper atmosphere, the ionosphere, and possibly the magnetosphere. In order to quantitatively study the effects of the lower atmosphere on the ionosphere, we have developed an ionosphere-atmosphere coupled model, which includes the whole neutral atmosphere and the ionosphere. It is planned that the model is coupled with our magnetosphere and solar MHD models, which will be used for space weather forecast. We will report the status and future plan of our ionosphere-atmosphere coupled modeling.

  14. Modeling of sub-ionospheric VLF signal anomalies associated with precursory effects of the latest earthquakes in Nepal

    NASA Astrophysics Data System (ADS)

    Sasmal, Sudipta; Chakrabarti, Sandip Kumar; Palit, Sourav; Chakraborty, Suman; Ghosh, Soujan; Ray, Suman

    2016-07-01

    We present the nature of perturbations in the propagation characteristics of Very Low Frequency (VLF) signals received at Ionospheric & Earthquake Research Centre (IERC) (Lat. 22.50 ^{o}N, Long. 87.48 ^{o}E) during and prior to the latest strong earthquakes in Nepal on 12 May 2015 at 12:50 pm local time (07:05 UTC) with a magnitude of 7.3 and depth 18 km at southeast of Kodari. The VLF signal emitted from JJI transmitter (22.2kHz) in Japan (Lat. 32.08 ^{o}N, Long. 130.83 ^{o}E) shows strong shifts in sunrise and sunset terminator times towards nighttime beginning three to four days prior to the earthquake. The shift in terminator times is numerically simulated using Long Wavelength Propagation Capability (LWPC) code. Electron density variation as a function of height is calculated for seismically quiet days using the Wait's exponential profile and it matches with the IRI model. The perturbed electron density is calculated using the effective reflection height (h') and sharpness parameter (β) and the rate of ionization due to earthquake is being obtained by the equation of continuity for ionospheric D-layer. We compute the ion production and recombination profiles during seismic and non-seismic conditions incorporating D-region ion chemistry processes and calculate the unperturbed and perturbed electron density profile and ionization rate at different heights which matches with the exponential profile. During the seismic condition, for both the cases, the rate of ionization and the electron density profile differ significantly from the normal values. We interpret this to be due to the seismo-ionospheric coupling processes.

  15. Exploring the Cigala/calibra Network Data Base for Ionosphere Monitoring Over Brazil

    NASA Astrophysics Data System (ADS)

    Vani, B. C.; Galera Monico, J. F.; Shimabukuro, M. H.; Pereira, V. A.; Aquino, M. H.

    2013-12-01

    The ionosphere in Brazil is strongly influenced by the equatorial anomaly, therefore GNSS based applications are widely affected by ionospheric disturbances. A network for continuous monitoring of the ionosphere has been deployed over its territory since February/2011, as part of the CIGALA and CALIBRA projects. Through CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America), which was funded by European Commission (EC) in the framework of the FP7-GALILEO-2009-GSA (European GNSS Agency), the first stations were deployed at Presidente Prudente, São Paulo state, in February 2011. CIGALA was finalized in February 2012 with eight stations distributed over the Brazilian territory. Through CALIBRA (Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in BRAzil), which is also funded by the European Commission now in the framework of the FP7-GALILEO-2011-GSA, new stations are being deployed. Some of the stations are being specifically placed according to geomagnetic considerations aiming to support the development of a local scintillation and TEC model. CALIBRA started in November 2012 and will have two years of duration, focusing on the development of improved and new algorithms that can be applied to high accuracy GNSS techniques in order to tackle the effects of ionospheric disturbances. PolarRxS-PRO receivers, manufactured by Septentrio, have been deployed at all stations This multi-GNSS receiver can collect data at rates of up to 100 Hz, providing ionospheric TEC, scintillation parameters like S4 and Sigma-Phi, and other signal metrics like locktime for all satellites and frequencies tracked. All collected data (raw and ionosphere monitoring records) is stored at a central facility located at the Faculdade de Ciências e Tecnologia da Universidade Estadual Paulista (FCT/UNESP) in Presidente Prudente. To deal with the large amount of data, an analysis infrastructure has also been established

  16. Equatorial and Low-Latitudes Ionospheric Reaction to Solar Flares

    NASA Astrophysics Data System (ADS)

    Nicoli Candido, C. M.; Becker-Guedes, F.; Paula, E. R.; Takahashi, H.

    2015-12-01

    Solar X-ray and extreme ultraviolet (EUV) photons are responsible for ionizing the terrestrial atmosphere and create the ionosphere. During solar flares, a fast increase in the electron density at different altitude regions takes place due to the abrupt enhance of the X-ray and EUV fluxes reaching Earth. With these changes in the ionosphere, radio communication and navigation can be drastically affected. The magnitudes of these Space Weather events can be related to the X-ray peak brightness and duration, which drive the intensity of the ionosphere response when the associated electromagnetic wave hit the sunlit side of the Earth's atmosphere. Other aspects defining these changes in a particular region are the local time, the solar zenith angle, and the position of the flare in the solar disc for each event. In order to improve the understand of radio signal degradation and loss in the Brazilian sector due to solar abrupt electromagnetic emissions, total electron content (TEC) data obtained by a GPS network formed by tents of dual-frequency receivers spread all over Brazilian territory were analyzed. It was observed different ionospheric local changes during several X-ray events identified by GOES satellite regarding the 0.1-0.8 nm range, and some case studies were ponder for a more detailed analysis of these effects. Considering the results, we have made an estimation of the ionospheric disturbances range for a particular event with great chance to affect space based communications in the equatorial and low-latitude regions.

  17. Effects of a solar wind pressure pulse in the magnetosphere and in the ionosphere

    NASA Astrophysics Data System (ADS)

    Juusola, Liisa; Andreeova, Katerina; Palmroth, Minna; Amm, Olaf

    2010-05-01

    On 17 July 2005, an earthward bound north-south oriented magnetic cloud and its sheath were observed by the Advanced Composition Explorer (ACE), the Solar and Heliospheric Observatory (SoHO), and the Wind solar wind monitors. A steplike increase of the solar wind dynamic pressure was related to the leading edge of the sheath. A timing analysis between the three spacecraft revealed that this front was not aligned with GSE y axis, but tilted by an angle of about 55° towards the x axis. Hence, the first contact with the magnetosphere occured on the dawnside rather than at the subsolar point. Fortunately, Cluster, Double Star 1, and Geotail happened to be distributed close to the magnetopause in this region, which made it possible to closely monitor the motion of the magnetopause. When the pressure pulse impacted the magnetosphere, the magnetopause was perceived first to move inward and then immediatelly correct the overshoot by slightly expanding again such that it ended up between the Cluster constellation with Double Star 1 inside the magnetosphere and Geotail in the magnetosheath. In the ionosphere, the AE index showed a relatively weak enhancement with a peak of less than 200 nT. This enhancement lasted for about 10 minutes and coincided with the inward and subsequent outward motion of the magnetopause observed by the magnetospheric spacecraft. The ground-based International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network was also located on the dawn side during the arrival of the pressure pulse. The 1-D equivalent currents showed a peak of eastward current in the region covered by IMAGE, where the westward electrojet generally dominates at that time. After 10 minutes, the region of weakening eastward current was divided in two by the recovering westward electrojet. The 2-D equivalent currents further revealed that while the region of eastward current expanded from the east, the recovery of the westward electrojet began from the western edge

  18. Artificial defocusing lens in ionosphere

    NASA Astrophysics Data System (ADS)

    Boyko, G. N.; Vaskov, V. V.; Golyan, S. F.; Gurevich, A. V.; Dimant, Y. S.; Zyuzkin, V. A.; Kim, V. Y.; Komrakov, G. P.; Lobacheviskiy, L. A.; Migulin, V. V.

    1984-10-01

    Strong defocusing of perturbing radio waves is detected, indicating the creation of an effective defocusing lens in the ionosphere. Modess in which there is not anomalous absorption are employed in order to isolate the defocusing effects unambiguously. The experimental setup incorporates a 300 MW SURG heating system with a narrow radiation pattern. The concentration perturbations are diagnosed in the vertical sounding mode at 8 frequencies by means of a Doppler system. The experimental results were obtained during May and July 1983 under daytime conditions. The amplitude and Doppler frequency shift behavior of the probe wave is analyzed, and the defocusing coefficient is computed as a function of the frequency of the probe wave and power of the heating wave. The artificial lens detected results in significant attenuation of radio waves passing through it.

  19. Influence of the ionospheric model on DCB computation and added value of LEO satellites

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Lestarquit, Laurent; Loyer, Sylvain; Mercier, Flavien; Perosanz, Félix

    2016-04-01

    In order to compute inter-frequency Differential Code Biases (DCBs), the Geometry-Free combination of a GNSS signal pair needs to be corrected from the ionospheric refraction effect. Such information is obtained using either Global Ionospheric Maps (GIMs) or local models. In this work we investigate the influence of GIMs on the final value and precision of DCB solution. The study covers different ionospheric conditions, ranging from very quiet ionospheric background up to a severe ionospheric storm. In a first step, the Slant Total Electron Content (STEC) between GIMs is assessed as a function of receiver latitude, elevation mask and ionospheric conditions. Then, daily DCBs are estimated using these different GIMs, receiver and satellite contributions being separated using a zero-mean constraint. If the precision of satellite DCBs is clearly dependent on ionospheric conditions and of the observing network, the choice of the GIM seems also to have a non negligible impact. At last, an independent estimation of DCBs is performed using Low Earth Orbit (LEO) observations (such as JASON's GPS data). This solution is compared with our ground network solution and with DCBs coming from the International GNSS Service.

  20. Geomagnetic Storm Main Phase effect on the Equatorial Ionosphere as measured from GPS observations at Ile-Ife

    NASA Astrophysics Data System (ADS)

    Olabode, Ayomide; Ariyibi, Emmanuel

    2016-07-01

    The effect of the main phase of two intense geomagnetic storm events which occurred on August 5-6 and September 26-27, 2011 on the equatorial ionosphere have been investigated using Global Positioning System (GPS) data obtained from an Ile-Ife station (geomagnetic lat. 9.84°N, long. 77.25°E). The WinTEC-P and GPS-TEC analysis software programs were used to process the GPS data to obtain Total Electron Content (TEC) and Scintillation Index (S4). TEC profiles during the main phase of the two geomagnetically disturbed days were compared with quiet time average profiles to examine the response of the equatorial ionosphere. International Reference Ionosphere (IRI) 2012 TEC model was also obtained from Virtual Ionosphere, Thermosphere, Mesosphere Observatory (VITMO) and the extents of deviation from measured GPS-derived TEC were examined for the main phase of the storm events. The results showed that the intensity of both storm events during the main phase which occurred at night-time correlated well with a strong southward direction of the z-component of the Interplanetary Magnetic Field (IMF-Bz) and Solar Wind Speed (Vsw), with the Disturbance storm time (Dst) profile showing multiple step development. TEC depletion was observed during the main phase of the August 5-6, 2011 storm event with TEC recording a maximum value of 9.31 TECU. A maximum TEC value of 55.8 TECU was recorded during the main phase of the September 26-27, 2011 storm event depicting TEC enhancement. Significant scintillation index value of 0.57 was observed when the main phase started on August 5-6, 2011 followed by a prolonged suppression while there was less significant scintillation impact on September 26-27, 2011 with a maximum value of 0.33. The study concluded that the intensification of the ring current during the main phase of geomagnetic storm events was responsible for the intensity of the storm events causing large variations in TEC and significant scintillation phenomenon.

  1. Ionospheric corrections for GPS time transfer

    NASA Astrophysics Data System (ADS)

    Rose, Julian A. R.; Watson, Robert J.; Allain, Damien J.; Mitchell, Cathryn N.

    2014-03-01

    A real-time ionospheric mapping system is tested to investigate its ability to compensate for the ionospheric delay in single-frequency Global Positioning System (GPS) time transfer over Europe. This technique is compared with two other single-frequency systems: one that does not incorporate any ionospheric correction and one that uses the broadcast Klobuchar model. A dual-frequency technique is also shown as a benchmark. A period in March 2003, during a solar maximum, has been used to display results when the ionospheric delays are large and variable. Data from two European GPS monitoring centers were used to test the time-transfer methods. For averaging times between several minutes and a few hours, the instabilities in the time transfers were dominated by ionospheric effects. The instabilities at longer averaging times were found to be due to clock noise and hardware instabilities. Improvements in time-transfer instabilities are shown by using the ionospheric tomography system.

  2. Interaction of Titan's ionosphere with Saturn's magnetosphere.

    PubMed

    Coates, Andrew J

    2009-02-28

    Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude. PMID:19073464

  3. Ionospheric variability over Japan

    NASA Astrophysics Data System (ADS)

    Ezquer, R. G.; Mosert, M.; Corbella, R.; Erazu, M.; de La Zerda, L.

    The understanding of ionospheric variability is important for the user of ionospheric models. A satellite designer or operator needs to know not only monthly average conditions but also the expected deviations from these mean values. In order to contribute to the studies on ionospheric variability, in this paper values of critical frequencies of F2, F1 and E regions and M(3000)F2 factor measured at 4 Japanese stations are used. Data correspond to equinoxes, solstices, high and low solar activity. Quartiles and median values are used to specify variability, because they have the advantage of being less affected by large deviations that can occur during magnetic storms. The results are similar for the considered stations and show that the highest variability correspond to foF2. For March high solar activity the variability of fof2 decreases during hours of maximum ionisation. The M3000F2 factor, in general, shown low variability. Akita (39.72° N, 140.13° E) showed the highest variability for the three frequencies. Moreover, it can be seen that quartiles are not equidistant from the median value.

  4. Ionospheric research for space weather service support

    NASA Astrophysics Data System (ADS)

    Stanislawska, Iwona; Gulyaeva, Tamara; Dziak-Jankowska, Beata

    2016-07-01

    Knowledge of the behavior of the ionosphere is very important for space weather services. A wide variety of ground based and satellite existing and future systems (communications, radar, surveillance, intelligence gathering, satellite operation, etc) is affected by the ionosphere. There are the needs for reliable and efficient support for such systems against natural hazard and minimalization of the risk failure. The joint research Project on the 'Ionospheric Weather' of IZMIRAN and SRC PAS is aimed to provide on-line the ionospheric parameters characterizing the space weather in the ionosphere. It is devoted to science, techniques and to more application oriented areas of ionospheric investigation in order to support space weather services. The studies based on data mining philosophy increasing the knowledge of ionospheric physical properties, modelling capabilities and gain applications of various procedures in ionospheric monitoring and forecasting were concerned. In the framework of the joint Project the novel techniques for data analysis, the original system of the ionospheric disturbance indices and their implementation for the ionosphere and the ionospheric radio wave propagation are developed since 1997. Data of ionosonde measurements and results of their forecasting for the ionospheric observatories network, the regional maps and global ionospheric maps of total electron content from the navigational satellite system (GNSS) observations, the global maps of the F2 layer peak parameters (foF2, hmF2) and W-index of the ionospheric variability are provided at the web pages of SRC PAS and IZMIRAN. The data processing systems include analysis and forecast of geomagnetic indices ap and kp and new eta index applied for the ionosphere forecasting. For the first time in the world the new products of the W-index maps analysis are provided in Catalogues of the ionospheric storms and sub-storms and their association with the global geomagnetic Dst storms is

  5. Effect of meteoroid ablation in the chemistry of the martian ionosphere

    NASA Astrophysics Data System (ADS)

    Pandya, B.; Haider, S.

    2014-07-01

    Comets release streams of dust particles at their perihelion distance due to the normal process of gas ejection. These particles of micron-size or larger are called micro-meteoroids and the meteoroids leave the comet nucleus at a speed of less than the orbital speed of the comets. When the planet Mars passes through such a meteoroid dust stream periodically, the meteoroids and micrometeoroids enter the martian atmosphere and encounter a suitable density of atmospheric gases, such as O_2, CO_2, CO, O, O_3, NO, N_2, to ablaze. This ablation produces ionization in the lower ionosphere at an altitude between 60-120 km. We use a coupled chemical model to calculate the density of abundant meteoric ions Mg, Fe, and Si with their neutrals and their compositions with atmospheric gases. We have observed that comets P/2003 WC7 (LINEAR Catalina) and 10P/ Tempel 2 intersected the orbit of Mars on 18 April 2004 and 11 May 2005, respectively. The meteoroids of fluxes 4.0×10^{-15} and 8.3×10^{-16} cm^{-2} s^{-1} and of masses 4.5×10^{-7} g and 1.0×10^{-3} g have produced a third ionospheric layer of electron densities, in good agreement with the electron density profiles observed by Mars Express and Mars Global Surveyor on April 18, 2004 and 11 May 11, 2005, respectively. The densities of 21 ions (CO_2+, O_2+, CO+, O+, NO+, N_2+, Mg+, Fe+, Si+, MgO+, FeO+, SiO+, MgCO_2+, MgO_2+, FeCO_2+, FeO_2+, SiCO_2+, SiO_2+, MgN_2+, FeN_2+, and SiN_2+) have been computed self-consistently for both days. It is observed that the lower ionosphere of Mars is strongly dependent on the incoming velocity, mass, and flux of the meteoroids. We have calculated a total ion production rate and a total ion density for meteoroids of with sizes from 10 g to 10^{-12} g entering the martian atmosphere with initial speeds of 10 km/s and 18 km/s. Micro-meteoroids with an incoming speed of 18 km/sec and mass between 10^{-5} g to 10^{-12} g ablaze and produce a significantly high total ion density between ˜0

  6. Toward More Effective Comparison of Measured and Modeled Ionospheric Data Using Madrigal During the International Polar Year

    NASA Astrophysics Data System (ADS)

    Rideout, W.; Holt, J. M.; van Eyken, A. P.; Heinselman, C.

    2007-12-01

    The International Polar Year is associated with an unprecedented increase in the measurement and modeling of the polar ionosphere. This has opened the opportunity to dramatically improve the quality of the models and the underlying physical understanding, allowing improved now-casting and forecasting of the ionosphere. The Madrigal database is the traditional database used for distributing upper atmospheric data, and is used by all the incoherent scatter radar sites. The Madrigal database has also been shown to be an effective tool for distributing modeling data. One critical issue in improving models through comparison with measurements is the non-standard data products presently used by the varying incoherent scatter radars. While the parameters measured are standard, the spatial and temporal cadences of the measurements often vary widely, even for a given incoherent scatter radar. While there are various technical and scientific reasons for these variations, they do make the comparison to model runs much more difficult. In this work we discuss a higher level data product that all incoherent scatter radars can produce. This higher level product would not contain all the information in the standard products of each incoherent scatter radar, but should include all the capabilities shared by all the radars. Our experience developing a prototype of such a data product here at Millstone Hill will be discussed, along with a discussion of how this higher level data product can be distributed via the Madrigal database and more easily compared with model runs.

  7. Model study of the effects of gravity wave dissipation on the thermosphere and ionosphere from deep convection worldwide

    NASA Astrophysics Data System (ADS)

    Vadas, Sharon; Liu, Hanli

    In this paper, we discuss the methods and results of a global modeling study for the effect of deep convection on the thermosphere and ionosphere through the dissipation of atmospheric gravity waves (GWs). The selected time periods are 15-27 June 2009, during the recent extreme solar minimum, and 15-27 June 2000, during the recent solar maximum. The convective plumes which overshot the tropopause are identified from IR images obtained by 5 satellites covering the Earth during each period. We model the excitation of GWs from these plumes, and ray trace them into the thermosphere using our ray trace model which has been upgraded to span the Earth. We then calculate the forcings/heatings/coolings which result when and where these GWs dissipate in the thermosphere. We input these forcings/heatings/coolings into the global TIME-GCM, and re-run the model. In this paper, we discuss these methods and models in detail. We then discuss how the thermosphere and ionosphere responded to the dissipation of these convectively-generated GWs worldwide. We show that the responses propagate westward due to wind filtering by tides in the lower thermosphere. We also show that the neutral temperature and wind perturbations are larger during extreme solar minimum than during solar maximum.

  8. Study of the effects of solar activities on the ionosphere as observed by VLF signals recorded at TNU station, Vietnam

    NASA Astrophysics Data System (ADS)

    Tan, L. M.

    2015-12-01

    A SuperSID monitor installed at Tay Nguyen University (TNU), Vietnam is used to detect the temporal variations of Very Low Frequency (VLF) signals during 2013 and 2014 to understand the responses of the ionosphere to sunset/sunrise transitions and solar flares. Two VLF station signals are tracked, JJI/22.2 kHz in Japan and NWC/19.8 kHz in Australia. Results show that the effects of sunrise, sunset and solar flares on the NWC signal are more significantly different than those on the JJI signal. Sunset and sunrise spikes only occur on the JJI-TNU path because of longitudinal differences between the receiver and transmitter. Two sunset dips and three sunrise dips appear on the NWC signal during summer season. During intense solar flares, the dips occur after the maximum disturbance of the VLF signals for the North-South path. The appearance of these dips is explained by modal interference patterns. Observing temporal variations of sunrise and sunset dips or spikes of VLF signals during different seasons enhances the understanding of the behavior of the ionosphere.

  9. Effects of a "day-time" substorm on the ionosphere and radio propagation

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskiy, Donat; MacDougall, John, , Dr; Kalishin, Aleksei

    Experimental studies were carried out using data from the Tromso ionosonde, the CUTLASS radar, the IMAGE system of magnetometers, the Finnish riometer chain, and oblique ionospheric sounding on a Murmansk - St. Petersburg path. An example of a day-time substorm with amplitude of about 200 nT for October 25, 2003 from 13:00 to 18:00 UT is described. During the substorm there was a southward movement of the region of particle precipitation causing a band of the irregularities to move to latitudes 62 - 64o. The velocity of displacement southward is about 15o per hour. Oblique ionograms on the Murmansk - St. Petersburg radio path showed diffuse traces caused by scatter due to the spread F, or by refraction from ionospheric gradients. Based on this, and a number of other substorm studies, the following conclusions are: 1) During an intensive substorm, precipitation regions with ionospheric irregularities are displaced to 62 - 64o maqgnetc latitude. 2) Increased absorption during the substorm most likely does not affect the amplitude of obliquely propagating signals. Blocking the F2-reflections by intense sporadic Es-layers with high conductivity plays rather a more important part. 3) The usual mechanism of radio propagation along the great circle arc is sometimes changed from reflections via the F2- and E-layers simultaneously to only the reflection via Es-layer. 4) Lateral oblique signal propagation is not observed for every substorm. It is possible if the path midpoint is located near the precipitation region where there are irregularities which are quickly displaced, during the substorm, from high latitudes to lower.

  10. Global effects on Ionospheric Weather over the Indian subcontinent at Sunrise and Sunset

    SciTech Connect

    Basak, Tamal; Pal, S.; Chakrabarti, S. K.

    2010-10-20

    Study of Very Low Frequency (VLF) electromagnetic wave is very important for knowing the behavior of the Ionospheric layers due to Sunrise-Sunset, Earthquakes, Solar flares, Solar eclipses and other terrestrial and extra terrestrial radiations. We study the properties of the variation of the VLF signal strength theoretically all over Indian sub-continent. As an example, we concentrate on the VLF signal transmitted by Indian Naval Transmitter VTX at Vijayanarayanam (Latitude 08 deg. 23', Longitude 77 deg. 45') near the southern tip of Indian subcontinent. As has been noticed, several receiving stations placed during the VLF campaign in all over India, the VLF signal strength varies significantly with place and time. To understand the diurnal and seasonal variation of the received signal, a complete knowledge of physics of intensity distribution of the VLF signal is essential. The spatial variation of VLF signal plays an important role in selecting future VLF stations. In the wave-hop theoretical model presented here, horizontally stratified ionospheric layers have been considered. The VLF wave emitted by the transmitter has both the ground wave and the sky wave components. The ground wave attenuates during propagation. The sky wave component experiences reflections by the ionosphere on its way to the receiver and its attenuation depends on the degree of ionization. Intensity variation occurs at a given receiver location for interference among singly and multiply reflected waves. This has been simulated considering some simplified and justifiable assumptions. This spatial variation wave-hop theoretical model developed here has been compared with LWPC code generated results.

  11. Effects of the large June 1975 meteoroid storm on earth's ionosphere

    NASA Astrophysics Data System (ADS)

    Kaufmann, P.; Kuntz, V. L. R.; Paes Leme, N. M.; Piazza, L. R.; Vilas Boas, J. W. S.

    1989-11-01

    The meteoroid storm of June, 1975 generated pronounced disturbances on the earth, recorded as unique phase anomalies on VLF radio-propagation paths in the low terrestrial ionosphere during the June 20-30 period. Large nocturnal phase-advances lasting several hours were detected on several days at all VLF transmissions; they are noted to have been comparable, for the shorter propagation path, to solar Ly-alpha diurnal ionization. The storm was sporadic, with an apparent origin in the sky over the Southern Hemisphere whose right ascension was 1-2 hours larger than that of the sun.

  12. GBAS Ionospheric Anomaly Monitoring Based on a Two-Step Approach

    PubMed Central

    Zhao, Lin; Yang, Fuxin; Li, Liang; Ding, Jicheng; Zhao, Yuxin

    2016-01-01

    As one significant component of space environmental weather, the ionosphere has to be monitored using Global Positioning System (GPS) receivers for the Ground-Based Augmentation System (GBAS). This is because an ionospheric anomaly can pose a potential threat for GBAS to support safety-critical services. The traditional code-carrier divergence (CCD) methods, which have been widely used to detect the variants of the ionospheric gradient for GBAS, adopt a linear time-invariant low-pass filter to suppress the effect of high frequency noise on the detection of the ionospheric anomaly. However, there is a counterbalance between response time and estimation accuracy due to the fixed time constants. In order to release the limitation, a two-step approach (TSA) is proposed by integrating the cascaded linear time-invariant low-pass filters with the adaptive Kalman filter to detect the ionospheric gradient anomaly. The performance of the proposed method is tested by using simulated and real-world data, respectively. The simulation results show that the TSA can detect ionospheric gradient anomalies quickly, even when the noise is severer. Compared to the traditional CCD methods, the experiments from real-world GPS data indicate that the average estimation accuracy of the ionospheric gradient improves by more than 31.3%, and the average response time to the ionospheric gradient at a rate of 0.018 m/s improves by more than 59.3%, which demonstrates the ability of TSA to detect a small ionospheric gradient more rapidly. PMID:27240367

  13. GBAS Ionospheric Anomaly Monitoring Based on a Two-Step Approach.

    PubMed

    Zhao, Lin; Yang, Fuxin; Li, Liang; Ding, Jicheng; Zhao, Yuxin

    2016-01-01

    As one significant component of space environmental weather, the ionosphere has to be monitored using Global Positioning System (GPS) receivers for the Ground-Based Augmentation System (GBAS). This is because an ionospheric anomaly can pose a potential threat for GBAS to support safety-critical services. The traditional code-carrier divergence (CCD) methods, which have been widely used to detect the variants of the ionospheric gradient for GBAS, adopt a linear time-invariant low-pass filter to suppress the effect of high frequency noise on the detection of the ionospheric anomaly. However, there is a counterbalance between response time and estimation accuracy due to the fixed time constants. In order to release the limitation, a two-step approach (TSA) is proposed by integrating the cascaded linear time-invariant low-pass filters with the adaptive Kalman filter to detect the ionospheric gradient anomaly. The performance of the proposed method is tested by using simulated and real-world data, respectively. The simulation results show that the TSA can detect ionospheric gradient anomalies quickly, even when the noise is severer. Compared to the traditional CCD methods, the experiments from real-world GPS data indicate that the average estimation accuracy of the ionospheric gradient improves by more than 31.3%, and the average response time to the ionospheric gradient at a rate of 0.018 m/s improves by more than 59.3%, which demonstrates the ability of TSA to detect a small ionospheric gradient more rapidly. PMID:27240367

  14. Response of Ionosphere to the Tropospheric disturbances

    NASA Astrophysics Data System (ADS)

    Maurya, A. K.; Dube, A.; Singh, R.; Cohen, M.

    2015-12-01

    The aim of the present work is to find out response of the ionosphere to the various cases of tropical cyclones. The main process involved is suggested through Atmospheric Gravity waves (AGWs) originating from strong convective systems, propagating upward upto the ionospheric heights and perturbing ionospheric parameters (Bishop et al., 2006). We have used ground and satellite data to extract cyclone induced perturbations at different ionospheric heights along with the various parameters of AGWs during cyclones and associated thunderstorm. The initial results suggest that there is increase in total electron content of the ionosphere with wave like signatures in ionosphere. The satellite observation in optical band shows presence of concentric gravity wave pattern associated with troposphere disturbances with horizontal wavelength of ~50-200km and periods ranging from hours to days. The ground based Very Low Frequency (VLF) measurement shows fluctuations in VLF navigational transmitter signal passing over the region of disturbance. The lightning data from GLD360 lightning network shows intense activity associated with cyclones and increase in lightning peak current and energy during main phase of cyclones which seems to be sufficient enough to derive ionospheric disturbances in the ionosphere. This multi-instrument analysis provide detail information of the three dimensional structure of cyclone and their effect at different altitudes of the ionosphere in the Indian subcontinent.

  15. Modelling ionospheric density structures

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.; Sojka, J. J.

    1989-01-01

    Large-scale density structures are a common feature in the high-latitude ionsphere. The structures were observed in the dayside cusp, polar cap, and nocturnal auroral region over a range of altitudes, including the E-region, F-region and topside ionosphere. The origins, lifetimes and transport characteristics of large-scale density structures were studied with the aid of a three-dimensional, time-dependent ionospheric model. Blob creation due to particle precipitation, the effect that structured electric fields have on the ionosphere, and the lifetimes and transport characteristics of density structures for different seasonal, solar cycle, and interplanetary magnetic field (IMF) conditions were studied. The main conclusions drawn are: (1) the observed precipitation energy fluxes are sufficient for blob creation if the plasma is exposed to the precipitation for 5 to 10 minutes; (2) structured electric fields produce structured electron densities, ion temperatures, and ion composition; (3) the lifetime of an F-region density structure depends on several factors, including the initial location where it was formed, the magnitude of the perturbation, season, solar cycle and IMF; and (4) depending on the IMF, horizontal plasma convection can cause an initial structure to break up into multiple structures of various sizes, remain as a single distorted structure, or become stretched into elongated segments.

  16. MLT Asymmetries in the Magnetospheric Wave Distribution and Their Effect on Ionospheric Conductivity and Global Transport

    NASA Astrophysics Data System (ADS)

    Thorne, R. M.; Li, W.; Bortnik, J.; Ni, B.; Jordanova, V.; Kletzing, C.; Kurth, W. S.; Hospodarsky, G. B.; Angelopoulos, V.

    2014-12-01

    Diffuse auroral precipitation is the major source of ionospheric conductivity at high latitudes, and the resulting global distribution of enhanced conductivity affects the penetration of magnetospheric electric fields and plasma transport into the inner magnetosphere. Recent work has demonstrated that diffuse auroral precipitation is caused by resonant scattering of plasma sheet electrons due to a combination of both electrostatic electron cyclotron harmonic waves and electromagnetic whistler mode chorus emissions. Each class of wave is excited, predominantly on the dawn side of the magnetosphere, following the convective injection and gradient drifting of plasma sheet electrons into the inner magnetosphere. During geomagnetically active periods, the resultant electron scattering can approach the limit of strong diffusion, and the timescale for scattering loss into the atmosphere becomes shorter than the time for transport of plasma to the dayside. This leads to a pronounced day/night asymmetry in the diffuse auroral precipitation and a localized enhancement in conductivity in the post midnight sector. Quantifying the rate of diffuse auroral scattering by each class of wave is therefore imperative for understanding the global distribution of enhanced ionospheric conductivity and its non-linear feedback on plasma transport in the inner magnetosphere. Recent attempts to model the observed global distribution of waves and the associated pattern of electron precipitation will be discussed.

  17. The terrestrial ionosphere

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.

    1983-01-01

    The theory relating to the basic physics governing the behavior of the terrestrial ionosphere is reviewed. The review covers the coupling of the ionosphere to both the neutral atmosphere and magnetosphere, the creation and transport of ionization in the ionosphere, and the ionospheric thermal structure. The review also covers the variation of the ionosphere with altitude, latitude, longitude, universal time, season, solar cycle, and geomagnetic activity. In addition, some unique ionospheric features are discussed, such as the polar ionization hole, the main electron density trough, the ion temperature hot spots, the high-latitude ionization tongue, the equatorial fountain, Appleton's peaks, and the polar wind.

  18. Studies on the dynamics of Venus ionosphere - Effects of varying the ionopause height and the onset of turbulence

    NASA Technical Reports Server (NTRS)

    Singhal, R. P.; Whitten, R. C.

    1991-01-01

    The conservation equations of plasma dynamics in the upper ionosphere of Venus have been solved by using a spectral method in the horizontal and finite differencing in the vertical direction. The effect of varying the ionopause height on the computed nightside ion densities is investigated. These ion densities show a sharp decrease as the ionopause altitude is reduced to 300 km. The effect of viscous forces on the horizontal plasma flow is investigated for a wide range of values of the coefficient of viscosity. The Reynolds numbers characteristics of the flow are calculated and the conditions for the onset of turbulence discussed. It is found that the Reynolds number can be large (greater than 1000) in the subsolar region for a coefficient of viscosity of up to 1.6 x 10 to the -10th g/cm s. The influence of magnetic fields on viscosity is also discussed.

  19. Effects of solar wind dynamic pressure on the ionospheric O+ fluence during the 31 August 2005 storm

    NASA Astrophysics Data System (ADS)

    Damiano, P. A.; Brambles, O. J.; Lotko, W.; Zhang, B.; Wiltberger, M.; Lyon, J.

    2010-11-01

    The Multifluid-Lyon-Fedder-Mobarry (MFLFM) global simulation model incorporating an ionospheric cusp O+ outflow model based on an empirical relation between downward DC Poynting flux and O+ outflow flux regulated by the precipitating electron number flux (Fen) is used to simulate the 31 August 2005 storm. A baseline run incorporating the original solar wind data is contrasted against a case where the solar wind dynamic pressure (Pdyn) is artificially adjusted to see what effects this variable has on the O+ fluence generated in the model. Consistent with data, it is found that both the fluence and O+ outflow flux have a positive correlation with the solar wind dynamic pressure. Additionally, changes in Pdyn affect the downward Poynting flux only marginally and regulates both outflow flux and cusp outflow area via Fen. Increases in Pdyn lead to increased cusp electron precipitation, which has the physical effect of enhancing the upwelling O+ population available for outflow.

  20. Effect of Mutation Order on Myeloproliferative Neoplasms

    PubMed Central

    Nangalia, Jyoti; Silber, Yvonne; Wedge, David C.; Grinfeld, Jacob; Baxter, E. Joanna; Massie, Charles E.; Papaemmanuil, Elli; Menon, Suraj; Godfrey, Anna L.; Dimitropoulou, Danai; Guglielmelli, Paola; Bellosillo, Beatriz; Besses, Carles; Döhner, Konstanze; Harrison, Claire N.; Vassiliou, George S.; Vannucchi, Alessandro; Campbell, Peter J.; Green, Anthony R.

    2015-01-01

    BACKGROUND Cancers result from the accumulation of somatic mutations, and their properties are thought to reflect the sum of these mutations. However, little is known about the effect of the order in which mutations are acquired. METHODS We determined mutation order in patients with myeloproliferative neoplasms by genotyping hematopoietic colonies or by means of next-generation sequencing. Stem cells and progenitor cells were isolated to study the effect of mutation order on mature and immature hematopoietic cells. RESULTS The age at which a patient presented with a myeloproliferative neoplasm, acquisition of JAK2 V617F homozygosity, and the balance of immature progenitors were all influenced by mutation order. As compared with patients in whom the TET2 mutation was acquired first (hereafter referred to as “TET2-first patients”), patients in whom the Janus kinase 2 (JAK2) mutation was acquired first (“JAK2-first patients”) had a greater likelihood of presenting with polycythemia vera than with essential thrombocythemia, an increased risk of thrombosis, and an increased sensitivity of JAK2-mutant progenitors to ruxolitinib in vitro. Mutation order influenced the proliferative response to JAK2 V617F and the capacity of double-mutant hematopoietic cells and progenitor cells to generate colony-forming cells. Moreover, the hematopoietic stem-and-progenitor-cell compartment was dominated by TET2 single-mutant cells in TET2-first patients but by JAK2–TET2 double-mutant cells in JAK2-first patients. Prior mutation of TET2 altered the transcriptional consequences of JAK2 V617F in a cell-intrinsic manner and prevented JAK2 V617F from up-regulating genes associated with proliferation. CONCLUSIONS The order in which JAK2 and TET2 mutations were acquired influenced clinical features, the response to targeted therapy, the biology of stem and progenitor cells, and clonal evolution in patients with myeloproliferative neoplasms. (Funded by Leukemia and Lymphoma Research

  1. Solitons versus parametric instabilities during ionospheric heating

    NASA Technical Reports Server (NTRS)

    Nicholson, D. R.; Payne, G. L.; Downie, R. M.; Sheerin, J. P.

    1984-01-01

    Various effects associated with ionospheric heating are investigated by numerically solving the modified Zakharov (1972) equations. It is shown that, for typical ionospheric parameters, the modulational instability is more important than the parametric decay instability in the spatial region of strongest heater electric field. It is concluded that the modulational instability leads to the formation of solitons, as originally predicted by Petviashvili (1976).

  2. Ionospheric disturbances produced by powerful explosives

    NASA Astrophysics Data System (ADS)

    Nagorskii, P. M.; Tarashchuk, Yu. E.

    1992-09-01

    Results of a study of wave-like ionospheric disturbances initiated by powerful explosives are presented and analyzed. Three types of wave processes with differing physical natures which propagate in the upper atmosphere and ionosphere to distances of thousands of kilometers are distinguished. The effect of shock-acoustic waves on indirect short wave radio propagation is considered.

  3. Effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using an analog model of the global atmospheric electric circuit

    NASA Astrophysics Data System (ADS)

    Rycroft, M. J.; Odzimek, A.

    2010-06-01

    A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (˜1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere (presumed to be an equipotential surface at 80 km altitude) to ˜250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair-weather atmosphere in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile, the effects of both negative and positive cloud-to-ground (CG) lightning discharges on the ionospheric potential have been estimated. A large positive CG discharge creates an electric field that exceeds the breakdown field from the ionosphere down to ˜74 km, thereby forming a halo, a column sprite, and some milliseconds later, from ˜67 km down to ˜55 km at ˜60 ms after the discharge, a “carrot” sprite. Estimates are made of the return stroke current and the thundercloud charge moment change of a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, (Coulomb.kilometers), respectively, and those at 70 km altitude are 45 kA and 360 C.km, respectively. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from recent observations. The current flowing in the highly conducting sprite reduces the ionospheric potential by ˜1 V.

  4. Effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using an analog model of the global atmospheric electric circuit

    NASA Astrophysics Data System (ADS)

    Rycroft, M. J.; Odzimek, A.

    2010-06-01

    A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (˜1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere (presumed to be an equipotential surface at 80 km altitude) to ˜250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair-weather atmosphere in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile, the effects of both negative and positive cloud-to-ground (CG) lightning discharges on the ionospheric potential have been estimated. A large positive CG discharge creates an electric field that exceeds the breakdown field from the ionosphere down to ˜74 km, thereby forming a halo, a column sprite, and some milliseconds later, from ˜67 km down to ˜55 km at ˜60 ms after the discharge, a "carrot" sprite. Estimates are made of the return stroke current and the thundercloud charge moment change of a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, (Coulomb.kilometers), respectively, and those at 70 km altitude are 45 kA and 360 C.km, respectively. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from recent observations. The current flowing in the highly conducting sprite reduces the ionospheric potential by ˜1 V.

  5. The effects of lightning and sprites on the ionospheric potential, and threshold effects on sprite initiation, obtained using a PSpice model

    NASA Astrophysics Data System (ADS)

    Rycroft, Michael J.; Odzimek, Anna

    2010-05-01

    A quantitative model of the global atmospheric electric circuit has been constructed using the PSpice electrical engineering software package. Currents (~ 1 kA) above thunderstorms and electrified rain/shower clouds raise the potential of the ionosphere, which is presumed to be an equipotential surface at 80 km altitude, to ~ 250 kV with respect to the Earth's surface. The circuit is completed by currents flowing down through the fair weather atmosphere, in the land/sea surface and up to the cloud systems. Using a model for the atmospheric conductivity profile (Rycroft et al., JASTP, 2007), the effects of both negative and positive cloud-to-ground (CG) lightning discharges ion the ionospheric potential have been estimated. A large positive CG discharge creates an electric field which exceeds the breakdown field from the ionosphere down to ~ 74 km, so forming a halo and a column sprite, and, some ms later, from ~ 67 km down to ~ 55 km at ~ 60 ms after the discharge, thereby forming a "carrot" sprite. Estimates are made of the return stroke current and the thundercloud charge moment change (CMC) for a +CG discharge required to exceed the threshold breakdown field, or the threshold field for creating and sustaining negative or positive streamers. The values for breakdown at 80 km altitude are 35 kA and 350 C.km, respectively, and 45 kA and 360 C.km at 70 km altitude. The different temporal and spatial developments of the mesospheric electric field distinguishing between column and carrot sprites agree with the latest deductions from from recent observations. A current flowing in the highly conducting sprite reduces the ionospheric potential by ~ 1 V.

  6. Effects of Meteorological Variability on the Thermosphere-Ionosphere System during the Moderate Geomagnetic Disturbed January 2013 Period As Simulated By Time-GCM

    NASA Astrophysics Data System (ADS)

    Maute, A. I.; Hagan, M. E.; Richmond, A. D.; Liu, H.; Yudin, V. A.

    2014-12-01

    The ionosphere-thermosphere system is affected by solar and magnetospheric processes and by meteorological variability. Ionospheric observations of total electron content during the current solar cycle have shown that variability associated with meteorological forcing is important during solar minimum, and can have significant ionospheric effects during solar medium to maximum conditions. Numerical models can be used to study the comparative importance of geomagnetic and meterological forcing.This study focuses on the January 2013 Stratospheric Sudden Warming (SSW) period, which is associated with a very disturbed middle atmosphere as well as with moderately disturbed solar geomagntic conditions. We employ the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) with a nudging scheme using Whole-Atmosphere-Community-Climate-Model-Extended (WACCM-X)/Goddard Earth Observing System Model, Version 5 (GEOS5) results to simulate the effects of the meteorological and solar wind forcing on the upper atmosphere. The model results are evaluated by comparing with observations e.g., TEC, NmF2, ion drifts. We study the effect of the SSW on the wave spectrum, and the associated changes in the low latitude vertical drifts. These changes are compared to the impact of the moderate geomagnetic forcing on the TI-system during the January 2013 time period by conducting numerical experiments. We will present select highlights from our study and elude to the comparative importance of the forcing from above and below as simulated by the TIME-GCM.

  7. Topside Ionospheric Sounder for CubeSats

    NASA Astrophysics Data System (ADS)

    Swenson, C.; Pratt, J.; Fish, C. S.; Winkler, C.; Pilinski, M.; Azeem, I.; Crowley, G.; Jeppesen, M.; Martineau, R.

    2014-12-01

    This presentation will outline the design of a Topside Ionospheric Sounder (TIS) for CubeSats. In the same way that an ionosonde measures the ionospheric profile from the ground, a Topside Sounder measures the ionospheric profile from a location above the F-region peak. The TIS will address the need for increased space situational awareness and environmental monitoring by estimating electron density profiles in the topside of the ionosphere. The TIS will measure topside electron density profiles for plasma frequencies ranging from 0.89 MHz to 28.4 MHz below the satellite altitude. The precision of the measurement will be 5% or 10,000 p/cm^3. The TIS average power consumption will be below 10 W and a mass of less than 10 kg, so it is appropriate for a 6U Cubesat (or multiple of that size). The sounder will operate via a transmitted frequency sweep across the desired plasma frequencies which, upon reception, can be differenced to determine range and density information of the topside ionosphere. The velocity of the spacecraft necessitates careful balancing of range resolution and frequency knowledge requirements as well as novel processing techniques to correctly associate the return signal with the correct plasma frequency. TIS is being designed to provide a low cost, low mass spacecraft that can provide accurate topside profiles of the ionospheric electron density in order to further understanding of ionospheric structure and dynamic processes in the ionosphere.

  8. Effect of dust on the ionosphere of 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Vigren, E.; Galand, M.; Lavvas, P.; Wahlund, J.-E.; Eriksson, A. I.

    2014-04-01

    The ESA Rosetta mission is a unique cometary mission consisting both of an orbiter and a lander. The orbiter will follow comet 67P/Churyumov- Gerasimenko (67P) closely from August 2014 to the end of the nominal mission in December 2015. The comet passes perihelion in August 2015, at heliocentric distance of ~1.3 AU. At that stage 67P is expected to be actively outgassing. The gas, dominated by H2O, carries with it dust particles to the coma and for 67P, near perihelion, the dust-to-gas mass emission ratio is anticipated to exceed 1. The well-developed coma/ionosphere, will be probed in situ e.g. by the dual Langmuir probe (LAP) [1] and the Mutual Impedance Probe (MIP) [2], which are parts of the Rosetta Plasma Consortium (RPC) [3], and by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) [4], providing e.g., electron and ion number densities down to cometocentric distances of ~5-20 km. We present a model of the ionization balance in the diamagnetic cavity of 67P near perihelion. The model builds upon an earlier presented pure gasphase model [5]. The updated model takes into account gas-dust interactions. We aim in particular to qualitatively address the potential role of grains in the ionization balance and discuss the possibility of a significant level of electron depletion due to electron attachment to grains of different sizes. The study is in part motivated by the discovery of a pronounced level of electron depletion in the plume of Enceladus, which has been attributed to nanograin charging [6,7]. On the one hand we argue that grains with radii of ~ 100 nm and more are unlikely to significantly affect the overall ionospheric particle balance of 67P at least for cometocentric distances >10 km. On the other hand, our simulations suggest that if nanograins with radii in the 1-3 nm range are as ubiquitous (~1% with respect to the gas in terms of mass) in the coma of 67P as in the Enceladus plume a pronounced level of electron depletion can

  9. Investigations into the properties, conditions, and effects of the ionosphere. Technical report, 4 December 1986-3 December 1987

    SciTech Connect

    Bussey, R.M.; Fremouw, E.J.; Reinisch, B.W.; Szuszczewicz, E.P.

    1988-01-15

    The investigations address ionospheric composition, structure, specification, scintillation, and chemistry, as well as remote sensing of the ionosphere through ultraviolet sensors. Specific work is carried out in the following six categories: laboratory measurements; field measurements; aircraft measurements; rocket, balloon, shuttle, and satellite measurements; analytical and theoretical investigations; and scientific and engineering analysis.

  10. The effect of the induced magnetic field on the electron density vertical profile of the Mars' ionosphere: A Mars Express MARSIS radar data analysis and interpretation, a case study

    NASA Astrophysics Data System (ADS)

    Ramírez-Nicolás, M.; Sánchez-Cano, B.; Witasse, O.; Blelly, P.-L.; Vázquez, L.; Lester, M.

    2016-07-01

    We report the indirect detection of an induced magnetic field in the ionosphere of Mars and its effects on the electron density behaviour. The observations were made by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) aboard Mars Express, in its Active Ionospheric Sounding mode. During several orbits on June 2006, the ionosphere showed an unusual behaviour, characterised by a compression of the plasma above the main ionospheric peak as observed by the topside total electron content, the plasma scale height, and the local plasma in the Mars Express surroundings. The compression was most likely due to an induced magnetic field originating from the solar wind and measured by the MARSIS antennas, which was able to penetrate into the ionosphere. In particular, for several profiles, the density distribution can be clearly defined by two different plasma scale heights, which indicates a transition region between both of them. From the balance of magnetic and thermal plasma pressures and from a comparison with a numerical model of the Martian ionosphere, the hypothesis of a penetrating induced magnetic field down to a transition altitude around 150 km is confirmed. This compressed ionosphere has also been compared with data from other orbits in the same location and at the same time period, i.e. 18.5 days of difference between first and last orbits, where there is no measured induced magnetic field, and the orbits show a clearly different behaviour.

  11. Speed-dependent collision effects on radar back-scattering from the ionosphere. [incoherent scatter radar

    NASA Technical Reports Server (NTRS)

    Behl, Y. K.; Theimer, O. H.

    1982-01-01

    The question whether the differences between fluctuation spectra for linearly speed-dependent and speed-independent collision frequencies could account for disagreements between rocket and incoherent scatter estimate was addressed. The basic theory used for computing the fluctuation spectrum is outlined. The speed-dependence of the charge-neutral collision frequency is discussed, with special emphasis on its derivation from the mobility measurements. Various developments of the computer code used for the computation of the fluctuation spectrum are described. The range of values of input parameters typical to the collision-dominated ionosphere are briefly described. The computational results are presented, and the significance and limitation of these results and the future scope of the research are discussed.

  12. Dipole Tilt Angle Effects on Joule and Particle Heating in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Chun, F. K.; Knipp, D. J.; McHarg, M. G.; Lu, G.; Emery, B. A.

    2002-12-01

    Previous work by Chun et al. [2002] presented spatial distributions of Joule heating as a function of the polar cap (PC) index and the season (summer, equinox, and winter). Noticeable differences in the Joule heating maps were observed with respect to both geomagnetic activity and the season. In this study, we present average patterns of height-integrated Pedersen and Hall conductivity, electric potential, Joule heating, and electron particle heating as a function of PC and dipole tilt angle using 56 days (approximately 12,800 individual patterns) of Assimilative Mapping of Ionospheric Electrodynamics (AMIE) data. We investigate differences in the spatial distributions as well as the hemispheric integrated Joule and particle heating. We also present spatial distributions of the ratios of the Joule to particle heating and the Hall to Pedersen conductance as a function of PC and dipole tilt angle.

  13. Electrodynamics of the Nighttime Equatorial Ionosphere: the Effects of Winds and Waves

    NASA Astrophysics Data System (ADS)

    Gelinas, L. J.; Kelley, M. C.; Clemmons, J.; Larsen, M.; Makela, J.

    2004-12-01

    In this paper we present initial results from two sounding rockets designed to study the coupling bewteen neutral winds and electric fields in the equatorial ionosphere. The combined instrumented and chemical release payloads were launched from Kwajalein in September 2004. The rockets carried instruments measuring electric fields, plasma densities, neutral densities, and was accompanied by a TMA release to profile neutral winds. Ground based airglow imagers and were used to determine mesospheric conditions; specifically, the presence of gravity waves. The goal of the experiment was to investigate correlations between the gravity wave wind structure and local electric fields. This coupling is expected to be appreciable at the equator, where the magnetic field is nearly horizontal. Here we present initial results and discuss plans for data analysis.

  14. Plasma effects of active ion beam injections in the ionosphere at rocket altitudes

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.; Cahill, L. J., Jr.; Kintner, P. M.; Moore, T. E.; Pollock, C. J.

    1992-01-01

    Data from ARCS rocket ion beam injection experiments are primarily discussed. There are three results from this series of active experiments that are of particular interest in space plasma physics. These are the transverse acceleration of ambient ions in the large beam volume, the scattering of beam ions near the release payload, and the possible acceleration of electrons very close to the plasma generator which produce intense high frequency waves. The ability of 100 ma ion beam injections into the upper E and F regions of the ionosphere to produce these phenomena appear to be related solely to the process by which the plasma release payload and the ion beam are neutralized. Since the electrons in the plasma release do not convect with the plasma ions, the neutralization of both the payload and beam must be accomplished by large field-aligned currents (milliamperes/square meter) which are very unstable to wave growth of various modes.

  15. The effect of the solar cycle on the maintenance of the nightside ionosphere of Venus

    NASA Technical Reports Server (NTRS)

    Kliore, Arvydas J.; Luhmann, Janet G.; Zhang, Martina H. G.

    1991-01-01

    The behavior of the Venus nightside ionosphere at solar maximum and solar minimum is discussed based on Pioneer Venus radio occultation measurements. Although some solar maximum measurements are similar to those observed at minimum, which have an average peak density of about 7000/cu cm, others show much higher peak densities, reaching values of about 40,000/cu cm. These elevated peak densities also occur at higher altitudes. The integrated electron column densities for these measurements indicate the presence of substantial ionization above the main peak. The magnitudes of both the peak density and the integrated content above the peak are anticorrelated with the solar wind dynamic pressure, indicating that these enhancements during solar maximum are due to transterminator transport of O(+) ions from the dayside. The resulting ionization peak can be many times the concentration produced by energetic electron fluxes impacting the neutral atmosphere on the nightside.

  16. Statistical study of possible pre-, co- (coeval to) and post- earthquake effects in the near-equatorial, low and mid latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Gousheva, Mariyana; Danov, Dimitar; Hristov, Plamen; Georgieva, Katya

    This paper presents the quasi-static electric field disturbances in the upper ionosphere observed from the satellite INTERCOSMOS-BULGARIA-1300 over earthquakes' source regions at different latitudes. The earthquake data were obtained from United State Geological Survey (USGS) website. In the present paper, an attempt of a statistical stady of ionospheric effects during seismic activity in August- November 1981 is presented. Present study focuses on four main areas- (i) satellite and seismic data selection, (ii) data processing and observations of some most important experimental results, (iii) comparison of observational new data with the results in our previous studies, (iiii) statistical study of possible pre-, co- (coeval to) and postearthquake effects in the near-equatorial, low and mid latitude ionosphere. After review of observational results we analyze an increase of about 5-10-15 mV/m in the vertical component of the quasi-static electric field observed by INTERCOSMOS-BULGARIA-1300 in the upper ionosphere above earthquakes sources during seismic activity. The obtained results strengthen our previous studies (Gousheva et al., 2005a, b; 2006a, b; 2007a, b).The paper discusses the observed effects. The main goal of this study is to generalize our results of possible connection between anomalous vertical electric fields penetrating from the earthquake zone into the ionosphere, and seismic activity. An additional goal of this study is to evaluate some morphological peculiarities of quasi-static electric field disturbances such as their appearance time before and after the main shock, sensitivity, amplitude and time duration.

  17. A Model of Callisto's Ionosphere

    NASA Astrophysics Data System (ADS)

    Hartkorn, O. A.; Saur, J.; Bloecker, A.; Strobel, D. F.; Simon, S.

    2014-12-01

    We develop a model of the ionosphere of Jupiter's moon Callisto, where we assume a stationary balance between sources and sinks of electrons and electron energy. Hence, effects of electron transport and electron energy transport are neglected. At Callisto, the production of electrons and electron energy is basically driven by photoionization, which is implemented using the EUVAC model for solar activity. Dissociative recombination is the main electron loss process, whereas electron energy loss is further driven by dissociation, electron impact ionization as well as vibrational and rotational excitations of neutral atmospheric particles. All these effects are incorporated within our model by considering the associated cross sections. The neutral atmosphere is assumed to be stationary and consists of molecular oxygen with a column density of 3 to 4 x 1020 m-2 (e.g. Kliore et al. (2002), Liang et al. (2005)). Our results can be compared to radio occultation observations of four Galileo spacecraft flybys reported by Kliore et al. (2002), which shows that this simple model can explain the general pattern of the observational data. Indeed, our results indicate that the detection of enhanced electron densities is very sensitive to the exact position of the tangential point of the radio occultation method. Our model shows that photoionization produces a strong asymmetry of the electron density distribution between day and night-side of the moon. Further, model results for the electron energy allow for an estimation of the day glow of Callisto's atmosphere. This can be compared to HST observations (Strobel et al. (2002)) in order to evaluate the density of the neutral oxygen atmosphere. Future studies imply the modeling of the modification of the ionospheric structure through interaction with upstreaming jovian magnetospheric plasma.

  18. Photochemistry of planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Nagy, Andrew F.

    1987-01-01

    The dominant photochemical reactions taking place in the ionospheres of Venus, Saturn, and Comet P/Halley are presented. It is shown that the differences in the ionospheres of these celestial bodies result from the different chemistry, energetics, and dynamics of the respective atmospheres. The role of photochemistry in the formation of the individual ionospheres is discussed.

  19. Ionospheric data assimilation and forecasting during storms

    NASA Astrophysics Data System (ADS)

    Chartier, Alex T.; Matsuo, Tomoko; Anderson, Jeffrey L.; Collins, Nancy; Hoar, Timothy J.; Lu, Gang; Mitchell, Cathryn N.; Coster, Anthea J.; Paxton, Larry J.; Bust, Gary S.

    2016-01-01

    Ionospheric storms can have important effects on radio communications and navigation systems. Storm time ionospheric predictions have the potential to form part of effective mitigation strategies to these problems. Ionospheric storms are caused by strong forcing from the solar wind. Electron density enhancements are driven by penetration electric fields, as well as by thermosphere-ionosphere behavior including Traveling Atmospheric Disturbances and Traveling Ionospheric Disturbances and changes to the neutral composition. This study assesses the effect on 1 h predictions of specifying initial ionospheric and thermospheric conditions using total electron content (TEC) observations under a fixed set of solar and high-latitude drivers. Prediction performance is assessed against TEC observations, incoherent scatter radar, and in situ electron density observations. Corotated TEC data provide a benchmark of forecast accuracy. The primary case study is the storm of 10 September 2005, while the anomalous storm of 21 January 2005 provides a secondary comparison. The study uses an ensemble Kalman filter constructed with the Data Assimilation Research Testbed and the Thermosphere Ionosphere Electrodynamics General Circulation Model. Maps of preprocessed, verticalized GPS TEC are assimilated, while high-latitude specifications from the Assimilative Mapping of Ionospheric Electrodynamics and solar flux observations from the Solar Extreme Ultraviolet Experiment are used to drive the model. The filter adjusts ionospheric and thermospheric parameters, making use of time-evolving covariance estimates. The approach is effective in correcting model biases but does not capture all the behavior of the storms. In particular, a ridge-like enhancement over the continental USA is not predicted, indicating the importance of predicting storm time electric field behavior to the problem of ionospheric forecasting.

  20. Developing an Error Model for Ionospheric Phase Distortions in L-Band SAR and InSAR Data

    NASA Astrophysics Data System (ADS)

    Meyer, F. J.; Agram, P. S.

    2014-12-01

    Many of the recent and upcoming spaceborne SAR systems are operating in the L-band frequency range. The choice of L-band has a number of advantages especially for InSAR applications. These include deeper penetration into vegetation, higher coherence, and higher sensitivity to soil moisture. While L-band SARs are undoubtedly beneficial for a number of earth science disciplines, their signals are susceptive to path delay effects in the ionosphere. Many recent publications indicate that the ionosphere can have detrimental effects on InSAR coherence and phase. It has also been shown that the magnitude of these effects strongly depends on the time of day and geographic location of the image acquisition as well as on the coincident solar activity. Hence, in order to provide realistic error estimates for geodetic measurements derived from L-band InSAR, an error model needs to be developed that is capable of describing ionospheric noise. With this paper, we present a global ionospheric error model that is currently being developed in support of NASA's future L-band SAR mission NISAR. The system is based on a combination of empirical data analysis and modeling input from the ionospheric model WBMOD, and is capable of predicting ionosphere-induced phase noise as a function of space and time. The error model parameterizes ionospheric noise using a power spectrum model and provides the parameters of this model in a global 1x1 degree raster. From the power law model, ionospheric errors in deformation estimates can be calculated. In Polar Regions, our error model relies on a statistical analysis of ionospheric-phase noise in a large number of SAR data from previous L-band SAR missions such as ALOS PALSAR and JERS-1. The focus on empirical analyses is due to limitations of WBMOD in high latitude areas. Outside of the Polar Regions, the ionospheric model WBMOD is used to derive ionospheric structure parameters for as a function of solar activity. The structure parameters are

  1. Driving mechanism of the nightside ionospheric convection

    NASA Astrophysics Data System (ADS)

    Kikuchi, T.

    2001-12-01

    Magnetometer and SuperDARN observations provided evidence of the instantaneous reaction of ionospheric convection on the dayside and nightside. The AMIE analyses revealed that the potential pattern did not move but remained nearly at fixed locations. SuperDARN observations demonstrated that the plasma motion in the nightside ionosphere was intensified immediately after the motion of dayside ionospheric plasma was intensified within a resolution of the measurement (2 min). The convection in the night-side polar ionosphere would cause the plasma convection in the near-earth magnetotail. In the companion paper (Hashimoto and Kikuchi, this meeting) we demonstrate that the growth phase signature at the geosynchronous orbit and the ground magnetic signatures of the partial ring currents developed several minutes after the magnetic reconnection at the dayside magnetopause. These results suggest that the electric field responsible for the convection in the near-Earth magnetotail propagated from the night-side polar ionosphere after having propagated from the magnetosphere to the polar ionosphere on the dayside. In order to explain the quick response of the nightside ionospheric convection, we examine possible propagation modes that could transmit the convection electric field from the dayside outer magnetosphere to the nightside ionosphere. The magnetospheric convection may be generated either by accumulation of the FTEs or by the dynamo action in the cusp and the HLBL. In either case, the electric field propagates from the dayside magnetosphere to the nightside ionosphere within a few minutes. One possible propagation mode would be the magnetosonic wave propagating across the geomagnetic field and the other is the shear Alfvén mode propagating parallel to the geomagnetic field. The magnetosonic waves would be totally reflected at the ionosphere and the resultant electric field would be vanished almost completely. On the other hand, the convective motion of the plasma can

  2. Effects of solar wind high-speed streams on the high-latitude ionosphere: Superposed epoch study

    NASA Astrophysics Data System (ADS)

    Grandin, M.; Aikio, A. T.; Kozlovsky, A.; Ulich, T.; Raita, T.

    2015-12-01

    Solar wind high-speed streams (HSSs) are the most important source of geomagnetic disturbances during the declining phase of the solar cycle. Their ionospheric response, especially at high latitudes, is not fully understood yet. We carried out a phase-locked superposed epoch analysis to study the effects of HSSs on the high-latitude ionospheric F region, using data from the Sodankylä ionosonde (L = 5.25) during 2006-2008. We found that the F layer critical frequency foF2 decreases between 12 and 23 magnetic local time (MLT) in summer and around equinoxes for several days. Our interpretation, supported by numerical estimations, is that increased electric fields in the evening sector of the auroral and subauroral regions create ion-neutral frictional heating. Frictional heating will increase the loss rate of O+ due to two reasons. The first one is neutral heating producing thermal expansion of the atmosphere and enhancing N2 and O2 contents at the F region peak. The second one is ion heating which may occur under strong enough electric fields (about 50-60 mV/m), leading to enhancement of the reaction coefficients. An increase in foF2 is observed in two different MLT sectors. First, a short-lived foF2 increase is visible during all seasons near noon on the first day after the arrival of the HSS, possibly triggered by the compressed solar wind plasma pressure pulse, which may produce particle precipitation from the dayside central plasma sheet. Second, foF2 is enhanced for several days in the morning sector during equinoxes and in winter. We suggest that this is caused by the low-energy tail of particle precipitation.

  3. Earthquake-Ionosphere Coupling Processes

    NASA Astrophysics Data System (ADS)

    Kamogawa, Masashi

    an ionospheric phenomenon attributed to tsunami, termed tsunamigenic ionospheric hole (TIH) [Kakinami and Kamogwa et al., GRL, 2012]. After the TEC depression accompanying a monoperiodic variation with approximately 4-minute period as an acoustic resonance between the ionosphere and the solid earth, the TIH gradually recovered. In addition, geomagnetic pulsations with the periods of 150, 180 and 210 seconds were observed on the ground in Japan approximately 5 minutes after the mainshock. Since the variation with the period of 180 seconds was simultaneously detected at the magnetic conjugate of points of Japan, namely Australia, field aligned currents along the magnetic field line were excited. The field aligned currents might be excited due to E and F region dynamo current caused by acoustic waves originating from the tsunami. This result implies that a large earthquake generates seismogenic field aligned currents. Furthermore, monoperiodical geomagnetic oscillation pointing to the epicenter of which velocity corresponds to Rayleigh waves occurs. This may occur due to seismogenic arc-current in E region. Removing such magnetic oscillations from the observed data, clear tsunami dynamo effect was found. This result implies that a large EQ generates seismogenic field aligned currents, seismogenic arc-current and tsunami dynamo current which disturb geomagnetic field. Thus, we found the complex coupling process between a large EQ and an ionosphere from the results of Tohoku EQ.

  4. Ray trace calculation of ionospheric propagation at lower frequencies

    NASA Astrophysics Data System (ADS)

    Reilly, Michael H.

    2006-10-01

    The Raytrace/Ionospheric Conductivity and Electron Density-Bent-Gallagher model has been revised to make it applicable to ionospheric propagation at low radio frequencies (0.5-5.0 MHz), where the ionosphere and magnetic anisotropy drastically alter propagation paths and provide a severe test of propagation model algorithms. The necessary revisions are discussed, and the model is applied to the problem of ionospheric penetration from a source below the ionosphere to a receiver above the ionosphere. It is necessary to include the electron collision frequency in the Appleton-Hartree index of refraction in order to permit ionospheric penetration for radio frequencies below the maximum plasma frequency (e.g., whistler modes). The associated reformulation of the ray trace equations for a complex index of refraction is straightforward. Difficulties with numerical methods are cited for the lowest frequencies, and future improvements are indicated.

  5. The Ionospheres of Europa, Ganymede, and Callisto

    NASA Astrophysics Data System (ADS)

    Kliore, A. J.; Anabtawi, A.; Nagy, A. F.

    2001-12-01

    The U.S. Galileo spacecraft, which has been in orbit around Jupiter since December, 1995, has provided opportunities to collect s-band radio occultation data using the 70 meter antennas of the NASA/JPL Deep Space Net(DSN) at Goldstone, California, Madrid, Spain, and Canberra, Australia. To date, four occultations and one near-occultation by Europa (J2) have been observed. They have shown the presence of electron plasma having a density near the surface of 10,000 to 20,000 cm-3 (Kliore, et al., Science, 277, 1997). If the underlying neutral atmosphere is assumed to consist of H2O or O2, the maximum neutral density near the surface can be inferred to be about 108 cm-3. Ganymede (J3) has also been observed five times by Galileo radio occultation. The results are almost entirely negative, with only one measurement out of ten yielding a possible observation of an ionosphere having a maximum density of about 5,000 cm-3 at an altitude of about 16 km. The failure to observe an ionosphere on Ganymede is at first glance surprising, in view of the detection of oxygen and hydrogen above its surface (c.f., Hall, et al., Astrophys. J., 499, 1998; Barth, et al., GRL, 24, 1997), and it was thought to be due to the shielding effect of Ganymede's magnetic field upon the impinging particles from Jupiter's magnetosphere. Callisto has occulted Galileo four times, and these observations have produced some interesting results. Of the eight individual measurements , two are negative, and six are positive. Two of those six, show unmistakable classic ionospheric layers, having peak electron densities of 15,000 to 20,000 cm-3 . A closer examination of all of these results has revealed a plausible reason for why some observations yield positive results , and some do not. It appears that in order for an ionosphere to be observed, the trailing hemisphere of the satellite must be in sunlight. In that way, the atmosphere created by sputtering effects of the Jovian magnetosphere can be ionized by

  6. Effects of a strong ICME on the Martian ionosphere as detected by Mars Express and Mars Odyssey

    NASA Astrophysics Data System (ADS)

    Morgan, D. D.; Diéval, C.; Gurnett, D. A.; Duru, F.; Dubinin, E. M.; Fränz, M.; Andrews, D. J.; Opgenoorth, H. J.; Uluşen, D.; Mitrofanov, I.; Plaut, J. J.

    2014-07-01

    We present evidence of a substantial ionospheric response to a strong interplanetary coronal mass ejection (ICME) detected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board the Mars Express (MEX) spacecraft. A powerful ICME impacted the Martian ionosphere beginning on 5 June 2011, peaking on 6 June, and trailing off over about a week. This event caused a strong response in the charged particle detector of the High-Energy Neutron Detector (HEND) on board the Odyssey spacecraft. The ion mass spectrometer of the Analyzer of Space Plasmas and Energetic Atoms instrument on MEX detected an increase in background counts, simultaneous with the increase seen by HEND, due to the flux of solar energetic particles (SEPs) associated with the ICME. Local densities and magnetic field strengths measured by MARSIS and enhancements of 100 eV electrons denote the passing of an intense space weather event. Local density and magnetosheath electron measurements and remote soundings show compression of ionospheric plasma to lower altitudes due to increased solar wind dynamic pressure. MARSIS topside sounding of the ionosphere indicates that it is extended well beyond the terminator, to about 116° solar zenith angle, in a highly disturbed state. This extension may be due to increased ionization due to SEPs and magnetosheath electrons or to plasma transport across the terminator. The surface reflection from both ionospheric sounding and subsurface modes of the MARSIS radar was attenuated, indicating increased electron content in the Mars ionosphere at low altitudes, where the atmosphere is dense.

  7. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

    Bernhardt, P.A.; Price, K.M.; da Rosa, A.V.

    1980-06-01

    This report describes experimental and theoretical studies related to ionospheric disturbances produced by rocket exhaust vapors. The purpose of our research was to estimate the ionospheric effects of the rocket launches which will be required to place the Satellite Power System (SPS) in operation. During the past year, we have developed computational tools for numerical simulation of ionospheric changes produced by the injection of rocket exhaust vapors. The theoretical work has dealt with (1) the limitations imposed by condensation phenomena in rocket exhaust; (2) complete modeling of the ionospheric depletion process including neutral gas dynamics, plasma physics, chemistry and thermal processes; and (3) the influence of the modified ionosphere on radio wave propagation. We are also reporting on electron content measurements made during the launch of HEAO-C on Sept. 20, 1979. We conclude by suggesting future experiments and areas for future research.

  8. Chemical releases in the ionosphere

    NASA Technical Reports Server (NTRS)

    Davis, T. N.

    1979-01-01

    The study of the interaction between the atmosphere, ionosphere and magnetosphere is identified as a major task worthy of pursuit. The present review demonstrates the major contributions to this complex problem already made by active experiments involving the injection of chemicals and energetic electron beams into the atmosphere, ionosphere and magnetosphere. Through the use of chemical releases, it has been possible to investigate a number of quantities including high-altitude winds and electric fields, the detailed configurations of the geomagnetic field within the ionosphere and the magnetosphere, as well as the propagation of energetic particle beams and their interaction with natural neutral and ionized constituents of the high atmosphere. So far, virtually all of this effort has been accomplished using rockets. In the future, it is obvious that satellite platforms will play a greater role, both in making injections and in observing their effects.

  9. Birth order effects on autism symptom domains.

    PubMed

    Reichenberg, Abraham; Smith, Christopher; Schmeidler, James; Silverman, Jeremy M

    2007-03-30

    Autism is predominantly genetically determined. Evidence supports familiality of the main sets of behavioral characteristics that define the syndrome of autism; however, possible non-genetic effects have also been suggested. The present study compared levels of autism symptom domains, as measured by the Autism Diagnostic Interview, and useful phrase speech scores between 106 pairs of first- and second-born siblings from multiply affected families. In addition, the intercorrelations between the measures were compared between siblings. The overall mean repetitive behavior total score was significantly higher (worse) in first-born than in second-born siblings. In contrast, first-born siblings had significantly lower (better) useful phrase speech than their younger siblings. Autism social and non-verbal communication scores were significantly correlated in first- and in second-born siblings. However, there was a significant difference in the coefficients between first- and second-born siblings. Performance on the non-verbal communication domain was also significantly and positively correlated with useful phrase speech score in both first- and second-born siblings. It is unclear at this time whether these results are of biologic origin. Nevertheless, the findings suggest that genetic studies in autism using specific levels of familial autism traits as phenotypes should take into account their intercorrelations and birth order effects embedded in the instrument. PMID:17289158

  10. Successes and Challenges in Ionosphere-Thermosphere Research

    NASA Astrophysics Data System (ADS)

    Ridley, A. J.; Spann, J.; Clemmons, J.

    2008-05-01

    As a society, we have known about the existence of the ionosphere in general terms for thousands of years through the displays of the aurora. We have known that currents are associated with the aurora for only a little more than a hundred years. In more recent times, we have learned about the overall characteristics of the ionosphere and thermosphere, such as the general temperature and density structure during non-disturbed time periods. We have a phenomenological understanding of how the magnetosphere, the sun, and the lower atmosphere influence the thermosphere and ionosphere environments. Finally, we have developed global-scale models to assist us in our ability to predict and better understand the complex upper atmosphere. While our understanding appears to be large, we have really only scratched the surface in our ability to describe even the first order effects of different energy inputs on the local and global ionosphere and thermosphere. This is clearly observed when model results are compared to data on anything more than orbit or daily averaged values. Further, as a community, we are beginning to understand that the upper atmosphere system is effected by energy inputs on many different scales, and that the global system must be examined in order to truly understand what is happening on a localized scale. The problem with this is that there aren't enough data sets to fully describe the system in a global context. This talk will describe some of the general outstanding scientific successes and challenges in the ionosphere thermosphere research. It will highlight some of the general major issues that need to be addressed so an understanding of the upper atmosphere system can move forward.

  11. Effect of Grid Definition and Data Distribution on Accuracy of Ionospheric Imaging

    NASA Astrophysics Data System (ADS)

    Burston, R.

    2011-12-01

    In tomography, the region to be imaged is divided into a grid and knowledge of the values of a parameter as measured along known paths through the region is used to reconstruct the interior of the region by assigning a value to each voxel of the grid. In the ionospheric case, slant Total Electron Content (sTEC) values for rays passing through the ionosphere can be used. The principle source of such data is recordings from Global Positioning System (GPS) ground receiver stations. Each ray is broken down into pieces, according to the path length within each voxel traversed. Each voxel is assigned an unknown value of electron concentration. A set of simultaneous equations in electron concentration and path length can then be constructed for each ray. In ideal circumstances enough rays from sufficient broadcast points to different receiver points exist so that a unique solution to the set of simultaneous equations can be determined. In practice the solution with the minimum error (usually in a least-squares sense) is found because there is always some error in the input measurements. In the case of the ionosphere and the set of broadcasting GPS satellites and ground based receivers, it is in principle impossible to determine a unique solution even in terms of a minimum error. The geometry is such that the set of simultaneous equations has more unknowns than equations. Hence it is necessary to constrain the solution by some additional method or methods [Bust and Mitchell, 2008]. The solution to this inverse problem is re-calculated for each epoch of interest. The Multi-Instrument Data Assimilation System algorithm developed at the University of Bath, UK, and used at the University of New Brunswick under licence uses empirical Orthogonal Functions (EOFs) to constrain the vertical dimension and spherical harmonics to constrain the locally horizontal dimensions. Two different grid boundaries are tested, using MIDAS. The larger of the two includes two ground receiver

  12. Dynamic processes in the ionosphere during magnetic storms from the Kharkov incoherent scatter radar observations

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.; Grigorenko, Ye. I.; Lysenko, V. N.; Taran, V. I.

    2007-10-01

    [1] Results of studying the ionosphere behavior during several magnetic storms of various intensities are presented. The features of pronounced negative ionospheric disturbances accompanying the severe magnetic storms on 25 September 1998 and 29-30 May 2003 (Kp ≍ 8) are considered. Among them there are a decrease in the electron density by a factor of 3-4, uplifting of the ionospheric F2 layer by 100-160 km, increase in the temperature of the charged and neutral atmospheric components, and infringement of plasma transfer processes and thermal balance in the ionosphere-plasmasphere system. In the morning of 25 September 1998, an unusual increase in the upward plasma drift velocity was registered. On 29-30 May 2003 during the storm main phase, a depletion of the relative density of hydrogen ions by more than an order of magnitude was observed that could manifest an emptying of the magnetic flux tube over Kharkov. These effects are explained in terms of thermospheric disturbances, Joule heating, particle precipitation, penetration of magnetospheric electric fields to midlatitudes, the shift of the main ionospheric trough and related structures toward the radar latitude, etc. The ionospheric storm on 20-21 March 2003 had two phases. Its strong negative phase proceeded against a background of a minor geomagnetic disturbance (Kp ≍ 5). The destabilizing impact of the electric field pulse and traveling atmospheric disturbance generated by magnetospheric substorms could be the cause of the change in the storm phase that occurred in the sunset period.

  13. The Nightside Ionosphere of Venus Under Varying Levels of Solar EUV Flux

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Stangeway, R. J.; Russell, C. T.; Luhmann, J. G.; Brace, L. H.

    1993-01-01

    Solar activity varied widely over the 14 year lifetime of the Pioneer Venus Orbiter, and these variations directly affected the properties of the nightside ionosphere. At solar maximum, when solar EUV was largest, the Venus ionosphere was found to extend to highest altitudes and nightward ion transport was the main source of the nightside ionosphere. At solar minimum, nightward ion transport was reduced, and electron precipitation was thought to be the main source. In this study, we have attempted a separation of spatial variations from temporal variations by examining the altitude profiles of the magnetic field, and electron density and temperature for three different solar EUV flux ranges. In the upper ionosphere and near-planet magnetotail (h greater than 1800 km), the solar EUV effects are significant. The electron density decreases about an order of magnitude from high to low EUV flux, while the electron temperature at least doubles. The magnetic field also increases 2 - 3 nT. In the lower ionosphere (200 - 600 km), lower EUV fluxes are associated with slightly reduced density, and higher temperature. These results are in accord with recent entry phase observations, where the electron density measured above the ionospheric density peak is lower than that observed at solar maximum during the early Pioneer Venus mission.

  14. The nightside ionosphere of Venus under varying levels of solar EUV flux

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Strangeway, R. J.; Russell, C. T.; Luhmann, J. G.; Brace, L. H.

    1993-01-01

    Solar activity varied widely over the 14 year lifetime of the Pioneer Venus Orbiter (PVO), and these variations directly affected the properties of the nightside ionosphere. At solar maximum, when solar EUV was largest, the Venus ionosphere was found to extend to highest altitudes and nightward ion transport was the main source of the nightside ionosphere. At solar minimum, nightward ion transport was reduced, and electron precipitation was thought to be the main source. In this study, we have attempted a separation of spatial variations from temporal variations by examining the altitude profiles of the magnetic field, and electron density and temperature for three different solar EUV flux ranges. In the upper ionosphere and near-planet magnetotail (h greater than 1800 km), the solar EUV flux effects are significant. The electron density decreases about an order of magnitude from high to low EUV flux, while the electron temperature at least doubles. The magnetic field also increases 2 - 3 nT. In the lower ionosphere (200 - 600 km), lower EUV fluxes are associated with slightly reduced density, and higher temperature. These results are in accord with recent entry phase observations, where the electron density measured above the ionospheric density peak is lower than that observed at solar maximum during the early Pioneer Venus mission.

  15. Overview of midlatitude ionospheric storms

    NASA Astrophysics Data System (ADS)

    Kintner, Paul; Coster, Anthea; Fuller-Rowell, Tim; Mannucci, Anthony J.

    Solar flares and coronal mass ejections erupting from the roiling Sun can smash into the Earth's magnetosphere causing geomagnetic storms that penetrate deep into the atmosphere, which can short out satellites, upset radio communications, disrupt navigation, and even damage terrestrial electrical power grids. Though effects on other regions of the atmosphere have been analyzed, the mechanism by which geomagnetic storms influence the ionosphere's middle latitudes remains poorly understood.This brief report provides an overview of current knowledge in midlatitude ionospheric dynamics and disturbances, from the historic record to recent discoveries presented at a January AGU Chapman Conference.

  16. Effects of geomagnetic storm on low latitude ionospheric total electron content: A case study from Indian sector

    NASA Astrophysics Data System (ADS)

    Chakraborty, Monti; Kumar, Sanjay; De, Barin Kumar; Guha, Anirban

    2015-07-01

    The effect of geomagnetic storms on low latitude ionosphere has been investigated with the help of Global Positioning System Total Electron Content (GPS-TEC) data. The investigation has been done with the aid of TEC data from the Indian equatorial region, Port Blair (PBR) and equatorial ionization anomaly region, Agartala (AGR). During the geomagnetic storms on 24th April and 15th July 2012, significant enhancement up to 150% and depression up to 72% in VTEC is observed in comparison to the normal day variation. The variations in VTEC observed from equatorial to EIA latitudes during the storm period have been explained with the help of electro-dynamic effects (prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF)) as well as mechanical effects (storm-induced equatorward neutral wind effect and thermospheric composition changes). The current study points to the fact that the electro-dynamic effect of geomagnetic storms around EIA region is more effective than at the lower latitude region. Drastic difference has been observed over equatorial region (positive storm impact) and EIA region (negative storm impact) around same longitude sector, during storm period on 24th April. This drastic change as observed in GPS-TEC on 24th April has been further confirmed by using the O/N2 ratio data from GUVI (Global Ultraviolet Imager) as well as VTEC map constructed from IGS data. The results presented in the paper are important for the application of satellite-based communication and navigational system.

  17. Real-time estimation of ionospheric delay using GPS measurements

    NASA Astrophysics Data System (ADS)

    Lin, Lao-Sheng

    1997-12-01

    When radio waves such as the GPS signals propagate through the ionosphere, they experience an extra time delay. The ionospheric delay can be eliminated (to the first order) through a linear combination of L1 and L2 observations from dual-frequency GPS receivers. Taking advantage of this dispersive principle, one or more dual- frequency GPS receivers can be used to determine a model of the ionospheric delay across a region of interest and, if implemented in real-time, can support single-frequency GPS positioning and navigation applications. The research objectives of this thesis were: (1) to develop algorithms to obtain accurate absolute Total Electron Content (TEC) estimates from dual-frequency GPS observables, and (2) to develop an algorithm to improve the accuracy of real-time ionosphere modelling. In order to fulfil these objectives, four algorithms have been proposed in this thesis. A 'multi-day multipath template technique' is proposed to mitigate the pseudo-range multipath effects at static GPS reference stations. This technique is based on the assumption that the multipath disturbance at a static station will be constant if the physical environment remains unchanged from day to day. The multipath template, either single-day or multi-day, can be generated from the previous days' GPS data. A 'real-time failure detection and repair algorithm' is proposed to detect and repair the GPS carrier phase 'failures', such as the occurrence of cycle slips. The proposed algorithm uses two procedures: (1) application of a statistical test on the state difference estimated from robust and conventional Kalman filters in order to detect and identify the carrier phase failure, and (2) application of a Kalman filter algorithm to repair the 'identified carrier phase failure'. A 'L1/L2 differential delay estimation algorithm' is proposed to estimate GPS satellite transmitter and receiver L1/L2 differential delays. This algorithm, based on the single-site modelling technique, is

  18. Periodic and quiescent solar activity effects in the low ionosphere, using SAVNET data

    NASA Astrophysics Data System (ADS)

    Bertoni, F. C. P.; Raulin, J.-P.; Gavilan, H. R.; Kaufmann, P.; Raymundo, T. E.

    2010-10-01

    Important results have been acquired using the measurements of VLF amplitude and phase signals from the South America VLF Network (SAVNET) stations. This network is an international project coordinated by CRAAM, Brazil in cooperation with Peru and Argentina. It started operating in April 2006, and now counts on eight stations (Atibaia, Palmas, Santa Maria and Estaça~o Antártica Comandante Ferraz in Brazil; Piura, Punta-Lobos and Ica, in Peru; CASLEO, in Argentina). Researches, through the last decades, have demonstrated the versatility of the VLF technique for many scientific and technological purposes. In this work, we summarize some recent results using SAVNET data base. We have obtained daily maximum diurnal amplitude time series that exhibited behavior patterns in different time scales: 1) 1ong term variations indicating the solar activity level control of the low ionosphere; 2) characteristic periods of alternated slow and fast variations, the former being related to solar illumination conditions, and the latter that have been associated with the winter anomaly at high latitudes; 3) 27-days period related to the solar rotation and consequently associated to the solar Lyman-α radiation flux variations, reinforcing earlier theories about the importance of this spectral line for the D-region formation. Finally, we conclude presenting preliminary results of simulation using LWPC, which showed very good agreement at times of observed modal amplitude minima for a given VLF propagation path.

  19. Ionospheric Correction Based on Ingestion of Global Ionospheric Maps into the NeQuick 2 Model

    PubMed Central

    Yu, Xiao; She, Chengli; Zhen, Weimin; Bruno, Nava; Liu, Dun; Yue, Xinan; Ou, Ming; Xu, Jisheng

    2015-01-01

    The global ionospheric maps (GIMs), generated by Jet Propulsion Laboratory (JPL) and Center for Orbit Determination in Europe (CODE) during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC) through ingesting the GIMs data from the previous day(s). The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az) versus modified dip latitude (MODIP) are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient function expression of Az versus MODIP. As more measurements from earlier days are involved in the Az optimization procedure, the accuracy may decrease. The results also reveal that more efforts are needed to improve the NeQuick 2 model capabilities to represent the ionosphere in the equatorial and high-latitude regions. PMID:25815369

  20. Ionospheric correction based on ingestion of global ionospheric maps into the NeQuick 2 model.

    PubMed

    Yu, Xiao; She, Chengli; Zhen, Weimin; Bruno, Nava; Liu, Dun; Yue, Xinan; Ou, Ming; Xu, Jisheng

    2015-01-01

    The global ionospheric maps (GIMs), generated by Jet Propulsion Laboratory (JPL) and Center for Orbit Determination in Europe (CODE) during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC) through ingesting the GIMs data from the previous day(s). The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az) versus modified dip latitude (MODIP) are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient function expression of Az versus MODIP. As more measurements from earlier days are involved in the Az optimization procedure, the accuracy may decrease. The results also reveal that more efforts are needed to improve the NeQuick 2 model capabilities to represent the ionosphere in the equatorial and high-latitude regions. PMID:25815369

  1. On the problem of detection of seismo-ionospheric phenomena by multi-instrumental radiophysical observations

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Zakharenkova, Irina; Shagimuratov, Irk; Suslova, Olga

    2012-07-01

    Analysis of the previous works on lithosphere-ionosphere interactions confirmed the necessity to use simultaneous observations from several independent diagnostics tools in order to raise the reliability of the observed seismo-ionospheric effects. The influence on the ionosphere from below is weaker in comparison with effects of solar or geomagnetic origin. Due to this reason it is very actual the problem of detection of seismo-ionospheric anomalies on the background of strong regular and quasi-regular variation of space weather parameters. For the given research we use integrated processing of the ionospheric data from different sources: total electron content (TEC) data obtained on the basis of regular GPS observations of IGS stations located in Sakhalin and Japan regions, ionospheric E and F2 layers peak parameters, derived from data of Japan ionosonde network and electron density profiles, obtained by FORMOSAT-3/COSMIC radio occultation measurements. As a case-study it was analyzed the Nevelsk earthquake (M 6.2) that took place at the Far East of Russian Federation on August 2, 2007. On July 29, 2007, several days prior to earthquake, the characteristic anomaly was found out as the day-time significant enhancement of TEC at the vicinity of earthquake. This enhancement reached the maximal value of 4-6 TECU in absolute values, that is 40-50% to the background conditions, and it was situated very close to the epicenter position. The noticeable enhancement of F2 peak critical frequency (foF2) was observed over Wakkanai ionosonde. For the evening hours (19-22 LT) it reached the value of 6.8-7.7 MHz whereas monthly median was 5.3-5.7 MHz. This foF2 increase was coincided in time with the appearance of TEC anomaly in TEC maps over the considered region (taken from GIMs IONEX). In order to separate seismo-ionospheric perturbations from geomagnetic disturbances it was done the comparative analysis of the revealed ionospheric effect possibly related with seismic activity

  2. A GPS/GNSS dense network used to monitor ionospheric positioning error

    NASA Astrophysics Data System (ADS)

    Wautelet, G.; Lejeune, S.; Warnant, R.

    2010-12-01

    GPS/GNSS networks are, for the last few years, quickly expanding their density all over the surface of the globe. The present idea is to use this density in order to assess the effect of ionospheric disturbances on relative positioning but also to monitor their propagation patterns. Local variability in the ionospheric electron density can dramaticaly affect the reliability of GPS/GNSS real time applications. In particular, Traveling Ionospheric Disturbances (TID's) or plasma instability due to geomagnetic storms can induce strong disturbances in relative positioning. It is therefore useful to develop an integrity monitoring service based on a GPS/GNSS dense network. To assess the effects of ionospheric activity on relative positioning, the SoDIPE-RTK software (Software for Determining the Ionospheric Positionning Error on RTK) has been developed at the Royal Meteorological Institute of Belgium. The approach consists in computing the positioning error due to the ionosphere and has been applied, as a proof of concept, on the Belgian dense network. This network called Active Geodetic Network (AGN) is composed of 66 GPS (dual-frequency) stations. In order to ensure a successful ambiguity resolution for both L1 and L2 carriers, baselines larger than 40 km are not taken into account in the analysis. In a first step, we assess the nominal RTK precision for each baseline during quiet ionospheric conditions (i.e. a background of low Total Electron Content (TEC) variability). The observed positioning accuracy is ~1 cm and depends mainly on baseline length and satellite geometry at the two considered stations. In a second step, the impact of two ionospheric events on positioning error (a medium scale TID and a powerful geomagnetic storm) is evaluated. As expected, the study demonstrates that the largest effects are observed during the occurrence of the geomagnetic storm with an ionospheric positioning error reaching 0.9 m. The maximal positioning error observed during the

  3. Ionospheric Challenges for GNSS Based Augmentation Systems

    NASA Astrophysics Data System (ADS)

    Doherty, P.; Valladares, C. E.

    2007-12-01

    The ionosphere is a highly dynamic physical phenomenon that presents a variable source of error for Global Navigation Satellite System (GNSS) signals and GNSS based operational systems. The Federal Aviation Administration's (FAA) Wide-Area Augmentation System (WAAS) was designed to enhance the GNSS standard positioning service by providing additional accuracy, availability and integrity that is sufficient for use in commercial aviation. It is the first of a number of planned regional Satellite Based Augmentation Systems (SBAS). Other systems in development include the European EGNOS system, the MSAS system in Japan and the GAGAN system in India. In addition, the South American countries are investigating the feasibility of operating an SBAS system in this region. Much of the WAAS ionospheric research and development focused on defining and mitigating ionospheric challenges characteristic of the mid-latitude regions, where the ionosphere is well studied and relatively quiescent. The EGNOS and MSAS systems will primarily operate under a similarly quiescent mid-latitude ionosphere. SBAS system development in South America, India and other low-latitude regions, however, will have to contend with much more extreme conditions. These conditions include strong spatial and temporal gradients, plasma depletions and scintillation. All of these conditions have a potential to limit SBAS performance in the low latitude regions. This presentation will review the effects that the ionosphere has on the mid-latitude WAAS system. It will present the techniques that are used to mitigate ionospheric disturbances induced on the system during severe geomagnetic activity and it will quantify the effect that this activity has on system performance. The presentation will then present data from the South American Low-latitude Ionospheric Sensor Network (LISN) that can be used to infer the ionospheric effects on SBAS performance in the most challenging low-latitude ionospheric environment

  4. Low/Mid-latitude Ionospheric irregularities and scintillation climatology

    NASA Astrophysics Data System (ADS)

    Abdallah, Amr; Groves, K. M.; Mahrous, Ayman; Hussein, Fayrouz

    Ionospheric scintillation occur when radio signals propagate through an irregular ionosphere (e.g., plasma bubbles). Since plasma bubbles are regions of depleted ion and electron densities, a plasma bubble located on the satellite-to-ground signal path will cause radio signals to fluctuate in phase and amplitude. Ionospheric scintillation data were analyzed in the magnetic latitudinal field-of-view 29° N -13.4° N, observed by a stand-alone SCINDA (Scintillation Network Decision Aid) - GPS receiver at Helwan, Egypt (29.86° N, 31.32° E). A minimum 20° elevation cut off angle has been set in order to minimize the multipath effect. During the enhancing phase of the current solar cycle 24 (years 2010, 2011, 2012 and 2013), the behaviour of the scintillation occurrence were characterized. The seasonal, annual and solar cycle variation of scintillation occurrence is investigated together with the Total Electron Content (TEC), to put in evidence the relation between the electron density gradients and the ionospheric irregularities causing scintillation. This study considers a first step to develop a scintillation climatology over Northern Africa.

  5. Empirical model of the Martian dayside ionosphere: Effects of crustal magnetic fields and solar ionizing flux at higher altitudes

    NASA Astrophysics Data System (ADS)

    Němec, F.; Morgan, D. D.; Gurnett, D. A.; Andrews, D. J.

    2016-02-01

    We use electron density profiles measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument on board the Mars Express spacecraft to investigate the effects of possible controlling parameters unconsidered in the empirical model of Němec et al. (2011, hereafter N11). Specifically, we focus on the effects of crustal magnetic fields and F10.7 proxy of the solar ionizing flux at higher altitudes. It is shown that while peak electron densities are nearly unaffected by crustal magnetic fields, electron densities at higher altitudes are significantly increased in areas of stronger magnetic fields. The magnetic field inclination appears to have only a marginal effect. Moreover, while the N11 empirical model accounted for the variable solar ionizing flux at low altitudes, the high-altitude diffusive region was parameterized only by the solar zenith angle and the altitude. It is shown that this can lead to considerable inaccuracies. A simple correction of the N11 model, which takes into account both the crustal magnetic field magnitude and the effect of F10.7 at higher altitudes, is suggested.

  6. Propagation in the ionosphere, A

    NASA Astrophysics Data System (ADS)

    Cannon, Paul S.

    1994-09-01

    The use of ionospheric models and ray tracing models as components of a propagation model are discussed. These can be used as decision aids to support human interpretation of ionospheric propagation. The physical basis for ionospheric decision aids is introduced by reference to ionospheric morphology and the basic theory of ionospheric propagation, which, along with ray tracing techniques, is then reviewed.

  7. 4D computerized ionospheric tomography by using GPS measurements and IRI-Plas model

    NASA Astrophysics Data System (ADS)

    Tuna, Hakan; Arikan, Feza; Arikan, Orhan

    2016-07-01

    Ionospheric imaging is an important subject in ionospheric studies. GPS based TEC measurements provide very accurate information about the electron density values in the ionosphere. However, since the measurements are generally very sparse and non-uniformly distributed, computation of 3D electron density estimation from measurements alone is an ill-defined problem. Model based 3D electron density estimations provide physically feasible distributions. However, they are not generally compliant with the TEC measurements obtained from GPS receivers. In this study, GPS based TEC measurements and an ionosphere model known as International Reference Ionosphere Extended to Plasmasphere (IRI-Plas) are employed together in order to obtain a physically accurate 3D electron density distribution which is compliant with the real measurements obtained from a GPS satellite - receiver network. Ionospheric parameters input to the IRI-Plas model are perturbed in the region of interest by using parametric perturbation models such that the synthetic TEC measurements calculated from the resultant 3D electron density distribution fit to the real TEC measurements. The problem is considered as an optimization problem where the optimization parameters are the parameters of the parametric perturbation models. Proposed technique is applied over Turkey, on both calm and storm days of the ionosphere. Results show that the proposed technique produces 3D electron density distributions which are compliant with IRI-Plas model, GPS TEC measurements and ionosonde measurements. The effect of the GPS receiver station number on the performance of the proposed technique is investigated. Results showed that 7 GPS receiver stations in a region as large as Turkey is sufficient for both calm and storm days of the ionosphere. Since the ionization levels in the ionosphere are highly correlated in time, the proposed technique is extended to the time domain by applying Kalman based tracking and smoothing

  8. The Impact of Ionospheric Disturbances on High Accuracy Positioning in Brazil

    NASA Astrophysics Data System (ADS)

    Yang, L.; Park, J.; Susnik, A.; Aquino, M. H.; Dodson, A.

    2013-12-01

    High positioning accuracy is a key requirement to a number of applications with a high economic impact, such as precision agriculture, surveying, geodesy, land management, off-shore operations. Global Navigation Satellite Systems (GNSS) carrier phase measurement based techniques, such as Real Time Kinematic (RTK), Network-RTK (NRTK) and Precise Point Positioning (PPP), have played an important role in providing centimetre-level positioning accuracy, and become the core of the above applications. However these techniques are especially sensitive to ionospheric perturbations, in particular scintillation. Brazil sits in one of the most affected regions of the Earth and can be regarded as a test-bed for scenarios of the severe ionospheric condition. Over the Brazilian territory, the ionosphere behaves in a considerably unpredictable way and scintillation activity is very prominent, occurring especially after sunset hours. NRTK services may not be able to provide satisfactory accuracy, or even continuous positioning during strong scintillation periods. CALIBRA (Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in BRAzil) started in late 2012 and is a project funded by the GSA (European GNSS Agency) and the European Commission under the Framework Program 7 to deliver improvements on carrier phase based high accuracy algorithms and their implementation in GNSS receivers, aiming to counter the adverse ionospheric effects over Brazil. As the first stage of this project, the ionospheric disturbances, which affect the applications of RTK, NRTK or PPP, are characterized. Typical problems include degraded positioning accuracy, difficulties in ambiguity fixing, NRTK network interpolation errors, long PPP convergence time etc. It will identify how GNSS observables and existing algorithms are degraded by ionosphere related phenomena, evaluating the impact on positioning techniques in terms of accuracy, integrity and availability. Through the

  9. Is Jupiter's ionosphere a significant plasma source for its magnetosphere?

    NASA Astrophysics Data System (ADS)

    Nagy, A. F.; Barakat, A. R.; Schunk, R. W.

    1986-01-01

    A semikinetic model was used to study the steady state, collisionless, polar wind outflow from the Jovian polar caps. H+ escape fluxes and energies were calculated for a range of conditions, including several values of the ambient electron temperature, different hot electron populations, and both with and without the effects of the centrifugal force. The calculations indicate that if hot electron populations exist over the Jovian polar caps, as they do on earth, polar wind escape fluxes of the order of 108cm-2s-1 are possible. When integrated over the polar cap area, escape fluxes of this order of magnitude imply an ionospheric source strength of 2×1028ions/s, which is comparable to the present estimate of the total magnetospheric plasma source population. Therefore, the ionosphere may play an important role in populating the Jovian magnetosphere, specifically the "hidden", low energy, light ion component of the population.

  10. Three-dimensional current systems and ionospheric effects associated with small dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Palin, L.; Jacquey, C.; Opgenoorth, H.; Connors, M.; Sergeev, V.; Sauvaud, J.-A.; Nakamura, R.; Reeves, G. D.; Singer, H. J.; Angelopoulos, V.; Turc, L.

    2015-05-01

    We present a case study of eight successive plasma sheet (PS) activations (usually referred to as bursty bulk flows or dipolarization fronts), associated with small individual BZGSM increases on 31 March 2009 (0200-0900 UT), observed by the Time History of Events and Macroscale Interactions During Substorms mission. This series of events happens during very quiet solar wind conditions, over a period of 7 h preceding a substorm onset at 1230 UT. The amplitude of the dipolarizations increases with time. The low-amplitude dipolarization fronts are associated with few (1 or 2) rapid flux transport events (RFT, Eh>2 mV/m), whereas the large-amplitude ones encompass many more RFT events. All PS activations are associated with small and localized substorm current wedge (SCW)-like current system signatures, which seems to be the consequence of RFT arrival in the near tail. The associated ground magnetic perturbations affect a larger part of the contracted auroral oval when, in the magnetotail, more RFT are embedded in PS activations (>5). Dipolarization fronts with very low amplitude, a type usually not included in statistical studies, are of particular interest because we found even those to be associated with clear small SCW-like current system and particle injections at geosynchronous orbit. This exceptional data set highlights the role of flow bursts in the magnetotail and leads to the conclusion that we may be observing the smallest form of a substorm or rather its smallest element. This study also highlights the gradual evolution of the ionospheric current disturbance as the plasma sheet is observed to heat up.

  11. Ionospheric effects of the March 1990 magnetic storm: Comparison of theory and measurement

    SciTech Connect

    Richards, P.G.; Torr, D.G.; Buonsanto, M.J.; Sipler, D.P.

    1994-12-01

    This paper presents a comparison of the measured and modeled inospheric response to magnetic storms at Millstone Hill and Arecibo during March 16-23, 1990. Magnetic activity was low until midday UT on day 18 when Kp reached 6, days 19 and 20 were quiet, but a large storm occurred around midnight UT on day 20 (Kp=7) and it was moderately disturbed (Kp=4) for the remainder of the study period. At Millstone Hill, the daytime peak electron density (NmF{sub 2}) showed only a modest 30% decrease in response to the first storm and recovered to prestorm values before the onset of the second storm. The model reproduces the daytime peak electron density well for this period. However, the severe storm on March 20 caused a factor of 4 depletion in electron density, while the model densities were not greatly affected. The inclusion of vibrationally excited nitrogen (N{sub 2}) in the model was unable to account for the observed large electron density depletions afterward March 20. The storm did not appear to affect the overall magnitude of the electron density at Arecibo very much, but did cause unusual wavelike structure in the peak density and peak height following the storm. The model reproduces the daytime NmF{sub 2} very well for Arecibo, but after sunset the model densities decay too rapidly. This study indicates that successful modeling of severe ionospheric storms will require better definition of the storm time inputs, especially of the neutral atmosphere. 26 refs., 10 figs.

  12. Ionospheric effects of the March 13, 1989, magnetic storm at low and equatorial latitudes

    SciTech Connect

    Batista, I.S.; De Paula, E.R.; Abdu, M.A.; Trivedi, N.B. ); Greenspan, M.E. )

    1991-08-01

    The great geomagnetic storm of March 13, 1989 caused severely anomalous behavior in the equatorial and low latitude ionosphere in the Brazilian longitude sector. The ionograms over Fortaleza indicated F region upward plasma drifts exceeding 200 m s{sup {minus}1} at 1,830 LT as compared to normal values of 40 m s{sup {minus}1} for this epoch. Large negative phases were observed in foF2 over Fortaleza and Cachoeira Paulista and in total electron content measured over Sao Jose dos Campos. The equatorial ionization anomaly was totally absent either because of its anomalous expansion to higher latitudes or because of inhibition of its development on the two nights following the storm. Many anomalous variations in F region peak density and height, occurring simultaneously with sharp variations on H component of magnetic field over Fortaleza and with auroral substorms, give strong evidence of penetration of magnetospheric electric fields to equatorial and low latitudes. Auroral type sporadic E and night E layers are observed after 1,830 LT over Cachoeira Paulista, the latter showing peak electron density of about 6 {times} 10{sup 4} el cm{sup {minus}3}, therefore comparable to the E layer peak density in the morning hours at that station. The Fortaleza ionograms show the presence of the F1 layer at night, a phenomenon that has never been observed over our two stations before. The role played by electric fields penetrating from high to low latitudes, particle precipitation, and composition changes in explaining the observations is discussed.

  13. The ionospheres of Ganymede and Callisto from Galileo radio occultations

    NASA Astrophysics Data System (ADS)

    Kliore, A. J.; Anabtawi, A.; Nagy, A. F.; Galileo Radio Propagation Science Team

    2001-11-01

    The U.S. Galileo spacecraft, which has been in orbit around Jupiter since December, 1995, has provided opportunities to collect s-band radio occultation data using the 70 meter antennas of the NASA/JPL Deep Space Net(DSN) at Goldstone, California, Madrid, Spain, and Canberra, Australia. Ganymede (J3) has been observed five times by Galileo radio occultation. The results are almost entirely negative, with only one measurement out of ten yielding a possible observation of an ionosphere having a maximum density of about 5,000 cm-3 at an altitude of about 16 km. The failure to observe an ionosphere on Ganymede is at first glance surprising, in view of the detection of oxygen and hydrogen above its surface (c.f., Hall, et al., Astrophys. J., 499, 1998; Barth, et al., GRL, 24, 1997), and it was thought to be due to the shielding effect of Ganymede's magnetic field upon the impinging particles from Jupiter's magnetosphere. Callisto has occulted Galileo four times, and these observations have produced some interesting results. Of the eight individual measurements , two are negative, and six are positive. Two of those six show unmistakable classic ionospheric layers, having peak electron densities of 15,000 to 20,000 cm-3 . A closer examination of all of these results has revealed a plausible reason for why some observations yield positive results , and some do not. It appears that in order for an ionosphere to be observed, the trailing hemisphere of the satellite must be in sunlight. In that way, the atmosphere created by sputtering effects of the Jovian magnetosphere can be ionized by solar EUV to produce an observable ionosphere. The research described in this paper has been conducted at the Jet Propulsion Laboratory and the University of Michigan with support from NASA contracts and grants.

  14. Global Assimilation of Ionospheric Measurements (GAIM)

    NASA Astrophysics Data System (ADS)

    Schunk, Robert W.; Scherliess, Ludger; Sojka, Jan J.; Thompson, Donald C.; Anderson, David N.; Codrescu, Mihail; Minter, Cliff; Fuller-Rowell, Timothy J.; Heelis, Roderick A.; Hairston, Marc; Howe, Bruce M.

    2004-02-01

    The ionosphere is a highly dynamic medium that exhibits weather disturbances at all latitudes, longitudes, and altitudes, and these disturbances can have detrimental effects on both military and civilian systems. In an effort to mitigate the adverse effects, we are developing a physics-based data assimilation model of the ionosphere and neutral atmosphere called the Global Assimilation of Ionospheric Measurements (GAIM). GAIM will use a physics-based ionosphere-plasmasphere model and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. Some of the data to be assimilated include in situ density measurements from satellites, ionosonde electron density profiles, occultation data, ground-based GPS total electron contents (TECs), two-dimensional ionospheric density distributions from tomography chains, and line-of-sight UV emissions from selected satellites. When completed, GAIM will provide specifications and forecasts on a spatial grid that can be global, regional, or local. The primary output of GAIM will be a continuous reconstruction of the three-dimensional electron density distribution from 90 km to geosynchronous altitude (35,000 km). GAIM also outputs auxiliary parameters, including NmF2, hmF2, NmE, hmE, and slant and vertical TEC. Furthermore, GAIM provides global distributions for the ionospheric drivers (neutral winds and densities, magnetospheric and equatorial electric fields, and electron precipitation patterns). In its specification mode, GAIM yields quantitative estimates for the accuracy of the reconstructed ionospheric densities.

  15. 42 CFR 2.61 - Legal effect of order.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Legal effect of order. 2.61 Section 2.61 Public... OF ALCOHOL AND DRUG ABUSE PATIENT RECORDS Court Orders Authorizing Disclosure and Use § 2.61 Legal effect of order. (a) Effect. An order of a court of competent jurisdiction entered under this subpart...

  16. Geomagnetic storm effect on the occurrence of ionospheric irregularities over African equatorial sector using GPS-TEC

    NASA Astrophysics Data System (ADS)

    Amaechi, Paul; Oyeyemi, Elijah; Akala, Andrew

    2016-07-01

    Total electron content (TEC) derived from Global Navigation Satellite Systems (GNSS) measurements provided by the International GNSS Service (IGS) network have been used to study the occurrence of large scale ionospheric irregularities over the African equatorial sector. The rate of change of TEC (ROT) as well as its standard deviation over five minutes (ROTI) were used to monitor the level of irregularities over 3 stations distributed across the three longitudinal sectors of Africa (eastern, central and western longitudinal sectors). The storm effect on irregularities occurrence has been studied in conjunction with the disturbance storm time (Dst) and the z component of the Interplanetary magnetic field (IMFBz) indices during four intense storms which were classified according to their season of occurrence during the year 2015. Irregularities were associated with GPS-TEC fluctuations as seen in the increased ROT and ROTI values especially in the post sunset period. Irregularities were inhibited over all the stations during the storm of March plausibly as a result of electric field conditioned by the southward turning of IMFBz during the pre and post midnight periods. The triggering of irregularities over the western and central stations and their inhibition over the eastern station during the storm of June was controlled by the ring current. The storm effect on irregularities was not evident over the western and central stations but inhibition of irregularities was observed over the eastern station during the storm of September.

  17. Effects of a Parallel Electric Field and the Geomagnetic Field in the Topside Ionosphere on Auroral and Photoelectron Energy Distributions

    NASA Technical Reports Server (NTRS)

    Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

    1993-01-01

    The consequences of electric field acceleration and an inhomogencous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one- dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogencous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of 0(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function in investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogencous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

  18. Effects of a parallel electric field and the geomagnetic field in the topside ionosphere on auroral and photoelectron energy distributions

    NASA Technical Reports Server (NTRS)

    Min, Q.-L.; Lummerzheim, D.; Rees, M. H.; Stamnes, K.

    1993-01-01

    The consequences of electric field acceleration and an inhomogeneous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one-dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogeneous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of O(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function is investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogeneous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

  19. Ionospherically reflected proton whistlers

    NASA Astrophysics Data System (ADS)

    Vavilov, D. I.; Shklyar, D. R.

    2014-12-01

    We present experimental observations and detailed investigation of the variety of proton whistlers that includes transequatorial and ionospherically reflected proton whistlers. The latter have previously been indicated from numerical modeling of spectrograms. The study is based on six-component ELF wave data from the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite which permits to obtain not only spectrograms displaying the power spectral density but also such wave properties as the polarization, wave normal angle, wave refractive index, and normalized parallel component of the Poynting vector. The explanation of various types of proton whistlers is based on the properties of ion cyclotron wave propagation in a multicomponent magnetoplasma, with special consideration of the effect of ion hybrid resonance reflection. Analysis of experimental data is supplemented by numerical modeling of spectrograms that reproduces the main features of experimental ones. As a self-contained result, we provide conclusive experimental evidences that the region illuminated by a lightning stroke in the Earth-ionosphere waveguide may spread over a distance of 4000 km in both hemispheres.

  20. Ionospheric irregularity physics modelling. Memorandum report

    SciTech Connect

    Ossakow, S.L.; Keskinen, M.J.; Zalesak, S.T.

    1982-02-09

    Theoretical and numerical simulation techniques have been employed to study ionospheric F region plasma cloud striation phenomena, equatorial spread F phenomena, and high latitude diffuse auroral F region irregularity phenomena. Each of these phenomena can cause scintillation effects. The results and ideas from these studies are state-of-the-art, agree well with experimental observations, and have induced experimentalists to look for theoretically predicted results. One conclusion that can be drawn from these studies is that ionospheric irregularity phenomena can be modelled from a first principles physics point of view. Theoretical and numerical simulation results from the aforementioned ionospheric irregularity areas will be presented.

  1. Climatology of low latitude ionosphere under effect of varying solar flux during solar cycle 23 and 24

    NASA Astrophysics Data System (ADS)

    Dashora, Nirvikar; Suresh, Sunanda

    2016-07-01

    The characteristics of quiet time equatorial and low latitude total electron content (TEC) over the Indian sector using GIM data (1998-2014) is obtained. For the first time the analysis is carried filtering out the solar flare and storm effects and time series of quiet time VTEC data from three locations namely dip equator and two low latitude conjugate locations in Indian sector are obtained. It is well known that a complex interplay among drivers of equatorial electrodynamics like Solar flux, dynamo electric field and meridional winds determine the daytime ionization and distribution in equatorial ionization anomaly zone. In this study, we have critically examined the role of varying solar flux and response of low latitude ionosphere with new and standardized definitions. The results are examined and interpreted in the context of large number of previous studies. The newly found features from this study are as follows. Marked difference in nature of equinoctial asymmetry is noted between solar cycle 23 and 24. Long absence of winter anomaly both during low and high solar activity (HSA) in LL (low latitude) regions is found. Climatology of the diurnal cycle is provided in four categories using new criteria for demarcation of solar activity levels. Highest correlation (~77%) between GIM ionospheric electron content (IEC) and PI (solar EUV proxy index) is noted over equator in contrast to previous studies. The minimum positive contribution of PI in variation of IEC requires minimum of 2 years of data and if more than 7-8 years of data is used, it saturates. RMS (root mean square) width of PI can be used to define the HSA. Strong QBO (quasi biennial oscillations) in IEC is noted in tune with the one in PI over both the LL location but QBO remains surprisingly subdued over equator. The semi-annual oscillations in GIM-IEC are found to be stronger at all locations during high solar activity and weaker between 2005 and 2011, whereas, the annual oscillations are found to

  2. On the feasibility of detecting the ionospheric effects of solar energetic particle events at Mars using spacecraft-spacecraft radio links

    NASA Astrophysics Data System (ADS)

    Withers, Paul

    2016-04-01

    Indirect evidence and theoretical modeling suggests that the effects of solar energetic particle (SEP) events on the ionosphere of Mars are substantial, but observations have not yet provided quantitative information on the magnitude or vertical distribution of the plasma produced below 100 km by SEP events. Strong radio wave absorption is anticipated during a SEP event due to the production of plasma at low altitudes where the neutral atmosphere is relatively dense. Here we test the feasibility of measuring the ionospheric effects of SEP events using power losses in spacecraft-spacecraft UHF radio links. Both lander-orbiter and orbiter-orbiter cases are considered for the UHF radio frequency of 400 MHz. A large SEP event should cause an ionospheric power loss at 400 MHz of 1.5 dB in lander-orbiter communications and, due to the longer path length, a larger power loss of 35 dB in orbiter-orbiter communications. Multiple SEP events occur each year that can cause a lander-orbiter power loss of 0.1 dB, which is shown to be theoretically detectable by current instrumentation, and an orbiter-orbiter power loss of 2 dB. The vertical profile of electron density at low altitudes can be determined from orbiter-orbiter power losses.

  3. Production of Ionospheric Perturbations by Cloud-to-Ground Lightning and the Recovery of the Lower Ionosphere

    NASA Astrophysics Data System (ADS)

    Liu, Ningyu; Dwyer, Joseph; Rassoul, Hamid

    2013-04-01

    The fact that lightning/thunderstorm activities can directly modify the lower ionosphere has long been established by observations of the perturbations of very low frequency (VLF) signals propagating in the earth-ionosphere waveguide. These perturbations are known as early VLF events [Inan et al., 2010, JGR, 115, A00E36, 2010]. More recently discovered transient luminous events caused by the lightning/thunderstorm activities only last ~1-100 ms, but studies of the early VLF events show that the lightning ionospheric effects can persist much longer, >10s min [Cotts and Inan, GRL, 34, L14809, 2007; Haldoupis et al., JGR, 39, L16801, 2012; Salut et al., JGR, 117, A08311, 2012]. It has been suggested that the long recovery is caused by long-lasting conductivity perturbations in the lower ionosphere, which can be created by sprites/sprite halos which in turn are triggered by cloud-to-ground (CG) lightning [Moore et al., JGR, 108, 1363, 2003; Haldoupis et al., 2012]. We recently developed a two-dimensional fluid model with simplified ionospheric chemistry for studying the quasi-electrostatic effects of lightning in the lower ionosphere [Liu, JGR, 117, A03308, 2012]. The model chemistry captures major ion species and reactions in the lower ionosphere. Additional important features of the model include self-consistent background ion density profiles and full description of electron and ion transport. In this talk, we present the simulation results on the dynamics of sprite halos caused by negative CG lightning. The modeling results indicate that electron density around 60 km altitude can be enhanced in a region as wide as 80 km. The enhancement reaches its full extent in ~1 s and recovers in 1-10 s, which are on the same orders as the durations of slow onset and post-onset peaks of some VLF events, respectively. In addition, long-lasting electron and ion density perturbations can occur around 80 km altitude due to negative halos as well as positive halos, which can explain

  4. Parallel Density-Based Clustering for Discovery of Ionospheric Phenomena

    NASA Astrophysics Data System (ADS)

    Pankratius, V.; Gowanlock, M.; Blair, D. M.

    2015-12-01

    Ionospheric total electron content maps derived from global networks of dual-frequency GPS receivers can reveal a plethora of ionospheric features in real-time and are key to space weather studies and natural hazard monitoring. However, growing data volumes from expanding sensor networks are making manual exploratory studies challenging. As the community is heading towards Big Data ionospheric science, automation and Computer-Aided Discovery become indispensable tools for scientists. One problem of machine learning methods is that they require domain-specific adaptations in order to be effective and useful for scientists. Addressing this problem, our Computer-Aided Discovery approach allows scientists to express various physical models as well as perturbation ranges for parameters. The search space is explored through an automated system and parallel processing of batched workloads, which finds corresponding matches and similarities in empirical data. We discuss density-based clustering as a particular method we employ in this process. Specifically, we adapt Density-Based Spatial Clustering of Applications with Noise (DBSCAN). This algorithm groups geospatial data points based on density. Clusters of points can be of arbitrary shape, and the number of clusters is not predetermined by the algorithm; only two input parameters need to be specified: (1) a distance threshold, (2) a minimum number of points within that threshold. We discuss an implementation of DBSCAN for batched workloads that is amenable to parallelization on manycore architectures such as Intel's Xeon Phi accelerator with 60+ general-purpose cores. This manycore parallelization can cluster large volumes of ionospheric total electronic content data quickly. Potential applications for cluster detection include the visualization, tracing, and examination of traveling ionospheric disturbances or other propagating phenomena. Acknowledgments. We acknowledge support from NSF ACI-1442997 (PI V. Pankratius).

  5. Geomagnetic storm effects on the thermosphere and the ionosphere revealed by in situ measurements from OGO 6

    NASA Technical Reports Server (NTRS)

    Marubashi, K.; Reber, C. A.; Taylor, H. A., Jr.

    1976-01-01

    The temporal response of the densities of upper-atmospheric ion and neutral constituents to a particular geomagnetic storm is studied using simultaneous ion and neutral-composition data obtained by the OGO 6 satellite during consecutive orbits at altitudes greater than 400 km. The investigated constituents include H(+), O(+), N2, O, He, and H. Derivation of the H density is reviewed, and the main effects of the storm are discussed, particularly temporal and global variations in the densities. It is found that: (1) the H and He densities began to decrease near the time of sudden commencement, with the decrease amounting to more than 40% of the quiet-time densities during the maximum stage at high latitudes; (2) the O and N2 densities exhibited an overall increase which began later than the change in H and He densities; (3) the H(+) density decreased differently in two distinct regions separated near the low-latitude boundary of the light-ion trough; and (4) the O(+) density showed an increase during earlier stages of the storm and decreased only in the Northern Hemisphere during the recovery phase. Certain physical and chemical processes are suggested which play principal roles in the ionospheric response to the storm

  6. Topside ionospheric effects of the annular solar eclipse of 15th January 2010 as observed by DEMETER satellite

    NASA Astrophysics Data System (ADS)

    Pal, Sujay; Chakrabarti, Sandip Kumar; Kanta Maji, Surya; Chakraborty, Suman; Sanki, Dipak

    2016-07-01

    We present effects of the annular solar eclipse of 15th January 2010 on the topside ionosphere using the DEMETER satellite data. Measurements of the electron-ion density and electron temperature by the ISL (Instrument Sonde de Langmuir) and IAP (Instrument Analyseur de Plasma) instruments on board the DEMETER satellite during the eclipse time over the low latitude (±40) Indian ocean area are presented. We found decrease in electron density by about 25% and decrease in ion density by about 33% from the reference orbits at the altitude of the satellite (~ 660 km). Electron and ion temperatures were also found to have decreased by 200-300 K at the same altitude. Instead of simple decrease as in ion density, electron temperature showed a complex wave-like oscillation as solar eclipse progressed. Electron density decreased to a minimum value before the maximum obscuration and again starts to increase before passing through another minimum at the time of maximum obscuration. Both the minima are located at the ±10 degree geomagnetic latitude. Variations of electron and ion densities were found to follow the average solar illumination experienced by the real and conjugate paths at satellite altitude, while the electron temperature showed no such correlation.

  7. Monitoring and modeling Hong Kong ionosphere using regional GPS networks

    NASA Astrophysics Data System (ADS)

    Gao, Shan

    centimeters modeling accuracy about ionospheric vertical delay, which is normally better than the traditional ionospheric model, and is able to support GPS precise positioning (e.g. the single frequency centimeter-level PPP and the millimeter-level DD positioning for 10 km baseline) in Hong Kong. Ionospheric disturbances have strong effects on GPS receiver performances. During periods of ionospheric disturbances, GPS measurement noise level (both pseudorange and carrier phase) increases dramatically, up to several decimeters, and the receivers frequently loss satellite signal lock, which have significant impacts on UPS applications in low latitudes.

  8. Ionosphere monitoring using NOAA's CORS network

    NASA Astrophysics Data System (ADS)

    Smith, D.

    NOAA's National Geodetic Survey is currently engaged in research to use the CORS (Continuously Operating GPS Reference Stations) network to model the ionosphere over the conterminous United States and surrounding areas. The CORS network consists of over 700 stations that continuously collect data from all GPS satellite vehicles in view; these data are available free of charge for (predominantly) positioning applications. However, the nature of the network makes it an excellent tool for continuously monitoring the nature of the ionosphere over and near the conterminous United States. From the standpoint of geodesy, the ionosphere effect is generally considered a nuisance parameter: that should be modeled and removed so that the ambiguity in dual frequency GPS carrier-phase signals may be resolved and accurate positions determined. As such, the initial direction of this research is toward modeling the ionosphere for geodetic use, using a single-layer "shell model". The results presented here show the first steps toward accurately modeling the ionosphere through the CORS network, in terms of absolute (non-differential) Total Electron Content Units (TECUs) through an innovative cross-over adjustment of "tracks". Each track is made by the intersection of a satellite/receiver vector with the ionosphere shell as the satellite moves overhead. Results of the initial research in applying the modeled ionosphere toward ambiguity resolution will be discussed. Limitations of using the one-dimensional shell will also be presented. Future plans for creating a time-stream of the ionosphere, increasing the complexity beyond the shell model, and applications toward nowcast and forecast of the ionosphere, will also be discussed.

  9. A simplified theory of ELF propagation in the earth-ionosphere transmission line

    NASA Astrophysics Data System (ADS)

    Booker, H. G.

    1980-12-01

    An approximate theory is developed for ELF wave propagation in the transmission-line mode between the conducting earth and the ionosphere. The theory combines the reflection theory of Booker and Lefeuvre (1977) with the treatment of Greifinger and Greifinger (1978, 1979) of ionization below the reflection level. The procedure for evaluating ionospheric effects involves the evaluation of the reflection heights of ordinary and extraordinary magnetoionic waves and of the complex refractive indexes and elliptical polarizations for the waves at these heights, followed by the calculation of the equivalent complex heights of reflection and of the bottom of the ionosphere in order to obtain the phase velocity and attenuation rate. Consideration is given to the effects of simultaneous reflection from the D and E regions, and to the cases of three and five reflection heights, corresponding to daytime and nighttime conditions, respectively.

  10. 49 CFR 511.57 - Effective date of order.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 6 2010-10-01 2010-10-01 false Effective date of order. 511.57 Section 511.57 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ADJUDICATIVE PROCEDURES Decision § 511.57 Effective date of order. (a) Consent orders. An order...

  11. The Effects of Presentation Order in Multitrial Free Recall.

    ERIC Educational Resources Information Center

    Maitland, Anthony J.

    The experiment tested the effects of presentation word orders in a multitrial free-recall task. Three types of presentation were used: (1) randomized; (2) constant order; and (3) maintained order (maintenance of subjects order of recall on the subsequent presentation). In addition, the effects of number of recalls per presentation (1 or 3) were…

  12. 17 CFR 201.531 - Initial decision on permanent order: Effect on temporary order.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 2 2013-04-01 2013-04-01 false Initial decision on permanent order: Effect on temporary order. 201.531 Section 201.531 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION RULES OF PRACTICE Rules of Practice Rules Relating to Temporary Orders and Suspensions § 201.531 Initial decision...

  13. Low Latitude Ionosphere Measurements by the Global-scale Observations of the Limb and Disk (GOLD) Mission

    NASA Astrophysics Data System (ADS)

    Eastes, R. W.; Anderson, D. N.; McClintock, W. E.; Aksnes, A.; Andersson, L.; Burns, A. G.; Budzien, S. A.; Codrescu, M. V.; Daniell, R. E.; Dymond, K. F.; England, S. L.; Eparvier, F. J.; Harvey, J. E.; Immel, T. J.; Krywonos, A.; Lankton, M. R.; Lumpe, J. D.; Richmond, A. D.; Rusch, D. W.; Siegmund, O. H.; Solomon, S. C.; Strickland, D. J.; Woods, T. N.

    2008-12-01

    The GOLD Mission of Opportunity will provide answers to key elements of an overarching question for Heliophysics science: what is the global-scale response of the thermosphere and ionosphere to forcing in the integrated Sun-Earth system? GOLD will perform remote-sensing measurements of the Earth's thermosphere and ionosphere, using an ultraviolet imager on board a commercial, geosynchronous satellite. The resulting measurements of the electron densities in the nighttime ionosphere as well as the neutral composition and temperature in the thermosphere, when combined with current modeling capabilities, will advance our understanding of Thermosphere-Ionosphere (T-I) forcing. GOLD will provide the first global- scale "snapshot" of temperature that can be compared with the coincident "snapshot" of composition changes to understand how these two major parameters simultaneously react to the various forcing mechanisms. GOLD will continue observing the same longitudes from the daytime into the night allowing the relationship between presunset conditions in the T-I system and the longitudinal dependence of variations in the ionosphere to be separated. One question that GOLD will address is: do vertical ion drifts, as manifested in the structure of the equatorial anomaly, affect the occurrence of ionospheric irregularities? Solar and geomagnetic forcing produces variations in the structure of the equatorial ionosphere at night (equatorial anomaly) and the occurrence of irregularities within the ionosphere. These ionospheric density variations, with scale sizes ranging from hundreds to tens of km, have profound effects on systems using radio frequencies. Irregularities at low latitudes are produced in the post-sunset ionosphere by the Rayleigh-Taylor (R-T) instability. The growth of these R-T instabilities into large-scale plasma bubbles has an optical signature and is the greatest source of ionospheric irregularities at low latitudes. Simulations of GOLD observations indicate

  14. Registration of ionospheric effect of 20 March 2015 solar eclipse from GPS data in single-frequency mode

    NASA Astrophysics Data System (ADS)

    Kolmogorov, Andrey; Ivanov, Vsevolod; Gorbachev, Oleg

    2015-12-01

    This article is devoted to the influence of solar eclipse of 20 March 2015 on the total electron content (TEC) of the ionosphere with using data from satellite navigation system GPS. In addition to considering TEC variations, one of the main aims was to show the possibility of using the data of the single-frequency receivers for the diagnostics of the ionosphere. Data from the single-frequency receivers were compared with dual-frequency receivers GPS. As a result, the possibility of using of the low-cost and mobile single-frequency devices for diagnostics of the ionosphere has been demonstrated. It should be noted that the data from the single-frequency receivers, as expected, showed a more noisy result, compared with the phase measurement on two-frequencies. However, after filtering high frequency harmonics result was very similar.

  15. Investigations into the properties, conditions, and effects of the ionosphere. Report No. 9, 16 December 1987-31 December 1988

    SciTech Connect

    Biello, G.D.; Fremouw, E.J.; Reinisch, B.W.; Szuszczewicz, E.P.

    1989-01-15

    Northwest Research Associates (NWRA), as prime contractor, and its two team subcontractors, Science Applications International Corp. (SAIC) and the University of Lowell Center for Atmospheric Research (ULCAR), provide members of their technical staffs to conduct and support scientific and engineering investigations of the ionosphere. The investigations address ionospheric composition, structure, specification, scintillation and chemistry as well as remote sensing of the ionosphere through ultraviolet sensors. Specific work is carried out under individual Task Requirement Notices (TRNs) written for conduct and/or support of investigations in the following six categories: laboratory measurements; field measurements; aircraft measurements; rocket, balloon, shuttle, and satellite measurements; analytical and theoretical investigations; and scientific and engineering analysis. This report provides a summary of the work performed during the period 16 December 1987 through 31 December 1988.

  16. Solar cycle effects on the structure of the electron density profiles in the dayside ionosphere of Venus

    NASA Technical Reports Server (NTRS)

    Kliore, Arvydas J.; Luhmann, Janet G.

    1991-01-01

    Results are presented of observations from the changes in the electron density structure of the dayside ionosphere of Venus that were brought about by changing solar activity. The ionopause height is generally low for values of the solar zenith angle below about 50 deg regardless of the phase in the solar cycle. At solar maximum, and at times of intermediate solar activity, the ionopause height for solar zenith angles greater than about 50 deg is highly variable, ranging from a minimum of about 200 km to a maximum of more than 1000 km. At times of solar minimum the great majority of all ionopause heights for all solar zenith angles are uniformly low, lying between 200 and 300 km. It is argued that the compressed nature of the Venus atmosphere at solar minimum is produced by permeation of the ionosphere by the solar wind magnetic field, which occurs when the solar wind dynamic pressure exceeds the ionospheric plasma pressure.

  17. The use of subionospheric VLF/LF propagation for the study of lower ionospheric perturbations associated with earthquakes

    SciTech Connect

    Hayakawa, M.

    2010-10-20

    It is recently recognized that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes (EQs), attracts a lot of attention as a very promising candidate for short-term EQ prediction. In this review we propose a possible use of VLF/LF (very low frequency (3-30 kHz)/low frequency (30-300 kHz)) radio sounding of seismo-ionospheric perturbations. We first present the first convincing evidence on the presence of ionospheric perturbations for the disastrous Kobe EQ in 1995. The significant shift in terminator times in the VLF/LF diurnal variation, is successfully interpreted in terms of lowering of the lower ionosphere prior to the EQ, which is the confirmation of seismo-ionospheric perturbations. In order to avoid the overlapping with my own previous reviews [1, 2], we try to present the latest results including the statistical evidence on the correlation between the VLF/LF propagation anomalies (ionospheric perturbations) and EQs (especially with large magnitude and with shallow depth), a case study on the Indonesia Sumatra EQ (wavelike structures in the VLF/LF data), medium-distance (6{approx}8 Mm) propagation anomalies, the fluctuation spectra of subionospheric VLF/LF data (atmospheric gravity waves effect, the effect of Earth's tides etc.), and the mechanism of lithosphere - atmosphere - ionosphere coupling. Finally, we indicate the present situation of this kind of VLF/LF activities going on in different parts of the globe and we suggest the importance of international collaboration in this seismo-electromagnetics study.

  18. Self-Consistent Magnetosphere-Ionosphere Coupling

    NASA Technical Reports Server (NTRS)

    Six, N. Frank (Technical Monitor); Khazanov, G. V.; Newman, T. S.; Liemohn, M. W.; Fok, M. C.; Spiro, R. W.

    2002-01-01

    A self-consistent ring current (RC) model has been developed that couples electron and ion magnetospheric dynamics with the calculation of the electric field. Two new features were taken into account in order to close the self-consistent magnetosphere-ionosphere coupling loop. First, in addition to the RC ions, we have solved an electron kinetic equation in our model. Second, using the relation of Galand and Richmond, we have calculated the height integrated ionospheric conductances as a function of the precipitated high energy magnetospheric electrons and ions that are produced by our model. To validate the results of our model we simulate the magnetic storm of May 2, 1986, a storm that has been comprehensively studied by Fok et al., and have compared our results with different theoretical approaches. The self-consistent inclusion of the hot electrons and their effect on the conductance results in deeper penetration of the magnetospheric electric field. In addition, a slight westward rotation of the potential pattern (compared to previous self-consistent results) is evident in the inner magnetosphere. These effects change the hot plasma distribution, especially by allowing increased access of plasma sheet ions and electrons to low L shells.

  19. Joule heating of Io's ionosphere by unipolar induction currents

    NASA Technical Reports Server (NTRS)

    Herbert, F.; Lichtenstein, B. R.

    1980-01-01

    Electrical induction in Io's ionosphere, due to the corotating plasma bound to the Jovian magnetosphere, is one possible source for the attainment of the high temperatures suggested by the large scale height of Io's ionosphere. Unipolar induction models are constructed to calculate ionospheric joule heating numerically, whose heating rates lie between 10 to the -9th and 10 to the -8th W/cu m. The binding and coupling of the ionosphere is due to the dense, and possibly ionized, neutral SO2 atmosphere, and there appears to be no need to postulate the existence of an intrinsic Ionian magnetic field in order to retain the observed ionnosphere.

  20. Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Mayr, H. G.; Curtis, S. A.; Taylor, H. A., Jr.

    1983-01-01

    A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.

  1. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.

    1993-01-01

    estimate a global grid of vertical ionospheric TEC as a function of time (i.e. every one half hour) in a sun-fixed longitude frame. Working in a sun-fixed longitude frame, one is not limited by the spatial decorrelation distance of the ionosphere, but instead is limited more by the temporal correlations of the ionosphere in the sun-fixed frame which are a smaller effect. It is the opinion of the authors that using the global sun-fixed TEC grid data, in particular, ingesting it into PRISM, offers the best possibility of meeting the 10 TECU ionospheric correction accuracy requirement, and should be the subject of further study.

  2. Magnetospheric disturbances associated with the 13 December 2006 solar flare and their ionospheric effects over North-East Asia

    NASA Astrophysics Data System (ADS)

    Zolotukhina, N.; Polekh, N.; Kurkin, V.; Pirog, O.; Samsonov, S.; Moiseyev, A.

    2012-03-01

    We present an observational study of magnetospheric and ionospheric disturbances during the December 2006 intense magnetic storm associated with the 4В/Х3.4 class solar flare. To perform the study we utilize the ground data from North-East Asian ionospheric and magnetic observatories (60-72°N, 88-152°E) and in situ measurements from LANL, GOES, Geotail and ACE satellites. The comparative analysis of ionospheric, magnetospheric and heliospheric disturbances shows that the interaction of the magnetosphere with heavily compressed solar wind and interplanetary magnetic field caused the initial phase of the magnetic storm. It was accompanied by the intense sporadic E and F2 layers and the total black-out in the nocturnal subauroral ionosphere. During the storm main phase, LANL-97A, LANL 1994_084, LANL 1989-046 and GOES_11 satellites registered a compression of the dayside magnetosphere up to their orbits. In the morning-noon sector the compression was accompanied by an absence of reflections from ionosphere over subauroral ionospheric station Zhigansk (66.8°N, 123.3°E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62°N, 129.7°E). At the end of the main phase, these stations registered a sharp foF2 increase in the afternoon sector. At Yakutsk the peak foF2 was 1.9 time higher than the undisturbed one. The mentioned ionospheric disturbances occurred simultaneously with changes in the temperature, density and temperature anisotropy of particles at geosynchronous orbit, registered by the LANL-97A satellite nearby the meridian of ionospheric and magnetic measurements. The whole complex of disturbances may be caused by radial displacement of the main magnetospheric domains (magnetopause, cusp/cleft, plasma sheet) with respect to the observation points, caused by changes in the solar wind dynamic pressure, the field of magnetospheric convection, and rotation of the Earth.

  3. Dynamic Agents of Magnetosphere-Ionosphere Coupling

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.; Rowland, Douglas E.; Moore, Thomas E.; Collier, Michael

    2011-01-01

    VISIONS sounding rocket mission (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) has been awarded to NASA/GSFC (PI Rowland) in order to provide the first combined remote sensing and in situ measurements of the regions where ion acceleration to above 5 e V is occurring, and of the sources of free energy and acceleration mechanisms that accelerate the ions. The key science question of VISIONS is how, when, and where, are ions accelerated to escape velocities in the auroral zone below 1000 km, following substorm onset? Sources of free energy that power this ion acceleration process include (but not limited) electron precipitation, field-aligned currents, velocity shears, and Alfvenic Poynting flux. The combine effect of all these processes on ionospheric ion outflows will be investigated in a framework of the kinetic model that has been developed by Khazanov et al. in order to study the polar wind transport in the presence of photoelectrons.

  4. 10 CFR 205.10 - Effective date of orders.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Effective date of orders. 205.10 Section 205.10 Energy DEPARTMENT OF ENERGY OIL ADMINISTRATIVE PROCEDURES AND SANCTIONS General Provisions § 205.10 Effective date of orders. Any order issued by the DOE or a State Office under this chapter is effective as...

  5. 42 CFR 2.61 - Legal effect of order.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Legal effect of order. 2.61 Section 2.61 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS CONFIDENTIALITY... effect of order. (a) Effect. An order of a court of competent jurisdiction entered under this subpart...

  6. 43 CFR 2450.6 - Effect of final order.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Effect of final order. 2450.6 Section 2450... Petition-Application Procedures § 2450.6 Effect of final order. (a) A final order of the Secretary shall continue in full force and effect so long as the lands remain subject to classification under...

  7. International reference ionosphere 1990

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter; Rawer, K.; Bossy, L.; Kutiev, I.; Oyama, K.-I.; Leitinger, R.; Kazimirovsky, E.

    1990-01-01

    The International Reference Ionosphere 1990 (IRI-90) is described. IRI described monthly averages of the electron density, electron temperature, ion temperature, and ion composition in the altitude range from 50 to 1000 km for magnetically quiet conditions in the non-auroral ionosphere. The most important improvements and new developments are summarized.

  8. Integrity monitoring in real-time precise point positioning in the presence of ionospheric disturbances

    NASA Astrophysics Data System (ADS)

    Wezka, K.; Galas, R.

    2013-12-01

    Ionospheric disturbances are characterized as fast and random variability in the ionosphere. Those phenomena are difficult to predict, detect and model. Occurrence of some strong ionospheric disturbances can cause, inter alia degradation and interruption of GNSS signals. Therefore they are especially harmful for real-time applications, as for example Precise Point Positioning (PPP) in real time, where one of the most important requirements is to ensure the high level of reliability. In such applications verification and confirmation of a high trust degree towards the estimated coordinates is a very critical issue. In one of the previous papers (K. Wezka, 2012 -Identification of system performance parameters and their usability) two sets of parameters have been proposed for enhance reliability of the PPP. The first one for data quality control (QC) of the raw GNSS observations and the second one for examination of the quality, robustness and performance of various processing approaches (strategies). To the second group the following parameters has been proposed: accuracy, precision, availability, integrity and convergence time. In consideration of perturbation of GNSS signal resulting from sudden ionospheric disturbances, one of the most important demands is effective autonomous integrity monitoring. The poster presents first preliminary results of the applicability of the proposed parameters in order to ensure the high level of reliability/integrity of GNSS observations and positioning results under the presence of strong ionospheric anomalies. The data-set from continuously operated GNSS station located at high latitude, where ionospheric disturbances occur more frequently, were used for the analysis. Various selected Receiver Autonomous Integrity Monitoring (RAIM) approaches for quality control of the GNSS observables are applied to the data sets recorded under different (low/quite and high) ionospheric activities. Based on those analyses the usability of the

  9. Modeling the global positioning system signal propagation through the ionosphere

    NASA Technical Reports Server (NTRS)

    Bassiri, S.; Hajj, G. A.

    1992-01-01

    Based on realistic modeling of the electron density of the ionosphere and using a dipole moment approximation for the Earth's magnetic field, one is able to estimate the effect of the ionosphere on the Global Positioning System (GPS) signal for a ground user. The lowest order effect, which is on the order of 0.1-100 m of group delay, is subtracted out by forming a linear combination of the dual frequencies of the GPS signal. One is left with second- and third-order effects that are estimated typically to be approximately 0-2 cm and approximately 0-2 mm at zenith, respectively, depending on the geographical location, the time of day, the time of year, the solar cycle, and the relative geometry of the magnetic field and the line of sight. Given the total electron content along a line of sight, the authors derive an approximation to the second-order term which is accurate to approximately 90 percent within the magnetic dipole moment model; this approximation can be used to reduce the second-order term to the millimeter level, thus potentially improving precise positioning in space and on the ground. The induced group delay, or phase advance, due to second- and third-order effects is examined for two ground receivers located at equatorial and mid-latitude regions tracking several GPS satellites.

  10. Improved geodetic earthquake source modelling through correction of ionospheric disturbances in L-band InSAR data

    NASA Astrophysics Data System (ADS)

    Sudhaus, Henriette; Gomba, Giorgio; Eineder, Michael

    2016-04-01

    The use of L-band InSAR data for observing the surface displacements caused by earthquakes can be very beneficial. The retrieved signal is generally more stable against temporal phase decorrelation with respect to C-band and X-band InSAR data, such that fault movements also in vegetated areas can be observed. Also, due to the longer wavelength, larger displacement gradients that occur close to the ruptures can be measured. A serious draw back of L-band data on the other hand is that it more strongly reacts to heterogeneities in the ionosphere. The spatial variability of the electron content causes spatially long wavelength trends in the interferometric phase, distorts the surface deformation signal therefore impacts on the earthquake source analysis. A well-known example of the long-wavelength distortions are the ALOS-1 InSAR observations of the 2008 Wenchuan earthquake. To mitigate the effect of ionospheric phase in the geodetic modelling of earthquake sources, a common procedure is to remove any obvious linear or quadratic trend in the surface displacement data that may have been caused by ionospheric phase delays. Additionally, remaining trends may be accounted for by including so-called ambiguity (or nuisance) parameters in the modelling. The introduced ionospheric distortion, however, is only approximated arbitrarily by such simple ramp functions with the true ionospheric phase screen unknown. As a consequence, either a remaining ionospheric signal may be mistaken for surface displacement or, the other way around, long-wavelength surface displacement may be attributed to ionospheric distortion and is removed. The bias introduced to the source modelling results by the assumption of linear or quadratic ionospheric effects is therefore unknown as well. We present a more informed and physics-based correction of the surface displacement data in earthquake source modelling by using a split-spectrum method to estimate the ionospheric phase screen superimposed to the

  11. Space weather. Ionospheric control of magnetotail reconnection.

    PubMed

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail. PMID:25013068

  12. Nonlinear unstable auroral-arc driven thermospheric winds in an ionosphere-magnetosphere coupled model

    NASA Technical Reports Server (NTRS)

    Keskinen, M. J.; Satyanarayana, P.

    1993-01-01

    The nonlinear evolution of thermospheric winds in an ionosphere-magnetosphere coupled model has been studied for the first time for a dynamic unstable auroral-arc environment. We treat the problem using a multi-layer, quasi-three-dimensional model which averages in altitude the thermospheric dynamics over each layer. For the upper thermosphere, we find that (1) the thermosphere can respond to the ionospheric Kelvin-Helmholtz (KH) instability on temporal scales on the order of an hour, depending on ambient conditions, and on spatial scales of tens to hundreds of kilometers, (2) strong thermospheric meridional and zonal vortical flows with embedded nonlinear jet-like structures can be generated by the ionospheric/magnetospheric KH instability and (3) neutral thermospheric winds, vortices, and associated power spectra develop in a distinctly different manner in the presence of magnetospheric coupling effects. Comparison with recent observations is made.

  13. A case study on effect of the magnetic storm of 20 November 2003 on GPS ionospheric scintillation at Vanimo station

    NASA Astrophysics Data System (ADS)

    Yang, Shenggao; Fang, HanXian; Weng, Libin; Luo, Jie; Zhou, Xiaoke

    2015-11-01

    The magnetic storm of November 20-21, 2003 was a super storm with minimum Dst -438 nT. Using the GPS ionospheric scintillation data recorded at Vanimo station near the magnetic equator, we investigate the behaviors of the ionospheric scintillations during the storm. The amplitude ionospheric scintillations were enhanced evidently at 19:00-20:00 LT on November 20 2003, corresponding to the sudden increased solar wind speed, steep increase and reorientation in IMF components, intensification of AE and decreased Dst (Sym-H). Severe density depletion region over Vanimo station, and density enhanced areas adjacent to its northern and southern directions were observed simultaneously. It is the prompt penetration of eastward electric field associated with the southward turning of the IMF and intensification of AE that elevate the ionospheric plasma to certain height through the E × B mechanism, then the plasma drifts along the magnetic lines to low latitude, thus forming the great north-south gradient of electron density. Therefore, the sudden change of the electron density during the period may be responsible for the storm-induced scintillation enhancements at Vanimo station.

  14. Interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from Cluster EDI observations

    NASA Astrophysics Data System (ADS)

    Förster, Matthias; Haaland, Stein

    2015-04-01

    Here, we present a study of ionospheric convection at high latitudes that is based on satellite measurements of the Electron Drift Instrument (EDI) on-board the Cluster satellites, which were obtained over a full solar cycle (2001-2013). The mapped drift measurements are covering both hemispheres and a variety of different solar wind and interplanetary magnetic field (IMF) conditions. The large amount of data allows us to perform more detailed statistical studies. We show that flow patterns and polar cap potentials can differ between the two hemispheres on statistical average for a given IMF orientation. In particular, during southward directed IMF conditions, and thus enhanced energy input from the solar wind, we find that the southern polar cap has a higher cross polar cap potential. We also find persistent north-south asymmetries which cannot be explained by external drivers alone. Much of these asymmetries can probably be explained by significant differences in the strength and configuration of the geomagnetic field between the Northern and Southern Hemisphere. Since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. Consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace. The average convection is higher during periods with high solar activity. Although local ionospheric conditions may play a role, we mainly attribute this to higher geomagnetic activity due to enhanced solar wind - magnetosphere interactions.

  15. Characterization of Ionospheric Scintillation Using Simultaneous Formosat-3/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements

    NASA Astrophysics Data System (ADS)

    Starks, M. J.; Lin, C. S.; Groves, K. M.; Pedersen, T. R.; Basu, S.; Syndergaard, S.; Rocken, C.

    2007-05-01

    Ionospheric scintillation at low latitudes has been studied using ionospheric radio occultation (RO) measurements by the FORMOSAT-3/COSMIC micro-satellites in conjunction with ground-based data from the Scintillation Network Decision Aid (SCINDA) station at Kwajalein Atoll. The Air Force Research Laboratory has developed the SCINDA network for monitoring low-latitude ionospheric total electron content (TEC) and scintillation associated with equatorial spread F. The network currently consists of sixteen stations distributed around the globe and the data have been used to conduct numerous studies on the characteristics and climatology of equatorial scintillation. The present study focuses on COSMIC RO and SCINDA data during the three COSMIC campaigns in 2006. Radio occultation events are selected by requiring that ionospheric scintillation was detected by the SCINDA VHF scintillation monitor at Kwajalein, and that the occultation ray path intersected the Kwajalein longitude below the satellite altitude, which varied from 500 to 800 km for the six FORMOSAT-3 satellites. In order to exclude tropospheric effects, only GPS signal amplitudes from FORMOSAT-3 with ray path tangent altitudes above 100 km are considered. Locations of ionospheric scintillation are estimated by triangulation using the satellites and the SCINDA ground station. Airglow images at Kwajalein are also used to confirm occurrence of equatorial ionospheric scintillations. For the selected events, large amplitude L1 and L2 scintillations tend to occur at altitudes below 200 km at frequencies around 0.5 Hz. The results are discussed as a potential path toward better specifying the occurrence of equatorial scintillations.

  16. Influence of interplanetary solar wind sector polarity on the ionosphere

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Liu, Libo; Zhao, Biqiang; Wan, Weixing

    2012-08-01

    Knowledge of solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day-to-day variability and "hysteresis" effect on foF2. Ionospheric response to changes in solar sector polarity has not been fully documented previously, partly due to the limitation of observations. In this study, a solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbances and ionospheric perturbations has been demonstrated. The increases in interplanetary solar wind speed within three days are seen after SB crossings, while the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings are confirmed by the superposed epoch analysis results. Furthermore, the interplanetary magnetic field (IMF) Bz component turns from northward to southward in March equinox and June solstice as the Earth passes from a solar sector of outward to inward directed magnetic fields, whereas the reverse situation occurs for the transition from toward to away sectors. The IMF Bz component for the same solar sector polarity has opposite signs between March equinox and September equinox, and also between June solstice and December solstice. In order to know how the ionosphere reacts to the interplanetary solar wind variations linkage of SB crossings, the F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998-2011 are utilized to extract the related information, revealing that they are not modified significantly and vary within the range of ±15% on average. The responses of the ionospheric TEC to SB crossings exhibit complex temporal and spatial variations and have strong dependencies on season, latitude, and solar cycle. This effect is more appreciable in equinoctial months than in solstitial months, which is mainly caused by larger southwardBzcomponents in equinox. In September equinox, latitudinal profile of relative

  17. The Ionosphere and the Latin America Very Low Frequency Network Mexico (LAVNet-Mex)

    NASA Astrophysics Data System (ADS)

    Borgazzi, A.; Lara, A.; Santiago, A.

    2013-05-01

    The radiation emitted by the most energetic transient events in the solar system, solar flares, covers a wide range of wavelengths, from radio waves to gamma rays. When the transient excess of high energy radiation produced by solar flares reach the Earth environment, the upper layers of the Earth atmosphere are affected and highly disturbed. The dynamics (particularly the conductivity) of the ionosphere, is altered during solar explosive events. In order to detect and study the ionospheric response to the transient solar radiative input, we have constructed a VLF receiver station: the `Latin American Very low frequency Network at Mexico' (LAVNet-Mex), which extends to the northern hemisphere the South American VLF Network. LAVNet-Mex detects electromagnetic waves generated by strong transmitters located around the world. These waves travel inside the Earth-Ionosphere waveguide, along the Great Circle Path formed between the emitter and the observer. By observing changes in the phase and amplitude of these waves, it is possible to study the dynamics of the lower layer of the ionosphere during solar eruptive events. In this work we present preliminary results of the analysis of the effects of solar flares (class M and X) occurred in 2012 and that were observed by LAVNet-Mex. We explore the relationship between VLF signals coming from different paths during these solar burst to infer the degree of correlation that can exist between different sectors of the ionosphere.

  18. Nonlinear Planetary Electromagnetic Vortex Structures in the Ionospheric F-Layer

    SciTech Connect

    Aburjaniya, G. D.; Khantadze, A. G.; Kharshiladze, O. A.

    2002-07-15

    A study is made of the dynamics of planetary-scale electromagnetic waves in the F-layer of the ionosphere. It is shown that, in this layer, a new branch of large-scale magneto-ionospheric wave perturbations is generated under the action of the latitudinal variations of the geomagnetic field, which are a constant property of the ionosphere. The waves propagate along the parallels with phase velocities of tens to hundreds of km/s. The pulsations of the geomagnetic field in the waves can be as strong as several tens of nT. A possible self-localization effect is revealed: these waves may form nonlinear localized solitary vortices moving either westward or eastward along the parallels with velocities much higher than the phase velocities of the linear waves. The characteristic dimension of a vortex is about 10{sup 4} km or even larger. The magnetic fields generated by vortex structures are one order of magnitude stronger than those in linear waves. The vortices are long-lived formations and may be regarded as elements of strong structural turbulence in the ionosphere. The properties of the wave structures under investigation are very similar to those of ultralow-frequency perturbations observed experimentally in the ionosphere at middle latitudes.

  19. Ionospheric Modelling using GPS to Calibrate the MWA. II: Regional Ionospheric Modelling using GPS and GLONASS to Estimate Ionospheric Gradients

    NASA Astrophysics Data System (ADS)

    Arora, B. S.; Morgan, J.; Ord, S. M.; Tingay, S. J.; Bell, M.; Callingham, J. R.; Dwarakanath, K. S.; For, B.-Q.; Hancock, P.; Hindson, L.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.

    2016-07-01

    We estimate spatial gradients in the ionosphere using the Global Positioning System and GLONASS (Russian global navigation system) observations, utilising data from multiple Global Positioning System stations in the vicinity of Murchison Radio-astronomy Observatory. In previous work, the ionosphere was characterised using a single-station to model the ionosphere as a single layer of fixed height and this was compared with ionospheric data derived from radio astronomy observations obtained from the Murchison Widefield Array. Having made improvements to our data quality (via cycle slip detection and repair) and incorporating data from the GLONASS system, we now present a multi-station approach. These two developments significantly improve our modelling of the ionosphere. We also explore the effects of a variable-height model. We conclude that modelling the small-scale features in the ionosphere that have been observed with the MWA will require a much denser network of Global Navigation Satellite System stations than is currently available at the Murchison Radio-astronomy Observatory.

  20. Effects of VLF heating of ionosphere on the transmission cone of MF waves propagating from ground to space

    NASA Astrophysics Data System (ADS)

    Lefeuvre, F.; Pincon, J.; Parrot, M.

    2012-12-01

    Global maps of VLF-MF waves observed by the low-altitude (~700 km) DEMETER satellite (Parrot et al., 2009) have pointed out localized enhancements of wave energy above the most powerful VLF transmitters and their conjugate regions, both in the 18-25 kHz frequency range (VLF transmitters) and in the 2.-2.5 MHz frequency range (emissions associated with lightning discharges). Under hypothesis made for the computation of the refractive index by the Appleton-Hartree formula, simulations are conducted to estimate the effect of VLF heating on the transmission cone of MF waves propagating from ground to space. The method used consists in the computation of the vertical variations of the Real part of the refractive index n and of the α attenuation factor (α = ω. Imag(n)/c), with an IRI electron density profile derived from the geophysical parameters of a DEMETER orbit and an hybrid collision frequency model taking into account of theoretical and experimental data. Half-angles of the transmission cone are estimated: first, at the X=1 (X=fpe2/f2) low altitude boundary (where Ordinary mode waves may be converted into Extraordinary mode waves), and second, at the high-altitude X=1 boundary (where Extraordinary mode waves may be converted into Ordinary mode waves). It is shown that enhancements in the collision frequencies, produced by VLF heating at altitudes where the product of the collision frequency ν by the electronic density Ne is maximum (i.e. at altitudes including the low-altitude and the high-altitude X=1 boundaries), open the half angle of the transmission cones for MF waves which cross the ionosphere, and so explain enhancements of wave energy observed in the 2. - 2.5 MHz band above the powerful VLF transmitters and their conjugate regions.

  1. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  2. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  3. 38 CFR 1.490 - Legal effect of order.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... exercise discretion pursuant to 38 U.S.C. 5701(b)(5) and 38 CFR 1.511 to disclose such records. It does not... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Legal effect of order. 1... PROVISIONS Court Orders Authorizing Disclosures and Use § 1.490 Legal effect of order. The records to...

  4. Multifractal behaviour of the ionospheric scintillation index time series over an Indian low latitude station Surat

    NASA Astrophysics Data System (ADS)

    Tanna, H. J.; Pathak, K. N.

    2014-03-01

    The amplitude scintillation information recorded by the GSV4004B GISTM (Global Ionospheric Scintillation TEC Monitor) GPS receiver at an Indian low latitude station Surat (21.16°N, 72.78°E) for 48 months during the years 2009, 2010, 2011 and 2012 are utilized in the present work. Multifractal detrended fluctuation analysis (MF-DFA) have been carried out along with computation of q-order fluctuation function, q-order Hurst exponent, q-order mass exponent and multifractal spectrums for each monthly post-sunset S4 index time series. The non-linear dependence of mass exponent and dependence of q-order Hurst exponent on q-values reflect the existence of nonlinear interaction between different scales and multifractal structure in the system, respectively. The comparison of broadness and shape of spectra with the occurrence of scintillation activities registered in the same period reveal the existence of multifractality/complexity in the turbulent ionosphere, which is influenced by the small-scale intermittency and solar flux indices. The truncation of the spectrum is the evidence of manifestation of small-scale intermittency of the turbulent ionosphere. The higher values of the Hölder exponent α0, calculated from the spectrum, imply the irregular nature of the underlying process. The present study suggests that, MF-DFA may act as an important non-linear technique for identifying the effect of large and small-scale fluctuations in complex and turbulent ionosphere.

  5. 37 CFR 251.57 - Effective date of order.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... ARBITRATION ROYALTY PANEL RULES AND PROCEDURES COPYRIGHT ARBITRATION ROYALTY PANEL RULES OF PROCEDURE Procedures of Copyright Arbitration Royalty Panels § 251.57 Effective date of order. An order...

  6. Effects of time ordering in quantum nonlinear optics

    NASA Astrophysics Data System (ADS)

    Quesada, Nicolás; Sipe, J. E.

    2014-12-01

    We study time-ordering corrections to the description of spontaneous parametric down-conversion (SPDC), four-wave mixing (SFWM), and frequency conversion using the Magnus expansion. Analytic approximations to the evolution operator that are unitary are obtained. They are Gaussian preserving, and allow us to understand order-by-order the effects of time ordering. We show that the corrections due to time ordering vanish exactly if the phase-matching function is sufficiently broad. The calculation of the effects of time ordering on the joint spectral amplitude of the photons generated in SPDC and SFWM are reduced to quadrature.

  7. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<−100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3–6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow. PMID:26167429

  8. Model of Jovian F region ionosphere (Saturnian ionosphere in offset dipole approximation)

    NASA Technical Reports Server (NTRS)

    Tan, A.

    1991-01-01

    Researchers investigated the offset effect of Saturn's dipole on its ionosphere. The magnetic field of Saturn is primarily that of a dipole closely aligned to the rotational axis, but displaced northward from the center by a distance approximately equal to 0.05 R sub S, R sub S being the reference radius of Saturn. This offset effect would manifest itself most prominently between the ionospheric profiles in the Northern and Southern Hemispheres of Saturn.

  9. Penetration characteristics of VLF wave from atmosphere into lower ionosphere

    NASA Astrophysics Data System (ADS)

    Zhao, Shufan; Shen, Xuhui; Pan, Weiyan; Zhang, Xuemin; Liao, Li

    2010-06-01

    The factors affecting the reflection and transmission coefficient of the ionosphere have been analyzed. These factors include wave frequency, incident angle, geomagnetic inclination, electron density and collision frequency in the ionosphere. The ionosphere refractive index is also analyzed. The ionosphere above 70 km is considered to be homogeneous and anisotropic, and the reflection and transmission coefficient matrix is calculated using matrix method. Simultaneously the Booker quartic equation is solved to get the refractive index in the ionosphere. The results show that when the wave frequency is higher, it is easier to penetrate into the ionosphere from its bottom boundary and the propagation attenuation in the ionosphere is smaller. TE (traverse electric) wave and TM (traverse magnetic) wave can both penetrate into the ionosphere with a small incident angle, while TE wave can hardly transmit into the ionosphere when the incident angle is large. The transmission coefficient decreases as the geomagnetic inclination increases. TE and TM wave cannot penetrate into the ionosphere at magnetic equator. When the electron collision frequency is higher, it is easier for VLF wave to penetrate into the ionosphere and the attenuation of ordinary wave is weaker, which may be caused by the energy transportation between the waves and the particles. The ordinary (O) wave experiences severer attenuation than extraordinary (X) wave, and X wave is a penetration mode whereas O wave is a non-penetration mode in the ionosphere. All the results indicate that VLF wave with higher frequency is easier to penetrate into the ionosphere and to be recorded by the satellites at high latitude. It is hard for ULF and the lower frequency VLF wave to transmit into the ionosphere directly for the severe reflection and attenuation. It may transmit into the ionosphere with a small incident angle due to the nonlinear effect, for example, the interaction between the waves and the particles or cross

  10. Statistical analysis of ionosphere parameters and atmospheric pressure correlations

    NASA Astrophysics Data System (ADS)

    Voloskov, Dmitriy; Bochkarev, Vladimir; Maslennikova, Yulia; Zagidullin, Bulat

    Ionosphere parameters such as Total electron content (TEC) and Doppler frequency shift characterize ionosphere influence on signals propagation, and therefore information about these parameters is important for radio communication tasks. Meteorological effects such as atmospheric pressure variations can influence on ionosphere parameters. This work is dedicated to analysis of correlations between meteorological and ionosphere parameters. NCEP/NCAR reanalysis meteorological maps, Jet Propulsion Laboratory (JPL) global TEC maps and data from Doppler phase goniometric complex “Spectr” were analysed. Data for 2009-2011 were investigated. Coherent oscillations with periods of 29-32 and 4 days were detected in atmospheric pressure and Doppler frequency shift variations.

  11. 49 CFR 511.57 - Effective date of order.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 6 2011-10-01 2011-10-01 false Effective date of order. 511.57 Section 511.57... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ADJUDICATIVE PROCEDURES Decision § 511.57 Effective date of order... effective upon the expiration of the statutory period for court review specified in section 508(c)(1) of...

  12. Toward the azimuthal characteristics of ionospheric and seismic effects of "Chelyabinsk" meteorite fall according to the data from coherent radar, GPS, and seismic networks

    NASA Astrophysics Data System (ADS)

    Berngardt, O. I.; Perevalova, N. P.; Dobrynina, A. A.; Kutelev, K. A.; Shestakov, N. V.; Bakhtiarov, V. F.; Kusonsky, O. A.; Zagretdinov, R. V.; Zherebtsov, G. A.

    2015-12-01

    We present the results of a study of the azimuthal characteristics of ionospheric and seismic effects of the meteorite `Chelyabinsk,' based on the data from the network of GPS receivers, coherent decameter radar EKB, and network of seismic stations, located near the meteorite fall trajectory. It is shown that 6-14 min after the bolide explosion, GPS network observed the cone-shaped wavefront of traveling ionospheric disturbances (TIDs) that is interpreted as a ballistic acoustic wave. The typical TIDs propagation velocity were observed 661 ± 256 m/s, which corresponds to the expected acoustic wave speed for 240 km height. Fourteen minutes after the bolide explosion, at distances of 200 km, we observed the emergence and propagation of a TID with annular wavefront that is interpreted as gravitational mode of internal atmospheric waves. The propagation velocity of this TID was 337 ± 89 m/s which corresponds to the propagation velocity of these waves in similar situations. At EKB radar, we observed TIDs in the sector of azimuthal angles close to the perpendicular to the meteorite trajectory. The observed TID velocity (400 m/s) and azimuthal properties correlate well with the model of ballistic wave propagating at 120-140 km altitude. It is shown that the azimuthal distribution of the amplitude of vertical seismic oscillations with periods 3-60 s can be described qualitatively by the model of vertical strike-slip rupture, propagating at 1 km/s along the meteorite fall trajectory to distance of about 40 km. These parameters correspond to the direction and velocity of propagation of the ballistic wave peak by the ground. It is shown that the model of ballistic wave caused by supersonic motion and burning of the meteorite in the upper atmosphere can satisfactorily explain the various azimuthal ionospheric effects, observed by the coherent decameter radar EKB, GPS receivers network, and the azimuthal characteristics of seismic waves at large distances.

  13. Ionosphere TEC disturbances before strong earthquakes: observations, physics, modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Namgaladze, A. A.

    2013-12-01

    The phenomenon of the pre-earthquake ionospheric disturbances is discussed. A number of typical TEC (Total Electron Content) relative disturbances is presented for several recent strong earthquakes occurred in different ionospheric conditions. Stable typical TEC deviations from quiet background state are observed few days before the strong seismic events in the vicinity of the earthquake epicenter and treated as ionospheric earthquake precursors. They don't move away from the source in contrast to the disturbances related with geomagnetic activity. Sunlit ionosphere approach leads to reduction of the disturbances up to their full disappearance, and effects regenerate at night. The TEC disturbances often observed in the magnetically conjugated areas as well. At low latitudes they accompany with equatorial anomaly modifications. The hypothesis about the electromagnetic channel of the pre-earthquake ionospheric disturbances' creation is discussed. The lithosphere and ionosphere are coupled by the vertical external electric currents as a result of ionization of the near-Earth air layer and vertical transport of the charged particles through the atmosphere over the fault. The external electric current densities exceeding the regular fair-weather electric currents by several orders are required to produce stable long-living seismogenic electric fields such as observed by onboard measurements of the 'Intercosmos-Bulgaria 1300' satellite over the seismic active zones. The numerical calculation results using the Upper Atmosphere Model demonstrate the ability of the external electric currents with the densities of 10-8-10-9 A/m2 to produce such electric fields. The sumulations reproduce the basic features of typical pre-earthquake TEC relative disturbances. It is shown that the plasma ExB drift under the action of the seismogenic electric field leads to the changes of the F2 region electron number density and TEC. The upward drift velocity component enhances NmF2 and TEC and

  14. Detection and Investigation of Ionospheric Disturbances using the SCIGN Network

    NASA Astrophysics Data System (ADS)

    Lee, S.; Garrison, J. L.; Calais, E.; Haase, J.

    2004-12-01

    Ionospheric perturbations associated with atmospheric disturbances, such as earthquakes, large explosions, or rocket launches have been detected in the past, through filtering of dual-frequency GPS phase data. To further study these phenomena, we extract GPS data from the SCIGN network in Southern California, and attempt to identify the direction and speed of propagation, particularly for examples in which no obvious source could be identified. The processing of data from about 250 stations in the SCIGN followed three general steps. First the IEC (Integrated Electron Contents) time series was bandpass-filtered between 3 and 8 minutes. Second, the filtered time series from each pair of two SIPs (Sub-ionospheric points) were cross-correlated, to detect the degree of similarity between the perturbations, and to estimate the time of travel between the SIP. Finally, the travel times, for all pairs of SIP's for which a disturbance was detected, were used to estimate the propagation velocity (speed and direction) of the disturbance using a least squares method. An effect, which is similar to the Doppler effect, is predicted to result from the motion of the SIP during the time in which the perturbations are recorded. Since the speeds of the SIPs, due to satellite motion, are on the same order of magnitude as the propagation speed of ionospheric disturbances, an apparent shift in the observed frequency of the disturbances would result, depending upon the orientation between the propagation directions of the SIP's and the ionospheric disturbance. In addition to experimental data, recorded on 07/07/2000, simulated data was also used to validate the data processing algorithms, and to assess their sensitivity.

  15. Ionospheric Variability and Storms on Mars

    NASA Technical Reports Server (NTRS)

    Mendillo, Michael

    2004-01-01

    The goal of this grant was to conduct the first-ever study of ionospheric variability on Mars. To do so, we used data from the Radio Science (RS) experiment onboard the Mars Global Surveyor (MGS) satellite. Dr. David Hinson of the RS team at Stanford University was a most helpful and valuable colleague throughout the studies we conducted. For the initial RS datasets available from the MGS mission, there were no severe storms caused by solar wind activity, so we concentrated on day-to-day effects. This turned out to be a wise approach since understanding "normal variability" had to be done before any claim could be made about "space weather" effects. Our approach was three-fold: (1) select a good dataset for characterization of ionosphere variability at Mars, one for which excellent terrestrial data were also available. This turned out to be the period 9-27 March 1999; (2) once the variability at Mars was described, develop and use a new photochemical model of the martian ionosphere to find the extent to which solar variability on those days caused or contributed to the observed patterns; (3) use the results from the above, together with additional datasets from the MGS/RS experiment, to describe some practical consequences that the martian ionosphere would have upon NASA s proposed navigation and communications systems for Mars. The results of these studies showed that: (a) solar variability is the dominant source of ionospheric variability at Mars (during periods of quiet solar wind), (b) that current models do a good job in portraying such effects at the height of the ionospheric peak electron density, and (c) that ionospheric structure on Mars can affect attempts at precise position-fixing at Mars should relatively high (GPS-like) frequencies not be used in a Mars communications and navigation system.

  16. Role of Ionospheric Plasmas in Earth's Magnetotail

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.

    2007-01-01

    This tutorial will summarize observations and theories indicating a prominent role of ionospheric plasma in the Earth's magnetotail. At the Global scale, I will argue that it is ionospheric plasma momentum and dynamic pressure that are responsible for the production of plasmoids, through the action of a transient near-Earth neutral or X-line, which serves to release excessive plasma pressure from the magnetotail field. Ionospheric plasma gains the momentum and energy to produce plasmoids and their related effects through its interaction with the solar wind, beginning at the dayside reconnection region and extending across the polar caps through the magnetotail lobes. This distant neutral line can be depicted as a feature much like that found in cometary magnetospheres, where disconnection limits the amount of IMF hung up on the cometary coma. On the other hand, the near-Earth neutral one can be seen as a feature unique to planets with an intrinsic magnetic field and internal source of plasma, the heating of which produces pressures too large to be restrained. Ionospheric plasmas also have other more local roles to play in the magnetotail. The circulation influences the composition of the plasma sheet, and the resultant wave environment, giving rise to reduced wave propagation speeds. Important heavy ion cyclotron resonances, and enhanced finite gyro-radius effects including non-adiabatic particle acceleration. At minimum, the presence of ionospheric plasma must influence the rate of reconnection via its enhanced mass density. Other non-MHD effects of ionospheric plasma presence are likely to be important but need much more investigation to be well understood. The MMS mission is designed to penetrate the subtle diffusion region physics that is involved, and its ability to observe ionospheric plasma involvement in reconnection will contribute significantly toward that goal.

  17. Ionospheric Storms in Equatorial Region: Digisonde Observations

    NASA Astrophysics Data System (ADS)

    Paznukhov, V.; Altadill, D.; Blanch, E.

    2011-12-01

    We present a study of the ionospheric storms observed in the low-latitude and equatorial ionosphere at several digisonde stations: Jicamarca (Geomagnetic Coordinates: 2.0 S, 355.3 E), Kwajalein Island (3.8 N, 238.2 E), Ascension Island (2.5 S, 56.8 E), Fortaleza (4.8 N, 33.7 W), and Ramey (28.6 N, 5.2 E). The strongest geomagnetic storms from years 1995-2009 have been analyzed. The main ionospheric characteristics, hmF2 and foF2 were used in the study, making it possible to investigate the changes in the ionosphere peak density and height during the storms. All digisonde data were manually processed to assure the accuracy of the measurements. Solar wind data, geomagnetic field variations, and auroral activity indices have been used to characterize the geomagnetic environment during the events. It was found in our analysis that the major drivers for the ionospheric storms, electric field and neutral wind have approximately equal importance at the low-latitude and equatorial latitudes. This is noticeably different from the behavior of the ionsphere in the middle latitudes, where the neutral wind is usually a dominant factor. It was found that the auroral index, AE is the best precursor of the ionospheric effects observed during the storms in this region. We analyze the difference between time delays of the storm effects observed at the stations located in different local time sectors. The overall statistics of the time delays of the storms as a function of the local time at the stations is also presented. Several very interesting cases of sudden very strong ionospheric uplifting and their possible relation to the equatorial super fountain effect are investigated in greater details.

  18. Radar Ionospheric Impact Mitigation

    NASA Astrophysics Data System (ADS)

    Bishop, G.; Decker, D.; Baker, C.

    2006-12-01

    New ionospheric modeling technology is being developed to improve correction of ionospheric impacts on the performance of ground-based space-surveillance radars (SSRs) in near-real-time. These radars, which detect and track space objects, can experience significant target location errors due to ionospheric delay and refraction of the radar signals. Since these radars must detect and track targets essentially to the radar horizon, it is necessary to accurately model the ionosphere as the radar would observe it, down to the local horizon. To correct for spatial and temporal changes in the ionosphere the model must be able to update in near-real-time using ionospheric sensor data. Since many radars are in isolated locations, or may have requirements to operate autonomously, an additional required capability is to provide accurate ionospheric mitigation by exploiting only sensor data from the radar site. However, the model must also be able to update using additional data from other types of sensors that may be available. The original radar ionospheric mitigation approach employed the Bent climatological model. This 35-year-old technology is still the means employed in the many DoD SSRs today. One more recent approach used capabilities from the PRISM model. PRISM technology has today been surpassed by `assimilative models' which employ better physics and Kalman filtering techniques. These models are not necessarily tailored for SSR application which needs to optimize modeling of very small regions using only data from a single sensor, or very few. The goal is to develop and validate the performance of innovative and efficient ionospheric modeling approaches that are optimized for the small regions applicable to ground-based radar coverage (radius of ~2000 km at ionospheric altitudes) and somewhat beyond. These approaches must adapt a continuous modeling scheme in near-real-time to be consistent with all observational data that may become available, and degrade

  19. Use of IRI to Model the Effect of Ionosphere Emission on Earth Remote Sensing at L-Band

    NASA Technical Reports Server (NTRS)

    Abraham, Saji; LeVine, David M.

    2004-01-01

    Microwave remote sensing in the window at 1.413 GHz (L-band) set aside for passive use only is important for monitoring sea surface salinity and soil moisture. These parameters are important for understanding ocean dynamics and energy exchange between the surface and atmosphere, and both NASA and ESA plan to launch satellite sensors to monitor these parameters at L-band (Aquarius, Hydros and SMOS). The ionosphere is an important source of error for passive remote sensing at this frequency. In addition to Faraday rotation, emission from the ionosphere is also a potential source of error at L-band. As an aid for correcting for emission, a regression model is presented that relates ionosphere emission to the integrated electron density (TEC). The goal is to use TEC from sources such as TOPEX, JASON or GPS to obtain estimates of emission over the oceans where the electron density profiles needed to compute emission are not available. In addition, data will also be presented to evaluate the use of the IRI for computing emission over the ocean.

  20. Dayside Ionospheric Superfountain

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Verkhoglyadova, Olga P.; Mannucci, Anthony J.

    2010-01-01

    The Dayside Ionospheric Super-fountain modified SAMI2 code predicts the uplift, given storm-time electric fields, of the dayside near-equatorial ionosphere to heights of over 800 kilometers during magnetic storm intervals. This software is a simple 2D code developed over many years at the Naval Research Laboratory, and has importance relating to accuracy of GPS positioning, and for satellite drag.

  1. Global Ionosphere Radio Observatory

    NASA Astrophysics Data System (ADS)

    Galkin, I. A.; Reinisch, B. W.; Huang, X. A.

    2014-12-01

    The Global Ionosphere Radio Observatory (GIRO) comprises a network of ground-based high-frequency vertical sounding sensors, ionosondes, with instrument installations in 27 countries and a central Lowell GIRO Data Center (LGDC) for data acquisition and assimilation, including 46 real-time data streams as of August 2014. The LGDC implemented a suite of technologies for post-processing, modeling, analysis, and dissemination of the acquired and derived data products, including: (1) IRI-based Real-time Assimilative Model, "IRTAM", that builds and publishes every 15-minutes an updated "global weather" map of the peak density and height in the ionosphere, as well as a map of deviations from the classic IRI climate; (2) Global Assimilative Model of Bottomside Ionosphere Timelines (GAMBIT) Database and Explorer holding 15 years worth of IRTAM computed maps at 15 minute cadence;. (3) 17+ million ionograms and matching ionogram-derived records of URSI-standard ionospheric characteristics and vertical profiles of electron density; (4) 10+ million records of the Doppler Skymaps showing spatial distributions over the GIRO locations and plasma drifts; (5) Data and software for Traveling Ionospheric Disturbance (TID) diagnostics; and (6) HR2006 ray tracing software mated to the "realistic" IRTAM ionosphere. In cooperation with the URSI Ionosonde Network Advisory Group (INAG), the LGDC promotes cooperative agreements with the ionosonde observatories of the world to accept and process real-time data of HF radio monitoring of the ionosphere, and to promote a variety of investigations that benefit from the global-scale, prompt, detailed, and accurate descriptions of the ionospheric variability.

  2. Effect of auroral substorms on the ionospheric range spread-F enhancements at high southern midlatitudes using real time vertical-sounding ionograms

    NASA Astrophysics Data System (ADS)

    Hajkowicz, Lech A.

    2016-03-01

    A comprehensive study has been undertaken on the effect of magnetic substorm onsets (as deduced from the auroral hourly electrojet AE-index) on the occurrence of high midlatitude (or sub-auroral latitude) ionospheric range spread-F (Sr). Unlike the previous reports real-time ionograms were used in this analysis thus eliminating ambiguities stemming from the correlating secondary evidence of spread-F with auroral substorms. The Australian southernmost ionosonde station Hobart (51.6°S geom.) proved to be uniquely suitable for the task as being sufficiently close to the southern auroral zone. Sr was assigned in km to each hourly nighttime ionogram at two sounding frequencies: Sr1 (at 2 MHz) and Sr2 (at 6 MHz) for four months in 2002: January and June (representing southern summer and winter solstices), and March and September (representing autumn and vernal equinoxes). It is evident that the southern winter solstitial period (June) is associated with high endemic midlatitude spread-F activity. All other seasons are closely linked with temporal sequences of enhanced spread-F activity following substorm onsets. For the first time it was possible not only find a simultaneous occurrence pattern of these diverse phenomena but to deduce numerical characteristics of the response of midlatitude ionosphere to the global auroral stimulus. Excellent case events, hitherto unpublished, are shown illustrating the presence of the AE peaks (in nT) being ahead of Sr peaks (in km) by a time shift ∆t (in h). Sr1 magnitude showed a significant correlation with the magnitudes of the preceding AE with a correlation coefficient (r) of 0.51 (probability of the occurrence by chance less than 0.01). Sr2 peaks were more sensitive to auroral disturbances but were not correlated with the AE magnitude variations. The time shift (∆t) was on average 4 h with a standard deviation of 3 h. The general pattern in the occurrence of magnetic substorms and spread-F is very similar. A number of

  3. Upper atmospheric effects of the hf active auroral research program ionospheric research instrument (HAARP IRI)

    SciTech Connect

    Eccles, V.; Armstrong, R.

    1993-05-01

    The earth's ozone layer occurs in the stratosphere, primarily between 10 and 30 miles altitude. The amount of ozone, O3, present is the result of a balance between production and destruction processes. Experiments have shown that natural processes such as auroras create molecules that destroy O. One family of such molecules is called odd nitrogen of which nitric oxide (NO) is an example. Because the HAARP (HF Active Auroral Research Program) facility is designed to mimic and investigate certain natural processes, a study of possible effects of HAARP on the ozone layer was conducted. The study used a detailed model of the thermal and chemical effects of the high power HF beam, which interacts with free electrons in the upper atmosphere above 50 miles altitude. It was found only a small fraction of the beam energy goes into the production of odd nitrogen molecules, whereas odd nitrogen is efficiently produced by auroras. Since the total energy emitted by HAARP in the year is some 200,000 times less than the energy deposited in the upper atmosphere by auroras, the study demonstrates that HAARP HF beam experiments will cause no measurable depletion of the earth's ozone layer.... Ozone, Ozone depletion, Ozone layer, Odd nitrogen, Nitric oxide, HAARP Emitter characteristics.

  4. Effect of third-order dispersion on dark solitons

    NASA Astrophysics Data System (ADS)

    Afanasjev, Vsevolod V.; Kivshar, Yuri S.; Menyuk, Curtis R.

    1996-12-01

    Third-order dispersion has a detrimental effect on dark solitons, leading to resonant generation of growing soliton tails and soliton decay. This effect is shown to be much stronger than that for bright solitons.

  5. On the convergence of ionospheric constrained precise point positioning (IC-PPP) based on undifferential uncombined raw GNSS observations.

    PubMed

    Zhang, Hongping; Gao, Zhouzheng; Ge, Maorong; Niu, Xiaoji; Huang, Ling; Tu, Rui; Li, Xingxing

    2013-01-01

    Precise Point Positioning (PPP) has become a very hot topic in GNSS research and applications. However, it usually takes about several tens of minutes in order to obtain positions with better than 10 cm accuracy. This prevents PPP from being widely used in real-time kinematic positioning services, therefore, a large effort has been made to tackle the convergence problem. One of the recent approaches is the ionospheric delay constrained precise point positioning (IC-PPP) that uses the spatial and temporal characteristics of ionospheric delays and also delays from an a priori model. In this paper, the impact of the quality of ionospheric models on the convergence of IC-PPP is evaluated using the IGS global ionospheric map (GIM) updated every two hours and a regional satellite-specific correction model. Furthermore, the effect of the receiver differential code bias (DCB) is investigated by comparing the convergence time for IC-PPP with and without estimation of the DCB parameter. From the result of processing a large amount of data, on the one hand, the quality of the a priori ionosphere delays plays a very important role in IC-PPP convergence. Generally, regional dense GNSS networks can provide more precise ionosphere delays than GIM and can consequently reduce the convergence time. On the other hand, ignoring the receiver DCB may considerably extend its convergence, and the larger the DCB, the longer the convergence time. Estimating receiver DCB in IC-PPP is a proper way to overcome this problem. Therefore, current IC-PPP should be enhanced by estimating receiver DCB and employing regional satellite-specific ionospheric correction models in order to speed up its convergence for more practical applications. PMID:24253190

  6. On the Convergence of Ionospheric Constrained Precise Point Positioning (IC-PPP) Based on Undifferential Uncombined Raw GNSS Observations

    PubMed Central

    Zhang, Hongping; Gao, Zhouzheng; Ge, Maorong; Niu, Xiaoji; Huang, Ling; Tu, Rui; Li, Xingxing

    2013-01-01

    Precise Point Positioning (PPP) has become a very hot topic in GNSS research and applications. However, it usually takes about several tens of minutes in order to obtain positions with better than 10 cm accuracy. This prevents PPP from being widely used in real-time kinematic positioning services, therefore, a large effort has been made to tackle the convergence problem. One of the recent approaches is the ionospheric delay constrained precise point positioning (IC-PPP) that uses the spatial and temporal characteristics of ionospheric delays and also delays from an a priori model. In this paper, the impact of the quality of ionospheric models on the convergence of IC-PPP is evaluated using the IGS global ionospheric map (GIM) updated every two hours and a regional satellite-specific correction model. Furthermore, the effect of the receiver differential code bias (DCB) is investigated by comparing the convergence time for IC-PPP with and without estimation of the DCB parameter. From the result of processing a large amount of data, on the one hand, the quality of the a priori ionosphere delays plays a very important role in IC-PPP convergence. Generally, regional dense GNSS networks can provide more precise ionosphere delays than GIM and can consequently reduce the convergence time. On the other hand, ignoring the receiver DCB may considerably extend its convergence, and the larger the DCB, the longer the convergence time. Estimating receiver DCB in IC-PPP is a proper way to overcome this problem. Therefore, current IC-PPP should be enhanced by estimating receiver DCB and employing regional satellite-specific ionospheric correction models in order to speed up its convergence for more practical applications. PMID:24253190

  7. Effects of chemical releases by the STS-3 Orbiter on the ionosphere

    NASA Technical Reports Server (NTRS)

    Pickett, J. S.; Murphy, G. B.; Kurth, W. S.; Goertz, C. K.; Shawhan, S. D.

    1983-01-01

    The Plasma Diagnostics Package, flown aboard STS-3 as part of the first Shuttle payload (OSS-1), recorded the effects of various chemical releases from the Orbiter. Changes in the plasma environment was observed during flash evaporator system releases, water dumps and maneuvering thruster operations. During flash evaporator operations, broadband Orbiter-generated electrostatic noise was enhanced and plasma density irregularities were observed to increase by 3 to 30 times with a spectrum which rose steeply and peaked below 6 Hz. In the case of water dumps, background electrostatic noise was enhanced at frequencies below about 3 kHz and suppressed at frequencies above 2 kHz. Thruster activity also stimulated electrostatic noise with a spectrum which peaked at approximately 0.5 kHz. In addition, ions with energies up to 1 keV were seen during some thruster events.

  8. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  9. 10 CFR 221.34 - Effect of order.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Effect of order. 221.34 Section 221.34 Energy DEPARTMENT OF ENERGY OIL PRIORITY SUPPLY OF CRUDE OIL AND PETROLEUM PRODUCTS TO THE DEPARTMENT OF DEFENSE UNDER THE DEFENSE PRODUCTION ACT Administrative Procedures and Sanctions § 221.34 Effect of order....

  10. Array-based GNSS Ionospheric Sensing: Estimability and Precision Analyses

    NASA Astrophysics Data System (ADS)

    Teunissen, Peter

    2016-04-01

    Array-based GNSS Ionospheric Sensing: Estimability and Precision Analyses PJG Teunissen1,2, A Khodabandeh1 and B Zhang1 1GNSS Research Centre, Curtin University, Perth, Australia 2Geoscience and Remote Sensing, Delft University of Technology, The Netherlands Introduction: The Global Navigation Satellite Systems (GNSS) have proved to be an effective means of measuring the Earth's ionosphere. The well-known geometry-free linear combinations of the GNSS data serve as the input of an external ionospheric model to capture both the spatial and temporal characteristics of the ionosphere. Next to the slant ionospheric delays experienced by the GNSS antennas, the geometry-free combinations also contain additional unknown delays that are caused by the presence of the carrier-phase ambiguous cycles and/or the code instrumental delays. That the geometry-free combinations, without an external ionospheric model, cannot unbiasedly determine the slant ionospheric delays reveals the lack of information content in the GNSS data. Motivation and objectives: With the advent of modernized multi-frequency signals, one is confronted with many different combinations of the GNSS data that are capable of sensing the ionosphere. Owing to such diversity and the lack of information content in the GNSS data, various estimable ionospheric delays of different interpretations (and of different precision) can therefore be formed. How such estimable ionospheric delays should be interpreted and the extent to which they contribute to the precision of the unbiased slant ionosphere are the topics of this contribution. Approach and results: In this contribution, we apply S-system theory to study the estimability and precision of the estimable slant ionospheric delays that are measured by the multi-frequency GNSS data. Two different S-systems are presented, leading to two different estimable parameters of different precision: 1) the phase-driven ionospheric delays and 2) the code-driven ionospheric delays

  11. Solar variability effects in equatorial F-region vertical plasma drifts over Africa ionosphere

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi

    . F-region vertical drifts were made using ionosonde for the Africa equatorial station Ouagadougou (12o N, 1.5o W; 5.9o N dip) from 3 years of data during January 1987 to December 1989 for solar cycle minimum, medium, and maximum conditions (F10.7 = 85, 141, and 214, respectively) under geomagnetic quiet-time. The variations are found to be dominated by the characteristics morning peak and evening prereversal enhancement (PRE) velocities. Seasonal and solar cycle effects are prominent near the dusk sector with an increase of PRE from solar minimum to maximum. The average equinoctial evening prereversal enhancement increases by almost a factor of three from low to high flux. On the average, the values of daytime and nighttime ionosonde-derived vertical drifts are smaller by about a factor of four than the magnitude often mentioned in publication for equatorial regions from other experimental techniques. In addition, the morning peak velocities maximize between about 0830-0930 LT with typical values of 12-18 m/s. In contrast, PRE have largest amplitude between about 1700-2200 LT with typical values of 5-10 m/s. The morning reversal times do not reveal any dependence on season and solar cycle; but the most probable time of occurrence is around 0530 LT. The evening reversal times are in excellent agreements for the three levels of solar activity periods apart from June solstice that exhibit considerable variations. The most likely time of occurrence is near 2000 LT. Of significance importance, the link between the onset / inhibition parameters of postsunset irregularities over Ouagadougou indicate anti-correlations with solar variability.

  12. Observing rapid quasi-wave ionospheric disturbance using amplitude charts

    NASA Astrophysics Data System (ADS)

    Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey

    Data from vertical (quasi-vertical) sounding are traditionally used for determining a number of ionospheric parameters such as critical frequencies of E and F layers, peaks of these layers, and for reconstructing electron density profiles. In this respect, radio sounding is not used to its full capacity. Modern ionosondes provide additional information encoded in ionospheric echoes, including information on reflected-signal amplitude. The time dependence of the amplitude-frequency characteristic of reflected signal has been named "amplitude chart" (A-chart). Ionosondes used by the ISTP SB RAS Geophysical Observatory for constructing A-charts employ the frequency-modulated continuous-wave (FMCW) signal in a range 1.3-15 MHz. One-minute sounding interval allows a more detailed study of dynamic processes in the ionosphere. The ionosonde has a direct digital synthesizer and direct sampling receiver without automatic gain control (AGC). The absence of AGC and the high dynamic range enable determination of the relative field strength at a receiving point and registration of relative long-term variations in reflected-signal amplitude over the entire range of operating frequencies of the ionosonde. We have revealed that the passage of travelling ionospheric disturbances (TID) along with height-frequency distortion modulates amplitude characteristics of signal. The characteristic depth of the modulation reaches 40 dB. The pronounced alternate vertical stripes typical for A-charts are likely to be associated with focusing properties of TID. In order to examine the space-time structure of TID able to induce such a focusing of the radio waves, we performed ray tracing simulations. We used geometrical-optics approximation, took magneto-ionic effects into account and prescribed electron density to be a stratified electron density profile on which an undulating disturbance was superimposed. This work was supported by the RFBR grant №14-05-00259-а.

  13. Fast ionospheric feedback instability and substorm onset

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Grieger, John; Song, Yan

    1992-01-01

    A study suggesting that the Alfven resonator can play an important role in modifying the ionosphere on the time and space scales required to play a significant role in substorm formation is presented. Although the effect of magnetosphere-ionosphere coupling on the onset of substorms has been studied, the effects due to gradients of the Alfven speed along auroral field line were neglected. The large increase of the Alfven speed with altitude above the ionosphere creates an effective resonant cavity, which can lead to fluctuations in the electric and magnetic fields as well as in particle fluxes in the range 0.1 to 1 Hz. Such fluctuations can be observed from the ground as PiB pulsations associated with substorm onset. These fluctuations can be excited by a fast feedback instability, which can grow on time scales much less than the Alfven travel time between the ionosphere and the plasma sheet. The instability enhances the value of both the Pedersen and Hall conductivity, and may play a role in preparing the ionosphere for substorm onset.

  14. Feedback instability of the ionospheric resonant cavity

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.

    1991-01-01

    A model is developed that provides a theoretical basis for previous numerical results showing a feedback instability with frequencies characteristic of Alfven travel times within the region of the large increase of Alfven speed above the ionosphere. These results have been extended to arbitrary ionospheric conductivity by developing a numerical solution of the cavity dispersion relation that involves Bessel functions of complex order and argument. It is concluded that the large contrast between the magnetospheric and ionospheric Alfven speed leads to the formation of resonant cavity modes with frequencies ranging from 0.1 to 1 Hz. The presence of the cavity leads to a modification of the reflection characteristics of Alfven waves with frequencies that compare to the cavity's normal modes.

  15. IGS-global ionospheric maps for accurate computation of GPS single- frequency ionospheric delay-simulation study

    NASA Astrophysics Data System (ADS)

    Farah, A.

    The Ionospheric delay is still one of the largest sources of error that affects the positioning accuracy of any satellite positioning system. This problem could be solved due to the dispersive nature of the Ionosphere by combining simultaneous measurements of signals at two different frequencies but it is still there for single- frequency users. Much effort has been made in establishing models for single- frequency users to make this effect as small as possible. These models vary in accuracy, input data and computational complexity, so the choice between the different models depends on the individual circumstances of the user. From the simulation point of view, the model needed should be accurate with a global coverage and good description to the Ionosphere's variable nature with both time and location. The author reviews some of these established models, starting with the BENT model, the Klobuchar model and the IRI (International Reference Ionosphere) model. Since quiet a long time, Klobuchar model considers the most widely used model ever in this field, due to its simplicity and time saving. Any GPS user could find Klobuchar model's coefficients in the broadcast navigation message. CODE, Centre for Orbit Determination in Europe provides a new set of coefficients for Klobuchar model, which gives more accurate results for the Ionospheric delay computation. IGS (International GPS Service) services include providing GPS community with a global Ionospheric maps in IONEX-format (IONosphere Map Exchange format) which enables the computation of the Ionospheric delay at the desired location and time. The study was undertaken from GPS-data simulation point of view. The aim was to select a model for the simulation of GPS data that gives a good description of the Ionosphere's nature with a high degree of accuracy in computing the Ionospheric delay that yields to better-simulated data. A new model developed by the author based on IGS global Ionospheric maps. A comparison

  16. LEISA: CubeSat for Ionospheric Characterization

    NASA Astrophysics Data System (ADS)

    Suddarth, S. C.; Vera, A.; Pollard, H.; Burgett, T.; King, B.; Hulem, D.; MacGillivray, J.; Montoya, M.; Stanton, W.; Trujillo, B.; Wilson, S.; Heileman, G.

    2012-12-01

    The University of New Mexico / Configurable Space Microsystems Innovation and Applications Center (COSMIAC) is designing a highly affordable research satellite called LEISA (Low Earth Ionospheric Spectrum Analyzer) to characterize Ionospheric properties that affect electromagnetic wave propagation. By measuring spectral distortion of both natural and man-made impulses LEISA will measure Total Electron Content (TEC), magnetic field strength, refractive effects, plasma properties, and higher-order electron density profile effects. Additionally, LEISA may shed light on the relationships between lightning effects and thunderstorm weather in the troposphere and the potential relationship between the acoustic/seismic events around thunderstorms and Ionospheric weather. The LEISA design effort has led to a number of innovations that may be relevant to other small science spacecraft. The design is particularly challenging because of the need to implement broadband RF reception from 20-200 MHz as well as to capture and process the resulting signals within a 1u spacecraft (10cm x 10cm x 10cm) with less than 2 watts of average available power. One particular challenge is the deployable electrically small biconic wideband UHF antenna that deploys to approximately 1.5m in length and .5 m in width. The resulting antenna system deploys from a diminutive 500 cubic centimeter volume. The remaining electronics must fit within the remaining 500 cubic centimeters, leading the team to develop a system-on-a-chip (SoC) design using a Xilinx Spartan 6 FPGA. The resulting circuit handles the spectrogram capture as well as all command and data handling functions within an average power footprint of approximately 200mW, reserving energy for analog-to-digital conversion (ADC) during capture events. LEISA builds upon prior work by Los Alamos National Laboratory with FORTE and Cibola Flight Experiment. In addition to being much more affordable, LEISA offers the potential of geo-locating events

  17. Ionospheric irregularity influences on GPS time delay

    NASA Astrophysics Data System (ADS)

    Mansoori, Azad Ahmad; Gwal, Ashok Kumar; Khan, Parvaiz A.; Bhawre, Purushottam

    All the trans-ionospheric signals interact with the ionosphere during their passage through ionosphere, hence are strongly influenced by the ionosphere. One of most important ionospheric effects on the trans-ionospheric signals is the delay both in range and time. Under this investigation we have studied the variability of ionospheric range delay in GPS signals. To accomplish this study we have used the GPS measurements at a low latitude station, IISC Bangalore (13.02N, 77.57E) during January 2012 to December 2012. We studied the diurnal monthly as well as seasonal variability of the range delay. We also selected five intense geomagnetic storms that occurred during 2012 and investigated the variability of delay during the disturbed conditions. From our study we found the diurnal variability of the range delay is similar to the diurnal pattern observed for TEC. The delay is maximum during the month of October while lowest delay is found to occur in the month of December. During summer season the range delay in GPS signals in less while the largest delay occurs during the equinox season. The variability of delay during the geomagnetic storms of 09 Mar. 2012, 24 Apr. 2012, 15 Jul. 2012, 01 Oct. 2012 and 14 Nov. 2012 were also studied. All these geomagnetic storms belonged to intense category. We found that the value of delay is strongly increased during the course of geomagnetic storms. We took the peak value of delay as well as calculated the enhancement in the delay during these geomagnetic storms and then investigated their correlation with the storm intensity index Dst. Both the delays follow a very good correlation with Dst index.

  18. Study of the effect of magnetic ordering on order-disorder transitions in binary alloys

    NASA Astrophysics Data System (ADS)

    Jena, Ambika Prasad; Sanyal, Biplab; Mookerjee, Abhijit

    2014-06-01

    We set up a mean-field approximation in a random Ising model characterized by two order parameters: the local sublattice magnetization and a mean-field occupation variable which act as an order parameter for the order-disorder transition. In the effective model Hamiltonian the two order-parameters are coupled. We solve the coupled equations arising from this to describe the total phase diagram. The exchange energies for FeCo alloys have then been accurately obtained from first-principles based on the technique of orbital peeling and a Monte Carlo analysis using a coupled Metropolis-Kawasaki updating has been carried out. Our results reasonably successfully agree with earlier experimental data.

  19. Robust detection of ionospheric irregularities

    NASA Technical Reports Server (NTRS)

    Walter, T.; Hansen, A.; Blanch, J.; Enge, P.; Mannucci, T.; Pi, X.; Sparks, L.; Iijima, B.; El-Arini, B.; Lejeune, R.; Hagen, M.; Altshuler, E.; Fries, R.; Chu, A.

    2000-01-01

    The approach outlined in this paper conservatively bounds the ionospheric errors even for the worst observed ionospheric conditions to date, using data sets taken from the operational receivers in the WAAS reference station network.

  20. Investigation of Radio Wave Propagation in the Martian Ionosphere Utilizing HF Sounding Techniques

    NASA Astrophysics Data System (ADS)

    Yowell, Robert J.

    1996-06-01

    This thesis presents a preliminary design of an ionospheric sounder to be carried aboard one or more of NASA's Mars Surveyor landers. Past Russian and American probes have indicated the existence of an ionosphere, but none of these missions remotely sensed this atmospheric layer from the surface. The rationale for utilizing a surface-based Martian ionospheric sounder is discussed. Based on NASA's choice of launch vehicle and power source, a low-weight, low-powered Chirp sounder using a horizontally-polarized dipole antenna is recommended for the sounder experiment. The sounder experiment should be conducted for at least one Martian year, in order to investigate significant changes in radio propagation during seasonal transitions. Specific data compression techniques are suggested in order to reduce the quantity of data transferred from each sounder. The Appendix presents an overview of Earth's ionospheric structure and solar cycle effects. Finally, a Matlab software model of a hypothetical ionogram as measured from the Martian surface is presented.

  1. Model study of the effects of gravity wave dissipation on the thermosphere and ionosphere from deep convection worldwide 15-27 June 2009

    NASA Astrophysics Data System (ADS)

    Vadas, S.; Liu, H.

    2013-12-01

    In this paper, we discuss the methods and results of a global modeling study for the effect of deep convection on the thermosphere and ionosphere through the dissipation of atmospheric gravity waves (GWs). The selected time period is 15-27 June 2009, during the recent extreme solar minimum. The convective plumes which overshot the tropopause are identified from IR images obtained by the instruments on 5 satellites covering Earth (from west to east: GOES11, GOES12, M9, M7, and MTS). We model the excitation of GWs from these plumes, and ray trace them into the thermosphere using our ray trace model which has been upgraded to span the Earth. We then calculate the forcings/heatings/coolings which result when and where these GWs dissipate in the thermosphere. We input these forcings/heatings/coolings into the global TIME-GCM, and re-run the model. In this paper, we discuss these methods and models in detail. We then discuss how the thermosphere and ionosphere responded to the dissipation of these convectively-generated GWs worldwide.

  2. Ionosphere/microwave beam interaction study. [satellite solar energy conversion

    NASA Technical Reports Server (NTRS)

    Duncan, L. M.; Gordon, W. E.

    1977-01-01

    A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results.

  3. Influence of ionospheric anomalies in the positioning

    NASA Astrophysics Data System (ADS)

    Rodriguez-Caderot, G.; Moreno, B.; de Lacy, M. C.

    2009-04-01

    GNSS observables depend on the satellite-receiver distance, atmospheric effects, satellite and receiver offsets and phase ambiguities, as well as satellite and receiver equipment delays. GNSS observations specific to a receiver and a satellite (undifferenced observations) can be used to estimate the ionospheric effect. In this study, different procedures are used to estimate the ionospheric delay from GNSS data belonging to permanent GPS stations. In particular, these tests intend to detect ionospheric anomalies under certain conditions in equatorial geographical latitudes. From the Slant Total Electron Content (STEC) estimated between one GPS station and several satellites the contribution of the anomalies is isolated and its amplitude and duration are computed. Finally, an analysis of the possible influence of these anomalies in the positioning estimation is carried out.

  4. First and Higher Order Effects on Zero Order Radiative Transfer Model

    NASA Astrophysics Data System (ADS)

    Neelam, M.; Mohanty, B.

    2014-12-01

    Microwave radiative transfer model are valuable tool in understanding the complex land surface interactions. Past literature has largely focused on local sensitivity analysis for factor priotization and ignoring the interactions between the variables and uncertainties around them. Since land surface interactions are largely nonlinear, there always exist uncertainties, heterogeneities and interactions thus it is important to quantify them to draw accurate conclusions. In this effort, we used global sensitivity analysis to address the issues of variable uncertainty, higher order interactions, factor priotization and factor fixing for zero-order radiative transfer (ZRT) model. With the to-be-launched Soil Moisture Active Passive (SMAP) mission of NASA, it is very important to have a complete understanding of ZRT for soil moisture retrieval to direct future research and cal/val field campaigns. This is a first attempt to use GSA technique to quantify first order and higher order effects on brightness temperature from ZRT model. Our analyses reflect conditions observed during the growing agricultural season for corn and soybeans in two different regions in - Iowa, U.S.A and Winnipeg, Canada. We found that for corn fields in Iowa, there exist significant second order interactions between soil moisture, surface roughness parameters (RMS height and correlation length) and vegetation parameters (vegetation water content, structure and scattering albedo), whereas in Winnipeg, second order interactions are mainly due to soil moisture and vegetation parameters. But for soybean fields in both Iowa and Winnipeg, we found significant interactions only to exist between soil moisture and surface roughness parameters.

  5. Magnetosphere-ionosphere waves

    NASA Astrophysics Data System (ADS)

    Russell, A. J. B.; Wright, A. N.

    2012-01-01

    Self-consistent electrodynamic coupling of the ionosphere and magnetosphere produces waves with clearly defined properties, described here for the first time. Large scale (ideal) disturbances to the equilibrium, for which electron inertia is unimportant, move in the direction of the electric field at a characteristic speed. This may be as fast as several hundred meters per second or approximately half the E × B drift speed. In contrast, narrow scale (strongly inertial) waves are nearly stationary and oscillate at a specific frequency. Estimates of this frequency suggest periods from several tenths of a second to several minutes may be typical. Both the advection speed and frequency of oscillation are derived for a simple model and depend on a combination of ionospheric and magnetospheric parameters. Advection of large scale waves is nonlinear: troughs in E-region number density move faster than crests and this causes waves to break on their trailing edge. Wavebreaking is a very efficient mechanism for producing narrow (inertial) scale waves in the coupled system, readily accessing scales of a few hundred meters in just a few minutes. All magnetosphere-ionosphere waves are damped by recombination in the E-region, suggesting that they are to be best observed at night and in regions of low ionospheric plasma density. Links with observations, previous numerical studies and ionospheric feedback instability are discussed, and we propose key features of experiments that would test the new theory.

  6. Assessment of ionospheric threat modeling techniques over Marmara Region

    NASA Astrophysics Data System (ADS)

    Onur Karslioglu, Mahmut; Yeganehsahab, Amir; Durmaz, Murat

    2016-04-01

    It is generally known that extreme ionospheric density associated with severe magnetic storm degrades the Global Navigation satellite Systems (GNSS) measurements also at mid - to high latitudes. Strong solar activity can cause large local spatial and temporal gradients in the delays induced on the GNSS signals by the ionosphere. The local nature of gradients can result in significant decorrelation between Ground Based Augmentation System (GBAS) Ground Stations and the GNSS receiver on board the aircraft. For the mitigation of this effect either a special functional architecture is established to monitor the ionosphere on the basis of so called Extended GBAS or ionospheric threat models can be constructed for a certain region. In this work two different techniques have been evaluated for the estimation of ionospheric threat model parameters consisting of width, slope and velocity of the ionospheric wave front by using real ground-based observations from both GPS and GLONASS in the Marmara Region. The data collected between 2012 and 2015 also containing high ionospheric activities are pre-processed to extract ionospheric gradients. Ionospheric delays at each ionospheric piercing point are determined by applying a local ionospheric Total Electron Content (TEC) modeling and filtering techniques on the basis of raw carrier-phase observations. The ionospheric fronts are searched by looking at high ionospheric gradients which result from ionospheric delay differences between ionospheric piercing points. The first technique of the threat model evaluation is based on the propagation of an ideal plane wave as a wave front, velocity of which is estimated on the basis of a Gauss Markov Model using an ordinary least square estimation procedure. The remaining parameters namely slope and width are calculated afterwards using rate of change gradients and the duration of the wave front in context with the estimated front velocity. In the second technique both the magnitude of the

  7. The effect of higher order harmonics on second order nonlinear phenomena

    NASA Astrophysics Data System (ADS)

    Shahverdi, Amin; Borji, Amir

    2015-05-01

    A new method which is a combination of the harmonic balance and finite difference techniques (HBFD) is proposed for complete time-harmonic solution of the nonlinear wave equation. All interactions between different harmonics up to an arbitrary order can be incorporated. The effect of higher order harmonics on two important nonlinear optical phenomena, namely, the second harmonic generation (SHG) and frequency mixing is investigated by this method and the results are compared with well-known analytical solutions. The method is quite general and can be used to study wave propagation in all nonlinear media.

  8. Ionospheric Specifications for SAR Interferometry (ISSI)

    NASA Technical Reports Server (NTRS)

    Pi, Xiaoqing; Chapman, Bruce D; Freeman, Anthony; Szeliga, Walter; Buckley, Sean M.; Rosen, Paul A.; Lavalle, Marco

    2013-01-01

    The ISSI software package is designed to image the ionosphere from space by calibrating and processing polarimetric synthetic aperture radar (PolSAR) data collected from low Earth orbit satellites. Signals transmitted and received by a PolSAR are subject to the Faraday rotation effect as they traverse the magnetized ionosphere. The ISSI algorithms combine the horizontally and vertically polarized (with respect to the radar system) SAR signals to estimate Faraday rotation and ionospheric total electron content (TEC) with spatial resolutions of sub-kilometers to kilometers, and to derive radar system calibration parameters. The ISSI software package has been designed and developed to integrate the algorithms, process PolSAR data, and image as well as visualize the ionospheric measurements. A number of tests have been conducted using ISSI with PolSAR data collected from various latitude regions using the phase array-type L-band synthetic aperture radar (PALSAR) onboard Japan Aerospace Exploration Agency's Advanced Land Observing Satellite mission, and also with Global Positioning System data. These tests have demonstrated and validated SAR-derived ionospheric images and data correction algorithms.

  9. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

    As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

  10. Geophysicochemical model of an ionospheric auroral gyroscope

    NASA Astrophysics Data System (ADS)

    Serban, Andreea I.; Geicu, Ovidiu I.; Serban, Florea

    2016-01-01

    This study presents a geophysicochemical model of an ionospheric auroral gyroscope. The gyroscopic effect occurs due to the electromagnetic interaction in Earth's polar regions between two types of vertical cavity auroras: the herpolhodic cone (proton cavity aurora), operating in the cusp polar region, and two polhodic cones (an electronic cone and a protonic cone), operating in the aurora region. The ratio between the angular speeds of the herpolhodic and polhodic cones is established by the angle between Earth's rotational axis and the geomagnetic dipole axis. We have developed a theory of the ionospheric auroral gyroscope as a kinematic part of the terrestrial magnetosphere and ionosphere that enables a unified explanation of important macroscopic phenomena that occur at this level. Accordingly, we have explained the oval shape of the polar auroras, Schumann resonances, geomagnetic micropulsation excitation, and the structuring of Earth's areas of radiation. The terrestrial gravitomagnetic field and dark matter are implicated in the initiation and behavior of the auroral ionospheric gyroscope, both of which provide stability and accuracy. Viewed in a wider context, the ionospheric auroral gyroscope theory could offer a way to experimentally investigate dark matter on Earth. Furthermore, it may have a potential value as a predictive tool, providing information about the large earthquakes and Earth's phenomena.

  11. Report from ionospheric science

    NASA Technical Reports Server (NTRS)

    Raitt, W. J.; Banks, Peter M.; Nagy, A. F.; Chappell, C. R.

    1989-01-01

    The general strategy to advance knowledge of the ionospheric component of the solar terrestrial system should consist of a three pronged attack on the problem. Ionospheric models should be refined by utilization of existing and new data bases. The data generated in the future should emphasize spatial and temporal gradients and their relation to other events in the solar terrestrial system. In parallel with the improvement in modeling, it will be necessary to initiate a program of advanced instrument development. In particular, emphasis should be placed on the area of improved imaging techniques. The third general activity to be supported should be active experiments related to a better understanding of the basic physics of interactions occurring in the ionospheric environment. These strategies are briefly discussed.

  12. Anomalies in the Ionosphere around the Southern faults of Haiti near the 2010 Earthquake

    NASA Astrophysics Data System (ADS)

    Cornely, P.; Daniell, R. E.

    2013-12-01

    In the last few decades, research on earthquake prediction has resulted in the recognition that there may exist many earthquake precursors in the lithosphere, atmosphere and ionosphere. The ionosphere is naturally perturbed by solar and geomagnetic disturbances and it is difficult to extract the variations connected with earthquakes particularly for the equatorial and high latitude ionosphere. Several researchers have contending theories on the mechanisms associated with pre-earthquake signals. The basic premise is that a thin layer of particles created before earthquakes due to ions originating from the earth's crust travel to the earth's surface and begin radiating from the earth's surface due to strong electric fields Namgaladze et al., [2009]. The ions can then travel from above earth's surface to the ionosphere where they can create ionospheric disturbances. When solar and geomagnetic disturbances can be ruled out, the effects of pre-seismic activities in the ionosphere can be assessed using fluctuations in the ionospheric electron density in the vicinity of fault lines. The Parameterized Ionospheric Model (PIM) is a fast global ionospheric model which produces electron density profiles (EDPs) between 90 and 25000 km altitude, which corresponds to critical altitudes of the ionosphere Daniell et al., [1995]. Since PIM only simulates a statistical mean ionosphere, sudden variations in ionospheric electron density will not be represented in the models, which make PIM ideal for background electron density predictions. The background predictions can then removed from the actual electron density data which could provide means for identifying pre-seismic electron density perturbations.

  13. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.; Markin, Robert E.

    1994-01-01

    This study is a preliminary analysis of the effectiveness (in terms of altimeter calibration accuracy) of various ionosphere models and the Global Positioning System (GPS) to calibrate single frequency altimeter height measurements for ionospheric path delay. In particular, the research focused on ingesting GPS Total Electron Content (TEC) data into the physical Parameterized Real-Time Ionospheric Specification Model (PRISM), which estimates the composition of the ionosphere using independent empirical and physical models and has the capability of adjusting to additional ionospheric measurements. Two types of GPS data were used to adjust the PRISM model: GPS receiver station data mapped from line-of-sight observations to the vertical at the point of interest and a grid map (generated at the Jet Propulsion Laboratory) of GPS derived TEC in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by the International Reference Ionosphere (IRI-90), a climatological (monthly mean) model of the ionosphere, were compared to TOPEX dual-frequency TEC measurements (considered as truth) for a number of TOPEX sub-satellite tracks. For a 13.6 GHz altimeter, a Total Electron Content (TEC) of 1 TECU 10(exp 16) electrons/sq m corresponds to approximately 0.218 centimeters of range delay. A maximum expected TEC (at solar maximum or during solar storms) of 10(exp 18) electrons/sq m will create 22 centimeters of range delay. Compared with the TOPEX data, the PRISM predictions were generally accurate within the TECU when the sub-satellite track of interest passed within 300 to 400 km of the GPS TEC data or when the track passed through a night-time ionosphere. If neither was the case, in particular if the track passed through a local noon ionosphere, the PRISM values differed by more than 10 TECU and by as much as 40 TECU. The IRI-90 model, with no current ability to unseat GPS data, predicted TEC to a slightly higher error of 12 TECU. The performance of

  14. Experimental evidence of electromagnetic pollution of ionosphere

    NASA Astrophysics Data System (ADS)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    The Earth’s ionosphere responds to external perturbations originated mainly in the Sun, which is the primary driver of the space weather (SW). But solar activity influences on the ionosphere and the Earth's atmosphere (i.e., the energy transfer in the direction of the Sun-magnetosphere-ionosphere-atmosphere-surface of the Earth), though important, is not a unique factor affecting its state - there is also a significant impact of the powerful natural and anthropogenic processes, which occur on the Earth’s surface and propagating in opposite direction along the Earth’s surface-atmosphere-ionosphere-magnetosphere chain. Numerous experimental data confirm that the powerful sources and consumers of electrical energy (radio transmitters, power plants, power lines and industrial objects) cause different ionospheric phenomena, for example, changes of the electromagnetic (EM) field and plasma in the ionosphere, and affect on the state of the Earth atmosphere. Anthropogenic EM effects in the ionosphere are already observed by the scientific satellites and the consequences of their impact on the ionosphere are not currently known. Therefore, it is very important and urgent task to conduct the statistically significant research of the ionospheric parameters variations due to the influence of the powerful man-made factors, primarily owing to substantial increase of the EM energy production. Naturally, the satellite monitoring of the ionosphere and magnetosphere in the frequency range from tens of hertz to tens of MHz with wide ground support offers the best opportunity to observe the EM energy release, both in the global and local scales. Parasitic EM radiation from the power supply lines, when entering the ionosphere-magnetosphere system, might have an impact on the electron population in the radiation belt. Its interaction with trapped particles will change their energy and pitch angles; as a result particle precipitations might occur. Observations of EM emission by

  15. Examining the effects of birth order on personality

    PubMed Central

    Rohrer, Julia M.; Egloff, Boris; Schmukle, Stefan C.

    2015-01-01

    This study examined the long-standing question of whether a person’s position among siblings has a lasting impact on that person’s life course. Empirical research on the relation between birth order and intelligence has convincingly documented that performances on psychometric intelligence tests decline slightly from firstborns to later-borns. By contrast, the search for birth-order effects on personality has not yet resulted in conclusive findings. We used data from three large national panels from the United States (n = 5,240), Great Britain (n = 4,489), and Germany (n = 10,457) to resolve this open research question. This database allowed us to identify even very small effects of birth order on personality with sufficiently high statistical power and to investigate whether effects emerge across different samples. We furthermore used two different analytical strategies by comparing siblings with different birth-order positions (i) within the same family (within-family design) and (ii) between different families (between-family design). In our analyses, we confirmed the expected birth-order effect on intelligence. We also observed a significant decline of a 10th of a SD in self-reported intellect with increasing birth-order position, and this effect persisted after controlling for objectively measured intelligence. Most important, however, we consistently found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. On the basis of the high statistical power and the consistent results across samples and analytical designs, we must conclude that birth order does not have a lasting effect on broad personality traits outside of the intellectual domain. PMID:26483461

  16. Examining the effects of birth order on personality.

    PubMed

    Rohrer, Julia M; Egloff, Boris; Schmukle, Stefan C

    2015-11-17

    This study examined the long-standing question of whether a person's position among siblings has a lasting impact on that person's life course. Empirical research on the relation between birth order and intelligence has convincingly documented that performances on psychometric intelligence tests decline slightly from firstborns to later-borns. By contrast, the search for birth-order effects on personality has not yet resulted in conclusive findings. We used data from three large national panels from the United States (n = 5,240), Great Britain (n = 4,489), and Germany (n = 10,457) to resolve this open research question. This database allowed us to identify even very small effects of birth order on personality with sufficiently high statistical power and to investigate whether effects emerge across different samples. We furthermore used two different analytical strategies by comparing siblings with different birth-order positions (i) within the same family (within-family design) and (ii) between different families (between-family design). In our analyses, we confirmed the expected birth-order effect on intelligence. We also observed a significant decline of a 10th of a SD in self-reported intellect with increasing birth-order position, and this effect persisted after controlling for objectively measured intelligence. Most important, however, we consistently found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. On the basis of the high statistical power and the consistent results across samples and analytical designs, we must conclude that birth order does not have a lasting effect on broad personality traits outside of the intellectual domain. PMID:26483461

  17. Analysis of Ionospheric Delay Estimates from GNSS Carrier Phase Measurements

    NASA Astrophysics Data System (ADS)

    Gao, Yang

    2016-07-01

    There is an increased demand for more precise ionospheric information such as ionospheric augmentation for fast ambiguity convergence and resolution in real-time kinematic (RTK) and precise point positioning (PPP). More precise ionospheric information is also highly desired to improve the understanding of the space weather dynamics and its impacts on various applications such as aviation and communication systems. Carrier phase measurements from GNSS offer the best precision for precise applications. Current ionospheric models, however, are mostly derived from code or carrier-smoothed code measurements. Ionopsheric models based on carrier phase measurements are expected to provide improved accuracy and should be investigated. In this contribution, various data analyses will be conducted on ionospheric estimates from carrier phase measurements. Since carrier phase measurements are ambiguous and they are also affected by fractional biases, proper observation model is necessary and will be developed. With proper observation model, the analysis results are used to investigate the differences and characteristics of the ionospheric estimates between the code and carrier phase derived estimates and subsequently to help develop methods for precise estimation of the biases in carrier phase measurements and the recovery of the ionospheric effects. Data acquired at different geographic locations and under different ionospheric conditions will be processed for numerical analysis.

  18. Ionospheric effects of the simultaneous occurrence of a solar proton event and relativistic electron precipitation as recorded by ground-based instruments at different latitudes

    NASA Astrophysics Data System (ADS)

    Shirochkov, A. V.; Makarova, L. N.; Sokolov, S. N.; Sheldon, W. R.

    2004-08-01

    The intense event of highly relativistic electron (HRE) precipitation of May 1992 has been analyzed using data from ground-based observations (riometers and VLF phase measurements). Special attention was given to some features of this event observed at high and very high geomagnetic latitudes, since this aspect of the event was not well documented in previous studies. A remarkable feature of the HRE event of May 1992 was the simultaneous occurrence of a strong solar proton event (SPE), although reliable evidence shows that the simultaneous appearance of SPE and HRE events is not unique. It was demonstrated that a meridian chain of riometers with high latitudinal resolution is an effective and low-cost (as compared with satellite observations) tool to separate the effects of solar proton and relativistic electrons in the lower ionosphere. A significant conclusion is that the polar cap area is free from relativistic electron precipitation. Other interesting aspects of this complex geophysical phenomenon are also discussed.

  19. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data.

    PubMed

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-01-01

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone. PMID:26266764

  20. Tomographic reconstruction of ionospheric electron density during the storm of 5-6 August 2011 using multi-source data

    PubMed Central

    Tang, Jun; Yao, Yibin; Zhang, Liang; Kong, Jian

    2015-01-01

    The insufficiency of data is the essential reason for ill-posed problem existed in computerized ionospheric tomography (CIT) technique. Therefore, the method of integrating multi-source data is proposed. Currently, the multiple satellite navigation systems and various ionospheric observing instruments provide abundant data which can be employed to reconstruct ionospheric electron density (IED). In order to improve the vertical resolution of IED, we do research on IED reconstruction by integration of ground-based GPS data, occultation data from the LEO satellite, satellite altimetry data from Jason-1 and Jason-2 and ionosonde data. We used the CIT results to compare with incoherent scatter radar (ISR) observations, and found that the multi-source data fusion was effective and reliable to reconstruct electron density, showing its superiority than CIT with GPS data alone. PMID:26266764

  1. Rocket studies of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Bowhill, Sidney A.

    1990-01-01

    The earth's ionosphere in the altitude range of 50 to 200 km was investigated by rocket-borne sensors, supplemented by ground-based measurement. The rocket payloads included mass spectrometers, energetic particle detectors, Langmuir probes and radio propagation experiments. Where possible, rocket flights were included in studies of specific phenomena, and the availability of data from other experiments greatly increased the significance of the results. The principal ionospheric phenomena studied were: winter anomaly in radiowave absorption, ozone and molecular oxygen densities, mid-latitude sporadic-E layers, energetic particle precipitation at middle and low latitudes, ionospheric instabilities and turbulence, and solar eclipse effects in the D and E regions. This document lists personnel who worked on the project, and provides a bibliography of resultant publications.

  2. Ionospheric and magnetospheric 'plasmapauses'

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Maynard, N. C.; Hoffman, J. H.

    1978-01-01

    The locations of Explorer 45 plasmapause crossings are studied as a likely indicator of ionospheric and magnetospheric trough locations. Attention is given to vertical flows of H(+) ions in the light ion trough, as detected by the magnetic ion mass spectrometer aboard Isis 2 (which was operating in conjunction with Explorer 45 during August 1972). The possibility of an equatorial plasmapause is discussed, whose field lines map into the ionosphere at latitudes poleward of the H(+) density decrease, probably due to the refilling of magnetic flux tubes in the outer plasmasphere.

  3. A quantum probability account of order effects in inference.

    PubMed

    Trueblood, Jennifer S; Busemeyer, Jerome R

    2011-01-01

    Order of information plays a crucial role in the process of updating beliefs across time. In fact, the presence of order effects makes a classical or Bayesian approach to inference difficult. As a result, the existing models of inference, such as the belief-adjustment model, merely provide an ad hoc explanation for these effects. We postulate a quantum inference model for order effects based on the axiomatic principles of quantum probability theory. The quantum inference model explains order effects by transforming a state vector with different sequences of operators for different orderings of information. We demonstrate this process by fitting the quantum model to data collected in a medical diagnostic task and a jury decision-making task. To further test the quantum inference model, a new jury decision-making experiment is developed. Using the results of this experiment, we compare the quantum inference model with two versions of the belief-adjustment model, the adding model and the averaging model. We show that both the quantum model and the adding model provide good fits to the data. To distinguish the quantum model from the adding model, we develop a new experiment involving extreme evidence. The results from this new experiment suggest that the adding model faces limitations when accounting for tasks involving extreme evidence, whereas the quantum inference model does not. Ultimately, we argue that the quantum model provides a more coherent account for order effects that was not possible before. PMID:21951058

  4. Ionospheric tomography using the FORTE satellite

    SciTech Connect

    Murphy, T.C.

    1993-08-01

    The possibility of obtaining ionospheric profile data via tomographic techniques has elicited considerable interest in recent years. The input data for the method is a set of total electron content measurements along intersecting lines of sight which form a grid. This can conveniently be provided by a fast-moving satellite with a VHF beacon which will generate the multiple paths needed for effective tomography. Los Alamos and Sandia National Laboratories will launch and operate the FORTE satellite for the US Department of Energy, with launch scheduled in 1995. FORTE will provide such a beacon. Additionally, wideband VHF receivers aboard the satellite will allow corraborative measurements of ionospheric profile parameters in some cases.

  5. Topside ionospheric response to solar EUV variability

    NASA Astrophysics Data System (ADS)

    Anderson, Phillip C.; Hawkins, Jessica M.

    2016-02-01

    We present an analysis of 23 years of thermal plasma measurements in the topside ionosphere from the Defense Meteorological Satellite Program (DMSP) spacecraft. The H+/O+ ratio and density vary dramatically with the solar cycle; cross-correlation coefficients between E10.7 and the daily averaged densities are greater than 0.85. The ionospheric parameters also vary dramatically with season, particularly at latitudes away from the equator where the solar zenith angle varies greatly with season. There are also 27 day solar rotation periodicities in the density, associated with periodicities in the directly measured solar EUV flux. Empirical orthogonal function analysis captures over 95% of the variation in the density in the first two principal components. The first principal component (PC1) is clearly associated with the solar EUV while the second principal component (PC2) is clearly associated with the solar zenith angle variation. The magnitude of the variation of the response of the topside ionosphere to solar EUV variability is shown to be closely related to the ionospheric composition. This is interpreted as the result of the effect of composition on the scale height in the topside ionosphere and the "pivot effect" in which the variation in density near the F2 peak is amplified by a factor of e at an altitude a scale height above the F2 peak. When the topside ionosphere is H+ dominated during solar minimum, DMSP may be much less than a scale height above the F2 peak while during solar maximum, when it is O+ dominated, DMSP may be several scale heights above the F2 peak.

  6. COSMIC-2: A Platform for Advanced Ionospheric Observations

    NASA Astrophysics Data System (ADS)

    Straus, P. R.; Betz, D. A.

    2013-12-01

    The equatorial component of the COSMIC-2 program will consist of 6 satellites to be flown in a 24 degree inclination/520 km altitude orbit. In addition to the primary GNSS radio occultation (RO) payload, to be provided by JPL, the USAF plans to fly a pair of space weather sensors: a multi-frequency radio beacon and the Velocity, Ion Density and Irregularities (VIDI) in-situ plasma sensor package. Together, these three instruments will provide data to address key issues related to the specification and forecast of ionospheric densities and the instabilities/irregularities associated with ionospheric scintillation. The TriG GNSS receiver will provide a substantial increase in the number of daily ionospheric observations relative to COSMIC-1, both in the RO limb-viewing and overhead geometries. These data will provide a significant improvement of assimilative model capabilities for providing accurate ionospheric specifications in the important equatorial region. In addition, TriG will make routine measurements of ionospheric scintillation at L-band frequencies, as pioneered by the CORISS instrument on C/NOFS. The radio beacon, together with a network of ground receivers, will enable direct measurement of scintillation effects on trans-ionospheric signal propagation across the UHF to S-band frequency spectrum. The VIDI sensors will measure the in-situ density depletions associated with scintillation-producing irregularities. Together, the beacon, TriG, and VIDI will provide an unprecedented ability to map equatorial ionospheric instabilities and their effects. The in-situ package will also provide observations of plasma drifts from which electric fields, the most important physical driver for equatorial ionospheric structure, can be inferred. This will enable advancements in ionospheric models to further improve specifications and forecasts. In addition to discussing ionospheric science and operational support aspects of the COSMIC-2 mission, this presentation will

  7. Ionospheric plasma dynamics and instability caused by upward currents above thunderstorms

    NASA Astrophysics Data System (ADS)

    Kuo, C. L.; Lee, L. C.

    2015-04-01

    Thunderstorms are electric generators, which drive currents upwardly into the ionosphere. In this paper, we examine the effects of thunderstorm upward current on the ionosphere. We use a thunderstorm model to calculate the three-dimensional current flows in the atmosphere and to simulate the upward current above the thunderstorm with the tripole-charge structure. The upward current flows into the ionosphere, while the associated electric field causes the plasma E × B motion. The caused plasma motion redistributes the plasma density, leading to ionospheric density variations. In the nighttime ionosphere, the E × B motion may also cause the formation of plasma bubbles.

  8. Mixed-Effects Analyses of Rank-Ordered Data.

    ERIC Educational Resources Information Center

    Bockenholt, Ulf

    2001-01-01

    Presents a synthesis of the nominal categories model of R. Bock (1972) and the choice model for mixed-effects analysis of rank-ordered data by R. Luce (1959). Shows that the proposed ranking model is both parsimonious and flexible in accounting for preference heterogeneity as well as fixed and random effects of covariates. Discusses relationships…

  9. Characteristics of ionospheric storms in East Asia

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Wang, Guojun; Shi, Jiankui

       The ionosphere experiences intense response during the geomagnetic storm and it varies with latitude and longitude. The DPS-4 digisonde measurements and GPS-TEC data of ionospheric stations located at different latitudes in the longitudinal sector of 90-130E during 2002 to 2012 were analyzed to investigate the ionospheric effects in the different latitude of East Asia during geomagnetic storm. About 70 geomagnetic storms are selected according to the Dst index and observed data and they are in different seasons and different solar activity levels. A few quiet days’ averages of data before geomagnetic storm were used as the undisturbed level. Results show that for the middle and high latitude, the short-lived positive disturbance associated with the initial phase of the every storm was observed in each season and then the disturbances were negative till the termination of storm. At the low latitude, storm-time disturbances of foF2 have obvious diurnal, seasonal and solar cycle characteristics. Generally, geomagnetic activity will cause foF2 to increase at daytime and decrease at nighttime except for the summer in low solar activity period. The intensity of response of foF2 is stronger at nighttime than that at daytime. The negative ionospheric storm effect is the strongest in summer and the positive ionospheric storm effect is the strongest in winter. In high solar activity period, the diurnal variation of the response of foF2 is very pronounced in each season, and the strong ionospheric response can last several days. In low solar activity period, ionospheric response has very pronounced diurnal variation in winter only. It’s notable that geomagnetic activities occurred at local time nighttime can cause stronger and longer responses of foF2 at the low latitude. All in all, the obvious negative phase ionospheric storms often occurred at the low latitude. Moreover a notable phenomenon was observed for the low latitude, there are the intensive

  10. Ionospheric monitoring by the Global Navigation Satellite System (GNSS)

    NASA Astrophysics Data System (ADS)

    Park, Jihye

    The ionosphere reacts to geophysical events, such as earthquakes, tsunamis, surface explosions, underground nuclear explosions (UNE), etc. The Global Navigation Satellite System (GNSS) remote sensing (RS) enables monitoring of the ionospheric disturbances excited by these events. The purpose of this dissertation is to use GNSS RS to detect, discriminate, model and monitor ionospheric disturbances induced by earthquakes and UNEs. Ionospheric delay, which can be derived from dual frequency GNSS signals, is converted to the total electron contents (TEC) along the signal path. After eliminating the main trend of TEC by taking the numerical third order horizontal 3-point derivatives, the traveling ionospheric disturbances (TIDs) are isolated. Since a TID can be generated due to various events, the source of TID must be verified. In this dissertation, the characteristics of the TID waves induced by an earthquake and an UNE are examined. The case studies are: (1) M9.0 2011 Tohoku, Japan earthquake, (2) 2006 North Korean UNE, and (3) 2009 North Korean UNE. From these experiments, the TIDs resulting from different types of events were characterized and discriminated due to the different waveform properties. In addition, the epicenter of the point source can be determined by TID observations. In experiment (2), the 2009 North Korean UNE was examined, using data from eleven nearby GNSS stations. Within a few hours from the explosion, the GNSS stations detected the TIDs, whose arrival time for each station formulated the linear model with respect to the distance to the station. TIDs were observed to propagate with speeds of roughly 150 - 400 m/s at stations about 365 km to 1330 km from the explosion site. Considering the wind effect, the wind-adjusted TIDs located the UNE to within about 2.7 km of its seismically determined epicenter. Through the case studies, the distinctive signatures of different events were demonstrated, which suggests the uniqueness of TIDs excited by

  11. Comparison of the effect of high-latitude and equatorial ionospheric scintillation on GPS signals during the maximum of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Jiao, Yu; Morton, Yu T.

    2015-09-01

    Radio signal scintillation caused by electron density irregularities in the ionosphere affects the accuracy and integrity of Global Navigation Satellite Systems, especially in the equatorial and high-latitude regions during solar maxima. Scintillation in these two regions, nevertheless, is usually influenced by different factors and thus has different characteristics that cause different effects on GNSS signals. This paper compares the characteristics of high-latitude and equatorial scintillation using multifrequency GPS scintillation data collected at Gakona, Alaska, Jicamarca, Peru, and Ascension Island during the 24th solar maximum. Several statistical distributions are established based on the data to characterize the intensity, duration, and occurrence frequency of scintillation. Results show that scintillation in the equatorial region is generally more severe and longer lasting, while high-latitude scintillation is, in general, more moderate and usually dominated by phase fluctuations. Results also reveal the different impacts of solar activity, geomagnetic activity, and seasons on scintillation in different geographic locations.

  12. Handling cycle slips in GPS data during ionospheric plasma bubble events

    NASA Astrophysics Data System (ADS)

    Banville, S.; Langley, R. B.; Saito, S.; Yoshihara, T.

    2010-12-01

    During disturbed ionospheric conditions such as the occurrence of plasma bubbles, the phase and amplitude of the electromagnetic waves transmitted by GPS satellites undergo rapid fluctuations called scintillation. When this phenomenon is observed, GPS receivers are more prone to signal tracking interruptions, which prevent continuous measurement of the total electron content (TEC) between a satellite and the receiver. In order to improve TEC monitoring, a study was conducted with the goal of reducing the effects of signal tracking interruptions by correcting for "cycle slips," an integer number of carrier wavelengths not measured by the receiver during a loss of signal lock. In this paper, we review existing cycle-slip correction methods, showing that the characteristics associated with ionospheric plasma bubbles (rapid ionospheric delay fluctuations, data gaps, increased noise, etc.) prevent reliable correction of cycle slips. Then, a reformulation of the "geometry-free" model conventionally used for ionospheric studies with GPS is presented. Geometric information is used to obtain single-frequency estimates of TEC variations during momentary L2 signal interruptions, which also provides instantaneous cycle-slip correction capabilities. The performance of this approach is assessed using data collected on Okinawa Island in Japan during a plasma bubble event that occurred on 23 March 2004. While an improvement in the continuity of TEC time series is obtained, we question the reliability of any cycle-slip correction technique when discontinuities on both GPS legacy frequencies occur simultaneously for more than a few seconds.

  13. Interplanetary magnetic field variations and the electromagnetic state of the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Patel, V. L.

    1978-01-01

    The Esq phenomena were selected in order to examine the effect of the interplanetary magnetic field (IMF) on the ionospheric plasma and to obtain insight into the interplanetary ionospheric coupling processes. January-March 1973 interplanetary magnetic field data of Explorer 43, Huancayo ionograms, and surface equatorial magnetograms were used. The IMF observations from Explorer 43 in the form of 15-sec averages were examined around the time of disappearance of the Esq. The IMF z-component was observed to change from a negative to a positive value before the disappearance of the Esq in four events where simultaneous data were available. The general explanation is that the induced electric field becomes westward from a previous eastward direction, coinciding with the IMF z-component reversal. Thus, just before the Esq disappears, the magnetosphere is subjected to the westward electric field. If this field is impressed to the low-latitude ionosphere, the resultant electric field in the equatorial ionosphere changes from eastward (westward) to westward (eastward) in the daytime (nighttime).

  14. The Upper Atmosphere and Ionosphere at Solar Minimum: Cyclical and Secular Variation (Invited)

    NASA Astrophysics Data System (ADS)

    Solomon, S. C.; Qian, L.; Luan, X.

    2009-12-01

    Solar activity during 2007 and 2008 was extremely low, including ultraviolet irradiance, solar wind parameters, and the interplanetary magnetic field. During this protracted solar minimum period, the terrestrial upper atmosphere and ionosphere were expectedly cooler, lower in density, and consequently lower in altitude, than usual. The question remains as to whether the terrestrial response to this solar minimum is significantly different from previous solar minima, and if so, how different. This question is posed against the backdrop of secular change due to increased levels of carbon dioxide and other greenhouse gases, which increase tropospheric temperature but have the inverse effect of cooling the upper atmosphere. In order to understand the causes of these changes, and to quantify the interplay of the solar cycle with the evolution of upper atmosphere and ionosphere climate, we present a combination of data analysis and global numerical simulation. Thermospheric density data from atmospheric drag on satellites, ionospheric measurements by the COSMIC mission and from ground-based sources, and cooling rate data from the SABER instrument on the TIMED mission are compared to model simulations by the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). Solar ultraviolet irradiance observations, solar wind and geomagnetic data, and measurements of anthropogenic greenhouse gases, provide the external forcing of the model. Changes during the descent into solar minimum are compared to previous solar minima, and to model simulations, to evaluate how much of the current phenomenon is attributable to solar variation, and how much to anthropogenic sources.

  15. Global ionospheric weather

    SciTech Connect

    Decker, D.T.; Doherty, P.H.

    1994-02-28

    In the last year, the authors have studied several issues that are critical for understanding ionospheric weather. Work on global F-region modeling has consisted of testing the Phillips Laboratory Global Theoretical Ionosphere Model. Comparisons with both data and other theoretical models have been successfully conducted and are ongoing. GPS observations, as well as data analysis, are also ongoing. Data have been collected for a study on the limitations in making absolute ionospheric measurements using GPS. Another study on ionospheric variability is the first of its kind using GPS data. The observed seasonal total electron content behavior is consistent with that determined from the Faraday rotation technique. Work on the FAA's Phase 1 Wide Area Differential GPS (WADGPS) Satellite Navigation Testbed Experiment also continues. Initial results indicate that stations using operational WADGPS should be located no greater than 430 km apart. Work comparing the authors electron-proton-H atom model to both observations and other models has been generally successful. They have successfully modeled the creation of high-latitude large-scale plasma structures using two separate mechanisms (time-varying global convection and meso-scale convection events).

  16. Solitons and ionospheric heating

    NASA Technical Reports Server (NTRS)

    Weatherall, J. C.; Goldman, M. V.; Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.

    1982-01-01

    It is noted that for parameters characterizing the Platteville ionospheric heating facility, the Langmuir wave evolution at the exact reflection point of the heater wave involves an oscillating two-stream instability followed by a collisionally damped three-dimensional soliton collapse. The result gives an alternative explanation for certain experimental observations.

  17. GNSS data filtering optimization for ionospheric observation

    NASA Astrophysics Data System (ADS)

    D'Angelo, G.; Spogli, L.; Cesaroni, C.; Sgrigna, V.; Alfonsi, L.; Aquino, M. H. O.

    2015-12-01

    In the last years, the use of GNSS (Global Navigation Satellite Systems) data has been gradually increasing, for both scientific studies and technological applications. High-rate GNSS data, able to generate and output 50-Hz phase and amplitude samples, are commonly used to study electron density irregularities within the ionosphere. Ionospheric irregularities may cause scintillations, which are rapid and random fluctuations of the phase and the amplitude of the received GNSS signals. For scintillation analysis, usually, GNSS signals observed at an elevation angle lower than an arbitrary threshold (usually 15°, 20° or 30°) are filtered out, to remove the possible error sources due to the local environment where the receiver is deployed. Indeed, the signal scattered by the environment surrounding the receiver could mimic ionospheric scintillation, because buildings, trees, etc. might create diffusion, diffraction and reflection. Although widely adopted, the elevation angle threshold has some downsides, as it may under or overestimate the actual impact of multipath due to local environment. Certainly, an incorrect selection of the field of view spanned by the GNSS antenna may lead to the misidentification of scintillation events at low elevation angles. With the aim to tackle the non-ionospheric effects induced by multipath at ground, in this paper we introduce a filtering technique, termed SOLIDIFY (Standalone OutLiers IDentIfication Filtering analYsis technique), aiming at excluding the multipath sources of non-ionospheric origin to improve the quality of the information obtained by the GNSS signal in a given site. SOLIDIFY is a statistical filtering technique based on the signal quality parameters measured by scintillation receivers. The technique is applied and optimized on the data acquired by a scintillation receiver located at the Istituto Nazionale di Geofisica e Vulcanologia, in Rome. The results of the exercise show that, in the considered case of a noisy

  18. Ionospheric manifestations of earthquakes and tsunamis in a dynamic atmosphere

    NASA Astrophysics Data System (ADS)

    Godin, Oleg A.; Zabotin, Nikolay A.; Zabotina, Liudmila

    2015-04-01

    the effects of the background ionospheric disturbances and uncertainty in atmospheric parameters on the feasibility and accuracy of retrieval of the open-ocean tsunami heights from observations of the ionosphere.

  19. Major magnetic storm of March 13-14, 1989 and associated ionosphere effects. (Reannouncement with new availability information)

    SciTech Connect

    Rich, F.J.; Denig, W.F.

    1993-06-30

    The geomagnetic storm of March 1989 was the largest geomagnetic storm of the decade and one of the largest of the century. The authors review many of the `high-latitude` ionospheric observations that were made during this storm. Most of the data presented here comes from the polar-orbiting satellites of the Defense Meteorological Satellite Program (DMSP) series. A review of the DMSP data shows that most of the high-latitude, top-side ionospheric disturbance occurred on March 13 and 14. The magnitudes of the particle energy flux (ergs cm 2) (1 erg = 10{minus}7 J) and Joule heating were not unusually large for a storm, but the area of the energy deposition, and thus the total energy deposition, was extremely large. At the peak of the storm (minimum in D(st) (disturbance with storm time) and midnight boundary indices) the auroral particle precipitation extended down to magnetic latitudes of 40.1 deg or L = 1.71 while the polar edge of the auroral zone expanded poleward only slightly. The storm was also a period of intense, hemispherically symmetric polar rain fluxes. The auroral electric field was clearly observed down to magnetic latitude of 35 deg. This is consistent with the auroral electrojet (AE) current density and the AE index having a saturation level beyond which the index will increase slowly or not at all as more energy is transferred from the solar wind to the magnetosphere, but the cross polar-cap potential during this storm shows no evidence of saturation. There are only two visible light images from DMSP available near the peak of the storm.

  20. Radiative transfer modeling of the OI 135.6 nm emission in the nighttime ionosphere

    NASA Astrophysics Data System (ADS)

    Qin, Jianqi; Makela, Jonathan J.; Kamalabadi, Farzad; Meier, R. R.

    2015-11-01

    Remote sensing of the nighttime OI 135.6 nm emissions has been a widely used method for measuring the F region ionospheric plasma densities. In this work, we first develop a comprehensive radiative transfer model from first principles to investigate the effects of different physical processes on the production and transport of the 135.6 nm photons in the ionosphere and then propose a new approach for estimating electron densities from the nightglow. The forward modeling investigation indicates that under certain conditions mutual neutralization can contribute up to ˜38% of the total production of the nighttime 135.6 nm emissions. Moreover, depending on the ionospheric conditions, resonant scattering by atomic oxygen and pure absorption by oxygen molecules can reduce the limb brightness observed by satellite-borne instruments by up to ˜40% while enhancing the brightness viewing in the nadir direction by typically ˜25%. Further analysis shows that without properly addressing these effects in the inversion process, the peak electron density in the F region (NmF2) obtained using limb observations can be overestimated by up to ˜24%. For accurate estimation of the ionospheric electron density, we develop a new type of inverse model that accounts for the effects of mutual neutralization, resonant scattering, and pure absorption. This inversion method requires the knowledge of O and O2 densities in order to solve the radiative transfer equations. Application of the inverse model to the nighttime ionosphere in the noiseless cases demonstrates that the electron density can be accurately quantified with only ˜1% error in NmF2 and hmF2.