WorldWideScience

Sample records for ionospheric scintillation effects

  1. Ionospheric Scintillation Effects on GPS

    Science.gov (United States)

    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.

  2. Detection of ionospheric scintillation effects using LMD-DFA

    Science.gov (United States)

    Tadivaka, Raghavendra Vishnu; Paruchuri, Bhanu Priyanka; Miriyala, Sridhar; Koppireddi, Padma Raju; Devanaboyina, Venkata Ratnam

    2017-08-01

    The performance and measurement accuracy of global navigation satellite system (GNSS) receivers is greatly affected by ionospheric scintillations. Rapid amplitude and phase variations in the received GPS signal, known as ionospheric scintillation, affects the tracking of signals by GNSS receivers. Hence, there is a need to investigate the monitoring of various activities of the ionosphere and to develop a novel approach for mitigation of ionospheric scintillation effects. A method based on Local Mean Decomposition (LMD)-Detrended Fluctuation Analysis (DFA) has been proposed. The GNSS data recorded at Koneru Lakshmaiah (K L) University, Guntur, India were considered for analysis. The carrier to noise ratio (C/N0) of GNSS satellite vehicles were decomposed into several product functions (PF) using LMD to extract the intrinsic features in the signal. Scintillation noise was removed by the DFA algorithm by selecting a suitable threshold. It was observed that the performance of the proposed LMD-DFA was better than that of empirical mode decomposition (EMD)-DFA.

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

    Science.gov (United States)

    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.

  4. Accuracy assessment of Precise Point Positioning with multi-constellation GNSS data under ionospheric scintillation effects

    Directory of Open Access Journals (Sweden)

    Marques Haroldo Antonio

    2018-01-01

    Full Text Available GPS and GLONASS are currently the Global Navigation Satellite Systems (GNSS with full operational capacity. The integration of GPS, GLONASS and future GNSS constellations can provide better accuracy and more reliability in geodetic positioning, in particular for kinematic Precise Point Positioning (PPP, where the satellite geometry is considered a limiting factor to achieve centimeter accuracy. The satellite geometry can change suddenly in kinematic positioning in urban areas or under conditions of strong atmospheric effects such as for instance ionospheric scintillation that may degrade satellite signal quality, causing cycle slips and even loss of lock. Scintillation is caused by small scale irregularities in the ionosphere and is characterized by rapid changes in amplitude and phase of the signal, which are more severe in equatorial and high latitudes geomagnetic regions. In this work, geodetic positioning through the PPP method was evaluated with integrated GPS and GLONASS data collected in the equatorial region under varied scintillation conditions. The GNSS data were processed in kinematic PPP mode and the analyses show accuracy improvements of up to 60% under conditions of strong scintillation when using multi-constellation data instead of GPS data alone. The concepts and analyses related to the ionospheric scintillation effects, the mathematical model involved in PPP with GPS and GLONASS data integration as well as accuracy assessment with data collected under ionospheric scintillation effects are presented.

  5. Accuracy assessment of Precise Point Positioning with multi-constellation GNSS data under ionospheric scintillation effects

    Science.gov (United States)

    Marques, Haroldo Antonio; Marques, Heloísa Alves Silva; Aquino, Marcio; Veettil, Sreeja Vadakke; Monico, João Francisco Galera

    2018-02-01

    GPS and GLONASS are currently the Global Navigation Satellite Systems (GNSS) with full operational capacity. The integration of GPS, GLONASS and future GNSS constellations can provide better accuracy and more reliability in geodetic positioning, in particular for kinematic Precise Point Positioning (PPP), where the satellite geometry is considered a limiting factor to achieve centimeter accuracy. The satellite geometry can change suddenly in kinematic positioning in urban areas or under conditions of strong atmospheric effects such as for instance ionospheric scintillation that may degrade satellite signal quality, causing cycle slips and even loss of lock. Scintillation is caused by small scale irregularities in the ionosphere and is characterized by rapid changes in amplitude and phase of the signal, which are more severe in equatorial and high latitudes geomagnetic regions. In this work, geodetic positioning through the PPP method was evaluated with integrated GPS and GLONASS data collected in the equatorial region under varied scintillation conditions. The GNSS data were processed in kinematic PPP mode and the analyses show accuracy improvements of up to 60% under conditions of strong scintillation when using multi-constellation data instead of GPS data alone. The concepts and analyses related to the ionospheric scintillation effects, the mathematical model involved in PPP with GPS and GLONASS data integration as well as accuracy assessment with data collected under ionospheric scintillation effects are presented.

  6. A Review of Ionospheric Scintillation Models.

    Science.gov (United States)

    Priyadarshi, S

    This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

  7. Broadband Ionospheric Scintillation Measurements from Space

    Science.gov (United States)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2014-12-01

    The U.S. Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 825 - 1100 MHz. In this paper, we present an overview of the RFProp on-orbit research and analysis effort with particular focus on an equatorial scintillation experiment called ESCINT. The 3-year ESCINT project is designed to characterize equatorial ionospheric scintillation in the upper HF and lower VHF portions of the radio spectrum (20 - 150 MHz). Both a 40 MHz continuous wave (CW) signal and 30 - 42 MHz swept frequency signal are transmitted to the satellite receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in four separate campaigns centered on the 2014 and 2015 equinoxes. Results from the first campaign conducted from April 22 - May 15, 2014 will be presented including (a) coherence bandwidth measurements over a full range of transmission frequencies and scintillation activity levels, (b) spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities, and (c) supporting ray-trace simulations. The broadband nature of the measurements is found to offer unique insight into both the structure of ionospheric irregularities and their impact on HF/VHF trans-ionospheric radio wave propagation.

  8. VHF Scintillation in an Artificially Heated Ionosphere

    Science.gov (United States)

    Suszcynsky, D. M.; Layne, J.; Light, M. E.; Pigue, M. J.; Rivera, L.

    2017-12-01

    As part of an ongoing project to characterize very-high-frequency (VHF) radio wave propagation through structured ionospheres, Los Alamos National Laboratory has been conducting a set of experiments to measure the scintillation effects of VHF transmissions under a variety of ionospheric conditions. Previous work (see 2015 Fall AGU poster by D. Suszcynsky et al.) measured the S4 index and ionospheric coherence bandwidth in the 32 - 44 MHz frequency range under naturally scintillated conditions in the equatorial region at Kwajalein Atoll during three separate campaigns centered on the 2014 and 2015 equinoxes. In this paper, we will present preliminary results from the February and September, 2017 High Altitude Auroral Research Project (HAARP) Experimental Campaigns where we are attempting to make these measurements under more controlled conditions using the HAARP ionospheric heater in a twisted-beam mode. Two types of measurements are made by transmitting VHF signals through the heated ionospheric volume to the Radio Frequency Propagation (RFProp) satellite experiment. The S4 scintillation index is determined by measuring the power fluctuations of a 135-MHz continuous wave signal and the ionospheric coherence bandwidth is simultaneously determined by measuring the delay spread of a frequency-modulated continuous wave (FMCW) signal in the 130 - 140 MHz frequency range. Additionally, a spatial Fourier transform of the CW time series is used to calculate the irregularity spectral density function. Finally, the temporal evolution of the time series is used to characterize spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities. All results are compared to theory and scaled for comparison to the 32 - 44 MHz Kwajalein measurements.

  9. Ionospheric scintillation monitoring and modelling

    Directory of Open Access Journals (Sweden)

    Mariusz Pozoga

    2009-06-01

    Full Text Available

    This paper presents a review of the ionospheric scintillation monitoring and modelling by the European groups

    involved in COST 296. Several of these groups have organized scintillation measurement campaigns at low and

    high latitudes. Some characteristic results obtained from the measured data are presented. The paper also addresses the modeling activities: four models, based on phase screen techniques, with different options and application domains are detailed. Finally some new trends for research topics are given. This includes the wavelet analysis, the high latitudes analysis, the construction of scintillation maps and the mitigation techniques.


  10. Some results of ionospheric scintillation observations at Lumping

    International Nuclear Information System (INIS)

    Huang, Yinn-Nien

    1983-01-01

    The ionospheric scintillation data obtained at Lunping by use of 136.1124 MHz beacon signal transmitted from the geostationary satellite, ETS-2, have been used to analyze the diurnal, seasonal and solar cycle variations of scintillation activity. The effect of the geomagnetic activity on the scintillation activity has been studied by use of superposed epoch method. The effect is not unique but depends on season and solar activity. (author)

  11. 4 GHz ionospheric scintillations observed at Taipei

    International Nuclear Information System (INIS)

    Huang, Y.N.; Jeng, B.S.

    1978-01-01

    In a study of ionospheric scintillations 3950 MHz beacon signals from geostationary communication satellites Intelsat-IV-F8 and Intelsat-IV-F1 were recorded on a strip chart and magnetic tape at the Taipei Earth Station. While the strip charts were used to monitor the occurrence of the scintillation, the magnetic tape output was digitized and processed by a computerized system to yield a detailed analysis of scintillation events. It was found that diurnal variations were similar to the diurnal patterns of sporadic E at greater than 5 MHz and VHF band ionospheric scintillations during daytime as reported by Huang (1978). Eight typical scintillation events were selected for the calculation of the scintillation index, S4, and other parameters. The mean S4 index for the 8 events was found to be 0.15. Numerical and graphic results are presented for the cumulative amplitude distributions, message reliability, autocorrelation functions and power spectra

  12. Predicting ionospheric scintillation: Recent advancements and future challenges

    Science.gov (United States)

    Carter, B. A.; Currie, J. L.; Terkildsen, M.; Bouya, Z.; Parkinson, M. L.

    2017-12-01

    Society greatly benefits from space-based infrastructure and technology. For example, signals from Global Navigation Satellite Systems (GNSS) are used across a wide range of industrial sectors; including aviation, mining, agriculture and finance. Current trends indicate that the use of these space-based technologies is likely to increase over the coming decades as the global economy becomes more technology-dependent. Space weather represents a key vulnerability to space-based technology, both in terms of the space environment effects on satellite infrastructure and the influence of the ionosphere on the radio signals used for satellite communications. In recent decades, the impact of the ionosphere on GNSS signals has re-ignited research interest into the equatorial ionosphere, particularly towards understanding Equatorial Plasma Bubbles (EPBs). EPBs are a dominant source of nighttime plasma irregularities in the low-latitude ionosphere, which can cause severe scintillation on GNSS signals and subsequent degradation on GNSS product quality. Currently, ionospheric scintillation event forecasts are not being routinely released by any space weather prediction agency around the world, but this is likely to change in the near future. In this contribution, an overview of recent efforts to develop a global ionospheric scintillation prediction capability within Australia will be given. The challenges in understanding user requirements for ionospheric scintillation predictions will be discussed. Next, the use of ground- and space-based datasets for the purpose of near-real time ionospheric scintillation monitoring will be explored. Finally, some modeling that has shown significant promise in transitioning towards an operational ionospheric scintillation forecasting system will be discussed.

  13. Ionosphere Scintillation at Low and High Latitudes (Modelling vs Measurement)

    Science.gov (United States)

    Béniguel, Yannick

    2016-04-01

    This paper will address the problem of scintillations characteristics, focusing on the parameters of interest for a navigation system. Those parameters are the probabilities of occurrence of simultaneous fading, the bubbles surface at IPP level, the cycle slips and the fades duration statistics. The scintillation characteristics obtained at low and high latitudes will be compared. These results correspond to the data analysis performed after the ESA Monitor ionosphere measurement campaign [1], [2]. A second aspect of the presentation will be the modelling aspect. It has been observed that the phase scintillation dominates at high latitudes while the intensity scintillation dominates at low latitudes. The way it can be reproduced and implemented in a propagation model (e.g. GISM model [3]) will be presented. Comparisons of measurements with results obtained by modelling will be presented on some typical scenarios. References [1] R. Prieto Cerdeira, Y. Beniguel, "The MONITOR project: architecture, data and products", Ionospheric Effects Symposium, Alexandria (Va), May 2011 [2] Y. Béniguel, R Orus-Perez , R. Prieto-Cerdeira , S. Schlueter , S. Scortan, A. Grosu "MONITOR 2: ionospheric monitoring network in support to SBAS and other GNSS and scientific purposes", IES Conference, Alexandria (Va), May 2015-05-22 [3] Y. Béniguel, P. Hamel, "A Global Ionosphere Scintillation Propagation Model for Equatorial Regions", Journal of Space Weather Space Climate, 1, (2011), doi: 10.1051/swsc/2011004

  14. Ionospheric scintillation forecasting model based on NN-PSO technique

    Science.gov (United States)

    Sridhar, M.; Venkata Ratnam, D.; Padma Raju, K.; Sai Praharsha, D.; Saathvika, K.

    2017-09-01

    The forecasting and modeling of ionospheric scintillation effects are crucial for precise satellite positioning and navigation applications. In this paper, a Neural Network model, trained using Particle Swarm Optimization (PSO) algorithm, has been implemented for the prediction of amplitude scintillation index (S4) observations. The Global Positioning System (GPS) and Ionosonde data available at Darwin, Australia (12.4634° S, 130.8456° E) during 2013 has been considered. The correlation analysis between GPS S4 and Ionosonde drift velocities (hmf2 and fof2) data has been conducted for forecasting the S4 values. The results indicate that forecasted S4 values closely follow the measured S4 values for both the quiet and disturbed conditions. The outcome of this work will be useful for understanding the ionospheric scintillation phenomena over low latitude regions.

  15. Seasonal ionospheric scintillation analysis during increasing solar activity at mid-latitude

    Science.gov (United States)

    Ahmed, Wasiu Akande; Wu, Falin; Agbaje, Ganiyu Ishola; Ednofri, Ednofri; Marlia, Dessi; Zhao, Yan

    2017-09-01

    Monitoring of ionospheric parameters (such as Total Electron Content and scintillation) is of great importance as it affects and contributes to the errors encountered by radio signals. It thus requires constant measurements to avoid disastrous situation for space agencies, parastatals and departments that employ GNSS applications in their daily operations. The research objective is to have a better understanding of the behaviour of ionospheric scintillation at midlatitude as it threatens the performances of satellite communication, navigation systems and military operations. This paper adopts seasonal ionospheric scintillation scenario. The mid-latitude investigation of ionospheric effect of scintillation was conducted during the increasing solar activity from 2011-2015. Ionospheric scintillation data were obtained from four ionospheric monitoring stations located at mid-latitude (i.e Shenzhen North Station, Beijing Changping North Station Branch, Beijing North Station and Beijing Miyun ground Station). The data was collected from January 2011 to December 2015. There were absence of data due to software problem or system failure at some locations. The scintillation phenomenon was computed using Global Ionospheric Scintillation and TEC Monitoring Model. There are four seasons which existed in China namely: Spring, Summer, Autumn and Winter. The relationship between TEC, amplitude and phase scintillation were observed for each of these seasons. The results indicated that the weak amplitude scintillation was observed as against phase scintillation which was high. Phase scintillation was gradually enhanced from 2011 to 2012 and later declined till 2014. TEC was also at peak around 00:00-10:00 UT (08:00-18:00 LT). The seasonal events temporal density characteristics comply with solar cycle prediction as such it ascended from 2011 to 2013 and then scintillation parameters declined significantly afterwards.

  16. Ionospheric scintillation observations over Kenyan region - Preliminary results

    Science.gov (United States)

    Olwendo, O. J.; Xiao, Yu; Ming, Ou

    2016-11-01

    Ionospheric scintillation refers to the rapid fluctuations in the amplitude and phase of a satellite signal as it passes through small-scale plasma density irregularities in the ionosphere. By analyzing ionospheric scintillation observation datasets from satellite signals such as GPS signals we can study the morphology of ionospheric bubbles. At low latitudes, the diurnal behavior of scintillation is driven by the formation of large-scale equatorial density depletions which form one to two hours after sunset via the Rayleigh-Taylor instability mechanism near the magnetic equator. In this work we present ionospheric scintillation activity over Kenya using data derived from a newly installed scintillation monitor developed by CRIRP at Pwani University (39.78°E, 3.24°S) during the period August to December, 2014. The results reveal the scintillation activity mainly occurs from post-sunset to post-midnight hours, and ceases around 04:00 LT. We also found that the ionospheric scintillation tends to appear at the southwest and northwest of the station. These locations coincide with the southern part of the Equatorial Ionization Anomaly crest over Kenya region. The occurrence of post-midnight L-band scintillation events which are not linked to pre-midnight scintillation observations raises fundamental question on the mechanism and source of electric fields driving the plasma depletion under conditions of very low background electron density.

  17. Research to Operations of Ionospheric Scintillation Detection and Forecasting

    Science.gov (United States)

    Jones, J.; Scro, K.; Payne, D.; Ruhge, R.; Erickson, B.; Andorka, S.; Ludwig, C.; Karmann, J.; Ebelhar, D.

    Ionospheric Scintillation refers to random fluctuations in phase and amplitude of electromagnetic waves caused by a rapidly varying refractive index due to turbulent features in the ionosphere. Scintillation of transionospheric UHF and L-Band radio frequency signals is particularly troublesome since this phenomenon can lead to degradation of signal strength and integrity that can negatively impact satellite communications and navigation, radar, or radio signals from other systems that traverse or interact with the ionosphere. Although ionospheric scintillation occurs in both the equatorial and polar regions of the Earth, the focus of this modeling effort is on equatorial scintillation. The ionospheric scintillation model is data-driven in a sense that scintillation observations are used to perform detection and characterization of scintillation structures. These structures are then propagated to future times using drift and decay models to represent the natural evolution of ionospheric scintillation. The impact on radio signals is also determined by the model and represented in graphical format to the user. A frequency scaling algorithm allows for impact analysis on frequencies other than the observation frequencies. The project began with lab-grade software and through a tailored Agile development process, deployed operational-grade code to a DoD operational center. The Agile development process promotes adaptive promote adaptive planning, evolutionary development, early delivery, continuous improvement, regular collaboration with the customer, and encourage rapid and flexible response to customer-driven changes. The Agile philosophy values individuals and interactions over processes and tools, working software over comprehensive documentation, customer collaboration over contract negotiation, and responding to change over following a rigid plan. The end result was an operational capability that met customer expectations. Details of the model and the process of

  18. Irregular ionization and scintillation of the ionosphere in equator region

    International Nuclear Information System (INIS)

    Shinno, Kenji

    1974-01-01

    The latest studies on the scintillation in satellite communication and its related irregularities of ionosphere are reviewed. They were made clear by means of spread-F, the direct measurement with scientific satellites, VHF radar observation, and radio wave propagation in equator region. The fundamental occurrence mechanism may be instability of plasma caused by the interaction of movement of neutral atmosphere and magnetic field. Comparison of the main characteristics of scintillation, namely the dependence on region, solar activity, season, local time, geomagnetic activity, movement in ionosphere, scattering source, frequency and transmission mode, was made and the correlation among spread-F, TEP and scintillation was summarized. The latest principal studies were the observations made by Intelsat and by ATS. Scintillation of Syncom-3 and Intelsat-II-F2 and spread-F by ionosphere observation were compared by Huang. It is reasonable to consider that the occurrence of scintillation is caused by the irregularities in ionosphere which are particular in equator region, because of the similar characteristics of spread-F and VHF propagation in the equator region. These three phenomena may occur in relation to the irregularities of ionosphere. Interpretation of spread-F and the abnormal propagation wave across the equator are given. The study using VHF radar and the movement of irregular ionization by the direct observation with artificial satellites are reviewd. (Iwakiri, K.)

  19. Radio tomography and scintillation studies of ionospheric electron density modification caused by a powerful HF-wave and magnetic zenith effect at mid-latitudes

    International Nuclear Information System (INIS)

    Tereshchenko, E.D.; Khudukon, B.Z.; Gurevich, A.V.; Zybin, K.P.; Frolov, V.L.; Myasnikov, E.N.; Muravieva, N.V.; Carlson, H.C.

    2004-01-01

    Observations of the ionospheric electron density modified by a powerful wave of the Sura HF heating facility were carried out in Russia at middle latitudes in August 2002. Amplitude scintillations and variations of the phase of VHF signals from Russian orbiting satellites passing over the heated region along the chain of three satellite receivers have been recorded. The experimental data were converted to electron density maps using a stochastic inversion. Tomographic measurements conducted during a low magnetic activity revealed that HF powerful waves can produce significant electron density disturbances up to heights significantly exceeding altitudes of the F layer peak. Both large-scale plasma enhancements and small-scale density irregularities can be generated by the HF radiation. Wavy density structures were also observed within a sector which is much wider than the area covered by the main lobe of the heating antenna. Small-scale density irregularities are mostly field-aligned although large-scale structures can be detected within a much larger area. A distinctive peculiarity of electron density changes occurred during heating is producing a zone of low density inside the area illuminated by the antenna beam. The results indicate that satellite radio tomography and scintillation measurements are effective diagnostic techniques giving a valuable information to studies of effects induced by HF modification. The complete system of plasma density disturbances describing by the theory of 'the magnetic zenith effect' has been for the first time studied in this Letter. A good agreement between the theory and experimental data has been obtained

  20. Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

    Directory of Open Access Journals (Sweden)

    L. Z. Biktash

    2004-09-01

    Full Text Available The equatorial ionosphere parameters, Kp, Dst, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

  1. GNSS-based Observations and Simulations of Spectral Scintillation Indices in the Arctic Ionosphere

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Hoeg, Per; von Benzon, Hans-Henrik

    During disturbed times, ionospheric scintillations can be severe and adversely impact satellite-based positioning and radio transmissions. The scintillation occurs in the amplitude, phase, polarization, and angle of arrival of the signal. Precise observation, classification, modeling, forecasting...

  2. Climatology of GNPs ionospheric scintillation at high and mid latitudes under different solar activity conditions

    International Nuclear Information System (INIS)

    Spogli, L.; Alfonsi, L.; De Franceschi, G.; Romano, V.; Aquino, M.H.O.; Dodson, A.

    2010-01-01

    We analyze data of ionospheric scintillation over North European regions for the same period (October to November) of two different years (2003 and 2008), characterized by different geomagnetic conditions. The work aims to develop a scintillation climatology of the high- and mid-latitude ionosphere, analyzing the behaviour of the scintillation occurrence as a function of the magnetic local time (MLT) and of the altitude adjusted corrected magnetic latitude (M lat), to characterize scintillation scenarios under different solar activity conditions. The results shown herein are obtained merging observations from a network of GISTMs (GPS Ionospheric Scintillation and TEC Monitor) located over a wide range of latitudes in the northern hemisphere. Our findings confirm the associations of the occurrence of the ionospheric irregularities with the expected position of the auroral oval and of the ionospheric trough walls and show the contribution of the polar cap patches even under solar minimum conditions.

  3. Spatial correlations in intense ionospheric scintillations - comparison between numerical computation and observation

    International Nuclear Information System (INIS)

    Kumagai, H.

    1987-01-01

    The spatial correlations in intense ionospheric scintillations were analyzed by comparing numerical results with observational ones. The observational results were obtained by spaced-receiver scintillation measurements of VHF satellite radiowave. The numerical computation was made by using the fourth-order moment equation with fairly realistic ionospheric irregularity models, in which power-law irregularities with spectral index 4, both thin and thick slabs, and both isotropic and anisotropic irregularities, were considered. Evolution of the S(4) index and the transverse correlation function was computed. The numerical result that the transverse correlation distance decreases with the increase in S(4) was consistent with that obtained in the observation, suggesting that multiple scattering plays an important role in the intense scintillations observed. The anisotropy of irregularities proved to act as if the density fluctuation increased. This effect, as well as the effect of slab thickness, was evaluated by the total phase fluctuations that the radiowave experienced in the slab. On the basis of the comparison, the irregularity height and electron-density fluctuation which is necessary to produce a particular strength of scintillation were estimated. 30 references

  4. Multi-frequency GNSS robust carrier tracking for ionospheric scintillation mitigation

    Directory of Open Access Journals (Sweden)

    Vilà-Valls Jordi

    2017-01-01

    Full Text Available Ionospheric scintillation is the physical phenomena affecting radio waves propagating from the space through the ionosphere to earth. The signal distortion induced by scintillation can pose a major threat to some GNSS application. Scintillation is one of the more challenging propagation scenarios, particularly affecting high-precision GNSS receivers which require high quality carrier phase measurements; and safety critical applications which have strict accuracy, availability and integrity requirements. Under ionospheric scintillation conditions, GNSS signals are affected by fast amplitude and phase variations, which can compromise the receiver synchronization. To take into account the underlying correlation among different frequency bands, we propose a new multivariate autoregressive model (MAR for the multi-frequency ionospheric scintillation process. Multi-frequency GNSS observations and the scintillation MAR are modeled in state-space, allowing independent tracking of both line-of-sight phase variations and complex gain scintillation components. The resulting joint synchronization and scintillation mitigation problem is solved using a robust nonlinear Kalman filter, validated using real multi-frequency scintillation data with encouraging results.

  5. Multi-frequency GNSS robust carrier tracking for ionospheric scintillation mitigation

    Science.gov (United States)

    Vilà-Valls, Jordi; Closas, Pau; Curran, James T.

    2017-10-01

    Ionospheric scintillation is the physical phenomena affecting radio waves propagating from the space through the ionosphere to earth. The signal distortion induced by scintillation can pose a major threat to some GNSS application. Scintillation is one of the more challenging propagation scenarios, particularly affecting high-precision GNSS receivers which require high quality carrier phase measurements; and safety critical applications which have strict accuracy, availability and integrity requirements. Under ionospheric scintillation conditions, GNSS signals are affected by fast amplitude and phase variations, which can compromise the receiver synchronization. To take into account the underlying correlation among different frequency bands, we propose a new multivariate autoregressive model (MAR) for the multi-frequency ionospheric scintillation process. Multi-frequency GNSS observations and the scintillation MAR are modeled in state-space, allowing independent tracking of both line-of-sight phase variations and complex gain scintillation components. The resulting joint synchronization and scintillation mitigation problem is solved using a robust nonlinear Kalman filter, validated using real multi-frequency scintillation data with encouraging results.

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

    Science.gov (United States)

    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.

  7. Some results of ionospheric total electron content and scintillation observations at Lunping

    International Nuclear Information System (INIS)

    Huang, Y.N.

    1981-01-01

    An analysis is conducted of the characteristic variations of the ionospheric total electron content (TEC), slab thickness, and scintillation activity observed at Lunping Observatory. The employed data have been obtained by measuring the Faraday rotation angle of the 136.1124 MHz beacon signal transmitted from the Japanese ETS-II geostationary satellite. Diurnal, seasonal, and solar cycle variations of TEC are discussed, taking into account real seasonal variations of TEC and geomagnetic storm effects. Geomagnetic storm effects on the variation of the slab thickness are studied by selecting 90 SC type geomagnetic storms which occurred during the period from March 1977 to June 1980

  8. New Opportunities for Remote Sensing Ionospheric Irregularities by Fitting Scintillation Spectra

    Science.gov (United States)

    Carrano, C. S.; Rino, C. L.; Groves, K. M.

    2017-12-01

    In a recent paper, we presented a phase screen theory for the spectrum of intensity scintillations when the refractive index irregularities follow a two-component power law [Carrano and Rino, DOI: 10.1002/2015RS005903]. More recently we have investigated the inverse problem, whereby phase screen parameters are inferred from scintillation time series. This is accomplished by fitting the spectrum of intensity fluctuations with a parametrized theoretical model using Maximum Likelihood (ML) methods. The Markov-Chain Monte-Carlo technique provides a-posteriori errors and confidence intervals. The Akaike Information Criterion (AIC) provides justification for the use of one- or two-component irregularity models. We refer to this fitting as Irregularity Parameter Estimation (IPE) since it provides a statistical description of the irregularities from the scintillations they produce. In this talk, we explore some new opportunities for remote sensing ionospheric irregularities afforded by IPE. Statistical characterization of irregularities and the plasma bubbles in which they are embedded provides insight into the development of the underlying instability. In a companion paper by Rino et al., IPE is used to interpret scintillation due to simulated EPB structure. IPE can be used to reconcile multi-frequency scintillation observations and to construct high fidelity scintillation simulation tools. In space-to-ground propagation scenarios, for which an estimate of the distance to the scattering region is available a-priori, IPE enables retrieval of zonal irregularity drift. In radio occultation scenarios, the distance to the irregularities is generally unknown but IPE enables retrieval of Fresnel frequency. A geometric model for the effective scan velocity maps Fresnel frequency to Fresnel scale, yielding the distance to the irregularities. We demonstrate this approach by geolocating irregularities observed by the CORISS instrument onboard the C/NOFS satellite.

  9. Characterization of the Ionospheric Scintillations at High Latitude using GPS Signal

    Science.gov (United States)

    Mezaoui, H.; Hamza, A. M.; Jayachandran, P. T.

    2013-12-01

    Transionospheric radio signals experience both amplitude and phase variations as a result of propagation through a turbulent ionosphere; this phenomenon is known as ionospheric scintillations. As a result of these fluctuations, Global Positioning System (GPS) receivers lose track of signals and consequently induce position and navigational errors. Therefore, there is a need to study these scintillations and their causes in order to not only resolve the navigational problem but in addition develop analytical and numerical radio propagation models. In order to quantify and qualify these scintillations, we analyze the probability distribution functions (PDFs) of L1 GPS signals at 50 Hz sampling rate using the Canadian High arctic Ionospheric Network (CHAIN) measurements. The raw GPS signal is detrended using a wavelet-based technique and the detrended amplitude and phase of the signal are used to construct probability distribution functions (PDFs) of the scintillating signal. The resulting PDFs are non-Gaussian. From the PDF functional fits, the moments are estimated. The results reveal a general non-trivial parabolic relationship between the normalized fourth and third moments for both the phase and amplitude of the signal. The calculated higher-order moments of the amplitude and phase distribution functions will help quantify some of the scintillation characteristics and in the process provide a base for forecasting, i.e. develop a scintillation climatology model. This statistical analysis, including power spectra, along with a numerical simulation will constitute the backbone of a high latitude scintillation model.

  10. Modeling of the Ionospheric Scintillation and Total Electron Content Observations during the 21 August 2017 Total Solar Eclipse

    Science.gov (United States)

    Datta-Barua, S.; Gachancipa, J. N.; Deshpande, K.; Herrera, J. A.; Lehmacher, G. A.; Su, Y.; Gyuk, G.; Bust, G. S.; Hampton, D. L.

    2017-12-01

    High concentration of free electrons in the ionosphere can cause fluctuations in incoming electromagnetic waves, such as those from the different Global Navigation Satellite Systems (GNSS). The behavior of the ionosphere depends on time and location, and it is highly influenced by solar activity. The purpose of this study is to determine the impact of a total solar eclipse on the local ionosphere in terms of ionospheric scintillations, and on the global ionosphere in terms of TEC (Total Electron Content). The studied eclipse occurred on 21 August 2017 across the continental United States. During the eclipse, we expected to see a decrease in the scintillation strength, as well as in the TEC values. As a broader impact part of our recently funded NSF proposal, we temporarily deployed two GNSS receivers on the eclipse's totality path. One GNSS receiver was placed in Clemson, SC. This is a multi-frequency GNSS receiver (NovAtel GPStation-6) capable of measuring high and low rate scintillation data as well as TEC values from four different GNSS systems. We had the receiver operating before, during, and after the solar eclipse to enable the comparison between eclipse and non-eclipse periods. A twin receiver collected data at Daytona Beach, FL during the same time, where an 85% partial solar eclipse was observed. Additionally, we set up a ground receiver onsite in the path of totality in Perryville, Missouri, from which the Adler Planetarium of Chicago launched a high-altitude balloon to capture a 360-degree video of the eclipse from the stratosphere. By analyzing the collected data, this study looks at the effects of partial and total solar eclipse periods on high rate GNSS scintillation data at mid-latitudes, which had not been explored in detail. This study also explores the impact of solar eclipses on signals from different satellite constellations (GPS, GLONASS, and Galileo). Throughout the eclipse, the scintillation values did not appear to have dramatic changes

  11. Effect of Magnetic Activity on Ionospheric Time Delay at Low ...

    Indian Academy of Sciences (India)

    E) using dual frequency (1575.42 and 1227.60 MHz) GPS measurements. Data from GSV4004A GPS Iono- spheric Scintillation and TEC monitor (GISTM) have been chosen to study these effects. This paper presents the results of ionospheric time delay during quiet and disturbed days for the year 2005. Results show that.

  12. Atmospheric Drag, Occultation ‘N’ Ionospheric Scintillation (ADONIS mission proposal

    Directory of Open Access Journals (Sweden)

    Hettrich Sebastian

    2015-01-01

    Full Text Available The Atmospheric Drag, Occultation ‘N’ Ionospheric Scintillation mission (ADONIS studies the dynamics of the terrestrial thermosphere and ionosphere in dependency of solar events over a full solar cycle in Low Earth Orbit (LEO. The objectives are to investigate satellite drag with in-situ measurements and the ionospheric electron density profiles with radio occultation and scintillation measurements. A constellation of two satellites provides the possibility to gain near real-time data (NRT about ionospheric conditions over the Arctic region where current coverage is insufficient. The mission shall also provide global high-resolution data to improve assimilative ionospheric models. The low-cost constellation can be launched using a single Vega rocket and most of the instruments are already space-proven allowing for rapid development and good reliability. From July 16 to 25, 2013, the Alpbach Summer School 2013 was organised by the Austrian Research Promotion Agency (FFG, the European Space Agency (ESA, the International Space Science Institute (ISSI and the association of Austrian space industries Austrospace in Alpbach, Austria. During the workshop, four teams of 15 students each independently developed four different space mission proposals on the topic of “Space Weather: Science, Missions and Systems”, supported by a team of tutors. The present work is based on the mission proposal that resulted from one of these teams’ efforts.

  13. Characteristics of ionospheric irregularities causing scintillations at VHF/UHF

    International Nuclear Information System (INIS)

    Vats, H.O.; Deshpande, M.R.; Rastogi, R.G.

    1978-01-01

    Some properties of ionization irregularities using amplitude scintillation records of radio beacons from ATS-6 (phase II) at Ootacamund, India have been investigated. For the estimation of scale-size and strength of the irregularities a simple diffraction model has been used which explains only weak and moderate equatorial scintillation observations. It was found that the scale sizes of day time E-region irregularities are smaller than those in the F-region during night time in addition, irregularities are generated initially at large scale sizes which later break up into smaller scale sizes

  14. Visual exploration and analysis of ionospheric scintillation monitoring data: The ISMR Query Tool

    Science.gov (United States)

    Vani, Bruno César; Shimabukuro, Milton Hirokazu; Galera Monico, João Francisco

    2017-07-01

    Ionospheric Scintillations are rapid variations on the phase and/or amplitude of a radio signal as it passes through ionospheric plasma irregularities. The ionosphere is a specific layer of the Earth's atmosphere located approximately between 50 km and 1000 km above the Earth's surface. As Global Navigation Satellite Systems (GNSS) - such as GPS, Galileo, BDS and GLONASS - use radio signals, these variations degrade their positioning service quality. Due to its location, Brazil is one of the places most affected by scintillation in the world. For that reason, ionosphere monitoring stations have been deployed over Brazilian territory since 2011 through cooperative projects between several institutions in Europe and Brazil. Such monitoring stations compose a network that generates a large amount of monitoring data everyday. GNSS receivers deployed at these stations - named Ionospheric Scintillation Monitor Receivers (ISMR) - provide scintillation indices and related signal metrics for available satellites dedicated to satellite-based navigation and positioning services. With this monitoring infrastructure, more than ten million observation values are generated and stored every day. Extracting the relevant information from this huge amount of data was a hard process and required the expertise of computer and geoscience scientists. This paper describes the concepts, design and aspects related to the implementation of the software that has been supporting research on ISMR data - the so-called ISMR Query Tool. Usability and other aspects are also presented via examples of application. This web based software has been designed and developed aiming to ensure insights over the huge amount of ISMR data that is fetched every day on an integrated platform. The software applies and adapts time series mining and information visualization techniques to extend the possibilities of exploring and analyzing ISMR data. The software is available to the scientific community through the

  15. Correlation analysis between the occurrence of ionospheric scintillation at the magnetic equator and at the southern peak of the Equatorial Ionization Anomaly

    Science.gov (United States)

    de Lima, G. R. T.; Stephany, S.; de Paula, E. R.; Batista, I. S.; Abdu, M. A.; Rezende, L. F. C.; Aquino, M. G. S.; Dutra, A. P. S.

    2014-06-01

    Ionospheric scintillation refers to amplitude and phase fluctuations in radio signals due to electron density irregularities associated to structures named ionospheric plasma bubbles. The phenomenon is more pronounced around the magnetic equator where, after sunset, plasma bubbles of varying sizes and density depletions are generated by plasma instability mechanisms. The bubble depletions are aligned along Earth's magnetic field lines, and they develop vertically upward over the magnetic equator so that their extremities extend in latitude to north and south of the dip equator. Over Brazil, developing bubbles can extend to the southern peak of the Equatorial Ionization Anomaly, where high levels of ionospheric scintillation are common. Scintillation may seriously affect satellite navigation systems, such as the Global Navigation Satellite Systems. However, its effects may be mitigated by using a predictive model derived from a collection of extended databases on scintillation and its associated variables. This work proposes the use of a classification and regression decision tree to perform a study on the correlation between the occurrence of scintillation at the magnetic equator and that at the southern peak of the equatorial anomaly. Due to limited size of the original database, a novel resampling heuristic was applied to generate new training instances from the original ones in order to improve the accuracy of the decision tree. The correlation analysis presented in this work may serve as a starting point for the eventual development of a predictive model suitable for operational use.

  16. The Equatorial Scintillations and Space Weather Effects on its Generation during Geomagnetic Storms

    Science.gov (United States)

    Biktash, Lilia

    Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transiono-spheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different mag-netospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintil-lations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of elec-tron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind -magnetosphere -ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scin-tillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere cur-rents and

  17. Ionospheric effects during severe space weather events seen in ionospheric service data products

    Science.gov (United States)

    Jakowski, Norbert; Danielides, Michael; Mayer, Christoph; Borries, Claudia

    Space weather effects are closely related to complex perturbation processes in the magnetosphere-ionosphere-thermosphere systems, initiated by enhanced solar energy input. To understand and model complex space weather processes, different views on the same subject are helpful. One of the ionosphere key parameters is the Total Electron Content (TEC) which provides a first or-der approximation of the ionospheric range error in Global Navigation Satellite System (GNSS) applications. Additionally, horizontal gradients and time rate of change of TEC are important for estimating the perturbation degree of the ionosphere. TEC maps can effectively be gener-ated using ground based GNSS measurements from global receiver networks. Whereas ground based GNSS measurements provide good horizontal resolution, space based radio occultation measurements can complete the view by providing information on the vertical plasma density distribution. The combination of ground based TEC and vertical sounding measurements pro-vide essential information on the shape of the vertical electron density profile by computing the equivalent slab thickness at the ionosonde station site. Since radio beacon measurements at 150/400 MHz are well suited to trace the horizontal structure of Travelling Ionospheric Dis-turbances (TIDs), these data products essentially complete GNSS based TEC mapping results. Radio scintillation data products, characterising small scale irregularities in the ionosphere, are useful to estimate the continuity and availability of transionospheric radio signals. The different data products are addressed while discussing severe space weather events in the ionosphere e.g. events in October/November 2003. The complementary view of different near real time service data products is helpful to better understand the complex dynamics of ionospheric perturbation processes and to forecast the development of parameters customers are interested in.

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

    Science.gov (United States)

    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.

  19. Observational study of ionospheric irregularities and GPS scintillations associated with the 2012 tropical cyclone Tembin passing Hong Kong

    Science.gov (United States)

    Yang, Zhe; Liu, Zhizhao

    2016-05-01

    This study presents the ionospheric responses observed in Hong Kong to a Typhoon, namely, Tembin, from the aspects of the occurrence of ionospheric irregularities and scintillations, using Global Positioning System (GPS) observations from a ground-based GPS scintillation monitoring station in Hong Kong and from GPS receivers on board the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. The ionospheric irregularities and scintillations are characterized by the rate of total electron content variation index (ROTI) and the amplitude scintillation index S4, respectively. The typhoon Tembin formed over the western North Pacific during 18-30 August 2012 and approached Hong Kong during 24-27 August 2012 with the closest distance 290 km from Hong Kong at around 17 universal time (UT) on 25 August 2012. The ground-based observations indicate that in the nighttime period of 20:00-02:00 local time (LT = UT + 8 h) on 26 August when Tembin passed closely to Hong Kong, the ionospheric irregularities and scintillations of GPS signals were observed in the south of Hong Kong, over the area of 13°N ~ 23°N in latitude and 110°E ~ 120°E in longitude. From the COSMIC observations, it shows that the number of radio occultation scintillation events peaks on 26 August 2012 during the passage of Tembin. Without the presence of strong geomagnetic or solar activity, it is suspected that gravity waves might be generated in the lower atmosphere and likely seed the formation of ionospheric plasma irregularities. This work for the first time from Hong Kong observes the sign of coupling between the lower atmosphere and ionosphere in a tropical cyclone event, combining both ground- and space-based GPS observation data.

  20. Study of GNSS Loss of Lock Characteristics under Ionosphere Scintillation with GNSS Data at Weipa (Australia) During Solar Maximum Phase.

    Science.gov (United States)

    Liu, Yang; Fu, Lianjie; Wang, Jinling; Zhang, Chunxi

    2017-09-25

    One of the adverse impacts of scintillation on GNSS signals is the loss of lock status, which can lead to GNSS geometry and visibility reductions that compromise the accuracy and integrity of navigation performance. In this paper the loss of lock based on ionosphere scintillation in this solar maximum phase has been well investigated with respect to both temporal and spatial behaviors, based on GNSS observatory data collected at Weipa (Australia; geographic: 12.45° S, 130.95° E; geomagnetic: 21.79° S, 214.41° E) from 2011 to 2015. Experiments demonstrate that the percentage of occurrence of loss of lock events under ionosphere scintillation is closely related with solar activity and seasonal shifts. Loss of lock behaviors under ionosphere scintillation related to elevation and azimuth angles are statistically analyzed, with some distinct characteristics found. The influences of daytime scintillation and geomagnetic storms on loss of lock have also been discussed in details. The proposed work is valuable for a deeper understanding of theoretical mechanisms of-loss of lock under ionosphere scintillation in global regions, and provides a reference for GNSS applications in certain regions at Australian low latitudes.

  1. MONITOR Ionospheric Network: two case studies on scintillation and electron content variability

    Directory of Open Access Journals (Sweden)

    Y. Béniguel

    2017-03-01

    Full Text Available The ESA MONITOR network is composed of high-frequency-sampling global navigation satellite systems (GNSS receivers deployed mainly at low and high latitudes to study ionosphere variability and jointly with global GNSS data and ionospheric processing software in support of the GNSS and its satellite-based augmentation systems (SBAS like the European EGNOS. In a recent phase of the project, the network was merged with the CNES/ASECNA network and new receivers were added to complement the latter in the western African sector. This paper summarizes MONITOR, presenting two case studies on scintillations (using almost 2 years of data measurements. The first case occurred during the major St. Patrick's Day geomagnetic storm in 2015. The second case study was performed in the last phase of the project, which was supported by ESA EGNOS Project Office, when we paid special attention to extreme events that might degrade the system performance of the European EGNOS.

  2. On the occurrence and strength of multi-frequency multi-GNSS Ionospheric Scintillations in Indian sector during declining phase of solar cycle 24

    Science.gov (United States)

    Srinivasu, V. K. D.; Dashora, N.; Prasad, D. S. V. V. D.; Niranjan, K.; Gopi Krishna, S.

    2018-04-01

    This study presents unique perspectives of occurrence and strength of low latitude ionospheric scintillations on multiple signals of Global Navigation Satellite System (GNSS) and its frequency dependence using continuous observation records of 780 nights. A robust comparative analysis is performed using scintillation index, S4 and its variation during pre-midnight and post-midnight duration from a GNSS receiver located at Waltair (17.7°N, 83.3°E), India, covering period from July 2014 to August 2016. The results, generally exhibit the impact of declining phase of solar cycle 24 on occurrence and strength of scintillations, which, however, is evidently different over different frequencies transmitted from different GNSS systems. A deeper quantitative analysis uniquely reveals that apart from the solar cycle and seasonal effects, the number of visible satellites of a selected GNSS markedly affect the occurrence and also the strength. Processing scheme of adopting 6 hourly time windows of pre-midnight and post-midnight brought a novel result that the strength and occurrence of strong scintillations decrease with declining solar activity during pre-midnight hours but remarkably increase for moderate and weak scintillations during post-midnight. The physical processes that dominate the post-midnight equatorial ionosphere are invoked to explain such variations that are special during declining solar activity. Finally, inter-GNSS signal analysis in terms of the effect of strong, moderate and weak scintillations is presented with due consideration of number of satellite passes affected and frequency dependence of mean S4. The quantitative results of this study emphasize for the first time effect of low latitude scintillation on GNSS signals in Indian zone under changing background solar and seasonal conditions.

  3. Experimental Evidence on the Dependence of the Standard GPS Phase Scintillation Index on the Ionospheric Plasma Drift Around Noon Sector of the Polar Ionosphere

    Science.gov (United States)

    Wang, Y.; Zhang, Q.-H.; Jayachandran, P. T.; Moen, J.; Xing, Z.-Y.; Chadwick, R.; Ma, Y.-Z.; Ruohoniemi, J. M.; Lester, M.

    2018-03-01

    First experimental proof of a clear and strong dependence of the standard phase scintillation index (σφ) derived using Global Positioning System measurements on the ionospheric plasma flow around the noon sector of polar ionosphere is presented. σφ shows a strong linear dependence on the plasma drift speed measured by the Super Dual Auroral Radar Network radars, whereas the amplitude scintillation index (S4) does not. This observed dependence can be explained as a consequence of Fresnel frequency dependence of the relative drift and the used constant cutoff frequency (0.1 Hz) to detrend the data for obtaining standard σφ. The lack of dependence of S4 on the drift speed possibly eliminates the plasma instability mechanism(s) involved as a cause of the dependence. These observations further confirm that the standard phase scintillation index is much more sensitive to plasma flow; therefore, utmost care must be taken when identifying phase scintillation (diffractive phase variations) from refractive (deterministic) phase variations, especially in the polar region where the ionospheric plasma drift is much larger than in equatorial and midlatitude regions.

  4. Rapid fluctuations in ionospheric Faraday rotation angle and 4GHz amplitude scintillation observed at Suva, Fiji

    International Nuclear Information System (INIS)

    Buonsanto, M.J.; Northcott, R.L.; Wright, R.W.H.

    1987-01-01

    Observations are reported of rapid fluctuations in Faraday rotation angle (FRA) recorded at 137MHz and amplitude scintillation at 4 GHz. The observations were made at Suva, Fiji Islands (average ionospheric coordinates 17 0 S, 178 0 E) and cover the period September, 1978 through March, 1983. Monthly occurrence of both the FRA fluctuations and the amplitude scintillation are positively correlated with sunspot number and negatively correlated with Ap and hmF2 at Tahiti. No events were seen in the summer months (November, December, and January) and it is suggested that the south to north neutral wind may be responsible for this. Maximum occurrence of both the 137 MHz FRA fluctuations and the 4 GHz scintillation is in April-May and August-September. The more rapid FRA fluctuations, termed here V-type, occur more often in months when the ambient electron density is larger. Most events occur in the pre-midnight sector, as observed elsewhere. Fewer 4 GHz events are observed at later times in the evening, as compared to the 137 MHz FRA fluctuations

  5. Validation of the α-μ Model of the Power Spectral Density of GPS Ionospheric Amplitude Scintillation

    Directory of Open Access Journals (Sweden)

    Kelias Oliveira

    2014-01-01

    Full Text Available The α-μ model has become widely used in statistical analyses of radio channels, due to the flexibility provided by its two degrees of freedom. Among several applications, it has been used in the characterization of low-latitude amplitude scintillation, which frequently occurs during the nighttime of particular seasons of high solar flux years, affecting radio signals that propagate through the ionosphere. Depending on temporal and spatial distributions, ionospheric scintillation may cause availability and precision problems to users of global navigation satellite systems. The present work initially stresses the importance of the flexibility provided by α-μ model in comparison with the limitations of a single-parameter distribution for the representation of first-order statistics of amplitude scintillation. Next, it focuses on the statistical evaluation of the power spectral density of ionospheric amplitude scintillation. The formulation based on the α-μ model is developed and validated using experimental data obtained in São José dos Campos (23.1°S; 45.8°W; dip latitude 17.3°S, Brazil, located near the southern crest of the ionospheric equatorial ionization anomaly. These data were collected between December 2001 and January 2002, a period of high solar flux conditions. The results show that the proposed model fits power spectral densities estimated from field data quite well.

  6. Ionospheric effects of thunderstorms and lightning

    Energy Technology Data Exchange (ETDEWEB)

    Lay, Erin H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-02-03

    Tropospheric thunderstorms have been reported to disturb the lower ionosphere (~65-90 km) by convective atmospheric gravity waves and by electromagnetic field changes produced by lightning discharges. However, due to the low electron density in the lower ionosphere, active probing of its electron distribution is difficult, and the various perturbative effects are poorly understood. Recently, we have demonstrated that by using remotely-detected ?me waveforms of lightning radio signals it is possible to probe the lower ionosphere and its fluctuations in a spatially and temporally-resolved manner. Here we report evidence of gravity wave effects on the lower ionosphere originating from the thunderstorm. We also report variations in the nighttime ionosphere atop a small thunderstorm and associate the variations with the storm’s electrical activity. Finally, we present a data analysis technique to map ionospheric acoustic waves near thunderstorms.

  7. Low and Mid-Latitude Ionospheric Irregularities Studies Using TEC and Radio Scintillation Data from the CITRIS Radio Beacon Receiver in Low-Earth-Orbit

    Science.gov (United States)

    Siefring, C. L.; Bernhardt, P. A.; Huba, J.; Krall, J.; Roddy, P. A.

    2009-12-01

    Unique data on ionospheric plasma irregularities from the Naval Research Laboratory (NRL) CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35° inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) beacons and 2) the global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons. The TEC measurements allow for tracking of ionospheric disturbances and irregularities while the measurements of scintillations can simultaneously characterize their effects. CITRIS was operated in a complementary fashion with the C/NOFS (Communication/Navigations Outages Forecasting System) satellite during most of its first year of operations. C/NOFS carries a three-frequency 150/400/1067 MHz CERTO beacon and is dedicated to the study of Spread-F. In the case of Spread-F, ionospheric irregularities start with large scale size density gradients (100s of km) and cascade through complex processes to short scale sizes (10s of meters). It is typically the 100m-1km scale features that harm communication and navigation systems through scintillations. A multi-sensor approach is needed to completely understand this complex system, such as, the combination of CITRIS remote radio sensing and C/NOFS in-situ data. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. Comparisons with the physics based SAMI3 model are being performed to help our understanding of the morphology of the irregularities.

  8. A study on ionospheric scintillation near the EIA crest in relation to equatorial electrodynamics

    Science.gov (United States)

    Chatterjee, S.; Chakraborty, S. K.; Veenadhari, B.; Banola, S.

    2014-02-01

    Equatorial electrojet (EEJ) data, which are considered as a proxy index of equatorial electric field, are analyzed in conjunction with equatorial ionosonde, total electron content (TEC) and scintillation data near the equatorial ionization anomaly (EIA) crest for the equinoctial months of high solar activity years (2011-2012) to identify any precursor index of postsunset evolution of equatorial electron density irregularities and subsequent occurrence of scintillation near the northern EIA crest. Only geomagnetically quiet and normal electrojet days are considered. The diurnal profiles of EEJ on the scintillation days exhibit a secondary enhancement in the afternoon to presunset hours following diurnal peaks. A series of electrodynamical processes conducive for generation of irregularities emerge following secondary enhancement of EEJ. Latitudinal profile of TEC exhibits resurgence in EIA structure around the postsunset period. Diurnal TEC profile near the EIA crest resembles postsunset secondary enhancement on the days with afternoon enhancement in EEJ. Occurrence of equatorial spread F and postsunset scintillation near the EIA crest seems to follow the secondary enhancement events in EEJ. Both the magnitude and duration of enhanced EEJ are found to be important for postsunset intensification of EIA structure and subsequent occurrence of equatorial irregularities. A critical value combining the two may be considered an important precursor for postsunset occurrence of scintillation near the EIA crest. The results are validated using archived data for the years 1989-1990 and explained in terms of modulation effects of enhanced equatorial fountain.

  9. Ionospheric scintillations on 3.925 GHz signal from Intelsat (701) at low latitude in the South Pacific region

    International Nuclear Information System (INIS)

    Kumar, S; Kishore, A; Ramachandran, V

    2007-01-01

    The morphological features of initial ionospheric scintillations on 3.925 GHz beacon signal from geostationary satellite Intelsat (701) at Suva (Lat., 18.08 0 S, Long., 178.3 0 E, Geom. Lat., 22.1 0 S), Fiji, a low latitude station in the South Pacific region have been studied during the period of December 2003 to June 2004. Scintillations were, in general, sparse, of which activity was more pronounced in the daytime. Scintillation occurrence was less in general, showing a peak value of about 2.5% at 09 h LT and a secondary peak of about 2% at around 16 h LT. Scintillations were weak (S 4 index ≤ 0.25) and occurred mostly in patches of short duration of 2-5 min. It is reported here that weak and short duration scintillations with more daytime occurrence are mainly due to (i) the higher frequency beacon signal used (ii) the recording station being situated off the equatorial ionisation anomaly belt, and (iii) the period of observation falling in the low solar activity phase of the current solar cycle

  10. Analysis of strong ionospheric scintillation events measured by means of GPS signals at low latitudes during disturbed conditions

    Science.gov (United States)

    Forte, B.

    2012-08-01

    Drifting structures characterized by inhomogeneities in the spatial electron density distribution at ionospheric heights cause the scintillation of radio waves propagating through. The fractional electron density fluctuations and the corresponding scintillation levels may reach extreme values at low latitudes during high solar activity. Different levels of scintillation were observed on experimental data collected in the Asian sector at low latitudes by means of a GPS dual frequency receiver under moderate solar activity (2005). The GPS receiver used in these campaigns was particularly modified in firmware in order to record power estimates on the C/A code as well as on the carriers L1 and L2. Strong scintillation activity was recorded in the post-sunset period (saturatingS4 and SI as high as 20 dB). Spectral modifications and broadening was observed during high levels of scintillation possibly indicating refractive scattering taking place instead of diffractive scattering. A possible interpretation of those events was attempted on the basis of the refractive scattering theory developed by Uscinski (1968) and Booker and MajidiAhi (1981).

  11. Ionospheric research at INPE

    International Nuclear Information System (INIS)

    Abdu, M.A.

    1984-01-01

    Ionosphere investigations at INPE are mainly concerned with the problems of equatorial and tropical ionospheres and their electrodynamic coupling with the high latitude ionosphere. Present research objectives include investigations in the following specific areas: equatorial ionospheric plasma dynamics; plasma irregularity generation and morphology, and effects on space borne radar operations; ionospheric response to disturbance dynamo and magnetospheric electric fields; aeronomic effcts of charged particle precipitation in the magnetic anomaly, etc. These problems are being investigated using experimental datacollected from ionospheric diagnostic instruments being operated at different locations in Brazil. These instruments are: ionosondes, VHF electronic polarimeters, L-band scintillation receivers, airglow photometers, riometers and VLF receivers. A brief summary of the research activities and some recnet results will be presented. (Author) [pt

  12. Ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Taieb, C [Centre National d' Etudes des Telecommunications (CNET), 92 - Issy-les-Moulineaux (France)

    1977-11-01

    This paper comprises four parts. The first one deals with the neutral atmosphere, its structure, its composition, its variations. The second one describes the ionospheric plasma, (the ionized part) and explains its formation. The influence of the geomagnetic field is discussed in the third chapter, the fourth one being concerned with the means of studying the ionosphere: ionograms obtained by ionosondes or incoherent scattering sounding or from satellite measurements.

  13. Effects of radiation on scintillating fiber performance

    International Nuclear Information System (INIS)

    Bauer, M.L.; Cohn, H.; Efremenko, Yu.; Gordeev, A.; Kamyshkov, Yu.; Onopienko, D.; Savin, S.; Shmakov, K.; Tarkovsky, E.; Young, K.G.; Carey, R.; Rothman, M.; Sulak, L.; Worstell, W.; Parr, H.

    1992-01-01

    Continued rapid improvements in formulations for scintillating fibers require the ability to parameterize and predict effects of radiation on detector performance. Experimental techniques necessary to obtain needed information and calculational procedures used in performing predications for hadron scintillating fiber calorimetry in the Superconducting Supercollider environment are described. The experimental techniques involve control of the testing environment, consideration of dose rate effects, and other factors. These calculations involve the behavior of particle showers in the detector, expected levels of radiation, and parameterization of the radiation effects. A summary of significant work is also presented

  14. Effects of radiation on scintillating fiber performance

    International Nuclear Information System (INIS)

    Young, K.G.; Bauer, M.L.; Cohn, H.; Efremenko, Yu.; Gordeev, A.; Kamyshkov, Yu.; Onopienko, D.; Savin, S.; Shmakov, K.; Tarkovsky, E.; Carey, R.; Rothman, M.; Sulak, L.; Worstell, W.; Paar, H.

    1993-01-01

    Continued rapid improvements in formulations for scintillating fibers require the ability to parameterize and predict effects of radiation on detector performance. Experimental techniques necessary to obtain desired information and calculational procedures used in performing predictions for hadron scintillating fiber calorimetry in the Superconducting Supercollider environment are described. The experimental techniques involve control of the testing environment, consideration of dose rate effects, and other factors. The calculations involve the behavior of particle showers in the detector, expected levels of radiation, and parameterization of the radiation effects. A summary of significant work is also presented

  15. Scintillators

    International Nuclear Information System (INIS)

    Cusano, D.A.; Holub, F.F.; Prochazka, S.

    1979-01-01

    Scintillator bodies comprising phosphor materials and having high optical translucency with low light absorption, and methods of making the scintillator bodies, are described. Fabrication methods include (a) a hot-pressing process, (b) cold-pressing followed by sintering, (c) controlled cooling from a melt, and (d) hot-forging. The scintillator bodies that result are easily machined to desired shapes and sizes. Suitable phosphors include BaFCl:Eu, LaOBr:Tb, CsI:Tl, CaWO 4 and CdWO 4 . (U.K.)

  16. Time and latitudinal distribution of the ionospheric irregularities in Brazil, through the VHF-scintillation and ionogram data analysis

    International Nuclear Information System (INIS)

    Nelson, O.R.

    1984-01-01

    Equatorial ionospheric irregularity distribution morphology, and dynamics, and the dynamics of the ambient ionosphere were investigated. Spread F data from ionograms over Fortaleza (4 0 S; 38 0 O) and Cachoeira Paulista (22,7 0 S; 45 0 O), and simultaneous VHF scintillations of geoestationary satellite beacon received over Natal (5,6 0 S; 33,7 0 O) were used to determine the irregularity local time versus seasonal distribution, over the equatorial and low latitude location, during the solar activity maximum as well as minimum epochs. Concept of flux tube alignment properties of the transequatorial plasma bubbles were used to determine statistical features of the plasma bubble rise velocities. Calculations of plasma bubble rise velocities were then carried out for different solar activity epochs and compared with prereversal enhancement amplitude in the F-layer vertical rise velocities, for the same epochs. Using theoretical considerations on the development of plasma bubble based on flux tube integrated properties, the observed dependence of the plasma bubble rise velocities and the F-region dynamo electric field has been analysed to estimate the average ionizations depletions in the plasma bubble. Possible causes for the lack of correlation often observed between bubble rise velocities and F-Layer velocities also are discussed. (Author) [pt

  17. Climatology of ionospheric scintillation over the Vietnam low-latitude region for the period 2006-2014

    Science.gov (United States)

    Tran, Thi Lan; Le, Huy Minh; Amory-Mazaudier, C.; Fleury, R.

    2017-10-01

    This paper presents the characteristics of the occurrence of ionospheric scintillations at low-latitude, over Vietnam, by using continuous data of three GSV4004 receivers located at PHUT/Hanoï (105.9°E, 21.0°N; magnetic latitude 14.4°N), HUES/Hue (107.6°E, 16.5°N; magnetic latitude 9.5°N) and HOCM/Ho Chi Minh city (106.6°E, 10.8°N; magnetic latitude 3.3°N) for the period 2006-2014. The results show that the scintillation activity is maximum during equinox months for all the years and depends on solar activity as expected. The correlations between the monthly percentage scintillation occurrence and the F10.7 flux are of 0.40, 0.52 and 0.67 for PHUT, HUES and HOCM respectively. The distribution of scintillation occurrences is dominant in the pre-midnight sector and around the northern crest of the equatorial ionization anomaly (EIA), from the 15°N to 20°N geographic latitude with a maximum at 16°N. The results obtained from the directional analysis show higher distributions of scintillations in the southern sky of PHUT and in the northern sky of HUES and HOCM, and in the elevation angles smaller than 40°. The correlation between ROTI and S4 is low and rather good at PHUT (under EIA) than HOCM (near equator). We found better correlation in the post-midnight hours and less correlation in the pre-midnight hours for all stations. When all satellites are considered during the period of 2009-2011, the range of variation of the ration between ROTI and S4 is from 1 to 7 for PHUT, from 0.3 to 6 for HUES and from 0.7 to 6 for HOCM.

  18. The measurement of temperature effect of light output of scintillators

    International Nuclear Information System (INIS)

    Ji Changsong; Zhou Zaiping; Zhang Longfang

    1999-01-01

    The author describes a experiment equipment used for measurement of temperature effect of light output of scintillators; gives some measurement results of temperature effect of light output for NaI(Tl), CsI(Tl), plastic scintillator, ZnS(Ag), anthracene crystal glass scintillator; analyzes the error factors affecting the measurement results. The total uncertainty of the temperature effect measurement for NaI(Tl) and plastic scintillator is 11%

  19. Atmospheric Drag, Occultation ‘N’ Ionospheric Scintillation (ADONIS) mission proposal

    Czech Academy of Sciences Publication Activity Database

    Hettrich, S.; Kempf, Y.; Perakis, N.; Górski, J.; Edl, M.; Urbář, Jaroslav; Dósa, M.; Gini, F.; Roberts, O. W.; Schindler, S.; Schemmer, M.; Steenari, D.; Joldžić, N.; Ødegaard, L.-K. G.; Sarria, D.; Volwerk, M.; Praks, J.

    2015-01-01

    Roč. 5, Article Number: A2 (2015), s. 1-14 ISSN 2115-7251 Institutional support: RVO:68378289 Keywords : ionosphere (general) * thermosphere * space weather * drag * missions Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.846, year: 2015 http://www.swsc-journal.org/articles/swsc/abs/2015/01/swsc140006/swsc140006.html

  20. Assessment of GPS Multifrequency Signal Characteristics During Periods of Ionospheric Scintillations from an Anomaly Crest Location

    Science.gov (United States)

    Goswami, S.; Paul, K. S.; Paul, A.

    2017-09-01

    Multifrequency GPS transmissions have provided the opportunity for testing the applicability of the principle of frequency diversity for scintillation mitigation. Published results addressing this issue with quantified estimates are not available in literature, at least from the anomaly crest location of the Indian longitude sector. Multifrequency scattering within the same L band is often the attributed cause behind simultaneous decorrelated signal fluctuations. The present paper aims to provide proportion of time during scintillation patches that decorrelations are found across GPS L1, L2, and L5 frequencies associated with high S4, corresponding high values of scattering coefficients, and large receiver position deviations thereby seriously compromising the performance of satellite-based navigation system. Results from the anomaly crest station at Calcutta indicate maximum 40% of scintillation time during February-April 2014 and 33% during August-October 2014 that the signals are decorrelated. It is important to note that it is only during these time intervals that the principle of frequency diversity could be applied for scintillation mitigation.

  1. The Scintillation and Tomography Receiver in Space (CITRIS) Instrument for Ionospheric Research

    Science.gov (United States)

    2008-01-01

    be used by data assimila- tion models to improve ionospheric density specifica- tions. Current assimilation models have been devel- oped to...geomagnetic latitude where the layer tends to be higher than at mid - latitudes . The west layer is near a mid - latitude region at –35° geomagnetic...CITRIS relative to the CERTO radio beacon transmitter on the COSMIC FM5 satellite. The orbits cross at a latitude of –35.5° N and a longitude of

  2. Effect of solar and magnetic activity on VHF scintillations near the equatorial anomaly crest

    Directory of Open Access Journals (Sweden)

    R. P. Singh

    2004-09-01

    Full Text Available The VHF amplitude scintillation recorded during the period January 1991 to December 1993 in the declining phase of a solar cycle and April 1998 to December 1999 in the ascending phase of the next solar cycle at Varanasi (geogr. lat.=25.3°, long.=83.0°, dip=37°N have been analyzed to study the behavior of ionospheric irregularities during active solar periods and magnetic storms. It is shown that irregularities occur at arbitrary times and may last for <30min. A rise in solar activity increases scintillations during winter (November-February and near equinoxes (March-April; September-October, whereas it depresses the scintillations during the summer (May-July. In general, the role of magnetic activity is to suppress scintillations in the pre-midnight period and to increase it in the post-midnight period during equinox and winter seasons, whilst during summer months the effect is reversed. The pre-midnight scintillation is sometimes observed when the main phase of Dst corresponds to the pre-midnight period. The annual variation shows suppression of scintillations on disturbed days, both during pre-midnight and post-midnight period, which becomes more effective during years of high solar activity. It is observed that for magnetic storms for which the recovery phase starts post-midnight, the probability of occurrence of irregularities is enhanced during this time. If the magnetic storm occurred during daytime, then the probability of occurrence of scintillations during the night hours is decreased. The penetration of magnetospheric electric fields to the magnetic equator affects the evolution of low-latitude irregularities. A delayed disturbance dynamo electric field also affects the development of irregularities.

  3. Solar eclipses at high latitudes: ionospheric effects in the lower ionosphere

    Science.gov (United States)

    Cherniakov, S.

    2017-12-01

    The partial reflection facility of the Polar Geophysical Institute (the Tumanny observatory, 69.0N, 35.7E) has observed behavior of the high-latitude lower ionosphere during the 20 March 2015 total solar eclipse. There were several effects during the eclipse. At the heights of 60-80 km the ionosphere has shown the effect of a "short night", but at the higher altitudes local enhanced electron concentration had a wave-like form. Data received by the riometer of the Tumanny observatory have also shown wave-like behavior. The behavior can be explained by influence of acoustic-gravity waves which originated after cooling of the atmosphere during the lunar shadow supersonic movement, and transport processes during the eclipse. During the 21 August 2017 solar eclipse there was a substorm at the high latitudes. But after the end of the substorm in the region of the Tumanny observatory the observed amplitudes of the reflected waves had wave effects which could be connected with the coming waves from the region of the eclipse. The wave features were also shown in the behavior of the total electron content (TEC) of the lower ionosphere. During several solar eclipses it was implemented observations of lower ionosphere behavior by the partial reflection facility of the Tumanny observatory. The consideration of the lower ionosphere TEC had revealed common features in the TEC behavior during the eclipses. The photochemical theory of processes in the lower ionosphere is very complicated and up to now it is not completely developed. Therefore introduction of the effective coefficients determining the total speed of several important reactions has been widely adopted when modeling the D-region of the ionosphere. However, experimental opportunities for obtaining effective recombination coefficients are rather limited. One of the methods to estimate effective recombination coefficients uses the phenomenon of a solar eclipse. During solar eclipses at the partial reflection facility of

  4. Effect of geomagnetic storms on VHF scintillations observed at low latitude

    Science.gov (United States)

    Singh, S. B.; Patel, Kalpana; Singh, A. K.

    2018-06-01

    A geomagnetic storm affects the dynamics and composition of the ionosphere and also offers an excellent opportunity to study the plasma dynamics. In the present study, we have used the VHF scintillations data recorded at low latitude Indian station Varanasi (Geomag. latitude = 14^{°}55^' }N, long. = 154^{°}E) which is radiated at 250 MHz from geostationary satellite UFO-02 during the period 2011-2012 to investigate the effects of geomagnetic storms on VHF scintillation. Various geomagnetic and solar indices such as Dst index, Kp index, IMF Bz and solar wind velocity (Vx) are used to describe the geomagnetic field variation observed during geomagnetic storm periods. These indices are very helpful to find out the proper investigation and possible interrelation between geomagnetic storms and observed VHF scintillation. The pre-midnight scintillation is sometimes observed when the main phase of geomagnetic storm corresponds to the pre-midnight period. It is observed that for geomagnetic storms for which the recovery phase starts post-midnight, the probability of occurrence of irregularities is enhanced during this time and extends to early morning hours.

  5. Thermospheric storms and related ionospheric effects

    International Nuclear Information System (INIS)

    Chandra, S.; Spencer, N.W.

    1976-01-01

    A comparative study of thermospheric storms for the equinox and winter conditions is presented based on the neutral composition measurements from the Aeros-A Nate (Neutral Atmosphere Temperature Experiment) experiment. The main features of the two storms as inferred from the changes in N 2 , Ar, He, and O are described, and their implications to 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 the various manifestations of thermospheric storms

  6. Scintillator quenching effects observed in the AMS-1 TOF data

    Science.gov (United States)

    Esquivel, O.; Reyes, T.; Menchaca-Rocha, A.

    2001-05-01

    An analytical expression for the light output response of plastic scintillators as a function of the energy and the z identity of the incident ion is proposed. The effect of the δ rays is considered in the calculation of the scintillation efficiency. .

  7. Magnetic and solar effects on ionospheric absorption at high latitude

    Directory of Open Access Journals (Sweden)

    M. Pietrella

    2002-06-01

    Full Text Available Some periods of intense solar events and of strong magnetic storms have been selected and their effects on the ionospheric D region have been investigated on the basis of ionospheric absorption data derived from riometer measurements made at the Italian Antarctic Base of Terra Nova Bay (geographic coordinates: 74.69 S, 164.12 E; geomagnetic coordinates: 77.34 S, 279.41 E. It was found that sharp increases in ionospheric absorption are mainly due to solar protons emission with an energy greater than 10 MeV. Moreover, the day to night ratios of the ionospheric absorption are greater than 2 in the case of strong events of energetic protons emitted by the Sun, while during magnetic storms, these ratios range between 1 and 2.

  8. The Effect of Ionospheric Variability on the Accuracy of High Frequency Position Location

    Science.gov (United States)

    1981-08-01

    these problems are not the major ones in radio source location 1H. Rishbeth and 0. K. Garriot, 1969, Introduction to Ionospheric Physics, Academic Press ...ionospheric distur- banca ; and (4) employ an integrated network of ionosondes. The firt option recognizes the basic constraints of the available ionospheric...Rishbeth, H., and 0. K. Garriot, 1969, Introduction to Ionospheric Physics, Academic Press , NY. 2. Georges, T. M., 1967, Ionospheric Effects of

  9. Effect of Ionosphere on Geostationary Communication Satellite Signals

    Science.gov (United States)

    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

  10. Radiation effects in polymers for plastic scintillation detectors

    International Nuclear Information System (INIS)

    Pla-Dalmau, A.; Bross, A.D.; Hurlbut, C.R.; Moser, S.W.

    1994-01-01

    Recent developments in both scintillating plastic optical fibers and photon detection devices have spawned new applications for plastic scintillator detectors. This renewed attention has encouraged research that addresses the radiation stability of plastic scintillators. The optical quality of the polymer degrades with exposure to ionizing radiation and thus the light yield of the detector decreases. A complete understanding of all the mechanisms contributing to this radiation-induced degradation of the polymer can lead to techniques that will extend the radiation stability of these materials. Various radiation damage studies have been performed under different atmospheres and dose rates. Currently, the use of additives to preserve the optical properties of the polymer matrix under radiation is being investigated. The authors discuss the effect of certain antioxidants, plasticizers, and cross-linking agents on the radiation resilience of plastic scintillators

  11. Ionospheric effects of magnetospheric substorms during SUNDIAL and their modelling

    International Nuclear Information System (INIS)

    Goncharova, E.E.; Kishcha, P.V.; Shashun'kina, V.M.; Telegin, V.A.

    1993-01-01

    Ionospheric effects of substorms are considered using the networks of the vertical probing stations during SUNDIAL periods. Calculations of electron concentration distribution and comparison of calculation results with experimental data are conducted on the basis of the developed technique of simulation of large-scale internal gravitational wave effects

  12. Modeling the effects of Multi-path propagation and scintillation on GPS signals

    Science.gov (United States)

    Habash Krause, L.; Wilson, S. J.

    2014-12-01

    GPS signals traveling through the earth's ionosphere are affected by charged particles that often disrupt the signal and the information it carries due to "scintillation", which resembles an extra noise source on the signal. These signals are also affected by weather changes, tropospheric scattering, and absorption from objects due to multi-path propagation of the signal. These obstacles cause distortion within information and fading of the signal, which ultimately results in phase locking errors and noise in messages. In this work, we attempted to replicate the distortion that occurs in GPS signals using a signal processing simulation model. We wanted to be able to create and identify scintillated signals so we could better understand the environment that caused it to become scintillated. Then, under controlled conditions, we simulated the receiver's ability to suppress scintillation in a signal. We developed a code in MATLAB that was programmed to: 1. Create a carrier wave and then plant noise (four different frequencies) on the carrier wave, 2. Compute a Fourier transform on the four different frequencies to find the frequency content of a signal, 3. Use a filter and apply it to the Fourier transform of the four frequencies and then compute a Signal-to-noise ratio to evaluate the power (in Decibels) of the filtered signal, and 4.Plot each of these components into graphs. To test the code's validity, we used user input and data from an AM transmitter. We determined that the amplitude modulated signal or AM signal would be the best type of signal to test the accuracy of the MATLAB code due to its simplicity. This code is basic to give students the ability to change and use it to determine the environment and effects of noise on different AM signals and their carrier waves. Overall, we were able to manipulate a scenario of a noisy signal and interpret its behavior and change due to its noisy components: amplitude, frequency, and phase shift.

  13. Transition effect of extensive air showers in thick scintillators

    International Nuclear Information System (INIS)

    Lidvanskij, A.S.; Navarra, Dzh.; Chernyaev, A.V.

    1985-01-01

    Transition effect of extensive air showers has been measured by means of the ''Kover'' facility of the Baksan neutrino laboratory. The transition effect represents the ratio of ''scintillation'' particle density detected with detectors and particle density under the facility concrete roof (21 gxcm -2 ). Measurement results are compared with data obtained by means of the program of electron-photon cascade gaming. Good agreement of experimental and calculational data has been obtained. It follows from the data in the paper that the transition effect for one scintillator in the absence of roof can be produced by the gaming rather reliably

  14. Ionospheric effect of the magnetospheric substorms at middle latitudes

    International Nuclear Information System (INIS)

    Cander, Lj.R.; Dominici, P.; Zolesi, B.

    1988-01-01

    A study is made of the F2-layer effect of magnetospheric substorms over the Mediterranean area using data from several ionospheric stations for selected events in the current sunspot cycle 21. The night-time enhancements in the critical frequency of the F2-layer (f 0 F2) and the total electron content (TEC) have been found with both premidnight and postmidnight f 0 F2 peaks and a subsequent decrease in the minimum virtual height of the F region (h'F). It is found that the enhancements occur through the nights under steady geomagnetic conditions and that the time at which it is seen at Rome and Grocka ionospheric stations is progressively earlier as geomagnetic activity increases. It has been further shown that this type of the f 0 F2 night-time increases is not always accompanied by an increase in TEC, although the reverse holds true during the nights of increased substorm activity. The fact that the considerable variability in f 0 F2, TEC and h'F at the onset of the substorm expansion are preceded by the ionospheric dynamics associated with these observations can be very useful in the identification of precursor indicative of short-term variations of ionospheric propagation conditions

  15. Study of spatial and temporal characteristics of L-band scintillations over the Indian low-latitude region and their possible effects on GPS navigation

    Directory of Open Access Journals (Sweden)

    P. V. S. Rama Rao

    2006-07-01

    Full Text Available The scintillation data (S4-index at the L-band frequency of 1.575GHz, recorded from a total of 18 GPS receivers installed at different locations in India under the GAGAN project, have provided us with a unique opportunity, for the first time in the Indian region, to make a simultaneous study of spatio-temporal and intensity characteristics of the trans-ionospheric scintillations during the 18-month, low sunspot activity (LSSA period from January 2004 to July 2005. During this period, the occurrence of scintillations is found to be maximum around the pre-midnight hours of equinox months, with very little activity during the post-midnight hours. No significant scintillation activity is observed during the summer and winter months of the period of observation. The intensity (S4 index of the scintillation activity is stronger around the equatorial ionization anomaly (EIA region in the geographic latitude range of 15° to 25° N in the Indian region. These scintillations are often accompanied by the TEC depletions with durations ranging from 5 to 25 min and magnitudes from 5 to 15 TEC units which affect the positional accuracy of the GPS by 1 to 3 m. Further, during the intense scintillation events (S4>0.45≈10 dB, the GPS receiver is found to lose its lock for a short duration of 1 to 4 min, increasing the error bounds effecting the integrity of the SBAS operation. During the present period of study, a total of 395 loss of lock events are observed in the Indian EIA region; this number is likely to increase during the high sunspot activity (HSSA period, creating more adverse conditions for the trans-ionospheric communications and the GPS-based navigation systems.

  16. Effect of Aspect Ratio on the Light Output of Scintillators

    CERN Document Server

    Pauwels, Kristof; Gundacker, S.; Knapitsch, A.; Lecoq, P.

    2012-01-01

    The influence of the geometry of the scintillators is presented in this paper. We focus on the effect of narrowing down the section of crystals that have a given length. The light output of a set of crystals with very similar scintillating properties but different geometries measured with several coupling/wrapping configurations is provided. We observe that crystals shaped in thin rods have a lower light output as compared to bulk or sliced crystals. The effect of unpolishing the crystal faces is also investigated, and it is shown that highest light outputs are not necessarily obtained with crystals having all faces polished. Simulation results based on a realistic model of the crystal that implements light scattering on the crystal edges are in agreement with the experimental data. Fine-tuning of this model would allow us to further explore the details of light propagation in scintillators and would be highly valuable to fast timing detection and highly granular detectors.

  17. Pulse widths effects on scintillator saturation

    International Nuclear Information System (INIS)

    Kohler, D.A.; Chase, L.F.

    1978-08-01

    A test was performed over an extensive range of irrradiance (approximately five orders of magnitude) to see to what extent organic scintillators responded linearly with x-ray input. At the highest levels of irradiance achievable with the experimental configuration, but only for pulses in the region of 4.0 ns or wider, a degree of nonlinear response was observed for some of the scintillators. The data suggest that at levels below 1 mJ/cm 2 -ns it is safe to asume that for pulses 6.5 ns and shorter there is no significant level of nonlinearity to x rays with spectrum. For the cases of undoped NE111 and NE111 doped with 10 percent benzophenone, experimental conditions were such that it was possible to accumulate data significantly above the 1 mJ/cm 2 -ns level of irradiance. It is with these cases that a nonlinear response was observed. It is assumed that the same nonlinearity would have also been noticed had experimental conditions been such that equivalent levels of irradiance could have been achieved at the time the other samples were studied

  18. Analytical study of nighttime scintillations using GPS at low latitude station Bhopal

    Energy Technology Data Exchange (ETDEWEB)

    Maski, Kalpana, E-mail: k-maski@rediffmail.com [Department of Physics, Regional Institute of Education, Bhopal (India); Vijay, S. K. [Institute for Excellence in Higher Education, Bhopal (India)

    2015-07-31

    Sporadically structured ionosphere (i.e. in-homogeneities in refractive index) can cause fluctuations (due to refraction effects) on the radio signal that is passing through it. These fluctuations are called ionospheric scintillations. Low latitude region is suitable for studying these scintillations. The influence of the ionosphere on the propagation of the radio wave becomes very marked with reference to communication or navigational radio system at very low frequency (VLF) to a high frequency (HF), which operate over the distances of 1000 km or more. Radio wave communication at different frequencies depends on structure of the ionosphere. With the advent of the artificial satellites, they are used as a prime mode of radio wave communication. Some natural perturbation termed as irregularities, are present in the form of electron density of the ionosphere that cause disruption in the radio and satellite communications. Therefore the study of the ionospheric irregularities is of practical importance, if one wishes to understand the upper atmosphere completely. In order to make these communications uninterrupted the knowledge of irregularities, which are present in the ionosphere are very important. These irregularities can be located and estimated with the help of Ionospheric TEC and Scintillation. Scintillation is generally confined to nighttime hours, particularly around equatorial and low latitudes.

  19. Geophysical analysis of coherent satellite scintillation data

    Science.gov (United States)

    Fremouw, E. J.; Lansinger, J. M.; Miller, D. A.

    1981-11-01

    In May of 1976, Air Force Satellite P76-5 was launched with the Defense Nuclear Agency's Wideband beacon, DNA-002, as its sole payload. Several researchers have employed the resulting data in studies of ionospheric structure and its effect on transionospheric radio communications. In the present work, recordings of amplitude and phase scintillation imposed on Wideband's VHF and UHF signals by the ionosphere have been used to study medium-scale structures in the auroral-zone F layer. Results include quantitative identification of a very close relationship between scintillation and solar/geomagnetic activity, together with lack of a seasonal variation in scintillation activity in the Alaskan sector. A surprisingly high correlation (90%) was found between monthly means of phase-scintillation index, on the one hand, and sunspot number and 10-cm solar radio flux, on the other. The high-latitude scintillation boundary was found to be very similar to the soft-electron precipitation boundary, including similarity in expansion rates with increasing magnetic activity. Interestingly, it is systematically shifted poleward of the precipitation boundary on the day side of the earth and equatorward on the night side. Taken together, the results of this research disclose a rather direct relationship between scintillation and soft-electron precipitation, with plasma convection likely playing an important role in generation of the scintillation-producing irregularities.

  20. Review of radio-frequency, nonlinear effects on the ionosphere

    International Nuclear Information System (INIS)

    Gordon, W.E.; Duncan, L.M.

    1983-01-01

    Modification of the ionosphere by high power radio waves in the megahertz band has been intensively investigated over the past two decades. This research has yielded advances in aeronomy, geophysics, and plasma physics with applications to radio communication and has provided a fruitful interaction of radio theorists and experimentalists. There being almost no linear effects of powerful radio waves on the ionosphere, we concentrate on the nonlinear effects. To put the subject in perspective we trace its history beginning in the early 1930s and highlight the important events up to the late 1960s. We then shift to a phenomenological approach and deal in order with ohmic heating, parametric instabilities, self-focusing and kilometer-scale irregularities, meter-scale irregularities, and a collection of recently discovered effects. We conclude with the observation that stronger international cooperation would benefit this research, and describe a list of promising, difficult challenges

  1. Co-doping effects on luminescence and scintillation properties of Ce doped Lu3Al5O12 scintillator

    International Nuclear Information System (INIS)

    Kamada, Kei; Nikl, Martin; Kurosawa, Shunsuke; Beitlerova, Alena; Nagura, Aya; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

    2015-01-01

    The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples

  2. The effect of scintillation in valve auto-oscillators (1961)

    International Nuclear Information System (INIS)

    Blaquiere, A.

    1961-01-01

    In a previous article was analysed the possible sources of fluctuations in a valve auto-oscillator having an oscillating circuit connected to the grid. In particular the shot-noise of the valve has been introduced into the theory by including in the grid circuit an imaginary resistance R L as shown in diagram I. We propose to use this model here for studying the effect of the abnormal background noise of the valve in the low frequency domain (scintillation effect) on the normal working of the auto-oscillator. We will thus bridge the gap between the phenomenological theory of M. Buyle-Bodin, which is only valid for the slow constituents of the scintillation noise, and our previous general theory. A delicate point will thus be resolved, in a region of the spectrum having a great importance in hertzian spectrometry. (author) [fr

  3. Validation of measured poleward TEC gradient using multi-station GPS with Artificial Neural Network based TEC model in low latitude region for developing predictive capability of ionospheric scintillation

    Science.gov (United States)

    Sur, D.; Paul, A.

    2017-12-01

    The equatorial ionosphere shows sharp diurnal and latitudinal Total Electron Content (TEC) variations over a major part of the day. Equatorial ionosphere also exhibits intense post-sunset ionospheric irregularities. Accurate prediction of TEC in these low latitudes is not possible from standard ionospheric models. An Artificial Neural Network (ANN) based Vertical TEC (VTEC) model has been designed using TEC data in low latitude Indian longitude sector for accurate prediction of VTEC. GPS TEC data from the stations Calcutta (22.58°N, 88.38°E geographic, magnetic dip 32°), Baharampore (24.09°N, 88.25°E geographic, magnetic dip 35°) and Siliguri (26.72°N, 88.39°E geographic; magnetic dip 40°) are used as training dataset for the duration of January 2007-September 2011. Poleward VTEC gradients from northern EIA crest to region beyond EIA crest have been calculated from measured VTEC and compared with that obtained from ANN based VTEC model. TEC data from Calcutta and Siliguri are used to compute VTEC gradients during April 2013 and August-September 2013. It has been observed that poleward VTEC gradient computed from ANN based TEC model has shown good correlation with measured values during vernal and autumnal equinoxes of high solar activity periods of 2013. Possible correlation between measured poleward TEC gradients and post-sunset scintillations (S4 ≥ 0.4) from northern crest of EIA has been observed in this paper. From the observation, a suitable threshold poleward VTEC gradient has been proposed for possible occurrence of post-sunset scintillations at northern crest of EIA along 88°E longitude. Poleward VTEC gradients obtained from ANN based VTEC model are used to forecast possible ionospheric scintillation after post-sunset period using the threshold value. It has been observed that these predicted VTEC gradients obtained from ANN based VTEC model can forecast post-sunset L-band scintillation with an accuracy of 67% to 82% in this dynamic low latitude

  4. Evaluation of Inversion Methods Applied to Ionospheric ro Observations

    Science.gov (United States)

    Rios Caceres, Arq. Estela Alejandra; Rios, Victor Hugo; Guyot, Elia

    The new technique of radio-occultation can be used to study the Earth's ionosphere. The retrieval processes of ionospheric profiling from radio occultation observations usually assume spherical symmetry of electron density distribution at the locality of occultation and use the Abel integral transform to invert the measured total electron content (TEC) values. This pa-per presents a set of ionospheric profiles obtained from SAC-C satellite with the Abel inversion technique. The effects of the ionosphere on the GPS signal during occultation, such as bending and scintillation, are examined. Electron density profiles are obtained using the Abel inversion technique. Ionospheric radio occultations are validated using vertical profiles of electron con-centration from inverted ionograms , obtained from ionosonde sounding in the vicinity of the occultation. Results indicate that the Abel transform works well in the mid-latitudes during the daytime, but is less accurate during the night-time.

  5. Ionospheric effects on terrestrial communications: Working Group 3 overview

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan; Bourdillon, A.

    2004-01-01

    Roč. 47, 2/3 (2004), s. 1269-1277 ISSN 1593-5213. [Final Meeting COST271 Action. Effects of the upper atmosphere on terrestrial and Earth-space communications (EACOS). Abingdon, 26.08.2004-27.08.2004] R&D Projects: GA MŠk OC 271.10; GA AV ČR IBS3012007 Institutional research plan: CEZ:AV0Z3042911 Keywords : ionospheric reflection * telecommunications * gravity waves * planetary waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.413, year: 2004 http://www.annalsofgeophysics.eu/index.php/annals/article/view/3299/3345

  6. Effects of energetic electrons on the electrodynamics in the ionosphere

    Directory of Open Access Journals (Sweden)

    A. Aksnes

    2004-01-01

    Full Text Available From the observations by the PIXIE and UVI cameras on board the Polar satellite, we derive global maps of the precipitating electron energy spectra from less than 1keV to 100keV. Based on the electron spectra, we generate instantaneous global maps of Hall and Pedersen conductances. The UVI camera provides good coverage of the lower electron energies contributing most to the Pedersen conductance, while PIXIE captures the high energy component of the precipitating electrons affecting the Hall conductance. By characterizing the energetic electrons from some tens of keV and up to about 100keV using PIXIE X-ray measurements, we will, in most cases, calculate a larger electron flux at higher energies than estimated from a simple extrapolation of derived electron spectra from UVI alone. Instantaneous global conductance maps derived with and without inclusion of PIXIE data have been implemented in the Assimilative Mapping of Ionospheric Electrodynamics (AMIE procedure, to study the effects of energetic electrons on electrodynamical parameters in the ionosphere. We find that the improved electron spectral characterization using PIXIE data most often results in a larger Hall conductance and a smaller inferred electric field. In some localized regions the increase in the Hall conductance can exceed 100%. On the contrary, the Pedersen conductance remains more or less unaffected by the inclusion of the PIXIE data. The calculated polar cap potential drop may decrease more than 10%, resulting in a reduction of the estimated Joule heating integrated over the Northern Hemisphere by up to 20%. Locally, Joule heating may decrease more than 50% in some regions. We also find that the calculated energy flux by precipitating electrons increases around 5% when including the PIXIE data. Combined with the reduction of Joule heating, this results in a decrease in the ratio between Joule heating and energy flux, sometimes exceeding 25%. An investigation of the relationship

  7. A modern trans-ionospheric propagation sensing system

    Science.gov (United States)

    Bishop, G. J.; Klobuchar, J. A.; Ronn, A. E.; Bedard, M. G.

    1989-09-01

    One of the most important potential problems with modern military systems which utilize spacecraft is the effect of the ionosphere on the radio signals which pass to and from the spacecraft. Such systems include active communications and navigation satellites as well as both ground-based and potential space-based ranging systems. The major effects the ionosphere can have on such systems are the additional time delay the electrons in the earth's ionosphere add to the free space path delay, the short term rate of change of this additional delay, amplitude scintillation or fading effects the signal encounters due to irregularities in the ionosphere, and Faraday rotation of linearly polarized radio waves transmitted through the ionosphere. While some of these effects were studied adequate models of these effects on military systems still do not exist. A modern trans-ionospheric sensing system, called TISS, is being procured which will consist of a number of stations located throughout the world, making real time measurements of the time delay of the ionosphere, and its rate of change, as well as amplitude scintillation, along several different viewing directions from each station. These trans-ionospheric measurements will be used to allow models, which currently provide only monthly propagation parameters. The real-time specifications of these parameters can then be used as decision aids in both the tactical and the strategic military environments. The TISS will include first order artificial intelligence design to aid in gathering the most appropriate sets of available real-time trans-ionospheric propagation data, and will communicate these data sets to the Air Weather Service Forecasting Center where they will be tailored to specific military customers.

  8. Effect of spherical aberration on scintillations of Gaussian beams in atmospheric turbulence

    International Nuclear Information System (INIS)

    Ji, Xiaoling; Deng, Jinping

    2014-01-01

    The effect of spherical aberration on scintillations of Gaussian beams in weak, moderate and strong turbulence is studied using numerical simulation method. It is found that the effect of the negative spherical aberration on the on-axis scintillation index is quite different from that of the positive spherical aberration. In weak turbulence, the positive spherical aberration results in a decrease of the on-axis scintillation index on propagation, but the negative spherical aberration results in an increase of the on-axis scintillation index when the propagation distance is not large. In particular, in weak turbulence the negative spherical aberration may cause peaks of the on-axis scintillation index, and the peaks disappear in moderate and strong turbulence, which is explained in physics. The strong turbulence leads to less discrepancy among scintillations of Gaussian beams with and without spherical aberration. - Highlights: • In weak turbulence scintillations can be suppressed using positive spherical aberration. • In weak turbulence scintillations may be very large due to negative spherical aberration. • The effect of spherical aberration on scintillations is less with increasing of turbulence

  9. Effect of spherical aberration on scintillations of Gaussian beams in atmospheric turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Xiaoling, E-mail: jiXL100@163.com; Deng, Jinping

    2014-07-18

    The effect of spherical aberration on scintillations of Gaussian beams in weak, moderate and strong turbulence is studied using numerical simulation method. It is found that the effect of the negative spherical aberration on the on-axis scintillation index is quite different from that of the positive spherical aberration. In weak turbulence, the positive spherical aberration results in a decrease of the on-axis scintillation index on propagation, but the negative spherical aberration results in an increase of the on-axis scintillation index when the propagation distance is not large. In particular, in weak turbulence the negative spherical aberration may cause peaks of the on-axis scintillation index, and the peaks disappear in moderate and strong turbulence, which is explained in physics. The strong turbulence leads to less discrepancy among scintillations of Gaussian beams with and without spherical aberration. - Highlights: • In weak turbulence scintillations can be suppressed using positive spherical aberration. • In weak turbulence scintillations may be very large due to negative spherical aberration. • The effect of spherical aberration on scintillations is less with increasing of turbulence.

  10. Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields

    Directory of Open Access Journals (Sweden)

    M. D. Sciffer

    2004-04-01

    Full Text Available Solutions for ultra-low frequency (ULF wave fields in the frequency range 1–100mHz that interact with the Earth's ionosphere in the presence of oblique background magnetic fields are described. Analytic expressions for the electric and magnetic wave fields in the magnetosphere, ionosphere and atmosphere are derived within the context of an inductive ionosphere. The inductive shielding effect (ISE arises from the generation of an "inductive" rotational current by the induced part of the divergent electric field in the ionosphere which reduces the wave amplitude detected on the ground. The inductive response of the ionosphere is described by Faraday's law and the ISE depends on the horizontal scale size of the ULF disturbance, its frequency and the ionosphere conductivities. The ISE for ULF waves in a vertical background magnetic field is limited in application to high latitudes. In this paper we examine the ISE within the context of oblique background magnetic fields, extending studies of an inductive ionosphere and the associated shielding of ULF waves to lower latitudes. It is found that the dip angle of the background magnetic field has a significant effect on signals detected at the ground. For incident shear Alfvén mode waves and oblique background magnetic fields, the horizontal component of the field-aligned current contributes to the signal detected at the ground. At low latitudes, the ISE is larger at smaller conductivity values compared with high latitudes.

    Key words. Ionosphere (ionosphere-magnetosphere interactions; electric fields and currents; wave propagation

  11. The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

    Science.gov (United States)

    Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

    Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

  12. Effects of High-Latitude Forcing Uncertainty on the Low-Latitude and Midlatitude Ionosphere

    Science.gov (United States)

    Pedatella, N. M.; Lu, G.; Richmond, A. D.

    2018-01-01

    Ensemble simulations are performed using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) in order to understand the role of high-latitude forcing uncertainty on the low-latitude and midlatitude ionosphere response to the April 2010 geomagnetic storm. The ensemble is generated by perturbing either the high-latitude electric potential or auroral energy flux in the assimilative mapping for ionosphere electrodynamics (AMIE). Simulations with perturbed high-latitude electric potential result in substantial intraensemble variability in the low-latitude and midlatitude ionosphere response to the geomagnetic storm, and the ensemble standard deviation for the change in NmF2 reaches 50-100% of the mean change. Such large intraensemble variability is not seen when perturbing the auroral energy flux. In this case, the effects of the forcing uncertainty are primarily confined to high latitudes. We therefore conclude that the specification of high-latitude electric fields is an important source of uncertainty when modeling the low-latitude and midlatitude ionosphere response to a geomagnetic storm. A multiple linear regression analysis of the results indicates that uncertainty in the storm time changes in the equatorial electric fields, neutral winds, and neutral composition can all contribute to the uncertainty in the ionosphere electron density. The results of the present study provide insight into the possible uncertainty in simulations of the low-latitude and midlatitude ionosphere response to geomagnetic storms due to imperfect knowledge of the high-latitude forcing.

  13. Measuring GNSS ionospheric total electron content at Concordia, and application to L-band radiometers

    Directory of Open Access Journals (Sweden)

    Vincenzo Romano

    2013-06-01

    Full Text Available In the framework of the project BIS - Bipolar Ionospheric Scintillation and Total Electron Content Monitoring, the ISACCO-DMC0 and ISACCO-DMC1 permanent monitoring stations were installed in 2008. The principal scope of the stations is to measure the ionospheric total electron content (TEC and to monitor the ionospheric scintillations, using high-sampling-frequency global positioning system (GPS ionospheric scintillation and TEC monitor (GISTM receivers. The disturbances that the ionosphere can induce on the electromagnetic signals emitted by the Global Navigation Satellite System constellations are due to the presence of electron density anomalies in the ionosphere, which are particularly frequent at high latitudes, where the upper atmosphere is highly sensitive to perturbations coming from outer space. With the development of present and future low-frequency space-borne microwave missions (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active Passive missions, there is an increasing need to estimate the effects of the ionosphere on the propagation of electromagnetic waves that affects satellite measurements. As an example, how the TEC data collected at Concordia station are useful for the calibration of the European Space Agency SMOS data within the framework of an experiment promoted by the European Space Agency (known as DOMEX will be discussed. The present report shows the ability of the GISTM station to monitor ionospheric scintillation and TEC, which indicates that only the use of continuous GPS measurements can provide accurate information on TEC variability, which is necessary for continuous calibration of satellite data.

  14. Performance evaluation of GPS receiver under equatorial scintillation

    Directory of Open Access Journals (Sweden)

    Alison de Oliveira Moraes

    2009-06-01

    Full Text Available Equatorial scintillation is a phenomenon that occurs daily in the equatorial region after the sunset and affects radio signals that propagate through the ionosphere. Depending on the temporal and spatial situation, equatorial scintillation can represent a problem in the availability and precision of the Global Positioning System (GPS. This work is concerned with evaluating the impact of equatorial scintillation on the performance of GPS receivers. First, the morphology and statistical model of equatorial scintillation is briefly presented. A numerical model that generates synthetic scintillation data to simulate the effects of equatorial scintillation is presented. An overview of the main theoretical principles on GPS receivers is presented. The analytical models that describe the effects of scintillation at receiver level are presented and compared with numerical simulations using a radio software receiver and synthetic data. The results achieved by simulation agreed quite well with those predicted by the analytical models. The only exception is for links with extreme levels of scintillation and when weak signals are received.

  15. Propagation and scattering of electromagnetic waves by the ionospheric irregularities

    International Nuclear Information System (INIS)

    Ho, A.Y.; Kuo, S.P.; Lee, M.C.

    1993-01-01

    The problem of wave propagation and scattering in the ionosphere is particularly important in the areas of communications, remote-sensing and detection. The ionosphere is often perturbed with coherently structured (quasiperiodic) density irregularities. Experimental observations suggest that these irregularities could give rise to significant ionospheric effect on wave propagation such as causing spread-F of the probing HF sounding signals and scintillation of beacon satellite signals. It was show by the latter that scintillation index S 4 ∼ 0.5 and may be as high as 0.8. In this work a quasi-particle theory is developed to study the scintillation phenomenon. A Wigner distribution function for the wave intensity in the (k,r) space is introduced and its governing equation is derived with an effective collision term giving rise to the attenuation and scattering of the wave. This kinetic equation leads to a hierarchy of moment equations in r space. This systems of equations is then truncated to the second moment which is equivalent to assuming a cold quasi-particle distribution In this analysis, the irregularities are modeled as a two dimensional density modulation on an uniform background plasma. The analysis shows that this two dimensional density grating, effectively modulates the intensity of the beacon satellite signals. This spatial modulation of the wave intensity is converted into time modulation due to the drift of the ionospheric irregularities, which then contributes to the scintillation of the beacon satellite signals. Using the proper plasma parameters and equatorial measured data of irregularities, it is shown that the scintillation index defined by S4=( 2 >- 2 )/ 2 where stands for spatial average over an irregularity wavelength is in the range of the experimentally detected values

  16. The effect of nonlinear ionospheric conductivity enhancement on magnetospheric substorms

    Directory of Open Access Journals (Sweden)

    E. Spencer

    2013-06-01

    Full Text Available We introduce the effect of enhanced ionospheric conductivity into a low-order, physics-based nonlinear model of the nightside magnetosphere called WINDMI. The model uses solar wind and interplanetary magnetic field (IMF parameters from the ACE satellite located at the L1 point to predict substorm growth, onset, expansion and recovery measured by the AL index roughly 50–60 min in advance. The dynamics introduced by the conductivity enhancement into the model behavior is described, and illustrated through using synthetically constructed solar wind parameters as input. We use the new model to analyze two well-documented isolated substorms: one that occurred on 31 July 1997 from Aksnes et al. (2002, and another on 13 April 2000 from Huang et al. (2004. These two substorms have a common feature in that the solar wind driver sharply decreases in the early part of the recovery phase, and that neither of them are triggered by northward turning of the IMF Bz. By controlling the model parameters such that the onset time of the substorm is closely adhered to, the westward auroral electrojet peaks during substorm expansion are qualitatively reproduced. Furthermore, the electrojet recovers more slowly with enhanced conductivity playing a role, which explains the data more accurately.

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

    Science.gov (United States)

    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.

  18. High effective atomic number polymer scintillators for gamma ray spectroscopy

    Science.gov (United States)

    Cherepy, Nerine Jane; Sanner, Robert Dean; Payne, Stephen Anthony; Rupert, Benjamin Lee; Sturm, Benjamin Walter

    2014-04-15

    A scintillator material according to one embodiment includes a bismuth-loaded aromatic polymer having an energy resolution at 662 keV of less than about 10%. A scintillator material according to another embodiment includes a bismuth-loaded aromatic polymer having a fluor incorporated therewith and an energy resolution at 662 keV of less than about 10%. Additional systems and methods are also presented.

  19. Solar wind effects on ionospheric convection: a review

    DEFF Research Database (Denmark)

    Lu, G.; Cowley, S.W.H.; Milan, S.E.

    2002-01-01

    ), and travelling convection vortices (TCVs). Furthermore, the large-scale ionospheric convection configuration has also demonstrated a strong correspondence to variations in the interplanetary medium and substorm activity. This report briefly discusses the progress made over the past decade in studies...

  20. Effects of geomagnetic storms on the bottomside ionospheric F region

    Czech Academy of Sciences Publication Activity Database

    Burešová, Dalia

    2005-01-01

    Roč. 35, - (2005), s. 429-439 ISSN 0273-1177 R&D Projects: GA AV ČR(CZ) IAA3042102 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * Geomagnetic storm * Bottomside F region electron density Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.706, year: 2005

  1. [Effects of ionizing radiation on scintillators and other particle detectors

    International Nuclear Information System (INIS)

    Proudfoot, J.

    1992-01-01

    It is my task to summarise the great variety of topics (covering a refreshing mix of physics, chemistry and technology) presented at this conference, which has focused on the effects of ionising radiation on scintillators and other particle detectors. One of the reasons and the central interest of many of the participants was the use of such detectors in experiments at two future large hadron colliders: the Superconducting Super Collider to be operating outside of Dallas in the United States by the turn of the decade and its European counterpart the Large Hadron Collider to be operating outside of Geneva in Switzerland on a similar time scale. These accelerators are the ''apple of the high energy physicist's eye.'' Their goal is to uncover the elusive Higgs particle and thereby set the cornerstone in our current knowledge of elementary particle interactions. This is the Quest, and from this lofty height the presentations rapidly moved on to the specific questions of experimental science: how such an experiment is carried out; why radiation damage is an issue; how radiation damage affects detectors; which factors affect radiation damage characteristics; which factors are not affected by radiation damage; and how better detectors may be constructed. These were the substance of this conference

  2. Ionospheric earthquake effects detection based on Total Electron Content (TEC) GPS Correlation

    Science.gov (United States)

    Sunardi, Bambang; Muslim, Buldan; Eka Sakya, Andi; Rohadi, Supriyanto; Sulastri; Murjaya, Jaya

    2018-03-01

    Advances in science and technology showed that ground-based GPS receiver was able to detect ionospheric Total Electron Content (TEC) disturbances caused by various natural phenomena such as earthquakes. One study of Tohoku (Japan) earthquake, March 11, 2011, magnitude M 9.0 showed TEC fluctuations observed from GPS observation network spread around the disaster area. This paper discussed the ionospheric earthquake effects detection using TEC GPS data. The case studies taken were Kebumen earthquake, January 25, 2014, magnitude M 6.2, Sumba earthquake, February 12, 2016, M 6.2 and Halmahera earthquake, February 17, 2016, M 6.1. TEC-GIM (Global Ionosphere Map) correlation methods for 31 days were used to monitor TEC anomaly in ionosphere. To ensure the geomagnetic disturbances due to solar activity, we also compare with Dst index in the same time window. The results showed anomalous ratio of correlation coefficient deviation to its standard deviation upon occurrences of Kebumen and Sumba earthquake, but not detected a similar anomaly for the Halmahera earthquake. It was needed a continous monitoring of TEC GPS data to detect the earthquake effects in ionosphere. This study giving hope in strengthening the earthquake effect early warning system using TEC GPS data. The method development of continuous TEC GPS observation derived from GPS observation network that already exists in Indonesia is needed to support earthquake effects early warning systems.

  3. On an effect of the interplanetary magnetic field sector structure on the upper Earth's ionosphere

    International Nuclear Information System (INIS)

    Kolomijtsev, O.P.; Livshits, M.A.; Soboleva, T.N.

    1985-01-01

    According to the data from vertical probing stations, changes are studied in the critical frequency and height of the ionosphere F2 layer after the Earth crosses the boundaries of the interplanetary magnetic field (IMF) sectors in the periods of equinox during decreases in the solar activity. A reversal of the IMF sign causes ionospheric effects, which in some cases are comparable, as to the value, with the effects observed in the presence of flares and strong geomagnetic perturbations. The IMF sector sign reversal is a key momentum, stimulating such changes in the Earth's magnetosphere state which result in the rearrangement of the ionosphere structure near the maximum of electron concentration on the planetary scale

  4. The effects of 450 kg surface explosions at the E layer of the ionosphere

    International Nuclear Information System (INIS)

    Fitzgerald, T.J.; Carlos, R.C.

    1992-01-01

    A network of hf ionospheric sounders consisting of two transmitter and two receiver stations was deployed to detect the effects of acoustic waves generated by surface ground motion following an underground nuclear test (UGT) at the Nevada Test Site. The frequency of the transmissions were chosen so that the hf radio waves were totally reflected in the E layer of the ionosphere at an altitude of approximately 100 km. The transmissions were highly stable cw tones at two frequencies separated by 100 kHz so that two altitudes separated by approximately .5 km could be sensed. The network sampled four geographic locations in the ionosphere ranging from almost directly overhead of the UGT out to a horizontal range of 60 km. The ionospheric sounders detected disturbances on all the paths beginning at approximately 325 s after the UGT which persisted for up to 100 s. These disturbances will be described in detail in a later paper. Shortly after the UGT an extended series of ionospheric disturbances were detected which we ascribe to the arrival of acoustic shock waves at the E layer caused by the surface detonation of ordinance with effective yields of 450 kg of high explosive during an unrelated exercise conducted by the U. S. Air Force at a nearby bombing range. The conjunction of these disturbances produced a direct comparison of the effects of UGT's and surface explosions in the ionosphere. In this paper we describe the effects produced by the surface explosions and interpret the disturbance in terms of diffraction induced by electron density changes accompanying the passage of the acoustic waves from the explosions through the reflection altitudes

  5. Electric field effects on ionospheric and thermospheric parameters above the EISCAT station for summer conditions

    Directory of Open Access Journals (Sweden)

    V. V. Klimenko

    Full Text Available Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude. We have studied the effects of various field-aligned current (FAC distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03–21 MLT for both regions with peak values of 2.5×10–7 A m–2 (region I and 1.25×10–7 A m–2 (region II. These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.

    Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting

  6. Electric field effects on ionospheric and thermospheric parameters above the EISCAT station for summer conditions

    Directory of Open Access Journals (Sweden)

    V. V. Klimenko

    1998-10-01

    Full Text Available Numerical calculations of the thermospheric and ionospheric parameters above EISCAT are presented for quiet geomagnetic conditions in summer. The Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP was used. The numerical results were obtained both with a self-consistent calculation of the electric fields of magnetospheric and dynamo-action origin and with the magnetospheric electric fields only. It was found that the dynamo-electric field has some effect on the ionospheric convection pattern during quiet geomagnetic conditions. It has a marked effect mainly on the zonal neutral wind component above EISCAT (±20 m/s at 140 km altitude. We have studied the effects of various field-aligned current (FAC distributions on thermosphere/ionosphere parameters and we show that a qualitative agreement can be obtained with region-I and -II FAC zones at 75° and 65° geomagnetic latitude, respectively. The maximum FAC intensities have been assumed at 03–21 MLT for both regions with peak values of 2.5×10–7 A m–2 (region I and 1.25×10–7 A m–2 (region II. These results are in agreement with statistical potential distribution and FAC models constructed by use of EISCAT data. The lack of decreased electron density in the night-time sector as observed by the EISCAT radar was found to be due to the spatial distribution of ionospheric convection resulting from electric fields of magnetospheric origin.Key words. Electric fields and currents · Ionosphere- atmosphere interactions · Modelling and forecasting

  7. Effect of TADs on the F-region of Low midlatitude ionosphere during intense geomagnetic storm.

    Science.gov (United States)

    Upadhayaya, Arun Kumar; Joshi, Shivani; Singh Dabas, Raj; Das, Rupesh M.; Yadav, Sneha

    Effect of TAD's on the F region ionosphere of low-mid latitude ionosphere during three intense storms of20 th Nov,2003(-422nT),30 th Oct 2003(-383nT),07Nov,2004(-373nT)respectively are studued using ionosonde data of Delhi(28ø N 77øE).It has been seen that the electon density profile in the F1 region are greatly influenced by the TAD's presence. Further the pre-existing F1 cusp become better devloped during the passage of TAD's.

  8. Effects of Abrupt Variations of Solar Wind Dynamic Pressure on the High-Latitude Ionosphere

    Directory of Open Access Journals (Sweden)

    Igino Coco

    2011-01-01

    Full Text Available We show the results of a statistical study on the effects in the high-latitude ionosphere of abrupt variations of solar wind dynamic pressure, using Super Dual Auroral Radar Network (SuperDARN data in both hemispheres. We find that, during periods of quiet ionospheric conditions, the amount of radar backscatter increases when a variation in the dynamic pressure occurs, both positive (increase of the pressure and negative (decrease of the pressure. We also investigate the behaviour of the Cross-Polar Cap Potential (CPCP during pressure variations and show preliminary results.

  9. WORKSHOP: Scintillating fibre detectors

    International Nuclear Information System (INIS)

    Anon.

    1989-01-01

    Scintillating fibre detector development and technology for the proposed US Superconducting Supercollider, SSC, was the subject of a recent workshop at Fermilab, with participation from the high energy physics community and from industry. Sessions covered the current status of fibre technology and fibre detectors, new detector applications, fluorescent materials and scintillation compositions, radiation damage effects, amplification and imaging structures, and scintillation fibre fabrication techniques

  10. Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

    Directory of Open Access Journals (Sweden)

    J. D. Nichols

    2005-03-01

    Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

  11. Ionospheric storm effects in the nighttime E region caused by neutralized ring current particles

    Directory of Open Access Journals (Sweden)

    R. Bauske

    1997-03-01

    Full Text Available During magnetic storms an anomalous increase in the ionization density of the nighttime E region is observed at low and middle latitudes. It has been suggested that this effect is caused by the precipitation of neutralized ring current particles. Here a coupled ring current decay-ionosphere model is used to confirm the validity of this explanation.

  12. Effect of Magnetic Activity on Ionospheric Time Delay at Low Latitude

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... The purpose of this work is to investigate the effect of magnetic activity on ionospheric time delay at low latitude Station Bhopal (geom. lat. 23.2°N, geom. long. 77.6°E) using ... Space Science Laboratory, Department of Physics, Barkatullah University, Bhopal 462 026, India. National Institute of Technical, ...

  13. Ionospheric Coherence Bandwidth Measurements in the Lower VHF Frequency Range

    Science.gov (United States)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2015-12-01

    The United States Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 820 - 1100 MHz. In this paper, we present simultaneous ionospheric coherence bandwidth and S4 scintillation index measurements in the 32 - 44 MHz frequency range collected during the ESCINT equatorial scintillation experiment. 40-MHz continuous wave (CW) and 32 - 44 MHz swept frequency signals were transmitted simultaneously to the RFProp receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in three separate campaigns during the 2014 and 2015 equinoxes. Results show coherence bandwidths as small as ~ 1 kHz for strong scintillation (S4 > 0.7) and indicate a high degree of ionospheric variability and irregularity on 10-m spatial scales. Spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities are also observed and are dominant at low elevation angles. The results are compared to previous measurements and available scaling laws.

  14. Equatorial Scintillation Study at Ilorin and Nsukka, Nigeria during Year 2011-2012

    Science.gov (United States)

    Akala, A.

    2017-12-01

    This study presents GNSS scintillations over Ilorin (8.48 oN, 4.54 oE, and mag lat: 1.83oS) and Nsukka (6.84 oN, 7.37 oE, and mag lat: 2.94oS), Nigeria during year 2011-2012. The two stations are located within the inner flank of the equatorial ionization anomaly. Firstly, we investigated the climatology of equatorial scintillations at the two stations. We suppressed multipath effects on the data by imposing a 300 elevation masking on the data. In addition, we investigated scintillation occurrences at the two locations on a satellite-by-satellite basis at varying elevation angles. The source of scintillation records at low-elevation angle is attributed to multipath, while that at high-elevation angle is attributed to ionospheric irregularities. Seasonally, scintillations recorded highest occurrences during March equinox, and the least during June solstice. The trend of scintillations, at both low- and high-elevation angles at the two stations were almost the same. EGNOS satellites signals scintillated at the two locations during the time intervals when GPS satellites signals experienced scintillations. These results could support the development of scintillation models for equatorial Africa, and could also be of benefit to GPS and EGNOS service providers and designers, with a view to providing robust services for GNSS user community in Africa.

  15. Cubesat-Based Dtv Receiver Constellation for Ionospheric Tomography

    Science.gov (United States)

    Bahcivan, H.; Leveque, K.; Doe, R. A.

    2013-12-01

    The Radio Aurora Explorer mission, funded by NSF's Space Weather and Atmospheric Research program, has demonstrated the utility of CubeSat-based radio receiver payloads for ionospheric research. RAX has primarily been an investigation of microphysics of meter-scale ionospheric structures; however, the data products are also suitable for research on ionospheric effects on radio propagation. To date, the spacecraft has acquired (1) ground-based UHF radar signals that are backscattered from meter-scale ionospheric irregularities, which have been used to measure the dispersion properties of meter-scale plasma waves and (2) ground-based signals, directly on the transmitter-spacecraft path, which have been used to measure radio propagation disturbances (scintillations). Herein we describe the application of a CubeSat constellation of UHF receivers to expand the latter research topic for global-scale ionospheric tomography. The enabling factor for this expansion is the worldwide availability of ground-based digital television (DTV) broadcast signals whose characteristics are optimal for scintillation analysis. A significant part of the populated world have transitioned, or soon to be transitioned, to DTV. The DTV signal has a standard format that contains a highly phase-stable pilot carrier that can be readily adapted for propagation diagnostics. A multi-frequency software-defined radar receiver, similar to the RAX payload, can measure these signals at a large number of pilot carrier frequencies to make radio ray and diffraction tomographic measurements of the ionosphere and the irregularities contained in it. A constellation of CubeSats, launched simultaneously, or in sequence over years, similar to DMSPs, can listen to the DTV stations, providing a vast and dense probing of the ionosphere. Each spacecraft can establish links to a preprogrammed list of DTV stations and cycle through them using time-division frequency multiplexing (TDFM) method. An on board program can

  16. Effect of the Ionosphere on Space and Terrestrial Systems

    Science.gov (United States)

    1978-01-01

    coordinates: with degree of precision 2m-1. If we let 25 x1 , 7r..xn be the zeros of g(x), i.e., Pa(a)=f ° pao( acosO ,asine)ad (10) g)’ (X-X-)( ..x2...abscissas x and y (11) weights Wk are obtained. It is stated hat there is no guarantee that the zeros of g(x) -ap( acosO ,aain6),8ɘɚv,o<a<-. will be...of the ionospheric conditions along the path. shown schematically in Figure 1. The energetic par- ticle data were obtained by the Space Sciences Labor

  17. Wind effect on the motion of medium-scale travelling ionospheric disturbances in the E region of the ionosphere

    International Nuclear Information System (INIS)

    Kikvilashvili, G.B.; Sharadze, Z.S.; Mosashvili, N.V.

    1988-01-01

    Madium-scale travelling ionospheric disturbances (MSTID) in the ionosphere E region in Tbilisi area are investigated by means of spectral analysis of f 0 E s and f b E s variations, synchronously recorded in the three scattered points. The winds at the E s layers formation heights were measured simultaneously by D1 method in one of these points. It is established, that the MSTID motion direction in summer-time E region is controlled by the background thermospheric winds: disturbances mostly more across and against the wind. Tidal winds make the main contribution into the MSTID rate day variations

  18. Statistical evaluation of GLONASS amplitude scintillation over low latitudes in the Brazilian territory

    Science.gov (United States)

    de Oliveira Moraes, Alison; Muella, Marcio T. A. H.; de Paula, Eurico R.; de Oliveira, César B. A.; Terra, William P.; Perrella, Waldecir J.; Meibach-Rosa, Pâmela R. P.

    2018-04-01

    The ionospheric scintillation, generated by the ionospheric plasma irregularities, affects the radio signals that pass through it. Their effects are widely studied in the literature with two different approaches. The first one deals with the use of radio signals to study and understand the morphology of this phenomenon, while the second one seeks to understand and model how much this phenomenon interferes in the radio signals and consequently in the services to which these systems work. The interest of several areas, particularly to those that are life critical, has increased using the concept of satellite multi-constellation, which consists of receiving, processing and using data from different navigation and positioning systems. Although there is a vast literature analyzing the effects of ionospheric scintillation on satellite navigation systems, the number of studies using signals received from the Russian satellite positioning system (named GLONASS) is still very rare. This work presents for the first time in the Brazilian low-latitude sector a statistical analysis of ionospheric scintillation data for all levels of magnetic activities obtained by a set of scintillation monitors that receive signals from the GLONASS system. In this study, data collected from four stations were used in the analysis; Fortaleza, Presidente Prudente, São José dos Campos and Porto Alegre. The GLONASS L-band signals were analyzed for the period from December 21, 2012 to June 20, 2016, which includes the peak of the solar cycle 24 that occurred in 2014. The main characteristics of scintillation presented in this study include: (1) the statistical evaluation of seasonal and solar activity, showing the chances that an user on similar geophysical conditions may be susceptible to the effects of ionospheric scintillation; (2) a temporal analysis based on the local time distribution of scintillation at different seasons and intensity levels; and (3) the evaluation of number of

  19. Effects of Photonic Crystals on the Light Output of Heavy Inorganic Scintillators

    CERN Document Server

    Knapitsch, Arno; Fabjan, Christian W; Leclercq, Jean-Louis; Letartre, Xavier; Mazurczyk, Radoslaw; Lecoq, Paul

    2013-01-01

    Photonic crystals (PhCs) are optical materials which can affect the propagation of light in multiple ways. In recent years PhCs contributed to major technological developments in the field of semiconductor lasers, light emitting diodes and photovoltaic applications. In our case we are investigating the capabilities of photonic crystal slabs with the aim to improve the performance of heavy inorganic scintillators. To study the combination of scintillators and PhCs we use a Monte-Carlo program to simulate the light propagation inside a scintillator and a rigorous coupled wave analysis (RCWA) framework to analyse the optical PhC properties. The simulations show light output improvements of a wide range of scintillating materials due to light scattering effects of the PhC slabs. First samples have been produced on top of 1.2 × 2.6 × 5 mm LSO (cerium-doped Lutetium Oxyorthosilicate, Lu_2SiO_5:Ce^3+) scintillators using electron beam lithography and reactive ion etching (RIE). Our samples show a 30-60% light outp...

  20. Effect of small-scale ionospheric variability on GNSS radio occultation data quality

    Science.gov (United States)

    Verkhoglyadova, O. P.; Mannucci, A. J.; Ao, C. O.; Iijima, B. A.; Kursinski, E. R.

    2015-09-01

    Global Navigation Satellite Systems (GNSS) radio occultation (RO) measurements are sensitive to thin ionization layers and small-scale ionosphere structures. To evaluate error bounds and possible biases in atmospheric retrievals, we characterized ionospheric irregularities encountered in the affected profiles by analyzing the L1 signal-to-noise ratio (SNR) variability at E layer altitudes (from 90 km to 130 km). New metrics to analyze statistical effects of small-scale ionospheric irregularities on refractivity retrievals are proposed. We analyzed refractivity (N) retrievals with Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ROs in 2011. Using refractivity from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis (NECMWF) as the reference data set, we studied statistical properties of the fractional refractivity bias (ΔN) defined by the difference (NECMWF - N)/NECMWF and averaged in the altitude range from 20 to 25 km for each individual profile. We found that (1) persistently larger variability of the L1 SNR as measured by the interquartile range (IQR) existed when the occultation tangent point was in the 90 km to 110 km altitude range than at higher E layer altitudes; (2) the upper limits on the fractional refractivity bias for COSMIC ROs are 0.06% (for daytime local time), 0.1% (for nighttime local time), and ~0.01% (for all local times); (3) distributions of ΔN are non-Gaussian (leptokurtic); (4) latitudinal distributions of small and large ΔN for different levels of ionospheric variability show large tails (NECMWF > N) occurring around the Himalaya and the Andes regions, which are possibly due to biases in ECMWF analysis. We conclude that the refractivity bias due to small-scale irregularities is small below 25 km altitude and can be neglected.

  1. arXiv Strong reduction of the effective radiation length in an oriented PWO scintillator crystal

    CERN Document Server

    Bandiera, L.; Romagnoni, M.; Argiolas, N.; Bagli, E.; Ballerini, G.; Berra, A.; Brizzolani, C.; Camattari, R.; De Salvador, D.; Haurylavets, V.; Mascagna, V.; Mazzolari, A.; Prest, M.; Soldani, M.; Sytov, A.; Vallazza, E.

    We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic field. The data collected at the external lines of CERN SPS were critically compared to Monte Carlo simulations based on the Baier Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of five in case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters/detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments as well as in satellite-borne gamma-telescopes.

  2. Effects of geomagnetic storms in the lower ionosphere, middle atmosphere and troposphere.

    Science.gov (United States)

    Lastovicka, J.

    1996-05-01

    Geomagnetic storm effects at heights of about 0-100 km are briefly (not comprehensively) reviewed, with emphasis being paid to middle latitudes, particularly to Europe. Effects of galactic cosmic rays, solar particle events, relativistic and highly relativistic electrons, and IMF sector boundary crossings are briefly mentioned as well. Geomagnetic storms disturb the lower ionosphere heavily at high latitudes and very significantly also at middle latitudes. The effect is almost simultaneous at high latitudes, while an after-effect dominates at middle latitudes. The lower thermosphere is disturbed significantly. In the mesosphere and stratosphere, the effects become weaker and eventually non-detectable. There is an effect in total ozone but only under special conditions. Surprisingly enough, correlations with geomagnetic storms seem to reappear in the troposphere, particularly in the Northern Hemisphere. Atmospheric electricity is affected by geomagnetic storms, as well. We essentially understand the effects of geomagnetic storms in the lower ionosphere, but there is a lack of mechanisms to explain correlations found deeper in the atmosphere, particularly in the troposphere. There seem to be two different groups of effects with possibly different mechanisms - those observed in the lower ionosphere, lower thermosphere and mesosphere, and those observed in the troposphere.

  3. Evaluating scintillators used in radiation detectors of medical imaging systems by the effective fidelity index method

    International Nuclear Information System (INIS)

    Kandarakis, I.; Cavouras, D.; Prassopoulos, P.; Kanellopoulos, E.; Nomicos, C.D.; Panayiotakis, G.S.

    1999-01-01

    Objective: The performance of medical X-ray image receptors depends: (1) on the scintillator light emission efficiency; and (2) on the compatibility of the scintillator light spectrum with the spectral sensitivity of the light detector (film, photocathode, or photodiode), employed in conjunction with the scintillator. In this study, a scintillator performance measure, the effective fidelity index (EFI), is defined as function of both the scintillator light emission efficiency and spectral compatibility. Materials and Method: CsI:Na, Gd 2 O 2 S:Tb and La 2 O 2 S:Tb scintillators were employed in the form of phosphor screens prepared in our laboratory with various coating thicknesses. The screens were irradiated with X-rays employing tube voltages ranging between 50-120 kVp. Results: The EFI performance of CsI:Na was found to increase with screen coating thickness and it was best when combined with the orthochromatic film or the ES/20 photocathode. Gd 2 O 2 S:Tb showed peak EFI performance at 70 mg/cm 2 coating thickness and it was well combined with the light detectors considered. Conclusion: In accordance with our results, CsI:Na may be employed in radiography when adequately protected against humidity. Gd 2 O 2 S:Tb suitability for conventional imaging was verified and it was found that it may be useful in all types of digital imaging. La 2 O 2 S:Tb could also be used in digital detectors of imaging applications demanding medium X-ray tube voltages

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

    International Nuclear Information System (INIS)

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

    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 450km. It is shown that an anomaly coefficient with a sharp peak of the order of 10 4 centered aroung the F 2 peak is consistent with observations

  5. Observation of seasonal effects in traveling ionospheric disturbances by the directional deviation technique

    International Nuclear Information System (INIS)

    Walton, E.K.; Bailey, A.D.

    1976-01-01

    An experiment was performed during the years 1962 through 1964 in which direction of arrival data were collected on pulse signals received over a 450 km east-west path. In order to determine the effect that traveling ionospheric disturbances (TIDs) had on these data, a ''corrugation'' model was proposed. The corrugation model assumes that TIDs can be treated as if they were moving cylindrical sinusoidal perturbations on the ionospheric reflecting surface. Lateral deviations in the experimental data of the type predicted by this model were found to be quite common. Variations in the detected TIDs as a function of time of year were found to be consistent with the ''seasonal effect'' studied by Munro in 1958, Jones 1969, and Davies and Jones in 1971

  6. The effect of vibrationally excited nitrogen on the low-latitude ionosphere

    Directory of Open Access Journals (Sweden)

    B. Jenkins

    1997-11-01

    Full Text Available The first five vibrationally excited states of molecular nitrogen have been included in the Sheffield University plasmasphere ionosphere model. Vibrationally excited molecular nitrogen reacts much more strongly with atomic oxygen ions than ground-state nitrogen; this means that more O+ ions are converted to NO+ ions, which in turn combine with the electrons to give reduced electron densities. Model calculations have been carried out to investigate the effect of including vibrationally excited molecular nitrogen on the low-latitude ionosphere. In contrast to mid-latitudes, a reduction in electron density is seen in all seasons during solar maximum, the greatest effect being at the location of the equatorial trough.

  7. Comparison of analysis techniques by liquid scintillation and Cerenkov Effect for 40K quantification in aqueous samples

    International Nuclear Information System (INIS)

    Miranda C, L.; Davila R, J. I.; Lopez del R, H.; Mireles G, F.

    2015-09-01

    In this work the counting by liquid scintillation and Cerenkov Effect to quantify 40 K in aqueous samples was used. The performance of both techniques was studied by comparing the response of three commercial liquid scintillation OptiPhase HiSafe 3, Ultima Gold Ab and OptiPhase TriSafe, the vial type and presentation conditions of the sample for counting. In liquid scintillation, the ability to form homogeneous mixtures depended on the ionic strength of the aqueous solutions. The scintillator OptiPhase HiSafe 3 showed a greater charge capacity for solutions with high ionic strength (<3.4), while the scintillator OptiSafe TriSafe no form homogeneous mixtures for solutions of ionic strength higher than 0.3. Counting efficiencies for different proportions of sample and scintillator near 100% for the scintillators OptiSafe HiSafe 3 and Ultima Gold Ab were obtained. In the counting by Cerenkov Effect, the efficiency and sensitivity depended of the vial type; polyethylene vials were more suitable for counting that the glass vials. The sample volume had not significant effect on counting efficiency, obtaining an average value of 44.8% for polyethylene vials and 37.3% for glass vials. Therefore, the liquid scintillation was more efficient and sensitive for the measurement of 40 K in aqueous solutions. (Author)

  8. Lunar Tidal Effects in the Electrodynamics of the Low-Latitude Ionosphere

    OpenAIRE

    Tracy, Brian David

    2013-01-01

    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 result...

  9. On an effect of interplanetary magnetic field on a distribution electric fields in the polar ionosphere

    International Nuclear Information System (INIS)

    Uvarov, V.M.; Barashkov, P.D.

    1985-01-01

    The problem on the effect of the interplanetary magnetic field (IMF) on the distribution of electric fields in polar ionosphere is discussed. The problem on excitation of electric fields is reduced to the solution of the system of continuity equations for the current in three regions-northern polar cap, southern cap and the region outside the caps. It is shown that one succeeds in reproducing the observed types of distributions of electric fields

  10. The Effect of Sub-Auroral Polarization Streams (SAPS) on Ionosphere and Thermosphere during 2015 St. Patrick's Day storm: Global Ionosphere-Thermosphere Model (GITM) Simulations

    Science.gov (United States)

    Guo, J.; Deng, Y.; Zhang, D.; Lu, Y.; Sheng, C.

    2017-12-01

    Sub-Auroral Polarization Streams (SAPS) are incorporated into the non-hydrostatic Global Ionosphere-Thermosphere Model (GITM), revealing the complex effects on neutral dynamics and ion-neutral coupling processes. The intense westward ion stream could enhance the neutral zonal wind within the SAPS channel. Through neutral dynamics the neutrals then divide into two streams, one turns poleward and the other turns equatorward, forming a two-cell pattern in the SAPS-changed wind. The significant Joule heating induced by SAPS also leads to traveling atmospheric disturbances (TAD) accompanied by traveling ionospheric disturbances (TID), increasing the total electron content (TEC) by 2-8 TECu in the mid-latitude ionosphere. We investigate the potential causes of the reported poleward wind surge during the St. Patrick's Day storm in 2015. It is confirmed that Coriolis force on the westward zonal wind can contribute the poleward wind during post-SAPS interval. In addition, the simulations imply that the sudden decrease of heating rate within auroral oval could result in a TAD propagating equatorward, which could also be responsible for the sudden poleward wind surge. This study highlights the complicated effects of SAPS on ion-neutral coupling and neutral dynamics.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  13. Longitudinal effects of ionospheric responses to substorms at middle and lower latitudes: a case study

    Directory of Open Access Journals (Sweden)

    X. Pi

    1995-08-01

    Full Text Available An ionospheric model is used to simulate total electron content (TEC disturbance events observed at middle and lower latitude sites near 75°W and 7°E longitudes. Within this longitudinal range, daytime TEC disturbances show patterns that are correlated with substrom activity seen in both auroral electrojet and ring current behavior. In modeling studies of the observed ionospheric effects, both electric field and neutral wind perturbations are examined as possible mechanisms. The morphological features of the required electric field perturbations near drawn and dusk are compared with those at other times to examine the local time characteristics of magnetospheric influence. Large-scale traveling atmospheric disturbances (TADs, an alternative candidate for the disturbance source, are also characterized and compared with known thermospheric behavior.

  14. Multiscale modeling and nested simulations of three-dimensional ionospheric plasmas: Rayleigh–Taylor turbulence and nonequilibrium layer dynamics at fine scales

    International Nuclear Information System (INIS)

    Mahalov, Alex

    2014-01-01

    Multiscale modeling and high resolution three-dimensional simulations of nonequilibrium ionospheric dynamics are major frontiers in the field of space sciences. The latest developments in fast computational algorithms and novel numerical methods have advanced reliable forecasting of ionospheric environments at fine scales. These new capabilities include improved physics-based predictive modeling, nesting and implicit relaxation techniques that are designed to integrate models of disparate scales. A range of scales, from mesoscale to ionospheric microscale, are included in a 3D modeling framework. Analyses and simulations of primary and secondary Rayleigh–Taylor instabilities in the equatorial spread F (ESF), the response of the plasma density to the neutral turbulent dynamics, and wave breaking in the lower region of the ionosphere and nonequilibrium layer dynamics at fine scales are presented for coupled systems (ions, electrons and neutral winds), thus enabling studies of mesoscale/microscale dynamics for a range of altitudes that encompass the ionospheric E and F layers. We examine the organizing mixing patterns for plasma flows, which occur due to polarized gravity wave excitations in the neutral field, using Lagrangian coherent structures (LCS). LCS objectively depict the flow topology and the extracted scintillation-producing irregularities that indicate a generation of ionospheric density gradients, due to the accumulation of plasma. The scintillation effects in propagation, through strongly inhomogeneous ionospheric media, are induced by trapping electromagnetic (EM) waves in parabolic cavities, which are created by the refractive index gradients along the propagation paths. (paper)

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

    International Nuclear Information System (INIS)

    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 31 H 2 O and H 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 29 exhaust molecules at about 480-km altitude. These react rapidly with the F2 region 0 + 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

  16. Ionospheric Effects of X-Ray Solar Bursts in the Brazilian Sector

    Science.gov (United States)

    Becker-Guedes, F.; Takahashi, H.; Costa, J. E.; Otsuka, Y.

    2011-12-01

    When the solar X-ray flux in the interplanetary medium reaches values above a certain threshold, some undesired effects affecting radio communications are expected. Basically, the magnitudes of these effects depend on 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 atmosphere. An important aspect defining the severity of damages to HF radio communications and LF navigation signals in a certain area is the local time when each event takes place. In order to create more accurate warnings referred to possible radio signal loss or degradation in the Brazilian sector, we analyze TEC maps obtained by a GPS network, formed by dual-frequency receivers spread all over the country, to observe ionospheric local changes during several X-ray events in the 0.1-0.8 nm range measured by GOES satellite. Considering the duration, peak brightness, and local time of the events, the final purpose of this study is to understand and predict the degree of changes suffered by the ionosphere during these X-ray bursts. We intend using these results to create a radio blackout warning product to be offered by the Brazilian space weather program named EMBRACE (Estudo e Monitoramento BRAsileiro do Clima Espacial): Brazilian Monitoring and Study of Space Weather.

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

    International Nuclear Information System (INIS)

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

    1993-01-01

    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

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

    Science.gov (United States)

    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.

  19. Ionospheric Storm Effects and Equatorial Plasma Irregularities During the 17-18 March 2015 Event

    Science.gov (United States)

    Zhou, Yun-Liang; Luhr, Hermann; Xiong, Chao; Pfaff, Robert F.

    2016-01-01

    The intense magnetic storm on 17-18 March 2015 caused large disturbances of the ionosphere. Based on the plasma density (Ni) observations performed by the Swarm fleet of satellites, the Gravity Recovery and Climate Experiment mission, and the Communications/Navigation Outage Forecasting System satellite, we characterize the storm-related perturbations at low latitudes. All these satellites sampled the ionosphere in morning and evening time sectors where large modifications occurred. Modifications of plasma density are closely related to changes of the solar wind merging electric field (E (sub m)). We consider two mechanisms, prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF), as the main cause for the Ni redistribution, but effects of meridional wind are also taken into account. At the start of the storm main phase, the PPEF is enhancing plasma density on the dayside and reducing it on the nightside. Later, DDEF takes over and causes the opposite reaction. Unexpectedly, there appears during the recovery phase a strong density enhancement in the morning/pre-noon sector and a severe Ni reduction in the afternoon/evening sector, and we suggest a combined effect of vertical plasma drift, and meridional wind is responsible for these ionospheric storm effects. Different from earlier studies about this storm, we also investigate the influence of storm dynamics on the initiation of equatorial plasma irregularities (EPIs). Shortly after the start of the storm main phase, EPIs appear in the post-sunset sector. As a response to a short-lived decline of E (sub m), EPI activity appears in the early morning sector. Following the second start of the main phase, EPIs are generated for a few hours in the late evening sector. However, for the rest of the storm main phase, no more EPIs are initiated for more than 12 hours. Only after the onset of recovery phase does EPI activity start again in the post-midnight sector, lasting more than 7 hours

  20. Scintillator structures

    International Nuclear Information System (INIS)

    Cusano, D.A.; Prener, J.S.

    1978-01-01

    Distributed phosphor scintillator structures providing superior optical coupling to photoelectrically responsive devices together with methods for fabricating said scintillator structures are disclosed. In accordance with one embodiment of the invention relating to scintillator structures, the phosphor is distributed in a 'layered' fashion with certain layers being optically transparent so that the visible wavelength output of the scintillator is better directed to detecting devices. In accordance with another embodiment of the invention relating to scintillator structures, the phosphor is distributed throughout a transparent matrix in a continuous fashion whereby emitted light is more readily transmitted to a photodetector. Methods for fabricating said distributed phosphor scintillator structures are also disclosed. (Auth.)

  1. On the effect of ionospheric delay on geodetic relative GPS positioning

    NARCIS (Netherlands)

    Georgiadou, P.Y.; Kleusberg, A.

    1988-01-01

    Uncorrected ionospheric delay is one of the factors limiting the accuracy in geodetic relative positioning with single frequency Global Positioning System (GPS) carrier phase observations. Dual frequency measurements can be combined to eliminate the ionospheric delay in the observations. A

  2. Obtaining Networked Scintillation and Total Electron Content Data Across Africa and Asia: Partnering with the IHY/UNBSSI Developing Nations Program

    Science.gov (United States)

    Groves, K. M.; Basu, S.; Erickson, T.; Sunanda, B.; David, B.

    2005-12-01

    Under the Scintillation Network Decision Aid (SCINDA) project, scientists at the Air Force Research Laboratory (AFRL) have developed a sensor network for the purpose of monitoring low-latitude ionospheric total electron content (TEC) and scintillations associated with equatorial Spread F. In addition to monitoring GPS scintillations, TEC and VHF scintillations, the sensor package measures ionospheric drifts when irregularities are present providing important data on vertical electric fields in the F-region .The network currently consists of twelve stations distributed around the globe and the data have been used to conduct numerous studies on the characteristics and climatology of equatorial scintillation, including the impacts of magnetic storms on the equatorial ionosphere. Notably absent from the existing network are observing sites in Africa where both satellite observations and limited historical data sets suggest significant scintillation activity, though the detailed behavior and longitudinal variations across the continent are largely unknown. The latter aspect, in particular, is of great interest because of substantial changes in the orientation of the geomagnetic field in extreme West Africa that transition to a more uniform field geometry spanning the rest of the continent. Understanding the effects of these changes on scintillation climatology will provide new insights into the processes that trigger equatorial Spread F and assist researchers in developing improved forecasts of such activity. AFRL aims to establish 5-8 monitoring sites across equatorial Africa in collaboration with host nations participating in the United Nations Basic Space Science Initiative during the IHY period. In addition to expanding scientific opportunities, it is hoped that these sites will lead to greater awareness of the significant space weather issues impacting Africa and result in enhanced international collaboration between both African and non-African scientists

  3. Low-latitude scintillation occurrences around the equatorial anomaly crest over Indonesia

    Directory of Open Access Journals (Sweden)

    P. Abadi

    2014-01-01

    Full Text Available We investigated low-latitude ionospheric scintillation in Indonesia using two GPS receivers installed at Bandung (107.6° E, 6.9° S; magnetic latitude 17.5° S and Pontianak (109.3° E, 0.02° S; magnetic latitude 8.9° S. This study aimed to characterise climatological and directional ionospheric scintillation occurrences, which are useful not only for the physics of ionospheric irregularities but also for practical use in GNSS (global navigation satellite system-based navigation. We used the deployed instrument's amplitude scintillation (S4 index data from 2009, 2010, and 2011; the yearly SSN (sunspot-smoothed numbers were 3.1, 16.5, and 55.9, respectively. In summary, (1 scintillation occurrences in the post-sunset period (18:00–01:00 LT during equinox months (plasma bubble season at the two sites can be ascribed to the plasma bubble; (2 using directional analyses of the two sites, we found that the distribution of scintillation occurrences is generally concentrated between the two sites, indicating the average location of the EIA (equatorial ionisation anomaly crest; (3 scintillation occurrence enhancements for the two sites in field-aligned directions are herein reported for the first time by ground-based observation in a low-latitude region; (4 distribution of scintillation occurrences at Pontianak are concentrated in the southern sky, especially in the southwest direction, which is very likely associated with the plasma bubble tilted westward with increasing latitude; and (5 scintillation occurrence in the post-midnight period in the non-plasma-bubble season is the most intriguing variable occurring between the two sites (i.e. post-midnight scintillations are observed more at Bandung than Pontianak. Most of the post-midnight scintillations observed at Bandung are concentrated in the northern sky, with low elevation angles. This might be due to the amplitude of irregularities in certain directions, which may be effectively enhanced by

  4. Scintillation scanner

    International Nuclear Information System (INIS)

    Mehrbrodt, A.W.; Mog, W.F.; Brunnett, C.J.

    1977-01-01

    A scintillation scanner having a visual image producing means coupled through a lost motion connection to the boom which supports the scintillation detector is described. The lost motion connection is adjustable to compensate for such delays as may occur between sensing and recording scintillations. 13 claims, 5 figures

  5. Ionospheric Anomalies of the 2011 Tohoku Earthquake with Multiple Observations during Magnetic Storm Phase

    Science.gov (United States)

    Liu, Yang

    2017-04-01

    days. Associated with geomagnetic storm at similar time, radio occultation data provided by COSMIC were deeply investigated within the whole month. It's quite different that the storm or earthquake didn't trigger scintillation burst. This is probably due to the storm occurrence local time was in noon sector, which has little impact on ionospheric irregularities increase, but help to enhance the effect of westward electricity, which on the other hand diminishes scintillation bubbles (Li et al 2008). A small geomagnetic disturbance was also found almost a week prior to the earthquake, the relationship of this event to the major earthquake is worth further discussion. Similar analysis of GNSS TECs have been done, the results indicated that it can be also referred as precursor to the major earthquake. Li G, Ning B, Zhao B, et al. Effects of geomagnetic storm on GPS ionospheric scintillations at Sanya[J]. Journal of Atmospheric and Solar-Terrestrial Physics, 2008, 70(7):1034-1045. Liu J Y, Chen Y I, Chuo Y J, et al. A statistical investigation of pre-earthquake ionospheric anomaly[J]. Journal of Geophysical Research Atmospheres, 2006, 111(A5). Liu J Y, Sun Y Y. Seismo-traveling ionospheric disturbances of ionograms observed during the 2011 Mw 9.0 Tohoku Earthquake[J]. Earth, Planets and Space, 2011, 63(7):897-902. Zhao B, Wang M, Yu T, et al. Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake?[J]. Journal of Geophysical Research Atmospheres, 2008, 113(A11):A11304. Pulinets S A. Seismic activity as a source of the ionospheric variability [J]. Advances in Space Research, 1998, 22(6):903-906.

  6. The effect of scintillation in valve auto-oscillators (1961); L'effet de scintillation dans les autooscillateurs a lampes (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Blaquiere, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    In a previous article was analysed the possible sources of fluctuations in a valve auto-oscillator having an oscillating circuit connected to the grid. In particular the shot-noise of the valve has been introduced into the theory by including in the grid circuit an imaginary resistance R{sub L} as shown in diagram I. We propose to use this model here for studying the effect of the abnormal background noise of the valve in the low frequency domain (scintillation effect) on the normal working of the auto-oscillator. We will thus bridge the gap between the phenomenological theory of M. Buyle-Bodin, which is only valid for the slow constituents of the scintillation noise, and our previous general theory. A delicate point will thus be resolved, in a region of the spectrum having a great importance in hertzian spectrometry. (author) [French] Dans un travail anterieur, nous avons analyse les sources de fluctuations qui interviennent dans un autooscillateur a lampe a circuit oscillant branche sur la grille. Notamment le bruit de grenaille de la lampe a ete introduit dans la theorie en placant dans le circuit de grille une resistance fictive R{sub L} conformement au schema I. Nous nous proposons d'utiliser, ici, ce modele pour etudier l'effet du bruit de fond anormal de la lampe dans le domaine des basses frequences (effet de scintillation) sur le regime de l'auto-oscillateur. Nous jetterons ainsi un pont entre la theorie phenomenologique de M. Buyle-Bodin, qui n'est valable que pour les composantes lentes du bruit de scintillation, et notre theorie generale anterieure. Ainsi, se trouvera precise un point delicat, dans une region du spectre qui est tres importante pour la spectrometrie hertzienne. (auteur)

  7. Effects of geomagnetic storm on low latitude ionospheric total ...

    Indian Academy of Sciences (India)

    1Department of Physics, Tripura University, Suryamaninagar, Tripura 799 022, India. ... the fact that the electro-dynamic effect of geomagnetic storms around EIA region is more effective than ... causes range of error in GPS communication.

  8. Analysis of strong scintillation events by using GPS data at low latitudes

    Science.gov (United States)

    Forte, Biagio; Jakowski, Norbert; Wilken, Volker

    2010-05-01

    Drifting structures charaterised by inhomogeneities in the spatial electron density distribution at ionospheric heights originate scintillation of radio waves propagating through. The fractional electron density fluctuations and the corresponding scintillation levels may reach extreme values at low latitudes during high solar activity. Strong scintillation events have disruptive effects on a number of technological applications. In particular, operations and services based on GPS signals and receivers may experience severe disruption due to a significant degradation of the signal-to-noise ratio, eventually leading to signal loss of lock. Experimental scintillation data collected in the Asian sector at low latitudes by means of a GPS dual frequency receiver under moderate solar activity (2006) have been analysed. The GPS receiver is particularly modified in firmware in order to record power estimates on the C/A code as well as on the carriers L1 and L2. Strong scintillation activity is recorded in the post-sunset period (saturating S4 and SI as high as 20 dB). An overview of these events is presented, by taking into account scintillation impact on the signal intensity, phase, and dynamics. In particular, the interpretation of these events based on a refined scattering theory is provided with possible consequences for standard scintillation models.

  9. Study on quench effects in liquid scintillation counting during tritium measurements

    International Nuclear Information System (INIS)

    Ivana Jakonic; Jovana Nikolov; Natasa Todorovic; Miroslav Veskovic; Branislava Tenjovic

    2014-01-01

    Quench effects can cause a serious reduction in counting efficiency for a given sample/cocktail mixture in liquid scintillation counting (LSC) experiments. This paper presents a simple experiment performed in order to test the influence of quenching on the LSC efficiency of 3 H. The aim of this study was to investigate the behavior of several quench agents with different quench strengths (nitromethane, nitric acid, acetone, dimethyl-sulfoxide) added in different amounts to tritiated water in order to obtain standard sets for quench calibration curves. The OptiPhase HiSafe 2 and OptiPhase HiSafe 3 scintillation cocktails were used in this study in order to compare their quench resistance. Measurements were performed using a low-level LS counter (Wallac, Quantulus 1220). (author)

  10. Temporal characteristics and saturation effects of organic scintillators to low-energy X-rays

    International Nuclear Information System (INIS)

    Pronko, J.G.; Chase, L.F.

    1979-01-01

    Rise time, short and long term decay characteristics and possible saturation effects of the fluorescence of NE102, NE111, and doped NE111 organic scintillators were investigated using low-energy X-rays from a laser produced plasma. The laser system consisted of a pulsed Nd:glass facility operating at a pulse width of 0.2 ns at levels up to 10 J. The NE111 samples consisted of a matrix of scintillators with benzophenone, acetophenone, and piperidine each at concentrations of 0, 1, 2, 5, and 10 percent. The rise time of NE102 was measured at (640+-50) ps while that of both the doped and undoped NE111 was 2 ns) of irradiance used in this investigation. (Auth.)

  11. The effect of volume and quenching on estimation of counting efficiencies in liquid scintillation counting

    International Nuclear Information System (INIS)

    Knoche, H.W.; Parkhurst, A.M.; Tam, S.W.

    1979-01-01

    The effect of volume on the liquid scintillation counting performance of 14 C-samples has been investigated. A decrease in counting efficiency was observed for samples with volumes below about 6 ml and those above about 18 ml when unquenched samples were assayed. Two quench-correction methods, sample channels ratio and external standard channels ratio, and three different liquid scintillation counters, were used in an investigation to determine the magnitude of the error in predicting counting efficiencies when small volume samples (2 ml) with different levels of quenching were assayed. The 2 ml samples exhibited slightly greater standard deviations of the difference between predicted and determined counting efficiencies than did 15 ml samples. Nevertheless, the magnitude of the errors indicate that if the sample channels ratio method of quench correction is employed, 2 ml samples may be counted in conventional counting vials with little loss in counting precision. (author)

  12. Cherenkov radiation effects on counting efficiency in extremely quenched liquid scintillation samples

    International Nuclear Information System (INIS)

    Grau Carles, A.; Grau Malonda, A.; Rodriguez Barquero, L.

    1993-01-01

    The CIEMAT/NIST tracer method has successfully standardized nuclides with diverse quench values and decay schemes in liquid scintillation counting. However, the counting efficiency is computed inaccurately for extremely quenched samples. This article shows that when samples are extremely quenched, the counting efficiency in high-energy beta-ray nuclides depends principally on the Cherenkov effect. A new technique is described for quench determination, which makes the measurement of counting efficiency possible when scintillation counting approaches zero. A new efficiency computation model for pure beta-ray nuclides is also described. The results of the model are tested experimentally for 89 Sr, 90 Y, 36 Cl and 204 Tl nuclides with independence of the quench level. (orig.)

  13. Effect of the IMF By component on the ionospheric flow overhead at EISCAT: observations and theory

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    Full Text Available We have analysed a database of ∼300 h of tristatic ionospheric velocity measurements obtained overhead at Tromsø (66.3° magnetic latitude by the EISCAT UHF radar system, for the presence of flow effects associated with the y-component of the IMF. Since it is already known that the flow depends upon IMF Bz, a least-squares multivariate analysis has been used to determine the flow dependence on both IMF By and Bz simultaneously. It is found that significant flow variations with IMF By occur, predominantly in the midnight sector (∼2100–0300 MLT, but also pre-dusk (∼1600–1700 MLT, which are directed eastward for IMF By positive and westward for IMF By negative. The flows are of magnitude 20–30 m s–1 nT–1 in the midnight sector, and smaller, 10–20 m s–1 nT–1, pre-dusk, and are thus associated with significant changes of flow of order a few hundred m s–1 over the usual range of IMF By of about ±5 nT. At other local times the IMF By-related perturbation flows are much smaller, less than ∼5 m s–1 nT–1, and consistent with zero within the uncertainty estimates. We have investigated whether these IMF By-dependent flows can be accounted for quantitatively by a theoretical model in which the equatorial flow in the inner magnetosphere is independent of IMF By, but where distortions of the magnetospheric magnetic field associated with a "penetrating" component of the IMF By field changes the mapping of the field to the ionosphere, and hence the ionospheric flow. We find that the principal flow perturbation produced by this effect is an east-west flow whose sense is determined by the north-south component of the unperturbed flow. Perturbations in the north-south flow are typically smaller by more than an order of magnitude, and generally negligible in terms of observations. Using equatorial flows which are determined from EISCAT data for zero IMF By, to which the corotation flow has been added, the theory predicts the presence

  14. Effect of the IMF By component on the ionospheric flow overhead at EISCAT: observations and theory

    Directory of Open Access Journals (Sweden)

    H. Khan

    2000-12-01

    Full Text Available We have analysed a database of ∼300 h of tristatic ionospheric velocity measurements obtained overhead at Tromsø (66.3° magnetic latitude by the EISCAT UHF radar system, for the presence of flow effects associated with the y-component of the IMF. Since it is already known that the flow depends upon IMF Bz, a least-squares multivariate analysis has been used to determine the flow dependence on both IMF By and Bz simultaneously. It is found that significant flow variations with IMF By occur, predominantly in the midnight sector (∼2100–0300 MLT, but also pre-dusk (∼1600–1700 MLT, which are directed eastward for IMF By positive and westward for IMF By negative. The flows are of magnitude 20–30 m s–1 nT–1 in the midnight sector, and smaller, 10–20 m s–1 nT–1, pre-dusk, and are thus associated with significant changes of flow of order a few hundred m s–1 over the usual range of IMF By of about ±5 nT. At other local times the IMF By-related perturbation flows are much smaller, less than ∼5 m s–1 nT–1, and consistent with zero within the uncertainty estimates. We have investigated whether these IMF By-dependent flows can be accounted for quantitatively by a theoretical model in which the equatorial flow in the inner magnetosphere is independent of IMF By, but where distortions of the magnetospheric magnetic field associated with a "penetrating" component of the IMF By field changes the mapping of the field to the ionosphere, and hence the ionospheric flow. We find that the principal flow perturbation produced by this effect is an east-west flow whose sense is determined by the north-south component of the unperturbed flow. Perturbations in the north-south flow are typically smaller by more than an order of magnitude, and generally negligible in terms of observations. Using equatorial flows which are determined from EISCAT data for zero IMF By, to which the corotation flow has been added, the theory predicts the presence

  15. Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection

    International Nuclear Information System (INIS)

    Blaeckberg, L.; Fay, A.; Jogi, I.; Biegalski, S.; Boman, M.; Elmgren, K.; Fritioff, T.; Johansson, A.; Martensson, L.; Nielsen, F.; Ringbom, A.; Rooth, M.; Sjoestrand, H.; Klintenberg, M.

    2011-01-01

    In this work Al 2 O 3 and SiO 2 coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al 2 O 3 coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.

  16. Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection

    Science.gov (United States)

    Bläckberg, L.; Fay, A.; Jõgi, I.; Biegalski, S.; Boman, M.; Elmgren, K.; Fritioff, T.; Johansson, A.; Mårtensson, L.; Nielsen, F.; Ringbom, A.; Rooth, M.; Sjöstrand, H.; Klintenberg, M.

    2011-11-01

    In this work Al2O3 and SiO2 coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al2O3 coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.

  17. Ionospheric propagation effects on spectral widths measured by SuperDARN HF radars

    Directory of Open Access Journals (Sweden)

    X. Vallières

    2004-06-01

    Full Text Available SuperDARN HF radars provide a global survey of the large-scale convection transversely to the Earth's magnetic field in the high-latitude ionosphere. In addition to the mean plasma velocity, this network also provides measurements of spectral widths which are related to the level of turbulence of the sounded plasma. There is an increasing interest in using spectral widths in geophysical studies, since they are used to monitor the footprints of several magnetospheric regions. In the present paper, we show the effect of radio wave propagation through a typical turbulent ionosphere on spectral widths measured by SuperDARN radars. This effect has already been evidenced experimentally in a previous paper. Here, we model the effects of meso-scale structures on a radar wave front and study their impact on a typical measurement. Numerical simulations reproduce the effect evidenced experimentally and show the role of meso-scale structures (1-10km in the systematic bias that affects spectral width values. As in experimental data, this effect is shown to be increasing with decreasing radar frequency.

  18. Ionospheric propagation effects on spectral widths measured by SuperDARN HF radars

    Directory of Open Access Journals (Sweden)

    X. Vallières

    2004-06-01

    Full Text Available SuperDARN HF radars provide a global survey of the large-scale convection transversely to the Earth's magnetic field in the high-latitude ionosphere. In addition to the mean plasma velocity, this network also provides measurements of spectral widths which are related to the level of turbulence of the sounded plasma. There is an increasing interest in using spectral widths in geophysical studies, since they are used to monitor the footprints of several magnetospheric regions. In the present paper, we show the effect of radio wave propagation through a typical turbulent ionosphere on spectral widths measured by SuperDARN radars. This effect has already been evidenced experimentally in a previous paper. Here, we model the effects of meso-scale structures on a radar wave front and study their impact on a typical measurement. Numerical simulations reproduce the effect evidenced experimentally and show the role of meso-scale structures (1-10km in the systematic bias that affects spectral width values. As in experimental data, this effect is shown to be increasing with decreasing radar frequency.

  19. GPS scintillations and total electron content climatology in the southern low, middle and high latitude regions

    Directory of Open Access Journals (Sweden)

    Luca Spogli

    2013-06-01

    Full Text Available In recent years, several groups have installed high-frequency sampling receivers in the southern middle and high latitude regions, to monitor ionospheric scintillations and the total electron content (TEC changes. Taking advantage of the archive of continuous and systematic observations of the ionosphere on L-band by means of signals from the Global Positioning System (GPS, we present the first attempt at ionospheric scintillation and TEC mapping from Latin America to Antarctica. The climatology of the area considered is derived through Ground-Based Scintillation Climatology, a method that can identify ionospheric sectors in which scintillations are more likely to occur. This study also introduces the novel ionospheric scintillation 'hot-spot' analysis. This analysis first identifies the crucial areas of the ionosphere in terms of enhanced probability of scintillation occurrence, and then it studies the seasonal variation of the main scintillation and TEC-related parameters. The results produced by this sophisticated analysis give significant indications of the spatial/ temporal recurrences of plasma irregularities, which contributes to the extending of current knowledge of the mechanisms that cause scintillations, and consequently to the development of efficient tools to forecast space-weather-related ionospheric events.

  20. Impact and Implementation of Higher-Order Ionospheric Effects on Precise GNSS Applications

    Science.gov (United States)

    Hadas, T.; Krypiak-Gregorczyk, A.; Hernández-Pajares, M.; Kaplon, J.; Paziewski, J.; Wielgosz, P.; Garcia-Rigo, A.; Kazmierski, K.; Sosnica, K.; Kwasniak, D.; Sierny, J.; Bosy, J.; Pucilowski, M.; Szyszko, R.; Portasiak, K.; Olivares-Pulido, G.; Gulyaeva, T.; Orus-Perez, R.

    2017-11-01

    High precision Global Navigation Satellite Systems (GNSS) positioning and time transfer require correcting signal delays, in particular higher-order ionospheric (I2+) terms. We present a consolidated model to correct second- and third-order terms, geometric bending and differential STEC bending effects in GNSS data. The model has been implemented in an online service correcting observations from submitted RINEX files for I2+ effects. We performed GNSS data processing with and without including I2+ corrections, in order to investigate the impact of I2+ corrections on GNSS products. We selected three time periods representing different ionospheric conditions. We used GPS and GLONASS observations from a global network and two regional networks in Poland and Brazil. We estimated satellite orbits, satellite clock corrections, Earth rotation parameters, troposphere delays, horizontal gradients, and receiver positions using global GNSS solution, Real-Time Kinematic (RTK), and Precise Point Positioning (PPP) techniques. The satellite-related products captured most of the impact of I2+ corrections, with the magnitude up to 2 cm for clock corrections, 1 cm for the along- and cross-track orbit components, and below 5 mm for the radial component. The impact of I2+ on troposphere products turned out to be insignificant in general. I2+ corrections had limited influence on the performance of ambiguity resolution and the reliability of RTK positioning. Finally, we found that I2+ corrections caused a systematic shift in the coordinate domain that was time- and region-dependent and reached up to -11 mm for the north component of the Brazilian stations during the most active ionospheric conditions.

  1. Effects of Temperature and X-rays on Plastic Scintillating Fiber and Infrared Optical Fiber.

    Science.gov (United States)

    Lee, Bongsoo; Shin, Sang Hun; Jang, Kyoung Won; Yoo, Wook Jae

    2015-05-11

    In this study, we have studied the effects of temperature and X-ray energy variations on the light output signals from two different fiber-optic sensors, a fiber-optic dosimeter (FOD) based on a BCF-12 as a plastic scintillating fiber (PSF) and a fiber-optic thermometer (FOT) using a silver halide optical fiber as an infrared optical fiber (IR fiber). During X-ray beam irradiation, the scintillating light and IR signals were measured simultaneously using a dosimeter probe of the FOD and a thermometer probe of the FOT. The probes were placed in a beaker with water on the center of a hotplate, under variation of the tube potential of a digital radiography system or the temperature of the water in the beaker. From the experimental results, in the case of the PSF, the scintillator light output at the given tube potential decreased as the temperature increased in the temperature range from 25 to 60 °C. We demonstrated that commonly used BCF-12 has a significant temperature dependence of -0.263 ± 0.028%/°C in the clinical temperature range. Next, in the case of the IR fiber, the intensity of the IR signal was almost uniform at each temperature regardless of the tube potential range from 50 to 150 kVp. Therefore, we also demonstrated that the X-ray beam with an energy range used in diagnostic radiology does not affect the IR signals transmitted via a silver halide optical fiber.

  2. Understanding the Effects of Lower Boundary Conditions and Eddy Diffusion on the Ionosphere-Thermosphere System

    Science.gov (United States)

    Malhotra, G.; Ridley, A. J.; Marsh, D. R.; Wu, C.; Paxton, L. J.

    2017-12-01

    The exchange of energy between lower atmospheric regions with the ionosphere-thermosphere (IT) system is not well understood. A number of studies have observed day-to-day and seasonal variabilities in the difference between data and model output of various IT parameters. It is widely speculated that the forcing from the lower atmosphere, variability in weather systems and gravity waves that propagate upward from troposphere into the upper mesosphere and lower thermosphere (MLT) may be responsible for these spatial and temporal variations in the IT region, but their exact nature is unknown. These variabilities can be interpreted in two ways: variations in state (density, temperature, wind) of the upper mesosphere or spatial and temporal changes in the small-scale mixing, or Eddy diffusion that is parameterized within the model.In this study, firstly, we analyze the sensitivity of the thermospheric and ionospheric states - neutral densities, O/N2, total electron content (TEC), peak electron density, and peak electron height - to various lower boundary conditions in the Global Ionosphere Thermosphere Model (GITM). We use WACCM-X and GSWM to drive the lower atmospheric boundary in GITM at 100 km, and compare the results with the current MSIS-driven version of GITM, analyzing which of these simulations match the measurements from GOCE, GUVI, CHAMP, and GPS-derived TEC best. Secondly, we analyze the effect of eddy diffusion in the IT system. The turbulence due to eddy mixing cannot be directly measured and it is a challenge to completely characterize its linear and non-linear effects from other influences, since the eddy diffusion both influences the composition through direct mixing and the temperature structure due to turbulent conduction changes. In this study we input latitudinal and seasonal profiles of eddy diffusion into GITM and then analyze the changes in the thermospheric and ionospheric parameters. These profiles will be derived from both WACC-X simulations

  3. Solar activity effects in the ionospheric D region

    Directory of Open Access Journals (Sweden)

    A. D. Danilov

    1998-12-01

    Full Text Available Variations in the D-region electron concentration within the solar activity cycle are considered. It is demonstrated that conclusions of various authors, who have analyzed various sets of experimental data on [e], differ significantly. The most reliable seem to be the conclusions based on analysis of the [e] measurements carried out by the Faraday rotation method and on the theoretical concepts on the D-region photochemistry. Possible QBO effects in the relation of [e] to solar activity are considered and an assumption is made that such effects may be the reason for the aforementioned disagreement in conclusions on the [e] relation to solar indices.Key words. Atmospheric composition and structure · Ion chemistry of the atmosphere · Middle atmosphere

  4. Positive ionospheric storm effects at Latin America longitude during the superstorm of 20–22 November 2003: revisit

    Directory of Open Access Journals (Sweden)

    B. Zhao

    2012-05-01

    Full Text Available Positive ionospheric storm effects that occurred during the superstorm on 20 November 2003 are investigated using a combination of ground-based Global Positioning System (GPS total electron content (TEC, and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E. Both the ground-based GPS TEC and ionosonde electron density profile data reveal significant enhancements at mid-low latitudes over the 280° E region during the main phase of the November 2003 superstorm. The maximum enhancement of the topside ionospheric electron content is 3.2–7.7 times of the bottomside ionosphere at the locations of the ionosondes distributed around the mid- and low latitudes. Moreover, the height of maximum electron density exceeds 400 km and increases by 100 km compared with the quiet day over the South American area from middle to low latitudes, which might have resulted from a continuous eastward penetration electric field and storm-generated equatorward winds. Our results do not support the conclusions of Yizengaw et al. (2006, who suggested that the observed positive storm over the South American sector was mainly the consequence of the changes of the bottomside ionosphere. The so-called "unusual" responses of the topside ionosphere for the November 2003 storm in Yizengaw et al. (2006 are likely associated with the erroneous usage of magnetometer and incomplete data.

  5. Space weather and the Earth ionosphere from auroral zone to equator

    Science.gov (United States)

    Biktash, L.

    2007-08-01

    , and the physical processes involved in the solar wind-magnetosphere interaction. Ionosphere effects of the solar wind is much complex. It is very difficult to separate the agents forming ionospheric disturbances during geomagnetic storms. It is considered that the storm wind driven electric fields are responsible for the larger amplitudes and longer lifetimes of the drift perturbations following sudden decreases in convection compared to those associated with sudden convection enhancements. In addition to these reasons we suppose that day-time and night-time equatorial ionosphere have to respond to westward and eastward auroral electrojets and the field-aligned currents by the different way while large-scale internal gravity waves and changes in neutral composition and in neutral wind system have to show the same effect in sign and there are problems to explain positive ionospheric storms. Furthermore, from the presented geomagnetic storms which AU and AL indices have very different amplitudes (nighttime auroral electrojets are much stronger daytime ones AL/AU˜5) and yet it is impossible from models to take account theses effects from termospheric models. It should be noted that amplitudes of AU and AL very variable during different storms, so there are different the IMF Bz and By patterns of auroral electrojets and related the field-aligned currents. Numerical modeling of auroral electrojets during geomagnetic disturbances effects of FAC as well as the polar cap potential drop difference in the auroral electrojet distribution and precipitation of high-energy auroral particles are considered. We suppose to explain of substorm effects in foF2 it is not enough to involve local processes but it is necessary to consider existential distribution of all parameters of near-Earth plasma. In our cases the IMF Bz and Joule heating can show the same effect to decrease of foF2 variations but quick foF2 depression and its correlation the negative the IMF Bz duration seems to show

  6. Investigating the effect of K-characteristic radiation on the performance of nuclear medicine scintillators by Monte Carlo methods

    International Nuclear Information System (INIS)

    Liaparinos, Panagiotis; Kandarakis, Ioannis; Cavouras, Dionisis; Delis, Harry; Panayiotakis, George

    2006-01-01

    The aim of this study was to evaluate the effect of K-characteristic radiation on the performance of scintillator crystals incorporated in nuclear medicine detectors (LSO, BGO, GSO). K-characteristic radiation is produced within materials of at least one high atomic number element (e.g. Lu, Gd, Bi). This radiation may either be reabsorbed or it may escape the scintillator. In both cases the light emission efficiency of the scintillator may be affected resulting in either spatial or energy resolution degradation. A computational program, based on Monte Carlo methods, was developed in order to simulate the transport of K-characteristic radiation within the most commonly used scintillator materials. Crystal thickness was allowed to vary from 0.5 up to 15 mm. A monoenergetic pencil beam, with energy varying from 0.60 to 0.511 MeV was considered to fall on the center of the crystal surface. The dominant γ-ray interactions (elastic and inelastic scattering and photoelectric absorption) were taken into account in the simulation. Results showed that, depending on crystal thickness, incident photon energy and scintillator's intrinsic properties (L or K-fluorescence yield, effective atomic number and density), the scintillator's emission efficiency may be significantly reduced and affect spatial or energy resolution

  7. Longitudinal effect in the night-time mid-latitude ionosphere according to the Interkosmos-19 data

    International Nuclear Information System (INIS)

    Deminov, M.G.; Karpachev, A.T.

    1988-01-01

    Longitudinal effects in the night-time mid-latitude external ionosphere for summer and winter conditions of the high solar activity period are analysed. The high amplitude of longitudinal changes of the external ionosphere, including changes of the height (upto 150 km) and the concentration (7-8 times) of the F2-layer maximum, is shown to be provided under winter mid-night-time conditions with high values of the zone component of the wind velocity and strong latitude gradients and with longitudinal changes of the meridional projection of the wind velocity. N changes with the longitude before the Sun setting, when the zone component of the wind velocity is maximum, made the main contribution in summer to longitudinal changes of the electron concentration of the N night ionosphere. The wind velocity phase shift during the season lleads to the fact that the maximum amplitude of N longitudinal changes is observed till midnight in summer and after midnight in winter

  8. Space weather effects on lower ionosphere: First investigation from Bharati station during 34th Indian scientific expedition to Antarctica

    Science.gov (United States)

    Guha, Anirban; Saha, Kumarjit; De, Barin Kumar; Subrahmanyam, Kandula Venkata; Shreedevi, P. R.

    2017-04-01

    We investigate the solar flare effects on the D-region of the ionosphere with the help of VLF (Very Low Frequency) radio waves using a portable E-field system from Antarctica during the summer period of 34th Indian scientific expedition. Two GPS time synchronized VLF receivers, one located at Bharati, Antarctica (geographical latitude 69.40°S, longitude 76.18°E) and another located at Tripura, India (geographical latitude 23.84°N, longitude 91.28°E) were operated simultaneously to infer common mode changes in the lower ionosphere for a number of solar flares events. The two systems constantly monitored the carrier amplitude and phase of the MSK (Minimum Shift Keying) modulated navy transmitter located in Australia (Callsign: NWC, 19.8 kHz, geographical latitude 21.88°S, longitude 114.13°E), around 5.6 Mm great circle distance from the two receivers. The results are interpreted in terms of Earth-ionosphere wave-guide characteristics. A Long Wave Propagation Capability (LWPC) model study is also performed to infer the changes in the daytime electron density in polar D-region ionosphere during the solar flares. The exponential fit of the modeled electron density change with average X-ray flux change shows an excellent correlation (R2 value 0.95). The exponential fit is utilized to infer the daytime electron density change in the polar ionosphere during solar flare events. The analyses indicate that small solar flares of class 'C' can be very effectively detected with the portable antenna system even if the receiver is located in polar coastal region compared to equatorial region. The expedition results also demonstrate the feasibility of using portable VLF receivers from the coastal stations for monitoring the polar lower ionosphere from Antarctica and open up new opportunities for long term exploration.

  9. Scintillators and other particle optical detectors

    International Nuclear Information System (INIS)

    Chipaux, R.

    2011-01-01

    The author reports and comments his researcher career in the field of particle optical detectors. He addresses the cases of organic scintillators (scintillating fibers, liquid scintillators), inorganic scintillators (crystals for electromagnetic calorimetry, crystals for solar neutrino spectroscopy), and Cherenkov Effect detectors. He also reports his works on Cd Te detectors and their modelling

  10. Performance of molded plastic scintillators

    International Nuclear Information System (INIS)

    Gen, N.S.; Leman, V.E.; Solomonov, V.M.

    1989-01-01

    The performance of molded plastic scintillators is studied. The plastic scintillators studied were formed by transfer molding and intrusion from a scintillation composition consisting of polystyrene and a standard system of luminescent additives: 2 mass % of paraterphenyl + 0.06 mass % 1,4-di-/2-[5-phenyloxazoyly]/benzene and a plasticizer. The combined effect of mechanical load and temperature was studied. The effect of radiation on molded plastic scintillators was studied using gamma radiation from a 60 Co source. The studies show that the main operating characteristics of molded plastic scintillators are on a par with those of polymerized plastic scintillators. At the same time, molded plastic scintillators are superior in thermal stability at temperatures below the glass transition temperature and with respect to their working temperature range

  11. The ionosphere

    International Nuclear Information System (INIS)

    Taieb, C.

    1977-01-01

    This paper comprises four parts. The first one is dealing with the neutral atmosphere, its structure, its composition, its variations. The second one describes the ionospheric plasma, (the ionized part) and explains its formation. The influence of the geomagnetic field is discussed in the third chapter, the fourth one being concerned with the means of studying the ionosphere: ionograms obtained by ionosondes or incoherent scattering sounding or from satellite measurements [fr

  12. Understanding Transient Forcing with Plasma Instability Model, Ionospheric Propagation Model and GNSS Observations

    Science.gov (United States)

    Deshpande, K.; Zettergren, M. D.; Datta-Barua, S.

    2017-12-01

    Fluctuations in the Global Navigation Satellite Systems (GNSS) signals observed as amplitude and phase scintillations are produced by plasma density structures in the ionosphere. Phase scintillation events in particular occur due to structures at Fresnel scales, typically about 250 meters at ionospheric heights and GNSS frequency. Likely processes contributing to small-scale density structuring in auroral and polar regions include ionospheric gradient-drift instability (GDI) and Kelvin-Helmholtz instability (KHI), which result, generally, from magnetosphere-ionosphere interactions (e.g. reconnection) associated with cusp and auroral zone regions. Scintillation signals, ostensibly from either GDI or KHI, are frequently observed in the high latitude ionosphere and are potentially useful diagnostics of how energy from the transient forcing in the cusp or polar cap region cascades, via instabilities, to small scales. However, extracting quantitative details of instabilities leading to scintillation using GNSS data drastically benefits from both a model of the irregularities and a model of GNSS signal propagation through irregular media. This work uses a physics-based model of the generation of plasma density irregularities (GEMINI - Geospace Environment Model of Ion-Neutral Interactions) coupled to an ionospheric radio wave propagation model (SIGMA - Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere) to explore the cascade of density structures from medium to small (sub-kilometer) scales. Specifically, GEMINI-SIGMA is used to simulate expected scintillation from different instabilities during various stages of evolution to determine features of the scintillation that may be useful to studying ionospheric density structures. Furthermore we relate the instabilities producing GNSS scintillations to the transient space and time-dependent magnetospheric phenomena and further predict characteristics of scintillation in different geophysical

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

    Science.gov (United States)

    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

  14. Scintillation Counters

    Science.gov (United States)

    Bell, Zane W.

    Scintillators find wide use in radiation detection as the detecting medium for gamma/X-rays, and charged and neutral particles. Since the first notice in 1895 by Roentgen of the production of light by X-rays on a barium platinocyanide screen, and Thomas Edison's work over the following 2 years resulting in the discovery of calcium tungstate as a superior fluoroscopy screen, much research and experimentation have been undertaken to discover and elucidate the properties of new scintillators. Scintillators with high density and high atomic number are prized for the detection of gamma rays above 1 MeV; lower atomic number, lower-density materials find use for detecting beta particles and heavy charged particles; hydrogenous scintillators find use in fast-neutron detection; and boron-, lithium-, and gadolinium-containing scintillators are used for slow-neutron detection. This chapter provides the practitioner with an overview of the general characteristics of scintillators, including the variation of probability of interaction with density and atomic number, the characteristics of the light pulse, a list and characteristics of commonly available scintillators and their approximate cost, and recommendations regarding the choice of material for a few specific applications. This chapter does not pretend to present an exhaustive list of scintillators and applications.

  15. Research of Ionospheric Scintillation in Asia (RISA)

    Science.gov (United States)

    2014-03-01

    data. 2. RINEX_HO Software was Developed by Marques, Sao Paulo , Brazil , its main objective is to improve rinex file for the correction of second...data 24hours since July 2010 to middle of October 2011. Due to devastating floods of Thailand in October 2011, AIT’s SCINDA station was shut down...unlimited. 8 restored after floods , this station is perfectly in operation with satisfactory data archive.Figure 4.6 shows the hardware setup of SCINDA

  16. Change in the F region structure of a polar ionosphere at the change of the Y component sighn of the interplanetary magnetic field. Svalgaard-Mansurov effect in the ionosphere

    International Nuclear Information System (INIS)

    Gal'perin, Yu.I.; Zosimova, A.G.; Larina, T.N.; Mozhaev, A.M.; Osipov, N.K.; Ponomarev, Yu.N.

    1980-01-01

    Model calculations of the planetary picture of the polar ionosphere characteristics taking into account modern models of magnetospheric convection are carried out. The results of direct measurements of the lateral component of the convection rate in the day polar cusp region obtained by the ''Kosmos-184'' satellite in 1967 indicative of rotation of the zonal convection component direction with tha change of the Bsub(y) component sign of the interplanetary magnetic field (IMF). It is shown that the change of the IMF Bsub(y) sign and the following change of the convection picture in the polar cap must cause a quick (10 3 s) change of the planetary picture of the polar ionosphere characteristics in the F region peak and higher, i.e. ''the Svalgard-Mansurov ionospheric effect''. The amplitude of the variations and their character are defined by the relation of the solar and auroral ionization, and, therefore, they strongly depend on the universal time, season and auroral activity, that hampers comparison of the calculations with the experiment. The experimental data obtained from satellites and indicative of the reality of the described ionospheric Bsub(y) effect are presented. Thus, the data of many years on the ionospheric measurements from the Earth and satellites parallel with the magnetic measurements can be used to specify parameters describing the magnetospheric convection picture [ru

  17. EFFECTS OF INTERMITTENT EMISSION: NOISE INVENTORY FOR THE SCINTILLATING PULSAR B0834+06

    International Nuclear Information System (INIS)

    Gwinn, C. R.; Johnson, M. D.; Smirnova, T. V.; Stinebring, D. R.

    2011-01-01

    We compare signal and noise for observations of the scintillating pulsar B0834+06, using very long baseline interferometry and a single-dish spectrometer. Comparisons between instruments and with models suggest that amplitude variations of the pulsar strongly affect the amount and distribution of self-noise. We show that noise follows a quadratic polynomial with flux density, in spectral observations. Constant coefficients, indicative of background noise, agree well with expectation; whereas second-order coefficients, indicative of self-noise, are ∼3 times values expected for a pulsar with constant on-pulse flux density. We show that variations in flux density during the 10 s integration accounts for the discrepancy. In the secondary spectrum, ∼97% of spectral power lies within the pulsar's typical scintillation bandwidth and timescale; an extended scintillation arc contains ∼3%. For a pulsar with constant on-pulse flux density, noise in the dynamic spectrum will appear as a uniformly distributed background in the secondary spectrum. We find that this uniform noise background contains 95% of noise in the dynamic spectrum for interferometric observations; but only 35% of noise in the dynamic spectrum for single-dish observations. Receiver and sky dominate noise for our interferometric observations, whereas self-noise dominates for single-dish. We suggest that intermittent emission by the pulsar, on timescales <300 μs, concentrates self-noise near the origin in the secondary spectrum, by correlating noise over the dynamic spectrum. We suggest that intermittency sets fundamental limits on pulsar astrometry or timing. Accounting of noise may provide means for detection of intermittent sources, when effects of propagation are unknown or impractical to invert.

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

    International Nuclear Information System (INIS)

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

    1988-01-01

    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 0 magnetic meridian and separated by about 5 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 0 --30 0 latitude, apparently due to such increased N 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

  19. A modeling study of the thermosphere-ionosphere interactions during the boreal winter and spring 2015-2016: Tidal and planetary-scale waves effect on the ionospheric structure.

    Science.gov (United States)

    Sassi, F.; McDonald, S. E.; McCormack, J. P.; Tate, J.; Liu, H.; Kuhl, D.

    2017-12-01

    The 2015-2016 boreal winter and spring is a dynamically very interesting time in the lower atmosphere: a minor high latitude stratospheric warming occurred in February 2016; an interrupted descent of the QBO was found in the tropical stratosphere; and a large warm ENSO took place in the tropical Pacific Ocean. The stratospheric warming, the QBO and ENSO are known to affect in different ways the meteorology of the upper atmosphere in different ways: low latitude solar tides and high latitude planetary-scale waves have potentially important implications on the structure of the ionosphere. In this study, we use global atmospheric analyses from a high-altitude version of the High-Altitude Navy Global Environmental Model (HA-NAVGEM) to constrain the meteorology of numerical simulations of the Specified Dynamics Whole Atmosphere Community Climate Model, extended version (SD-WACCM-X). We describe the large-scale behavior of tropical tides and mid-latitude planetary waves that emerge in the lower thermosphere. The effect on the ionosphere is captured by numerical simulations of the Navy Highly Integrated Thermosphere Ionosphere Demonstration System (Navy-HITIDES) that uses the meteorology generated by SD-WACCM-X to drive ionospheric simulations during this time period. We will analyze the impact of various dynamical fields on the zonal behavior of the ionosphere by selectively filtering the relevant dynamical modes.

  20. Multi-instrument observations of the solar eclipse on 20 March 2015 and its effects on the ionosphere over Belgium and Europe

    Science.gov (United States)

    Stankov, Stanimir M.; Bergeot, Nicolas; Berghmans, David; Bolsée, David; Bruyninx, Carine; Chevalier, Jean-Marie; Clette, Frédéric; De Backer, Hugo; De Keyser, Johan; D'Huys, Elke; Dominique, Marie; Lemaire, Joseph F.; Magdalenić, Jasmina; Marqué, Christophe; Pereira, Nuno; Pierrard, Viviane; Sapundjiev, Danislav; Seaton, Daniel B.; Stegen, Koen; Van der Linden, Ronald; Verhulst, Tobias G. W.; West, Matthew J.

    2017-08-01

    A total solar eclipse occurred on 20 March 2015, with a totality path passing mostly above the North Atlantic Ocean, which resulted in a partial solar eclipse over Belgium and large parts of Europe. In anticipation of this event, a dedicated observational campaign was set up at the Belgian Solar-Terrestrial Centre of Excellence (STCE). The objective was to perform high-quality observations of the eclipse and the associated effects on the geospace environment by utilising the advanced space- and ground-based instrumentation available to the STCE in order to further our understanding of these effects, particularly on the ionosphere. The study highlights the crucial importance of taking into account the eclipse geometry when analysing the ionospheric behaviour during eclipses and interpreting the eclipse effects. A detailed review of the eclipse geometry proves that considering the actual obscuration level and solar zenith angle at ionospheric heights is much more important for the analysis than at the commonly referenced Earth's surface or at the plasmaspheric heights. The eclipse occurred during the recovery phase of a strong geomagnetic storm which certainly had an impact on (some of) the ionospheric characteristics and perhaps caused the omission of some "low-profile" effects. However, the analysis of the ionosonde measurements, carried out at unprecedented high rates during the eclipse, suggests the occurrence of travelling ionospheric disturbances (TIDs). Also, the high temporal and spatial resolution measurements proved very important in revealing and estimating some finer details of the delay in the ionospheric reaction and the ionospheric disturbances.

  1. Scintillation camera

    International Nuclear Information System (INIS)

    Zioni, J.; Klein, Y.; Inbar, D.

    1975-01-01

    The scintillation camera is to make pictures of the density distribution of radiation fields created by the injection or administration radioactive medicaments into the body of the patient. It contains a scintillation crystal, several photomultipliers and computer circuits to obtain an analytical function at the exits of the photomultiplier which is dependent on the position of the scintillations at the time in the crystal. The scintillation crystal is flat and spatially corresponds to the production site of radiation. The photomultipliers form a pattern whose basic form consists of at least three photomultipliers. They are assigned to at least two crossing parallel series groups where a vertical running reference axis in the crystal plane belongs to each series group. The computer circuits are each assigned to a reference axis. Each series of a series group assigned to one of the reference axes in the computer circuit has an adder to produce a scintillation dependent series signal. Furthermore, the projection of the scintillation on this reference axis is calculated. A series signal is used for this which originates from a series chosen from two neighbouring photomultiplier series of this group. The scintillation must have appeared between these chosen series. They are termed as basic series. The photomultiplier can be arranged hexagonally or rectangularly. (GG/LH) [de

  2. Magnetic storm effect on the occurrence of ionospheric irregularities at an equatorial station in the African sector

    Directory of Open Access Journals (Sweden)

    Olushola Abel Oladipo

    2014-01-01

    Full Text Available Large-scale ionospheric irregularities usually measured by GPS TEC fluctuation indices are regular occurrence at the equatorial region shortly after sunset around solar maximum. Magnetic storm can trigger or inhibit the generation of these irregularities depending on the local time the main phase of a particular storm occurs. We studied the effect of nine (9 distinct storms on the occurrence of ionospheric irregularities at Fraceville in Gabon (Lat = −1.63˚, Long = 13.55˚, dip lat. = −15.94˚, an equatorial station in the African sector. These storms occurred between November 2001 and September 2002. We used TEC fluctuation indices (i.e. ROTI and ROTIAVE estimated from 30 s interval Rinex data and also we used the storm indices (i.e. Dst, dDst/dt, and IMF BZ to predict the likely effect of each storm on the irregularities occurrence at this station. The results obtained showed that most of the storms studied inhibited ionospheric irregularities. Only one out of all the storms studied (i.e. September 4, 2002 storms with the main phase on the night of September 7-8 triggered post-midnight ionospheric irregularities. There are two of the storms during which ionospheric irregularities were observed. However, these may not be solely attributed to the storms event because the level of irregularities observed during these two storms is comparable to that observed during previous days before the storms. For this station and for the storms investigated, it seems like a little modification to the use of Aarons categories in terms of the local time the maximum negative Dst occurs could lead to a better prediction. However, it would require investigating many storms during different level of solar activities and at different latitudes to generalize this modification.

  3. SiPM optical crosstalk amplification due to scintillator crystal: effects on timing performance

    International Nuclear Information System (INIS)

    Gola, Alberto; Ferri, Alessandro; Tarolli, Alessandro; Zorzi, Nicola; Piemonte, Claudio

    2014-01-01

    For a given photon detection efficiency (PDE), the primary, Poisson distributed, dark count rate of the detector (DCR 0 ) is one of the most limiting factors affecting the timing resolution of a silicon photomultiplier (SiPM) in the scintillation light readout. If the effects of DCR 0  are removed through a suitable baseline compensation algorithm or by cooling, it is possible to clearly observe another phenomenon that limits the PDE, and thus the timing resolution of the detector. It is caused by the optical crosstalk of the SiPM, which is significantly increased by the presence of the scintillator. In this paper, we describe this phenomenon, which is also easily observed from the reverse I–V curve of the device, and we relate it to the measured coincidence resolving time in 511 keV γ-ray measurements. We discuss its consequences on the SiPM design and, in particular, we observe that there is an optimal cell size, dependent on both SiPM and crystal parameters, that maximizes the PDE in presence of optical crosstalk. Finally, we report on a crosstalk simulator developed to study the phenomenon and we compare the simulation results obtained for different SiPM technologies, featuring different approaches to the reduction of the crosstalk. (paper)

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

    International Nuclear Information System (INIS)

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

  5. Ionospheric effects of rocket exhaust products: Skylab and HEAO-C

    International Nuclear Information System (INIS)

    Zinn, J.; Sutherland, C.D.; Duncan, L.M.; Stone, S.N.

    1981-01-01

    This paper is about ionospheric F-layer depletions produced by chemical reactions with exhaust gases from large rockets. It describes a 2-dimensional computer model of the ionosphere, and it compares model results with experimental data on the structure and variability of the natural ionosphere, as well as data on ionospheric holes produced by the launches of Skylab (May, 1973) and HEAO-C (September, 1979). It also describes measurements made in conjunction with the HEAO-C launch. The computer model includes an approximate representation of thermospheric tidal winds and E fields in addition to vertical motions associated with diurnal changes in temperature. The computed ionospheric structure is sensitive to all the above. For a small number of cases, results are compared of computations of the normal diurnal variations of ionospheric structure with incoherent scatter and total electron content data. Computations of ionospheric depletions from the Skylab and HEAO-C launches are in satisfactory agreement with the observations. The winds appear to be essential for interpretation of the Skylab results

  6. Ionospheric effects on DInSAR measurements of interseismic deformation in China

    Science.gov (United States)

    Gong, W.; Shan, X.; Song, X.; Liao, H.; Meyer, F. J.

    2017-12-01

    Interseismic deformation signals are small ground displacement that is critical to monitor the strain accumulates of major faults to foresee the potential seismic hazard. Accurate measurements of surface deformation could help recognize and interpret even subtle displacement and to give a better understanding of active fault behavior. However, the value and applicability of InSAR for inter-seismic monitoring problems is limited by the influence of temporal decorrelation and electromagnetic path delay variations (atmospheric disturbance), both reducing the sensitivity and accuracy of the technique. Ionospheric signal, a major part of atmospheric disturbance in InSAR, is related to the density of free electrons along the ray path, thus, that is dependent on the SAR signal frequency. Ionosphere induced phase distortions can lead to azimuth/range defocusing, geometry distortions and interferometric phase distortions. Some ionosphere phenomenon have been reported more severe at equatorial region and polar zones, e.g., ionosphere irregularity, while for middle latitude regions like West China it has not been thoroughly analyzed. Thus, this study is focus on the evaluation of ionosphere impacts in middle latitude zone, and its impacts in monitoring interseismic deformation in West China. The outcome would be useful to provide an empiric prior error condition of ionosphere disturbance, which can further benefit InSAR result interpretation and geophysical inversion, as well as the SAR data arrangement in future operational-(cloud) InSAR processing system. The study focus on two parts: 1. We will analyze the temporal-spatial variation of ionosphere and its magnitude at middle latitude zone, and investigate its impacts to current satellite SAR (C-band (Sentinel-1) and L-band (ALOS2) dataset) in earthquake-related deformation studies, especially inter-seismic study. 2. Ionosphere phase patterns at mid latitudes is typically small and the structure is compatibly smooth. This

  7. Dynamics of the polar ionosphere structure disturbance in the Svalgaard-Mansurov effect

    International Nuclear Information System (INIS)

    Osipov, N.K.; Mozhaev, A.M.; Larina, T.N.; Ponomarev, Yu.N.

    1988-01-01

    Nonstationary disturbance model of the ionsphere of polar caps caused by change of B y component sign of interplanetary magnetic field is considered. It is shown that nonstationary convection transfer of ionospheric plasma represents the main and the most fast mechanism regulating reconstruction of ionosphere structure in polar caps during magnetosphere substorms, caused by the change of B y sign. Calculations show that characteristic time of sufficient change of ionosphere structure at ∼1500 km distances is on the order of 10-25 min

  8. Using GPS TEC measurements to probe ionospheric spatial spectra at mid-latitudes

    Science.gov (United States)

    Lay, E. H.; Parker, P. A.; Light, M. E.; Carrano, C. S.; Debchoudhury, S.; Haaser, R. A.

    2017-12-01

    The physics of how random ionospheric structure causes signal degradation is well understood as weak forward scattering through an effective diffraction grating created by plasma irregularities in the ionosphere. However, the spatial scale spectrum of those irregularities required for input into scintillation models and models of traveling ionospheric disturbances is poorly characterized, particularly at the kilometer to tens of kilometer scale lengths important for very-high-frequency (VHF) scintillation prediction. Furthermore, the majority of characterization studies have been performed in low-latitude or high-latitude regions where geomagnetic activity dominates the physical processes. At mid-latitudes, tropospheric and geomagnetic phenomena compete in disturbing the ionosphere, and it is not well understood how these multiple sources affect the drivers that influence the spatial spectrum. In this study, we are interested in mid-latitude electron density irregularities on the order of 10s of kilometers that would affect VHF signals. Data from the GPS networks Japan GEONET and the Plate Boundary Observatory (PBO, UNAVCO) in the western United States were analyzed for this study. Japan GEONET is a dense network of GPS receivers (station spacing of tens of km), with fairly evenly spaced positions over all of Japan. The PBO, on the other hand, has several pockets of extremely dense coverage (station spacing within a few km), but is less dense on average. We analyze a day with a large solar storm (2015/03/17, St. Patrick's Day Storm) to allow high scintillation potential at mid-latitudes, a day with low geomagnetic activity and low thunderstorm activity (2016/01/31), and a day with low geomagnetic activity and high thunderstorm activity (2015/08/02). We then perform two-dimensional spatial analyses on the TEC data from these two networks on scale lengths of 20 to 200 km to infer the spatial scale spectra.

  9. Plastic scintillator

    International Nuclear Information System (INIS)

    Andreeshchev, E.A.; Kilin, S.F.; Kavyrzina, K.A.

    1978-01-01

    A plastic scintillator for ionizing radiation detectors with high time resolution is suggested. To decrease the scintillation pulse width and to maintain a high light yield, the 4 1 , 4 5 -dibromo-2 1 , 2 5 , 5 1 , 5 5 -tetramethyl-n-quinquiphenyl (Br 2 Me 4 Ph) in combination with n-terphenyl (Ph 3 ) or 2, 5-diphenyloxadiazol-1, 3, 4 (PPD) is used as a luminescent addition. Taking into consideration the results of a special study, it is shown, that the following ratio of ingradients is the optimum one: 3-4 mass% Ph 3 or 4-7 mas% PPD + 2-5 mass% Br 2 Me 4 Ph + + polymeric base. The suggested scintillator on the basis of polystyrene has the light yield of 0.23-0.26 arbitrary units and the scintillation pulse duration at half-height is 0.74-0.84 ns

  10. Analysis of thermal treatment effects upon optico-luminescent and scintillation characteristics of oxide and chalcogenide crystals

    International Nuclear Information System (INIS)

    Ryzhikov, Vladimir D.; Grinyov, Boris V.; Pirogov, Evgeniy N.; Galkin, Sergey N.; Nagornaya, Lyudmila L.; Bondar, Vladimir G.; Babiychuk, Inna P.; Krivoshein, Vadim I.; Silin, Vitaliy I.; Lalayants, Alexandr I.; Voronkin, Evgeniy F.; Katrunov, Konstantin A.; Onishchenko, Gennadiy M.; Vostretsov, Yuriy Ya.; Malyi, Pavel Yu.; Lisetskaya, Elena K.; Lisetskii, Longin N.

    2005-01-01

    This work has been aimed at analyzing the effects of various thermal treatment factors upon optical-luminescent, scintillation and other functional characteristics of complex oxide and chalcogenide crystals. The crystals considered in this work are scintillators with intrinsic (PWO, CWO, BGO), activator (GSO:Ce) or complex-defect ZnSe(Te) type of luminescence. Important factors of thermal treatment are not only the temperature and its variation with time, but also the chemical composition of the annealing medium, its oxidation-reduction properties

  11. Detection and Characterization of Equatorial Scintillation for Real-Time Operational Support

    National Research Council Canada - National Science Library

    McNeil, W

    1997-01-01

    The Phillips Laboratory Scintillation Network Decision Aid (PL-SCINDA) is a software tool which uses real-time data from remote sites to model ionospheric plasma depletions in the equatorial region...

  12. Tsunami Ionospheric warning and Ionospheric seismology

    Science.gov (United States)

    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

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

    International Nuclear Information System (INIS)

    Proelss, G.W.

    1993-01-01

    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

  14. Ion Internal Excitation and Co++ 2 Reactivity: Effect On The Titan, Mars and Venus Ionospheric Chemistry

    Science.gov (United States)

    Nicolas, C.; Zabka, J.; Thissen, R.; Dutuit, O.; Alcaraz, C.

    In planetary ionospheres, primary molecular and atomic photoions can be produced with substantial electronic and vibrational internal energy. In some cases, this is known to strongly affect both the rate constants and the branching ratio between the reac- tion products. A previous experimental study (Nicolas et al.) made at the Orsay syn- chrotron radiation facility has shown that many endothermic charge transfer reactions which were not considered in the ionospheric chemistry models of Mars, Venus and Earth have to be included because they are driven by electronic excitation of the parent ions. New measurements on two important reactions for Titan and Mars ionospheres, N+ + CH4 and O+ + CO2, will be presented. Branching ratios between products are very different when the parent atomic ions are prepared in their ground states, N+(3P) and O+(4S), or in their first electronic metastable states N+(1D) and O+(2D or P). 2 As the lifetime of these states are long enough, they survive during the mean time be- tween two collisions in the ionospheric conditions. So, the reactions of these excited states must be included in the ionospheric models. Absolute cross section measurements of the reactivity of stable doubly charged molec- ular ions CO++ and their implications for the Martian ionosphere will also be pre- 2 sented. The molecular dication CO++ production by VUV photoionisation and elec- 2 tron impact in the upper ionosphere of Mars is far from being negligible. However, to determine its concentration, it was necessary to evaluate the major loss channels of these ions. For this purpose, we measured the absolute reaction cross section of the sta- ble dications with CO2, the major neutral species of the Mars ionosphere. CO++ ions 2 were produced either by photoionisation or by electron impact, and a reaction cross section of 45 Å2 with 13CO2 was measured. The reaction leads to charge transfer or to collision induced dissociation. These results were integrated in a model

  15. Occurrence and zonal drifts of small-scale ionospheric irregularities over an equatorial station during solar maximum - Magnetic quiet and disturbed conditions

    Science.gov (United States)

    Muella, M. T. A. H.; de Paula, E. R.; Kantor, I. J.; Rezende, L. F. C.; Smorigo, P. F.

    2009-06-01

    A statistical study of L-band amplitude scintillations and zonal drift velocity of Fresnel-scale ionospheric irregularities is presented. Ground-based global positioning system (GPS) data acquired at the equatorial station of São Luís (2.33°S, 44.21°W, dip latitude 1.3°S), Brazil, during the solar maximum period from March 2001 to February 2002 are used in the analysis. The variation of scintillations and irregularity drift velocities with local time, season and magnetic activity are reported. The results reveal that for the near overhead ionosphere (satellite elevation angle >45°) a broad maximum in the occurrence of scintillation is seen from October to February. In general, weak scintillations (S 4 90%) during equinox (March-April; September-October) and December solstice (November-February) quiet time conditions and, many of the scintillations, occurred during pre-midnight hours. The mean zonal velocities of the irregularities are seen to be ˜30 m s -1 larger near December solstice, while during the equinoctial period the velocities decay faster and the scintillations tend to cease earlier. On geomagnetically disturbed nights, scintillation activity seems to be strongly affected by the prompt penetration of magnetospheric electric fields and disturbance dynamo effects. On disturbed days, during the equinox and December solstice seasons, the scintillations tend to be suppressed in the pre-midnight hours, whereas during June solstice months (May-August) the effect is opposite. In the post-midnight period, the mostly marked increase in the scintillation occurrence is observed during the equinox months. The results show that during disturbed conditions only one type of storm (when the main phase maximum takes place during the daytime hours) agrees with the Aarons' description, that is the suppression of L-band scintillations in the first recovery phase night. The results also reveal that the storm-time irregularity drifts become more spread in velocity and

  16. Effects of polar field-aligned currents on the distribution of the electric field and current in the middle and low latitudes ionosphere

    International Nuclear Information System (INIS)

    Maekawa, Koichiro

    1978-01-01

    According to the analysis of the magnetic records from the Triad satellite, it has been found that there are two regions of the field-aligned current of magnetospheric origin along the auroral oval; Region 1 in higher latitude and Region 2 in lower latitude. These currents seem to have important effect on the distribution of electric field and current in the ionosphere, in addition to the Sq electric field and current of ionospheric origin. The global current systems generated by the field-aligned current were calculated, using some simplified ionospheric models. The effect of the field-aligned current on the distribution of electric field and current of the ionosphere at middle and low latitudes was investigated. (Yoshimori, M.)

  17. Effective electron recombination coefficient in ionospheric D-region during the relaxation regime after solar flare from February 18, 2011

    Energy Technology Data Exchange (ETDEWEB)

    Nina, A. [Institute of Physics, University of Belgrade, P.O. Box 57, Belgrade (Serbia); Cadez, V. [Astronomical Observatory, Volgina 7, 11060 Belgrade (Serbia); Sulic, D., E-mail: dsulic@ipb.ac.rs [Faculty of Ecology and Environmental Protection, Union - Nikola Tesla University, Cara Dusana 62, 11000 Belgrade (Serbia); Sreckovic, V. [Institute of Physics, University of Belgrade, P.O. Box 57, Belgrade (Serbia); Zigman, V. [University of Nova Gorica, Vipavska 13, Rona Dolina, SI-5000 Nova Gorica (Slovenia)

    2012-05-15

    In this paper, we present a model for determination of a weakly time dependent effective recombination coefficient for the perturbed terrestrial ionospheric D-region plasma. We study consequences of a class M1.0 X-ray solar flare, recorded by GOES-15 satellite on February 18, 2011 between 14:00 and 14:15 UT, by analyzing the amplitude and phase real time variations of very low frequency (VLF) radio waves emitted by transmitter DHO (located in Germany) at frequency 23.4 kHz and recorded by the AWESOME receiver in Belgrade (Serbia). Our analysis is limited to ionospheric perturbations localized at altitudes around 70 km where the dominant electron gain and electron loss processes are the photo-ionization and recombination, respectively.

  18. Effective electron recombination coefficient in ionospheric D-region during the relaxation regime after solar flare from February 18, 2011

    International Nuclear Information System (INIS)

    Nina, A.; Čadež, V.; Šulić, D.; Srećković, V.; Žigman, V.

    2012-01-01

    In this paper, we present a model for determination of a weakly time dependent effective recombination coefficient for the perturbed terrestrial ionospheric D-region plasma. We study consequences of a class M1.0 X-ray solar flare, recorded by GOES-15 satellite on February 18, 2011 between 14:00 and 14:15 UT, by analyzing the amplitude and phase real time variations of very low frequency (VLF) radio waves emitted by transmitter DHO (located in Germany) at frequency 23.4 kHz and recorded by the AWESOME receiver in Belgrade (Serbia). Our analysis is limited to ionospheric perturbations localized at altitudes around 70 km where the dominant electron gain and electron loss processes are the photo-ionization and recombination, respectively.

  19. Full Polarimetric Synthetic Aperture Radar (SAR) Data for ionosphere observation - A comparative study

    Science.gov (United States)

    Mohanty, S.; Singh, G.

    2017-12-01

    Ionosphere, predominantly, govern the propagation of radio waves, especially at L-band and lower frequencies. Small-scale, rapid fluctuations in the electron density, termed as scintillation phenomenon, cause rapid variations in signal amplitude and phase. Scintillation studies have been done using ground-based radio transmitter and beacon GPS signals. In this work, attempt has been made to utilize full polarimetric synthetic aperture radar (SAR) satellite signal at L-band (1.27 GHz) to develop a new measurement index for SAR signal intensity fluctuation. Datasets acquired from Japan's latest Advanced Land Observation Satellite (ALOS)-2 over the Indian subcontinent on two different dates, with varying ionospheric activities, have been utilized to compare the index. A 20% increase in the index values for a scintillation-affected day has been observed. The result coincides with the nature of ionospheric scintillation pattern typically observed over the equatorial belt. Total electron content values, for the two dates of acquisition, obtained from freely available Ionosphere Exchange (IONEX) data have been used to validate the varying ionospheric activities as well as the trend in index results. Another interesting finding of the paper is the demarcation of the equatorial anomaly belt. The index values are comparatively higher at these latitudes on a scintillation-affected day. Furthermore, the SAR signal intensity fluctuation index has great potential in being used as a preliminary measurement index to identify low frequency SAR data affected by ionospheric scintillation.

  20. A statistical study on the effect of earthquakes on the ionosphere, based on the subionospheric LF propagation data in Japan

    Directory of Open Access Journals (Sweden)

    S. Maekawa

    2006-09-01

    Full Text Available A superimposed epoch analysis has been undertaken, in order to find the correlation of the ionospheric perturbations with seismic activity. We take the wave path from the Japanese LF transmitter (frequency=40 kHz and an observing station of Kochi (wave path length of 770 km, and a much longer period (of five years than before, is considered. This subionospheric LF propagation can be called "an integrated measurement" in the sense that any earthquakes in the LF sensitive area just around the great-circle path can influence the observed LF signals, so that we define the "effective magnitude" (Meff by integrating the total energy from different earthquakes in the sensitive area on a current day and by converting it back into magnitude. A superimposed epoch analysis for the effective magnitude greater than 6.0 has yielded that the ionosphere is definitely disturbed in terms of both amplitude and dispersion, and that these perturbations tend to take place prior to an earthquake. The statistical z-test has also been performed, which has indicated that the amplitude is definitely depleted 2–6 days before the earthquake day and also that the dispersion is very much enhanced during the same period. This statistical study has given strong support to the existence of seismo-ionospheric perturbations for high seismic activity.

  1. Effects of the 2017 Solar Eclipse on HF Radio Propagation and the D-Region Ionosphere: Citizen Science Investigation

    Science.gov (United States)

    Fry, C. D.; Adams, M.; Gallagher, D. L.; Habash Krause, L.; Rawlins, L.; Suggs, R. M.; Anderson, S. C.

    2017-12-01

    August 21, 2017 provided a unique opportunity to investigate the effects of the total solar eclipse on high frequency (HF) radio propagation and ionospheric variability. In Marshall Space Flight Center's partnership with the US Space and Rocket Center (USSRC) and Austin Peay State University (APSU), we engaged students and citizen scientists in an investigation of the eclipse effects on the mid-latitude ionosphere. The Amateur Radio community has developed several automated receiving and reporting networks that draw from widely-distributed, automated and manual radio stations to build a near-real time, global picture of changing radio propagation conditions. We used these networks and employed HF radio propagation modeling in our investigation. A Ham Radio Science Citizen Investigation (HamSCI) collaboration with the American Radio Relay League (ARRL) ensured that many thousands of amateur radio operators would be "on the air" communicating on eclipse day, promising an extremely large quantity of data would be collected. Activities included implementing and configuring software, monitoring the HF Amateur Radio frequency bands and collecting radio transmission data on days before, the day of, and days after the eclipse to build a continuous record of changing propagation conditions as the moon's shadow marched across the United States. Our expectations were the D-Region ionosphere would be most impacted by the eclipse, enabling over-the-horizon radio propagation on lower HF frequencies (3.5 and 7 MHz) that are typically closed during the middle of the day. Post-eclipse radio propagation analysis provided insights into ionospheric variability due to the eclipse. We report on results, interpretation, and conclusions of these investigations.

  2. Plastic scintillator with effective pulse shape discrimination for neutron and gamma detection

    Science.gov (United States)

    Zaitseva, Natalia P.; Carman, M Leslie; Cherepy, Nerine; Glenn, Andrew M.; Hamel, Sebastien; Payne, Stephen A.; Rupert, Benjamin L.

    2016-04-12

    In one embodiment, a scintillator material includes a polymer matrix; and a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount of 5 wt % or more; wherein the scintillator material exhibits an optical response signature for neutrons that is different than an optical response signature for gamma rays. In another embodiment, a scintillator material includes a polymer matrix; and a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount greater than 10 wt %.

  3. Effects of Zr4+ codoping on the Lu0.8Sc0.2BO3:Ce scintillation materials

    International Nuclear Information System (INIS)

    Wu, Yuntao; Ren, Guohao; Ding, Dongzhou; Shang, Shanshan; Sun, Dandan; Zhang, Guoqing; Wang, Jiayu; Pan, Shangke; Yang, Fan

    2013-01-01

    Both Zr-codoped Lu 0.8 Sc 0.2 BO 3 :Ce polycrystalline powders and single crystals were obtained by solid-state reaction and Czochralski method, respectively. The effects of Zr codoping on the optical absorption, Ce 3+ /Ce 4+ ratio, scintillation efficiency, decay time and point defect in Lu 0.8 Sc 0.2 BO 3 :Ce materials were examined systematically. Our results show that there is no positive contribution of Zr 4+ ion codoping to the scintillation efficiency. And the reasons for the deterioration of scintillation efficiency by codoping Zr 4+ were revealed. - Highlights: ► No positive contribution of the Zr 4+ ions on the scintillation efficiency was found. ► New optical absorption band was in the region from 200 to 225 nm. ► Continuously accelerated decay time indicated that Zr 4+ codoping induced new point defects. ► The induced hole trap located at 1.91 eV below the conduction band.

  4. MESSENGER Spacecraft Phase Scintillation due to Plasma ductting effect on RF beam propagation at Superior Solar Conjunction

    Science.gov (United States)

    Mosavi, N.; Sequeira, H.; Copeland, D.; Menyuk, C.

    2017-12-01

    We investigate the evolution of a radio frequency (RF) X-band signal as it propagates through the solar corona turbulence in superior solar conjunction at low Sun-Earth-Probe (SEP) angles.Data that was obtained during several MESSENGER (MErcury Surface, Space ENivornment, GEochmeisty, and Ranging) conjunctions reveal a short-term and long-term effect. Amplitude scintillation is evident on a short time scale. Phase scintillations are stronger, but occur over a longer time scale. We examine different possible phenomena in the solar plasma that could be the source of the different time scales of the amplitude and phase scintillations. We propose a theoretical model in which the amplitude scintillations are due to local fluctuations of the index of refraction that scatter the RF signal. These rapidly varying fluctuations randomly attenuate the signal without affecting its phase. By contrast, we propose a model in which phase fluctuations are due to long ducts in the solar plasma, streaming from the sun, that trap some parts of the RF signal. These ducts act as waveguides, changing the phase velocity of the RF beam as it travels a zigzag path inside a duct. When the radiated wave exits from a duct, its phase is changed with respect to the signal that did not pass through the duct, which can lead to destructive interference and carrier suppression. The trapping of the wave is random in nature and can be either a fast or slow process. The predictions of this model are consistent with observations.

  5. Interpretation of observed relations between solar wind characteristics and effects at ionospheric altitudes

    International Nuclear Information System (INIS)

    Cowley, S.W.H.

    1983-01-01

    This chapter discusses recent developments and remaining questions concerning the behavior of high latitude ionospheric flows and how they depend on solar wind conditions via magnetospheric coupling to the latter. The magnitude and direction of the interplanetary magnetic field (IMF) is found to be the primary factor. The relationships which have been found between the strength of high-latitude flows and solar wind and IMF conditions, and the inferences which can be drawn therefrom concerning the solar wind-magnetosphere coupling processes which result in convection are examined. The east-west asymmetries in highlatitude flows which are found to be associated with the B /SUB y/ (dawn-dusk) component of the IMF are investigated. Related asymmetries are shown to occur in the magnetosphere at large, and the unity of these effects as arising from one straightforward cause is stressed. Recent work on the ''reversed'' sunward flows which occur at high latitudes in association with strong B /SUB z/ in the IMF is described

  6. Effects on noise properties of GPS time series caused by higher-order ionospheric corrections

    Science.gov (United States)

    Jiang, Weiping; Deng, Liansheng; Li, Zhao; Zhou, Xiaohui; Liu, Hongfei

    2014-04-01

    Higher-order ionospheric (HOI) effects are one of the principal technique-specific error sources in precise global positioning system (GPS) analysis. These effects also influence the non-linear characteristics of GPS coordinate time series. In this paper, we investigate these effects on coordinate time series in terms of seasonal variations and noise amplitudes. Both power spectral techniques and maximum likelihood estimators (MLE) are used to evaluate these effects quantitatively and qualitatively. Our results show an overall improvement for the analysis of global sites if HOI effects are considered. We note that the noise spectral index that is used for the determination of the optimal noise models in our analysis ranged between -1 and 0 both with and without HOI corrections, implying that the coloured noise cannot be removed by these corrections. However, the corrections were found to have improved noise properties for global sites. After the corrections were applied, the noise amplitudes at most sites decreased, among which the white noise amplitudes decreased remarkably. The white noise amplitudes of up to 81.8% of the selected sites decreased in the up component, and the flicker noise of 67.5% of the sites decreased in the north component. Stacked periodogram results show that, no matter whether the HOI effects are considered or not, a common fundamental period of 1.04 cycles per year (cpy), together with the expected annual and semi-annual signals, can explain all peaks of the north and up components well. For the east component, however, reasonable results can be obtained only based on HOI corrections. HOI corrections are useful for better detecting the periodic signals in GPS coordinate time series. Moreover, the corrections contributed partly to the seasonal variations of the selected sites, especially for the up component. Statistically, HOI corrections reduced more than 50% and more than 65% of the annual and semi-annual amplitudes respectively at the

  7. ULF wave effects on high frequency signal propagation through the ionosphere

    Directory of Open Access Journals (Sweden)

    C. L. Waters

    2009-07-01

    Full Text Available Variations in the total electron content (TEC of the ionosphere alter the propagation characteristics of EM radiation for frequencies above a few megahertz (MHz. Spatial and temporal variations of the ionosphere TEC influence highly sensitive, ground based spatial measurements such as those used in radio astronomy and Global Positioning System (GPS applications. In this paper we estimate the magnitudes of the changes in TEC and the time delays of high frequency signals introduced by variations in the ionosphere electron density caused by the natural spectrum of ultra-low frequency (ULF wave activity that originates in near-Earth space. The time delays and associated phase shifts depend on the frequency, spatial structure and amplitude of the ULF waves.

  8. Effect of the interplanetary magnetic field on the distribution of electric fields in the polar ionosphere

    Science.gov (United States)

    Uvarov, V. M.; Barashkov, P. D.

    1985-08-01

    Heppner (1972), in an analysis of satellite data, observed 12 types of electric-field distributions in the polar ionosphere along the morning-evening meridian. In the present paper it is shown that these distribution types can be described by the analytical model of Uvarov and Barashkov (1984). In this model the excitation of the electric fields is investigated by solving the set of continuity equations for current in three regions (the north and south polar caps and a region outside the caps) with allowance for the magnetic conjugacy of the ionosphere in the two hemispheres.

  9. An ionospheric index suitable for estimating the degree of ionospheric perturbations

    Science.gov (United States)

    Wilken, Volker; Kriegel, Martin; Jakowski, Norbert; Berdermann, Jens

    2018-03-01

    Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ(ϕ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.

  10. Memory effect, resolution, and efficiency measurements of an Al2O3 coated plastic scintillator used for radioxenon detection

    International Nuclear Information System (INIS)

    Bläckberg, L.; Fritioff, T.; Mårtensson, L.; Nielsen, F.; Ringbom, A.; Sjöstrand, H.; Klintenberg, M.

    2013-01-01

    A cylindrical plastic scintillator cell, used for radioxenon monitoring within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, has been coated with 425 nm Al 2 O 3 using low temperature Atomic Layer Deposition, and its performance has been evaluated. The motivation is to reduce the memory effect caused by radioxenon diffusing into the plastic scintillator material during measurements, resulting in an elevated detection limit. Measurements with the coated detector show both energy resolution and efficiency comparable to uncoated detectors, and a memory effect reduction of a factor of 1000. Provided that the quality of the detector is maintained for a longer period of time, Al 2 O 3 coatings are believed to be a viable solution to the memory effect problem in question

  11. Memory effect, resolution, and efficiency measurements of an Al2O3 coated plastic scintillator used for radioxenon detection

    Science.gov (United States)

    Bläckberg, L.; Fritioff, T.; Mårtensson, L.; Nielsen, F.; Ringbom, A.; Sjöstrand, H.; Klintenberg, M.

    2013-06-01

    A cylindrical plastic scintillator cell, used for radioxenon monitoring within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, has been coated with 425 nm Al2O3 using low temperature Atomic Layer Deposition, and its performance has been evaluated. The motivation is to reduce the memory effect caused by radioxenon diffusing into the plastic scintillator material during measurements, resulting in an elevated detection limit. Measurements with the coated detector show both energy resolution and efficiency comparable to uncoated detectors, and a memory effect reduction of a factor of 1000. Provided that the quality of the detector is maintained for a longer period of time, Al2O3 coatings are believed to be a viable solution to the memory effect problem in question.

  12. Severe ionosphere disturbances caused by the sudden response of evening subequatorial ionospheres to geomagnetic storms

    International Nuclear Information System (INIS)

    Tanaka, T.

    1981-01-01

    By monitoring C band beacon signals from geostationary satellites in Japan, we have observed anomalously strong ionospheric scintillations several times during three years from 1978 to 1980. These severe scinitillations occur associated with geomagnetic storms and accompany sudden and intense ionospheric perturbations in the low-latiude region. Through the analysis of these phenomena we have identified a new type of ionospheric disturbances characterized by intensifications of equatorial anomalies and successive severe ionospheric scintillations that extend to the C band range. The events occur only during a limited local time interval after the sunset, when storm time decreases of midlatitude geomagnetic fields in the same meridan take place during the same time interval. From the viewpoint of ionospheric storms, these disturbances precede the occurrence of midlatitude negative phases and storm time depressions of equatorial anomalies to indicate that the cause of the events is different from distrubed thermospheric circulations. The timing and magnitude of substorms at high-latitudes not always correlate with the events. We have concluded that the phenomena are closely related with penetrations toward low-latitudes of electric fields owing to the partial closure of asymmetrical ring currents

  13. BGO as a hybrid scintillator / Cherenkov radiator for cost-effective time-of-flight PET

    Science.gov (United States)

    Brunner, S. E.; Schaart, D. R.

    2017-06-01

    Due to detector developments in the last decade, the time-of-flight (TOF) method is now commonly used to improve the quality of positron emission tomography (PET) images. Clinical TOF-PET systems based on L(Y)SO:Ce crystals and silicon photomultipliers (SiPMs) with coincidence resolving times (CRT) between 325 ps and 400 ps FWHM have recently been developed. Before the introduction of L(Y)SO:Ce, BGO was used in many PET systems. In addition to a lower price, BGO offers a superior attenuation coefficient and a higher photoelectric fraction than L(Y)SO:Ce. However, BGO is generally considered an inferior TOF-PET scintillator. In recent years, TOF-PET detectors based on the Cherenkov effect have been proposed. However, the low Cherenkov photon yield in the order of  ˜10 photons per event complicates energy discrimination-a severe disadvantage in clinical PET. The optical characteristics of BGO, in particular its high transparency down to 310 nm and its high refractive index of  ˜2.15, are expected to make it a good Cherenkov radiator. Here, we study the feasibility of combining event timing based on Cherenkov emission with energy discrimination based on scintillation in BGO, as a potential approach towards a cost-effective TOF-PET detector. Rise time measurements were performed using a time-correlated single photon counting (TCSPC) setup implemented on a digital photon counter (DPC) array, revealing a prompt luminescent component likely to be due to Cherenkov emission. Coincidence timing measurements were performed using BGO crystals with a cross-section of 3 mm  ×  3 mm and five different lengths between 3 mm and 20 mm, coupled to DPC arrays. Non-Gaussian coincidence spectra with a FWHM of 200 ps were obtained with the 27 mm3 BGO cubes, while FWHM values as good as 330 ps were achieved with the 20 mm long crystals. The FWHM value was found to improve with decreasing temperature, while the FWTM value showed the opposite trend.

  14. BGO as a hybrid scintillator / Cherenkov radiator for cost-effective time-of-flight PET.

    Science.gov (United States)

    Brunner, S E; Schaart, D R

    2017-06-07

    Due to detector developments in the last decade, the time-of-flight (TOF) method is now commonly used to improve the quality of positron emission tomography (PET) images. Clinical TOF-PET systems based on L(Y)SO:Ce crystals and silicon photomultipliers (SiPMs) with coincidence resolving times (CRT) between 325 ps and 400 ps FWHM have recently been developed. Before the introduction of L(Y)SO:Ce, BGO was used in many PET systems. In addition to a lower price, BGO offers a superior attenuation coefficient and a higher photoelectric fraction than L(Y)SO:Ce. However, BGO is generally considered an inferior TOF-PET scintillator. In recent years, TOF-PET detectors based on the Cherenkov effect have been proposed. However, the low Cherenkov photon yield in the order of  ∼10 photons per event complicates energy discrimination-a severe disadvantage in clinical PET. The optical characteristics of BGO, in particular its high transparency down to 310 nm and its high refractive index of  ∼2.15, are expected to make it a good Cherenkov radiator. Here, we study the feasibility of combining event timing based on Cherenkov emission with energy discrimination based on scintillation in BGO, as a potential approach towards a cost-effective TOF-PET detector. Rise time measurements were performed using a time-correlated single photon counting (TCSPC) setup implemented on a digital photon counter (DPC) array, revealing a prompt luminescent component likely to be due to Cherenkov emission. Coincidence timing measurements were performed using BGO crystals with a cross-section of 3 mm  ×  3 mm and five different lengths between 3 mm and 20 mm, coupled to DPC arrays. Non-Gaussian coincidence spectra with a FWHM of 200 ps were obtained with the 27 mm 3 BGO cubes, while FWHM values as good as 330 ps were achieved with the 20 mm long crystals. The FWHM value was found to improve with decreasing temperature, while the FWTM value showed the opposite

  15. Liquid scintillation solutions

    International Nuclear Information System (INIS)

    Long, E.C.

    1976-01-01

    The liquid scintillation solution described includes a mixture of: a liquid scintillation solvent, a primary scintillation solute, a secondary scintillation solute, a variety of appreciably different surfactants, and a dissolving and transparency agent. The dissolving and transparency agent is tetrahydrofuran, a cyclic ether. The scintillation solvent is toluene. The primary scintillation solute is PPO, and the secondary scintillation solute is dimethyl POPOP. The variety of appreciably different surfactants is composed of isooctylphenol-polyethoxyethanol and sodium dihexyl sulphosuccinate [fr

  16. A different approach to the analysis of GPS scintillations data

    International Nuclear Information System (INIS)

    Forte, B.; Radicella, S.M.; Ezquer, R.G.

    2001-09-01

    Amplitude scintillations data from GPS have been analyzed. The objective is to estimate the impact of ionospheric scintillations at Satellite-Based Augmentation System (SBAS) Ranging and Integrity Monitoring Station (RIMS) level and at GPS user level. For this purpose a new approach to the problem has been considered. Data have been studied from the point of view of the impact of scintillations on the calculation of VTEC at pierce points and ionospheric grid points. An ionospheric grid of 5 deg. by 5 deg. surface squares has been assumed. From geometrical considerations and taking into account the basic principle to compute VTEC at grid points, with the data analyzed it is shown that very seldom scintillations can affect the calculation of a grid point VTEC. Data from all the RIMS and for the entire GPS satellites network must be analyzed simultaneously to describe a realistic scenario for the impact of scintillations on SBAS. Finally, GPS scintillation data have been analyzed at user level: service availability problems have been encountered. (author)

  17. Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

    Directory of Open Access Journals (Sweden)

    M. M. Echim

    2008-05-01

    Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (ΣP. Here we introduce an ionospheric feedback as the variation of ΣP with the energy flux of precipitating magnetospheric electrons (εem. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φm, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φi (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j|| of the order of tens of μA/m2 in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j|| and εem are higher than in the case of a uniform ΣP. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and ionospheric plasma properties. Brighter arcs are obtained for increased velocity shear in the LLBL; their spatial scale remains virtually unmodified. The field

  18. Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

    Directory of Open Access Journals (Sweden)

    M. M. Echim

    2008-05-01

    Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (ΣP. Here we introduce an ionospheric feedback as the variation of ΣP with the energy flux of precipitating magnetospheric electrons (εem. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φm, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φi (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j|| of the order of tens of μA/m2 in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j|| and εem are higher than in the case of a uniform ΣP. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and

  19. Modeling the UT effect in global distribution of ionospheric electric fields

    DEFF Research Database (Denmark)

    Lukianova, R.; Christiansen, Freddy

    2008-01-01

    A new approach for modeling the global distribution of ionospheric electric potentials utilizing high-precision maps of field-aligned currents (FACs) derived from measurements by the Orsted and Magsat satellites as input to a comprehensive numerical scheme is presented. We simulate the universal ...

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

    International Nuclear Information System (INIS)

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

    1989-01-01

    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 max and h max between ±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 0 F 2 and h 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

  1. November 2003 event: effects on the Earth's ionosphere observed from ground-based ionosonde and GPS data

    Czech Academy of Sciences Publication Activity Database

    Blanch, E.; Altadill, D.; Boška, Josef; Burešová, Dalia; Hernández-Pajares, M.

    2005-01-01

    Roč. 23, - (2005), s. 3027-3034 ISSN 0992-7689 R&D Projects: GA AV ČR 1QS300120506 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere (Mid-latitude ionosphere, Ionospheric Disturbances, Particle Precipitation) Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.450, year: 2005

  2. The variability of Joule heating, and its effects on the ionosphere and thermosphere

    Directory of Open Access Journals (Sweden)

    A. S. Rodger

    2001-07-01

    Full Text Available A considerable fraction of the solar wind energy that crosses the magnetopause ends up in the high-latitude thermosphere-ionosphere system as a result of Joule heating, the consequences of which are very significant and global in nature. Often Joule heating calculations use hourly averages of the electric field, rather than the time-varying electric field. This leads to an underestimation of the heating. In this paper, we determine the magnitude of the underestimation of Joule heating by analysing electric field data from the EISCAT Incoherent Scatter Radar, situated at the 67° E magnetic latitude. We find that the underestimation, using hourly-averaged electric field values, is normally ~20%, with an upper value of about 65%. We find that these values are insensitive to changes in solar flux, magnetic activity and magnetic local time, implying that the electric field fluctuations are linear related to the amplitude of the electric field. Assuming that these changes are representative of the entire auroral oval, we then use a coupled ionosphere-thermosphere model to calculate the local changes these underestimations in the heating rate cause to the neutral temperature, mean molecular mass and meridional wind. The changes in each parameter are of the order of a few percent but they result in a reduction in the peak F-region concentration of ~20% in the summer hemisphere at high latitudes, and about half of this level in the winter hemisphere. We suggest that these calculations could be used to add corrections to modelled values of Joule heating.Key words. Ionosphere (eletric fields and currents; ionospheric disturbances; polar ionosphere

  3. WE-DE-BRA-04: A Cost-Effective Pixelated EPID Scintillator for Enhanced Contrast and DQE

    Energy Technology Data Exchange (ETDEWEB)

    Rottmann, J; Myronakis, M; Hu, Y; Berbeco, R [Brigham and Woman’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA (United States); Shedlock, D; Wang, A; Humber, D; Star-Lack, J [Varian Medical Systems, Palo Alto, CA (United States); Morf, D; Fueglistaller, R [Varian Medical Systems, Daettwil (Switzerland)

    2016-06-15

    Purpose: Beams-eye-view imaging applications such as real-time soft-tissue motion estimation and MV-CBCT are hindered by the inherently low image contrast of electronic portal imaging devices (EPID) currently in clinical use. We investigate a cost effective scintillating glass that provides substantially increased detective quantum efficiency (DQE) and contrast to noise ratio (CNR). Methods: A pixelated scintillator prototype was built from LKH-5 glass. The array is 12mm thick; 42.4×42.4cm2 wide and features 1.51mm pixel pitch with 20µm separation (glue+septa). The LKH-5 array was mounted on the active matrix flat panel imager (AMPFI) of an AS-1200 (Varian) with the GdO2S2:Tb removed. A second AS-1200 was utilized as reference detector. The prototype EPID was characterized in terms of CNR, modulation transfer function (MTF) and DQE. Additionally, the visibility of various fiducial markers typically used in the clinic as well as a realistic 3D-printed lung tumor model was assessed. All items were placed in a 12cm thick solid water phantom. CNR is estimated using a Las Vegas contrast phantom, presampled MTF is estimated using a slanted slit technique and the DQE is calculated from measured normalized noise power spectra (NPS) and the MTF. Results: DQE(0) for the LKH-5 prototype increased by a factor of 8× to about 10%, compared to the AS-1200 equipped with its standard GdO2S2:Tb scintillator. CNR increased by a factor of 5.3×. Due to the pixel size the MTF50 decreased by about 55% to 0.23lp/mm. The visibility of all fiducial markers as well as the tumor model were however markedly improved in comparison to an acquisition with the same parameters using the GdO2S2:Tb scintillator. Conclusion: LKH-5 scintillating glasses allow the cost effective construction of thick pixelated scintillators for portal imaging which can yield a substantial increase in DQE and CNR. Soft tissue and fiducial marker visibility was found to be markedly improved. The project was supported

  4. Atmosphere-Ionosphere Electrodynamic Coupling

    Science.gov (United States)

    Sorokin, V. M.; Chmyrev, V. M.

    Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the formation of plasma density inhomogeneities, the excitation of gamma ray bursts and atmospheric emissions in different spectral bands, the generation of ULF/ELF/VLF electromagnetic waves and plasma turbulence in the ionosphere, the stimulation of radiation belt electron precipitations and the acceleration of ions in the upper ionosphere. The most interesting results of experimental and theoretical studies of these phenomena are discussed below. The ionosphere is subject to the action of the conductive electric current flowing in the atmosphere-ionosphere circuit. We present a physical model of DC electric field and current formation in this circuit. The key element of this model is an external current, which is formed with the occurrence of convective upward transport of charged aerosols and their gravitational sedimentation in the atmosphere. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization and change of electrical conductivity. Variation of conductivity and external current in the lower atmosphere leads to perturbation of the electric current flowing in the global atmosphere-ionosphere circuit and to the associated DC electric field perturbation both on the Earth's surface and in the ionosphere. Description of these processes and some results of the electric field and current calculations are presented below. The seismic-induced electric field perturbations produce noticeable effects in the ionosphere by generating the electromagnetic field and plasma disturbances. We describe the generation mechanisms of such experimentally

  5. GPS phase scintillation and auroral electrojet currents during geomagnetic storms of March 17, 2013 and 2015

    DEFF Research Database (Denmark)

    Prikryl, P.; Ghoddousi-Fard, R.; Viljanen, A.

    2017-01-01

    in the context of solar wind coupling to the magnetosphere-ionosphere system. Phase scintillation is observed at high latitudes by arrays of high-rate GNSS Ionospheric Scintillation and TEC Monitors (GISTMs) and geodetic-quality GPS receivers sampling at 1 Hz. The high-rate GPS receivers are distributed...... in the northern and in the southern high latitudes with sparser coverage. In addition to GPS receivers, the high-latitude ionosphere dynamics is studied using arrays of ground-based instruments including HF radars, ionosondes, riometers, magnetometers, optical imagers as well as particle detectors and ultraviolet...

  6. Scintillating camera

    International Nuclear Information System (INIS)

    Vlasbloem, H.

    1976-01-01

    The invention relates to a scintillating camera and in particular to an apparatus for determining the position coordinates of a light pulse emitting point on the anode of an image intensifier tube which forms part of a scintillating camera, comprising at least three photomultipliers which are positioned to receive light emitted by the anode screen on their photocathodes, circuit means for processing the output voltages of the photomultipliers to derive voltages that are representative of the position coordinates; a pulse-height discriminator circuit adapted to be fed with the sum voltage of the output voltages of the photomultipliers for gating the output of the processing circuit when the amplitude of the sum voltage of the output voltages of the photomultipliers lies in a predetermined amplitude range, and means for compensating the distortion introduced in the image on the anode screen

  7. Scintillator structure

    International Nuclear Information System (INIS)

    Cusano, D.A.; Prener, J.S.

    1979-01-01

    A scintillator structure comprises at least one layer of transparent fused quartz with a phosphor coating on one or both sides adjacent to at least one transparent layer of epoxy resin which directs light from the phosphor to a detector. The phosphor layer may be formed from a powder optionally with a binder, a single crystal or a melt, or by evaporation or sintering. A plurality of multiple layers may be used or the structure tilted for greater absorption. The structure may be surrounded by another such structure optionally operating in cascade with the first. Many phosphors are specified. A scintillator structure comprises phosphor particles dispersed in epoxy resin or copoly imide-silicone and cast in a multi-compartment box with long sides transparent to X-rays and dividers opaque to X-rays. (UK)

  8. Scintillating fibres

    International Nuclear Information System (INIS)

    Nahnhauer, R.

    1990-01-01

    In the search for new detector techniques, scintillating fibre technology has already gained a firm foothold, and is a strong contender for the extreme experimental conditions of tomorrow's machines. Organized by a group from the Institute of High Energy Physics, Berlin-Zeuthen, a workshop held from 3-5 September in the nearby village of Blossin brought together experts from East and West, and from science and industry

  9. Scintillating fibres

    Energy Technology Data Exchange (ETDEWEB)

    Nahnhauer, R. [IHEP Zeuthen (Germany)

    1990-11-15

    In the search for new detector techniques, scintillating fibre technology has already gained a firm foothold, and is a strong contender for the extreme experimental conditions of tomorrow's machines. Organized by a group from the Institute of High Energy Physics, Berlin-Zeuthen, a workshop held from 3-5 September in the nearby village of Blossin brought together experts from East and West, and from science and industry.

  10. Kilometer-Spaced GNSS Array for Ionospheric Irregularity Monitoring

    Science.gov (United States)

    Su, Yang

    This dissertation presents automated, systematic data collection, processing, and analysis methods for studying the spatial-temporal properties of Global Navigation Satellite Systems (GNSS) scintillations produced by ionospheric irregularities at high latitudes using a closely spaced multi-receiver array deployed in the northern auroral zone. The main contributions include 1) automated scintillation monitoring, 2) estimation of drift and anisotropy of the irregularities, 3) error analysis of the drift estimates, and 4) multi-instrument study of the ionosphere. A radio wave propagating through the ionosphere, consisting of ionized plasma, may suffer from rapid signal amplitude and/or phase fluctuations known as scintillation. Caused by non-uniform structures in the ionosphere, intense scintillation can lead to GNSS navigation and high-frequency (HF) communication failures. With specialized GNSS receivers, scintillation can be studied to better understand the structure and dynamics of the ionospheric irregularities, which can be parameterized by altitude, drift motion, anisotropy of the shape, horizontal spatial extent and their time evolution. To study the structuring and motion of ionospheric irregularities at the sub-kilometer scale sizes that produce L-band scintillations, a closely-spaced GNSS array has been established in the auroral zone at Poker Flat Research Range, Alaska to investigate high latitude scintillation and irregularities. Routinely collecting low-rate scintillation statistics, the array database also provides 100 Hz power and phase data for each channel at L1/L2C frequency. In this work, a survey of seasonal and hourly dependence of L1 scintillation events over the course of a year is discussed. To efficiently and systematically study scintillation events, an automated low-rate scintillation detection routine is established and performed for each day by screening the phase scintillation index. The spaced-receiver technique is applied to cross

  11. Multiple scattering effects in fast neutron polarization experiments using high-pressure helium-xenon gas scintillators as analyzers

    International Nuclear Information System (INIS)

    Tornow, W.; Mertens, G.

    1977-01-01

    In order to study multiple scattering effects both in the gas and particularly in the solid materials of high-pressure gas scintillators, two asymmetry experiments have been performed by scattering of 15.6 MeV polarized neutrons from helium contained in stainless steel vessels of different wall thicknesses. A monte Carlo computer code taking into account the polarization dependence of the differential scattering cross sections has been written to simulate the experiments and to calculate corrections for multiple scattering on helium, xenon and the gas containment materials. Besides the asymmetries for the various scattering processes involved, the code yields time-of-flight spectra of the scattered neutrons and pulse height spectra of the helium recoil nuclei in the gas scintillator. The agreement between experimental results and Monte Carlo calculations is satisfactory. (Auth.)

  12. Plastic scintillation dosimetry: Optimal selection of scintillating fibers and scintillators

    International Nuclear Information System (INIS)

    Archambault, Louis; Arsenault, Jean; Gingras, Luc; Sam Beddar, A.; Roy, Rene; Beaulieu, Luc

    2005-01-01

    Scintillation dosimetry is a promising avenue for evaluating dose patterns delivered by intensity-modulated radiation therapy plans or for the small fields involved in stereotactic radiosurgery. However, the increase in signal has been the goal for many authors. In this paper, a comparison is made between plastic scintillating fibers and plastic scintillator. The collection of scintillation light was measured experimentally for four commercial models of scintillating fibers (BCF-12, BCF-60, SCSF-78, SCSF-3HF) and two models of plastic scintillators (BC-400, BC-408). The emission spectra of all six scintillators were obtained by using an optical spectrum analyzer and they were compared with theoretical behavior. For scintillation in the blue region, the signal intensity of a singly clad scintillating fiber (BCF-12) was 120% of that of the plastic scintillator (BC-400). For the multiclad fiber (SCSF-78), the signal reached 144% of that of the plastic scintillator. The intensity of the green scintillating fibers was lower than that of the plastic scintillator: 47% for the singly clad fiber (BCF-60) and 77% for the multiclad fiber (SCSF-3HF). The collected light was studied as a function of the scintillator length and radius for a cylindrical probe. We found that symmetric detectors with nearly the same spatial resolution in each direction (2 mm in diameter by 3 mm in length) could be made with a signal equivalent to those of the more commonly used asymmetric scintillators. With augmentation of the signal-to-noise ratio in consideration, this paper presents a series of comparisons that should provide insight into selection of a scintillator type and volume for development of a medical dosimeter

  13. Effective Solar Indices for Ionospheric Modeling: A Review and a Proposal for a Real-Time Regional IRI

    Science.gov (United States)

    Pignalberi, A.; Pezzopane, M.; Rizzi, R.; Galkin, I.

    2018-01-01

    The first part of this paper reviews methods using effective solar indices to update a background ionospheric model focusing on those employing the Kriging method to perform the spatial interpolation. Then, it proposes a method to update the International Reference Ionosphere (IRI) model through the assimilation of data collected by a European ionosonde network. The method, called International Reference Ionosphere UPdate (IRI UP), that can potentially operate in real time, is mathematically described and validated for the period 9-25 March 2015 (a time window including the well-known St. Patrick storm occurred on 17 March), using IRI and IRI Real Time Assimilative Model (IRTAM) models as the reference. It relies on foF2 and M(3000)F2 ionospheric characteristics, recorded routinely by a network of 12 European ionosonde stations, which are used to calculate for each station effective values of IRI indices IG_{12} and R_{12} (identified as IG_{{12{eff}}} and R_{{12{eff}}}); then, starting from this discrete dataset of values, two-dimensional (2D) maps of IG_{{12{eff}}} and R_{{12{eff}}} are generated through the universal Kriging method. Five variogram models are proposed and tested statistically to select the best performer for each effective index. Then, computed maps of IG_{{12{eff}}} and R_{{12{eff}}} are used in the IRI model to synthesize updated values of foF2 and hmF2. To evaluate the ability of the proposed method to reproduce rapid local changes that are common under disturbed conditions, quality metrics are calculated for two test stations whose measurements were not assimilated in IRI UP, Fairford (51.7°N, 1.5°W) and San Vito (40.6°N, 17.8°E), for IRI, IRI UP, and IRTAM models. The proposed method turns out to be very effective under highly disturbed conditions, with significant improvements of the foF2 representation and noticeable improvements of the hmF2 one. Important improvements have been verified also for quiet and moderately disturbed

  14. The worldwide ionospheric data base

    Science.gov (United States)

    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.

  15. The worldwide ionospheric data base

    International Nuclear Information System (INIS)

    Bilitza, D.

    1989-04-01

    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

  16. Effects of Na co-doping on optical and scintillation properties of Eu:LiCaAlF.sub.6./sub. scintillator single crystals

    Czech Academy of Sciences Publication Activity Database

    Tanaka, Ch.; Yokota, Y.; Kurosawa, S.; Yamaji, A.; Ohashi, Y.; Kamada, K.; Nikl, Martin; Yoshikawa, A.

    2017-01-01

    Roč. 468, Jun (2017), s. 399-402 ISSN 0022-0248 R&D Projects: GA MŠk(CZ) LH14266 Institutional support: RVO:68378271 Keywords : doping * single crystal growth * lithium compounds * scintillator materials Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.751, year: 2016

  17. A STUDY ON THE KOREAN IONOSPHERIC VARIABILITY

    Directory of Open Access Journals (Sweden)

    Seok-Hee Bae

    1992-06-01

    Full Text Available The ionosphere in accordance with solar activity can affect the transmission of radio waves. The effect of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. The present study is based on the Korean ionospheirc data obtained at the AnYang Radio Research Laboratory from January 1985 through October 1989. The data are analyzed to show the daily and the annual variations of the ionosphere. The data are also used to simulate the density distribution of the Korean ionosphere following the Chapman law.

  18. COMPENSATION OF THE IONOSPHERIC EFFECTS ON SAR INTERFEROGRAM BASED ON RANGE SPLIT-SPECTRUM AND AZIMUTH OFFSET METHODS – A CASE STUDY OF YUSHU EARTHQUAKE

    Directory of Open Access Journals (Sweden)

    Y. F. He

    2018-04-01

    Full Text Available InSAR technique can measure the surface deformation with the accuracy of centimeter-level or even millimeter and therefore has been widely used in the deformation monitoring associated with earthquakes, volcanoes, and other geologic process. However, ionospheric irregularities can lead to the wavy fringes in the low frequency SAR interferograms, which disturb the actual information of geophysical processes and thus put severe limitations on ground deformations measurements. In this paper, an application of two common methods, the range split-spectrum and azimuth offset methods are exploited to estimate the contributions of the ionosphere, with the aim to correct ionospheric effects in interferograms. Based on the theoretical analysis and experiment, a performance analysis is conducted to evaluate the efficiency of these two methods. The result indicates that both methods can mitigate the ionospheric effect in SAR interferograms and the range split-spectrum method is more precise than the other one. However, it is also found that the range split-spectrum is easily contaminated by the noise, and the achievable accuracy of the azimuth offset method is limited by the ambiguous integral constant, especially with the strong azimuth variations induced by the ionosphere disturbance.

  19. Climatology of the scintillation onset over southern Brazil

    Science.gov (United States)

    Sousasantos, Jonas; de Oliveira Moraes, Alison; Sobral, José H. A.; Muella, Marcio T. A. H.; de Paula, Eurico R.; Paolini, Rafael S.

    2018-04-01

    This work presents an analysis of the climatology of the onset time of ionospheric scintillations at low latitude over the southern Brazilian territory near the peak of the equatorial ionization anomaly (EIA). Data from L1 frequency GPS receiver located in Cachoeira Paulista (22.4° S, 45.0° W; dip latitude 16.9° S), from September 1998 to November 2014, covering a period between solar cycles 23 and 24, were used in the present analysis of the scintillation onset time. The results show that the start time of the ionospheric scintillation follows a pattern, starting about 40 min earlier, in the months of November and December, when compared to January and February. The analyses presented here show that such temporal behavior seems to be associated with the ionospheric prereversal vertical drift (PRVD) magnitude and time. The influence of solar activity in the percentage of GPS links affected is also addressed together with the respective ionospheric prereversal vertical drift behavior. Based on this climatological study a set of empirical equations is proposed to be used for a GNSS alert about the scintillation prediction. The identification of this kind of pattern may support GNSS applications for aviation and oil extraction maritime stations positioning.

  20. The harmful effects of sintering aids in Pr:LuAG optical ceramic scintillator

    Czech Academy of Sciences Publication Activity Database

    Shen, Y.; Shi, Y.; Feng, X.; Pan, Y.; Li, J.; Zeng, J.-Y.; Nikl, Martin; Krasnikov, A.; Vedda, A.; Moretti, F.

    2012-01-01

    Roč. 95, č. 7 (2012), s. 2130-2132 ISSN 0002-7820 R&D Projects: GA MŠk LH12185 Institutional research plan: CEZ:AV0Z10100521 Keywords : scintillator * optical ceramics * sintering aids * luminescence Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.107, year: 2012

  1. Effect of gamma irradiation on optical properties of Ce 3+ - doped phosphate and silicate scintillating glasses

    Czech Academy of Sciences Publication Activity Database

    Baccaro, S.; Cecilia, A.; Chen, B.; Mareš, Jiří A.; Mihóková, Eva; Nikl, Martin; Polato, P.; Zanella, G.; Zannoni, R.

    2002-01-01

    Roč. 63, - (2002), s. 231-234 ISSN 0969-806X R&D Projects: GA MŠk ME 519 Institutional research plan: CEZ:AV0Z1010914 Keywords : glass scintillator * radiation hardness * colour centres Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.738, year: 2002

  2. Longitudinal effect in the ionospheric plasma density in the evening sector during the magnetic storm on 18-19.12.1978

    International Nuclear Information System (INIS)

    Besprozvannaya, A.S.; Gdalevich, G.L.; Eliseev, A.Yu.; Kolomijtsev, O.P.

    1986-01-01

    The longitidinal effect in the ionospheric plasma density in the evening sector during the magnetic storm on 18-19 December 1978 is investigated. The quantitative confirmation of substantial role of the F2 layer vertical drifts in formation of the ionization level at the height of approximately 500 km is obtained. The observed at these heights plasma density variati ons can be explained by penetration of magnetospheric electrical fields into mean latitudes. It is shown that in case of simulation of disturbance development in the evening sector longitudinal asymmetry in the development of ionospheric disturbance should be taken into account. This effect can provide electron density variations comparable with variations caused by penetration of electrical field of magnetoshperic origin into mean-latitudinal ionosphere

  3. Effects of multiple scatter on the propagation and absorption of electromagnetic waves in a field-aligned-striated cold magneto-plasma: implications for ionospheric modification experiments

    Directory of Open Access Journals (Sweden)

    T. R. Robinson

    Full Text Available A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found that the interaction layer is much broader than the wavelength of the test wave. This is due to the combined electric fields of the scattered waves becoming localised on the contour of a fixed plasma density, which corresponds to a constant value for the local upper-hybrid resonance frequency over the whole interaction region. The results are applied to the calculation of the refractive index of an ordinary mode test wave during modification experiments in the ionospheric F-region. Although strong anomalous absorption arises, no new cutoffs occur at the upper-hybrid resonance, so that in contrast to the predictions of previous single scatter theories, no additional reflections occur there. These results are consistent with observations made during ionospheric modification experiments at Tromsø, Norway.

    Key words. Ionosphere (active experiments; ionospheric irregularities Radio science (ionospheric propagation

  4. Dose rate effects in the radiation damage of the plastic scintillators of the CMS Hadron Endcap Calorimeter

    CERN Document Server

    INSPIRE-00314584

    2016-10-07

    We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.

  5. Ionospheric disturbance dynamo

    International Nuclear Information System (INIS)

    Blanc, M.; Richmond, A.D.

    1980-01-01

    A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes

  6. Sub-nanosecond plastic scintillators

    International Nuclear Information System (INIS)

    Lyons, P.B.; Caldwell, S.E.; Hocker, L.P.; Crandall, D.G.; Zagarino, P.A.; Cheng, J.; Tirsell, G.; Hurlbut, C.R.

    1977-01-01

    Quenched plastic scintillators have been developed that yield much faster short decay components and greatly reduced long decay components compared to conventional plastic scintillators. The plastics are produced through the addition of selected quench agents to NE111 plastic scintillator that result in reduced total light output. Eight different agents have been studied. Benzophenone and piperidine are two of the most effective quench agents. Data are presented both for short and long decay components. The plastics are expected to make significant contributions in areas of plasma diagnostics

  7. Sub-nanosecond plastic scintillators

    International Nuclear Information System (INIS)

    Lyons, P.B.; Caldwell, S.E.; Hocker, L.P.; Crandall, D.G.; Zagarino, P.A.; Cheng, J.; Tirsell, G.; Hurlbut, C.R.

    1976-01-01

    Quenched plastic scintillators have been developed that yield much faster short decay components and greatly reduced long decay components compared to conventional plastic scintillators. The plastics are produced through the addition of selected quench agents to NE111 plastic scintillator that result in reduced total light output. Eight different agents have been studied. Benzophenone and piperidine are two of the most effective quench agents. Data are presented both for short and long decay components. The plastics are expected to make significant contributions in areas of plasma diagnostics

  8. Effects of mid-latitude ionosphere observed from ground-based ionosonde data obtained at Alma-Ata station during strong geomagnetic storms

    International Nuclear Information System (INIS)

    Gordienko, G.I.; Vodynnikov, V.V.; Yakovets, A.E.

    2006-01-01

    The ionospheric effects of fourteen great geomagnetic storms occurred in the 1986-2005 time period observed over Alma-Ata (43.25 N , 76.92 E ) were studied experimentally using ground-based ionosonde. The observations showed a number of unusual (for the Alma-Ata location) ionospheric phenomena during the active phase of geomagnetic storms, along with a negative phase in the ionospheric F2-layer disturbance an anomalous formation of the E, E2, and F1 layers at nighttime, and the appearance of aurora-type sporadic E layers were found. Processes of interaction of energetic neutrals with the upper atmosphere modeled by Bauske et al. (1997) for magnetically distributed condition seem to explain the phenomena of ionization of F1 and E region at night. (author)

  9. Effects of detector-source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors.

    Science.gov (United States)

    Ermis, E E; Celiktas, C

    2012-12-01

    Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. (133)Ba and (207)Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. The role of cerium variable charge state in the luminescence and scintillation mechanism in complex oxide scintillators: the effect of air annealing

    Czech Academy of Sciences Publication Activity Database

    Nikl, Martin; Babin, Vladimir; Mareš, Jiří A.; Kamada, K.; Kurosawa, S.; Yoshikawa, A.; Touš, J.; Houžvička, J.; Blažek, K.

    2016-01-01

    Roč. 169, Jan (2016), s. 539-543 ISSN 0022-2313. [International Conference on Luminescence and Optical Spectroscopy of Condensed Matter /17./. Wroclaw, 13.07.2014-18.07.2014] R&D Projects: GA ČR GA13-09876S; GA TA ČR TA04010135 Institutional support: RVO:68378271 Keywords : scintillator * aluminum garnets * perovskites * air annealing Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.686, year: 2016

  11. Ionospheric effects of earthquakes in Japan in March 2011 obtained from observations of lightning electromagnetic radio signals

    Directory of Open Access Journals (Sweden)

    V. A. Mullayarov

    2012-10-01

    Full Text Available Manifestations of disturbances in the lower ionosphere caused by a complex series of earthquakes (the strong earthquakes with M = 7.3 and M = 9 – known as M9 Tohoku EQ – and the subsequent aftershocks that occurred near the Japanese island of Honshu have been considered with the use of monitoring measurements of the amplitude of lightning electromagnetic signals (atmospherics received at Yakutsk. Some data of one-point lightning location systems have been compared with the data of the WWLLN network.

    The analysis of hourly values variation of the atmospheric amplitude passing over the earthquake epicenters shows that during the initial period (the strong earthquakes on 9 March and 11 March a typical pattern of variations was observed. It was manifested in the increased amplitude after both earthquakes. There were also possible precursors in the form of the increase in amplitude 12–14 days before the events. Though the focuses of these earthquakes were very close to each other, the registration of both precursors may indicate that both of the lithospheric processes developed to a certain extent independently.

    During all the days of the atmospheric amplitude enhancement the quasi-periodic variation trains were recorded. Together with the delay of earthquake effects relative to the time of the events, they may testify in favor of transferring the energy of lithospheric processes into the lower ionosphere by means of atmospheric gravity waves.

  12. Geomagnetic storm effects in ionospheric TEC at an euatorial station: contribution of EXB drifts and meridional neutral winds

    International Nuclear Information System (INIS)

    Dabas, R.S.; Jain, A.R.

    1985-01-01

    Storm-time variations in TEC measurements at the Indian station Ootacamund with IEC data for four stations in the anomaly region. Variations in Nsub(T)(OOTY) are found to be smaller compared to those observed at anomaly stations. The equatorial electrojet control of Nsub(T)(OOTY) is weaker compared to that of Nsub(m)F2. This result and absence of midday biteout in Nsub(T)(OOTY) are interpreted in terms of plasma exchange between ionosphere and plasmasphere which, to some extent, compensates the loss of plasma in the column due to E x B drifts. The anomaly depth is found to be well correlated with the electrojet strength. It is also noticed that for the same anomaly is weaker on a storm day than for quiet days. This is interpreted in terms of converging equatorward meridional winds. Thus, ionosphere-plasmasphere plasma exchange and, during disturbed period, the converging equatorward meridional winds also have significant effects on the distribution of ionization at these latitudes though the E x B drifts are most important in affecting the ionization distribution at low latitudes. (author)

  13. Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A new method, useful for SuperDarn radar

    Science.gov (United States)

    Eisenbeis, J.; Roy, C.; Bland, E. C.; Occhipinti, G.

    2017-12-01

    Most recent methods in ionospheric tomography are based on the inversion of the total electron content measured by ground-based GPS receivers. As a consequence of the high frequency of the GPS signal and the absence of horizontal raypaths, the electron density structure is mainly reconstructed in the F2 region (300 km), where the ionosphere reaches the maximum of ionization, and is not sensitive to the lower ionospheric structure. We propose here a new tomographic method of the lower ionosphere (Roy et al., 2014), based on the full inversion of over-the-horizon (OTH) radar data and applicable to SuperDarn data. The major advantage of our methodology is taking into account, numerically and jointly, the effect that the electron density perturbations induce not only in the speed of electromagnetic waves but also on the raypath geometry. This last point is extremely critical for OTH/SuperDarn data inversions as the emitted signal propagates through the ionosphere between a fixed starting point (the radar) and an unknown end point on the Earth surface where the signal is backscattered. We detail our ionospheric tomography method with the aid of benchmark tests in order to highlight the sensitivity of the radar related to the explored observational parameters: frequencies, elevations, azimuths. Having proved the necessity to take into account both effects simultaneously, we apply our method to real backscattered data from Super Darn and OTH radar. The preliminary solution obtained with the Hokkaido East SuperDARN with only two frequencies (10MHz and 11MHz), showed here, is stable and push us to deeply explore a more complete dataset that we will present at the AGU 2017. This is, in our knowledge, the first time that an ionospheric tomography has been estimated with SuperDarn backscattered data. Reference: Roy, C., G. Occhipinti, L. Boschi, J.-P. Moliné, and M. Wieczorek (2014), Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A

  14. Effects of a mid-latitude solar eclipse on the thermosphere and ionosphere: a modelling study

    OpenAIRE

    Müller-Wodarg, I. C. F.; Aylward, A. D.; Lockwood, Mike

    1998-01-01

    A modelling study is presented which investigates in-situ generated changes of the thermosphere and ionosphere during a solar eclipse. Neutral temperatures are expected to drop by up to 40 degrees K at 240 km height in the totality footprint, with neutral winds of up to 26 m/s responding to the change of pressure. Both temperatures and winds are found to respond with a time lag of 30 min after the passing of the Moon's shadow. A gravity wave is generated in the neutral atmosphere and propagat...

  15. Radiation Damage in Scintillating Crystals

    CERN Document Server

    Zhu Ren Yuan

    1998-01-01

    Crystal Calorimetry in future high energy physics experiments faces a new challenge to maintain its precision in a hostile radiation environment. This paper discusses the effects of radiation damage in scintillating crystals, and concludes that the predominant radiation damage effect in crystal scintillators is the radiation induced absorption, or color center formation, not the loss of the scintillation light yield. The importance of maintaining crystal's light response uniformity and the feasibility to build a precision crystal calorimeter under radiation are elaborated. The mechanism of the radiation damage in scintillating crystals is also discussed. While the damage in alkali halides is found to be caused by the oxygen or hydroxyl contamination, it is the structure defects, such as oxygen vacancies, cause damage in oxides. Material analysis methods used to reach these conclusions are presented in details.

  16. Effects of surface coatings on the light collection in plastic scintillators used for radioxenon detection

    International Nuclear Information System (INIS)

    Bläckberg, L; Klintenberg, M; Sjöstrand, H; Ringbom, A

    2012-01-01

    Atomic layer deposition coatings are under investigation to reduce the diffusion of radioxenon into plastic scintillators. This paper investigates the impact of such surface coating on the light collection efficiency in a cylindrical geometry. A high and uniform light collection efficiency is important to preserve detector resolution. Monte Carlo simulations and measurements have been carried out to study the influence of coating thickness, refractive index and surface quality. It was found that it is important to achieve a smooth coating and good optical match between the refractive indices of the coating and the plastic scintillator. Taking into account these considerations, the detector under study could be coated without a significant degradation of its resolution.

  17. Ionospheric Digital Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The ionosphere is that part of the Earth's atmosphere that results mainly from the photo ionization of the upper atmosphere. Traditionally, the following ionospheric...

  18. Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 10: Towards LET detection: A study on the effects of scintillator doping

    Energy Technology Data Exchange (ETDEWEB)

    Nusrat, Humza; Pang, Geordi; Ahmad, Syed; Keller, Brian; Sarfehnia, Arman [Ryerson University, Sunnybrook Health Sciences Centre (Canada)

    2016-08-15

    Purpose: In radiotherapy, the amount of radiation delivered is determined by optimizing the amount of absorbed dose to the tumor. Dose does not always correlate well with the actual biological effects of radiation. This work seeks to validate the LET-dependence of doped plastic scintillators for use in a radiation beam quality (LET) detector. Methods: The LET spectrum ([Φ]) can be resolved knowing the measured signals of uniquely LET-dependent detectors, [S], and the response of each LET-dependent detector to specific LETs ([R]), through the relation [Φ]=[S][R]{sup −1}. Plastic scintillator response is intrinsically LET dependent and can be varied via doping. Initial prototype consists of plastic scintillator and glass taper coupled to an optical fiber; components are housed in black acrylic, reducing effect of ambient light. In order to determine [R], the light response matrix, GEANT4.10.1 Monte Carlo (MC) was used. To validate MC, measurements were done using high energy electrons (9,12,15MeV) and orthovoltage x-rays (100,250kV); scintillator signal was normalized to dose measured simultaneously. Results: Stopping power was varied by changing particle type/energy; measurements indicated that as stopping power increased from 1.9 to 6.6MeV/cm, detector response increased by 263% (+/−29.2%) for 5%Pb-doped scintillator (155% in MC); 52% (+/−7.8%) increase observed when undoped scintillator was used (49% in MC). 5%Pb-doped discrepancy (100kV x-rays) is being investigated. Conclusions: This work validates that doping effects LET/energy response of scintillators; an effect that can be utilized for construction of an LET detector.

  19. Liquid scintillation solution

    International Nuclear Information System (INIS)

    Long, E.C.

    1977-01-01

    A liquid scintillation solution is described which includes (1) a scintillation solvent (toluene and xylene), (2) a primary scintillation solute (PPO and Butyl PBD), (3) a secondary scintillation solute (POPOP and Dimethyl POPOP), (4) a plurality of substantially different surfactants and (5) a filter dissolving and/or transparentizing agent. 8 claims

  20. Scintillator structure

    International Nuclear Information System (INIS)

    Cusano, D.A.; Swank, R.K.; White, P.J.

    1978-01-01

    Scintillator structures are described in which the phosphor is embedded or suspended in an optically transparent matrix which is selected or adjusted to have an index of refraction which is approximately equal to that of the phosphor at the wavelength of the light emitted by the phosphor. The matrix may be glass, copoly 2-vinyl naphthalene/vinyl toluene or a liquid e.g. Br-naphthalene and optionally CH 3 I, the ratio of components being adjusted to give the desired refractive index. The polymer may be made in situ or a mixture of phosphor and polymer formed e.g. by freeze drying a solution and pulverizing, and then heating. Specified dyes may be used for converting the emitted light to other wavelengths. (author)

  1. Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

    Directory of Open Access Journals (Sweden)

    A. A. Namgaladze

    Full Text Available The seasonal effects in the thermosphere and ionosphere responses to the precipitating electron flux and field-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF By < 0. In the first variant, the model input data for the summer and winter precipitating fluxes and field-aligned currents have been taken as geomagnetically symmetric and equal to those used earlier in the calculations for the equinoctial conditions. It has been found that both ionospheric and thermospheric disturbances are more intensive in the winter cusp region due to the lower conductivity of the winter polar cap ionosphere and correspondingly larger electric field variations leading to the larger Joule heating effects in the ion and neutral gas temperature, ion drag effects in the thermospheric winds and ion drift effects in the F2-region electron concentration. In the second variant, the calculations have been performed for the events of 28–29 January, 1992 when precipitations were weaker but the magnetospheric convection was stronger than in the first variant. Geomagnetically asymmetric input data for the summer and winter precipitating fluxes and field-aligned currents have been taken from the patterns derived by combining data obtained from the satellite, radar and ground magnetometer observations for these events. Calculated patterns of the ionospheric convection and thermospheric circulation have been compared with observations and it has been established that calculated patterns of the ionospheric convection for both winter and summer hemispheres are in a good agreement with the observations. Calculated patterns of the thermospheric circulation are in a good agreement with the average circulation for the Southern (summer Hemisphere obtained

  2. Temperature dependence of plastic scintillators

    Science.gov (United States)

    Peralta, L.

    2018-03-01

    Plastic scintillator detectors have been studied as dosimeters, since they provide a cost-effective alternative to conventional ionization chambers. Several articles have reported undesired response dependencies on beam energy and temperature, which provides the motivation to determine appropriate correction factors. In this work, we studied the light yield temperature dependency of four plastic scintillators, BCF-10, BCF-60, BC-404, RP-200A and two clear fibers, BCF-98 and SK-80. Measurements were made using a 50 kVp X-ray beam to produce the scintillation and/or radioluminescence signal. The 0 to 40 °C temperature range was scanned for each scintillator, and temperature coefficients were obtained.

  3. Upper ionosphere and magnetospheric-ionospheric coupling

    International Nuclear Information System (INIS)

    Manzano, J.R.

    1989-02-01

    After a presentation of the ionospheric physics and of the earth magnetosphere morphology, generation and dynamics, the magnetosphere-ionosphere coupling in quiet and perturbed conditions is discussed. Some summary information about other planetary magnetospheres, particularly Venus and Jupiter magnetospheres, are finally given. 41 refs, 24 figs

  4. Studies of the Origin and Evolution of Ionospheric Irregularities and Their Effects on AF Systems

    Science.gov (United States)

    2008-06-30

    GPS scintillations at the Jica- marca longitude. Figure 5b shows that on this day the TEC depletions have depths smaller than the depletions seen...data source, each of which suffers from its own drawback mentioned above. The Jica- marca data range from about -20 to -60m/s for solar fluxes...zonal F-region plasma drifts over Jica- marca , J. Geophys. Res., 96, 13901,1991. Fejer, B. G, Farley, D. T., Gonzales, C. A., Woodman, R. F, and

  5. Ionospheric control of the magnetosphere: conductance

    Directory of Open Access Journals (Sweden)

    A. J. Ridley

    2004-01-01

    Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function. Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

  6. Ionospheric control of the magnetosphere: conductance

    Directory of Open Access Journals (Sweden)

    A. J. Ridley

    2004-01-01

    Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function.

    Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

  7. Influence of water vapour on the height distribution of positive ions, effective recombination coefficient and ionisation balance in the quiet lower ionosphere

    Directory of Open Access Journals (Sweden)

    V. Barabash

    2014-03-01

    Full Text Available Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO+ and O2+ primary ions (i.e. NO+.H2O and O2+.H2O, respectively, and the channel forming H+(H2On proton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl2+ proton hydrate layer upper border, comprising the NO+(H2On and O2+(H2On hydrated cluster ions, and the Cl1+ hydrate cluster layer lower border, comprising the H+(H2On pure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, αeff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water

  8. Geomagnetic storm effects on the occurrences of ionospheric irregularities over the African equatorial/low-latitude region

    Science.gov (United States)

    Amaechi, P. O.; Oyeyemi, E. O.; Akala, A. O.

    2018-04-01

    The study investigated the effects of intense geomagnetic storms of 2015 on the occurrences of large scale ionospheric irregularities over the African equatorial/low-latitude region. Four major/intense geomagnetic storms of 2015 were analyzed for this study. These storms occurred on 17th March 2015 (-229 nT), 22nd June 2015 (-204 nT), 7th October 2015 (-124 nT), and 20th December 2015 (-170 nT). Total Electron Content (TEC) data obtained from five African Global Navigation Satellite Systems (GNSS) stations, grouped into eastern and western sectors were used to derive the ionospheric irregularities proxy indices, e.g., rate of change of TEC (ROT), ROT index (ROTI) and ROTI daily average (ROTIAVE). These indices were characterized alongside with the disturbance storm time (Dst), the Y component of the Interplanetary Electric Field (IEFy), polar cap (PC) index and the H component of the Earth's magnetic field from ground-based magnetometers. Irregularities manifested in the form of fluctuations in TEC. Prompt penetration of electric field (PPEF) and disturbance dynamo electric field (DDEF) modulated the behaviour of irregularities during the main and recovery phases of the geomagnetic storms. The effect of electric field over both sectors depends on the local time of southward turning of IMF Bz. Consequently, westward electric field inhibited irregularities during the main phase of March and October 2015 geomagnetic storms, while for the June 2015 storm, eastward electric field triggered weak irregularities over the eastern sector. The effect of electric field on irregularities during December 2015 storm was insignificant. During the recovery phase of the storms, westward DDEF suppressed irregularities.

  9. Ionospheric TEC Weather Map Over South America

    Science.gov (United States)

    Takahashi, H.; Wrasse, C. M.; Denardini, C. M.; Pádua, M. B.; de Paula, E. R.; Costa, S. M. A.; Otsuka, Y.; Shiokawa, K.; Monico, J. F. Galera; Ivo, A.; Sant'Anna, N.

    2016-11-01

    Ionospheric weather maps using the total electron content (TEC) monitored by ground-based Global Navigation Satellite Systems (GNSS) receivers over South American continent, TECMAP, have been operationally produced by Instituto Nacional de Pesquisas Espaciais's Space Weather Study and Monitoring Program (Estudo e Monitoramento Brasileiro de Clima Especial) since 2013. In order to cover the whole continent, four GNSS receiver networks, (Rede Brasileiro de Monitoramento Contínuo) RBMC/Brazilian Institute for Geography and Statistics, Low-latitude Ionospheric Sensor Network, International GNSS Service, and Red Argentina de Monitoreo Satelital Continuo, in total 140 sites, have been used. TECMAPs with a time resolution of 10 min are produced in 12 h time delay. Spatial resolution of the map is rather low, varying between 50 and 500 km depending on the density of the observation points. Large day-to-day variabilities of the equatorial ionization anomaly have been observed. Spatial gradient of TEC from the anomaly trough (total electron content unit, 1 TECU = 1016 el m-2 (TECU) 80) causes a large ionospheric range delay in the GNSS positioning system. Ionospheric plasma bubbles, their seeding and development, could be monitored. This plasma density (spatial and temporal) variability causes not only the GNSS-based positioning error but also radio wave scintillations. Monitoring of these phenomena by TEC mapping becomes an important issue for space weather concern for high-technology positioning system and telecommunication.

  10. Storming the Bastille: the effect of electric fields on the ionospheric F-layer

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    2010-04-01

    Full Text Available We discuss different phenomena occurring during ionospheric F-region storms that in principle might be caused by electric fields and point out challenges that must be faced when considering the physical processes at work. We consider the transport of plasma across many degrees of latitude at sub-auroral latitudes, the origin of patches of so-called "storm enhanced density" at high mid-latitudes, and the very high reported heights of the F2 peak at low latitudes. We discuss the role that electric fields might play in changing locally the net production of ionization as well as transporting it. We suggest that the local change in ionization production should be considered as a more important process for producing plasma density enhancements than transport from a more remote source of enhanced density.

  11. Effects of electric field methods on modeling the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics

    Science.gov (United States)

    Yu, Yiqun; Jordanova, Vania K.; Ridley, Aaron J.; Toth, Gabor; Heelis, Roderick

    2017-05-01

    We report a self-consistent electric field coupling between the midlatitude ionospheric electrodynamics and inner magnetosphere dynamics represented in a kinetic ring current model. This implementation in the model features another self-consistency in addition to its already existing self-consistent magnetic field coupling with plasma. The model is therefore named as Ring current-Atmosphere interaction Model with Self-Consistent magnetic (B) and electric (E) fields, or RAM-SCB-E. With this new model, we explore, by comparing with previously employed empirical Weimer potential, the impact of using self-consistent electric fields on the modeling of storm time global electric potential distribution, plasma sheet particle injection, and the subauroral polarization streams (SAPS) which heavily rely on the coupled interplay between the inner magnetosphere and midlatitude ionosphere. We find the following phenomena in the self-consistent model: (1) The spatially localized enhancement of electric field is produced within 2.5 penetration as found in statistical observations. (2) The electric potential contours show more substantial skewing toward the postmidnight than the Weimer potential, suggesting the resistance on the particles from directly injecting toward the low-L region. (3) The proton flux indeed indicates that the plasma sheet inner boundary at the dusk-premidnight sector is located further away from the Earth than in the Weimer potential, and a "tongue" of low-energy protons extends eastward toward the dawn, leading to the Harang reversal. (4) SAPS are reproduced in the subauroral region, and their magnitude and latitudinal width are in reasonable agreement with data.

  12. Effects of detector–source distance and detector bias voltage variations on time resolution of general purpose plastic scintillation detectors

    International Nuclear Information System (INIS)

    Ermis, E.E.; Celiktas, C.

    2012-01-01

    Effects of source-detector distance and the detector bias voltage variations on time resolution of a general purpose plastic scintillation detector such as BC400 were investigated. 133 Ba and 207 Bi calibration sources with and without collimator were used in the present work. Optimum source-detector distance and bias voltage values were determined for the best time resolution by using leading edge timing method. Effect of the collimator usage on time resolution was also investigated. - Highlights: ► Effect of the source-detector distance on time spectra was investigated. ► Effect of the detector bias voltage variations on time spectra was examined. ► Optimum detector–source distance was determined for the best time resolution. ► Optimum detector bias voltage was determined for the best time resolution. ► 133 Ba and 207 Bi radioisotopes were used.

  13. Physical chemical radiation effects in scintillator solutions content PPO and POPOP

    International Nuclear Information System (INIS)

    Fernandes Neto, Jose Mari; Hamada, Margarida Mizue; Duarte, Celina Lopes; Mesquita, Carlos Henrique de

    2005-01-01

    Samples containing PPO (1%, g/mL), diluted in toluene, were irradiated in a 60 Co irradiator (6.46 kGy/h) at different doses. The PPO concentration decay bi-exponentially with the dose, generating the degradation products: benzoic acid, benzamide and benzilic alcohol. The liquid scintillator system was not sensitive to the radiation damage until 20 kGy. Otherwise, the pulse height analysis showed that doses between 30 and 40 kGy generated significant loss of quality of the sensor (scintillating liquid) and the light yield was reduced in half with the dose of (34.04 ± 0.80) kGy. This value was confirmed by the photopeak position analysis that resulted in D1/2 = (31.7 ± 1.4) kGy. The transmittance, at 360 nm, of the irradiated solution decreased exponentially. The compartmental model using five compartments (fast decay PPO, slow decay PPO, benzamide, benzoic acid and benzilic alcohol) was satisfactory to explain the decay of the PPO in its degradation products as a function of the dose. The explanation coefficient r2 = 0.985636 demonstrates that the model was capable to explain 98.6% of the experimental variations. The energies involved in the chemical reactions were w = (0.239 ± 0.031) eV/damage (fast decay) and w (1.834 ± 0.301) eV/damage (slow decay). (author)

  14. Morphology of auroral zone radio wave scintillation

    International Nuclear Information System (INIS)

    Rino, C.L.; Matthews, S.J.

    1980-01-01

    This paper describes the morphology of midnight sector and morning sector auroral zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation activity followed the general pattern of local magnetic activity. The most prominent feature in the nightime data is a localized amplitude and phase scintillation enhancement at the point where the propagation vector lies within an L shell. A geometrical effect due to a dynamic slab of sheetlike structures in the F region is hypothesized as the source of his enhancement. The data have been sorted by magnetic activity, proximity to local midnight, and season. The general features of the data are in agreement with the accepted morphology of auroral zone scintillation

  15. Earth-ionosphere cavity

    International Nuclear Information System (INIS)

    Tran, A.; Polk, C.

    1976-01-01

    To analyze ELF wave propagation in the earth-ionosphere cavity, a flat earth approximation may be derived from the exact equations, which are applicable to the spherical cavity, by introducing a second-order or Debye approximation for the spherical Hankel functions. In the frequency range 3 to 30 Hz, however, the assumed conditions for the Debye approximation are not satisfied. For this reason an exact evaluation of the spherical Hankel functions is used to study the effects of the flat earth approximation on various propagation and resonance parameters. By comparing the resonance equation for a spherical cavity with its flat earth counterpart and by assuming that the surface impedance Z/sub i/ at the upper cavity boundary is known, the relation between the eigenvalue ν and S/sub v/, the sine of the complex angle of incidence at the lower ionosphere boundary, is established as ν(ν + 1) = (kaS/sub v/) 2 . It is also shown that the approximation ν(ν + 1) approximately equals (ν + 1/2) 2 which was used by some authors is not adequate below 30 Hz. Numerical results for both spherical and planar stratification show that (1) planar stratification is adequate for the computation of the lowest three ELF resonance frequencies to within 0.1 Hz; (2) planar stratification will lead to errors in cavity Q and wave attenuation which increase with frequency; (3) computation of resonance frequencies to within 0.1 Hz requires the extension of the lower boundary of the ionosphere to a height where the ratio of conduction current to displacement current, (sigma/ωepsilon 0 ), is less than 0.3; (4) atmospheric conductivity should be considered down to ground level in computing cavity Q and wave attenuation

  16. High efficiency scintillation detectors

    International Nuclear Information System (INIS)

    Noakes, J.E.

    1976-01-01

    A scintillation counter consisting of a scintillation detector, usually a crystal scintillator optically coupled to a photomultiplier tube which converts photons to electrical pulses is described. The photomultiplier pulses are measured to provide information on impinging radiation. In inorganic crystal scintillation detectors to achieve maximum density, optical transparency and uniform activation, it has been necessary heretofore to prepare the scintillator as a single crystal. Crystal pieces fail to give a single composite response. Means are provided herein for obtaining such a response with crystal pieces, such means comprising the combination of crystal pieces and liquid or solid organic scintillator matrices having a cyclic molecular structure favorable to fluorescence. 8 claims, 6 drawing figures

  17. Equatorial Ionospheric Irregularities Study from ROCSAT Data

    Science.gov (United States)

    2017-10-20

    UNLIMITED: PB Public Release 13. SUPPLEMENTARY NOTES 14. ABSTRACT Ionospheric irregularity/scintillation occurrences can be caused by external driving ...Academia Sinica, Taipei, Taiwan e-mail: chliu2@gate.sinica.edu.tw phone :886-3-4227151x34757 CoPI: Shin-Yi Su Institution: National Central...University, Chung-Li, Taiwan e-mail: sysu@csrsr.ncu.edu.tw phone :886-3-4227151x57643 CoPI: Lung-Chi Tsai Institution: National Central University, Chung-Li

  18. Comprehensive Analysis of the Geoeffective Solar Event of 21 June 2015: Effects on the Magnetosphere, Plasmasphere, and Ionosphere Systems

    Science.gov (United States)

    Piersanti, Mirko; Alberti, Tommaso; Bemporad, Alessandro; Berrilli, Francesco; Bruno, Roberto; Capparelli, Vincenzo; Carbone, Vincenzo; Cesaroni, Claudio; Consolini, Giuseppe; Cristaldi, Alice; Del Corpo, Alfredo; Del Moro, Dario; Di Matteo, Simone; Ermolli, Ilaria; Fineschi, Silvano; Giannattasio, Fabio; Giorgi, Fabrizio; Giovannelli, Luca; Guglielmino, Salvatore Luigi; Laurenza, Monica; Lepreti, Fabio; Marcucci, Maria Federica; Martucci, Matteo; Mergè, Matteo; Pezzopane, Michael; Pietropaolo, Ermanno; Romano, Paolo; Sparvoli, Roberta; Spogli, Luca; Stangalini, Marco; Vecchio, Antonio; Vellante, Massimo; Villante, Umberto; Zuccarello, Francesca; Heilig, Balázs; Reda, Jan; Lichtenberger, János

    2017-11-01

    A full-halo coronal mass ejection (CME) left the Sun on 21 June 2015 from active region (AR) NOAA 12371. It encountered Earth on 22 June 2015 and generated a strong geomagnetic storm whose minimum Dst value was -204 nT. The CME was associated with an M2-class flare observed at 01:42 UT, located near disk center (N12 E16). Using satellite data from solar, heliospheric, and magnetospheric missions and ground-based instruments, we performed a comprehensive Sun-to-Earth analysis. In particular, we analyzed the active region evolution using ground-based and satellite instruments (Big Bear Solar Observatory (BBSO), Interface Region Imaging Spectrograph (IRIS), Hinode, Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), covering Hα, EUV, UV, and X-ray data); the AR magnetograms, using data from SDO/ Helioseismic and Magnetic Imager (HMI); the high-energy particle data, using the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) instrument; and the Rome neutron monitor measurements to assess the effects of the interplanetary perturbation on cosmic-ray intensity. We also evaluated the 1 - 8 Å soft X-ray data and the {˜} 1 MHz type III radio burst time-integrated intensity (or fluence) of the flare in order to predict the associated solar energetic particle (SEP) event using the model developed by Laurenza et al. ( Space Weather 7(4), 2009). In addition, using ground-based observations from lower to higher latitudes ( International Real-time Magnetic Observatory Network (INTERMAGNET) and European Quasi-Meridional Magnetometer Array (EMMA)), we reconstructed the ionospheric current system associated with the geomagnetic sudden impulse (SI). Furthermore, Super Dual Auroral Radar Network (SuperDARN) measurements were used to image the global ionospheric polar convection during the SI and during the principal phases of the geomagnetic storm. In addition

  19. Effect of Grid Definition and Data Distribution on Accuracy of Ionospheric Imaging

    Science.gov (United States)

    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

  20. Effects of a solar wind dynamic pressure increase in the magnetosphere and in the ionosphere

    Directory of Open Access Journals (Sweden)

    L. Juusola

    2010-10-01

    Full Text Available On 17 July 2005, an earthward bound north-south oriented magnetic cloud and its sheath were observed by the ACE, SoHO, and Wind solar wind monitors. A steplike increase of the solar wind dynamic pressure during northward interplanetary magnetic field conditions was related to the leading edge of the sheath. A timing analysis between the three spacecraft revealed that this front was not aligned with the GSE y-axis, but had a normal (−0.58,0.82,0. Hence, the first contact with the magnetosphere occurred 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. After the pressure front had impacted the magnetosphere, the magnetopause was perceived first to move inward and then immediately to 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. Coinciding with the inward and subsequent outward motion, the ground-based magnetic field at low latitudes was observed to first strengthen and then weaken. As the magnetopause position stabilised, so did the ground-based magnetic field intensity, settling at a level slightly higher than before the pressure increase. Altogether the magnetopause was moving for about 15 min after its first contact with the front. The high latitude ionospheric signature consisted of two parts: a shorter (few minutes and less intense preliminary part comprised a decrease of AL and a negative variation of PC. A longer (about ten minutes and more intense main part of the signature comprised an increase of AU and a positive variation of PC. Measurements from several ground-based magnetometer networks (210 MM CPMN, CANMOS, CARISMA, GIMA, IMAGE, MACCS, SuperMAG, THEMIS, TGO were used to obtain information on the

  1. Scintillation counting apparatus

    International Nuclear Information System (INIS)

    Noakes, J.E.

    1978-01-01

    Apparatus is described for the accurate measurement of radiation by means of scintillation counters and in particular for the liquid scintillation counting of both soft beta radiation and gamma radiation. Full constructional and operating details are given. (UK)

  2. GNSS monitoring of the ionosphere for Space Weather services

    Science.gov (United States)

    Krankowski, A.; Sieradzki, R.; Zakharenkova, I. E.; Cherniak, I. V.

    2012-04-01

    The International GNSS Service (IGS) Ionosphere Working Group routinely provides the users global ionosphere maps (GIMs) of vertical total electron content (vTEC). The IGS GIMs are provided with spatial resolution of 5.0 degrees x 2.5 degrees in longitude and latitude, respectively. The current temporal resolution is 2 hours, however, 1-hour maps are delivered as a pilot project. There are three types IGS GIMs: the final, rapid and predicted. The latencies of the IGS ionospheric final and rapid products are 10 days and 1 day, respectively. The predicted GIMs are generated for 1 and 2 days in advance. There are four IGS Associate Analysis Centres (IAACs) that provide ionosphere maps computed with independent methodologies using GNSS data. These maps are uploaded to the IGS Ionosphere Combination and Validation Center at the GRL/UWM (Geodynamics Research Laboratory of the University of Warmia and Mazury in Olsztyn, Poland) that produces the IGS official ionospheric products, which are published online via ftp and www. On the other hand, the increasing number of permanently tracking GNSS stations near the North Geomagnetic Pole allow for using satellite observations to detect the ionospheric disturbances at high latitudes with even higher spatial resolution. In the space weather service developed at GRL/UWM, the data from the Arctic stations belonging to IGS/EPN/POLENET networks were used to study TEC fluctuations and scintillations. Since the beginning of 2011, a near real-time service presenting the conditions in the ionosphere have been operational at GRL/UWM www site. The rate of TEC index (ROTI) expressed in TECU/min is used as a measure of TEC fluctuations. The service provides 2-hour maps of the TEC variability. In addition, for each day the daily map of the ionospheric fluctuations as a function geomagnetic local time is also created. This presentation shows the architecture, algorithms, performance and future developments of the IGS GIMs and this new space

  3. Reduction of reabsorption effects in scintillators by employing solutes with large Stokes shifts

    International Nuclear Information System (INIS)

    Harrah, L.A.; Renschler, C.L.

    1986-01-01

    A radiation or high energy particle responsive system is described useful as a scintillator, and comprising, a first component which interacts with the radiation or high energy particle to emit photons in a certain first wavelength range; and at least one additional solute component which absorbs the photons in the first wavelength range and thereupon emits photons in another wavelength range higher than the first range; the improvement wherein at least one of the components absorbs substantially no photons in the wavelength range in which it emits photons, due to large Stokes shift caused by an excited states intramolecular rearrangement, with the proviso that the component having a large Stokes shift is not methyl salicylate or salicyclic acid

  4. High latitude ionospheric structure

    International Nuclear Information System (INIS)

    1984-06-01

    The Earth's ionosphere is an important element in solar-terrestrial energy transfer processes. As a major terrestrial sink for many solar and magnetospheric events, the ionosphere has characteristic features that are traced to such seemingly remote phenomena as solar flares, radiation belt wave-particle interactions and magnetospheric substorms. In considering the multiple of solar-terrestrial plasma interactions, it is important to recognize that the high-latitude ionosphere is not altogether a simple receptor of various energy deposition processes. The high-altitude ionosphere plays an active feedback role by controlling the conductivity at the base of far-reaching magnetic field lines and by providing a plasma source for the magnetosphere. Indeed, the role of the ionosphere during magnetospheric substorms is emerging as a topic for meaningful study in the overall picture of magnetospheric-ionospheric coupling

  5. Periodic and quiescent solar activity effects in the low ionosphere, using SAVNET data

    Science.gov (United States)

    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.

  6. Liquid scintillation solution

    International Nuclear Information System (INIS)

    Long, E.C.

    1976-01-01

    The invention deals with a liquid scintillation solution which contains 1) a scintillation solvent (toluol), 2) a primary scintillation solute (PPO), 3) a secondary scintillation solute (dimethyl POPOP), 4) several surfactants (iso-octyl-phenol polyethoxy-ethanol and sodium di-hexyl sulfosuccinate) essentially different from one another and 5) a filter resolution and/or transparent-making agent (cyclic ether, especially tetrahydrofuran). (HP) [de

  7. Southern European ionospheric TEC maps based on Kriging technique to monitor ionosphere behavior

    Science.gov (United States)

    Rodríguez-Bouza, Marta; Paparini, Claudia; Otero, Xurxo; Herraiz, Miguel; Radicella, Sandro M.; Abe, Oladipo E.; Rodríguez-Caderot, Gracia

    2017-10-01

    Global or regional Maps of the ionospheric Total Electron Content (TEC) are an efficient tool to monitor the delay introduced by the ionosphere in the satellite signals. Ionospheric disturbance periods are of particular interest because these conditions can strongly affect satellite navigation range measurements. This work presents post-processing regional vertical TEC maps over Southern Europe ([35°N-50°N] latitude) obtained by applying Kriging interpolation to GPS derived TEC over more than 100 Global Navigation Satellite System (GNSS) stations. These maps are used to study the behavior of the ionosphere during space weather events and their effects. To validate these maps, hereafter called Southern European Ionospheric Maps (SEIMs), their TEC values have been compared with those obtained from EGNOS Message Server (EMS) and with direct experimental TEC data from GNSS stations. Ionospheric space weather events related to geomagnetic storms of March 17th, 2013, February 19th, 2014 and March 17th, 2015 have been selected. To test the methodology, one period of quiet days has been also analyzed. TEC values obtained by SEIMs in the Ionospheric Grid Points (IGPs) defined by EGNOS are very close to those given by EMS and in the period of major geomagnetic storms the difference does not exceed 6 TEC units. These results confirm the good performance of the technique used for obtaining the SEIMs that can be a useful tool to study the ionosphere behavior during geomagnetic storms and their effects in the region of interest.

  8. Scintillator manufacture at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Mellott, K.; Bross, A.; Pla-Dalmau, A.

    1998-08-01

    A decade of research into plastic scintillation materials at Fermilab is reviewed. Early work with plastic optical fiber fabrication is revisited and recent experiments with large-scale commercial methods for production of bulk scintillator are discussed. Costs for various forms of scintillator are examined and new development goals including cost reduction methods and quality improvement techniques are suggested.

  9. Liquid scintillation measurement. I

    International Nuclear Information System (INIS)

    Rexa, R.; Tykva, R.

    1983-01-01

    The individual components of scintillation solutions and their tasks are listed. Explained briefly is the scintillation process in a liquid scintillator. Factors are discussed which influence this process as are methods applied to supress their influence. They include: ionization quenching, quenching by dilution and concentration, chemical, colour, phase and photon quenching and single-photon events causing an undesirable backgorund. (M.D.)

  10. Scintillation response of organic and inorganic scintillators

    CERN Document Server

    Papadopoulos, L M

    1999-01-01

    A method to evaluate the scintillation response of organic and inorganic scintillators to different heavy ionizing particles is suggested. A function describing the rate of the energy consumed as fluorescence emission is derived, i.e., the differential response with respect to time. This function is then integrated for each ion and scintillator (anthracene, stilbene and CsI(Tl)) to determine scintillation response. The resulting scintillation responses are compared to the previously reported measured responses. Agreement to within 2.5% is observed when these data are normalized to each other. In addition, conclusions regarding the quenching parameter kB dependence on the type of the particle and the computed values of kB for certain ions are included. (author)

  11. GPS phase scintillation at high latitudes during the geomagnetic storm of 17-18 March 2015

    DEFF Research Database (Denmark)

    Prikryl, P.; Ghoddousi-Fard, R.; Weygand, J. M.

    2016-01-01

    The geomagnetic storm of 17–18 March 2015 was caused by the impacts of a coronal mass ejection and a high-speed plasma stream from a coronal hole. The high-latitude ionosphere dynamics is studied using arrays of ground-based instruments including GPS receivers, HF radars, ionosondes, riometers......, and magnetometers. The phase scintillation index is computed for signals sampled at a rate of up to 100 Hz by specialized GPS scintillation receivers supplemented by the phase scintillation proxy index obtained from geodetic-quality GPS data sampled at 1 Hz. In the context of solar wind coupling...... to the magnetosphere-ionosphere system, it is shown that GPS phase scintillation is primarily enhanced in the cusp, the tongue of ionization that is broken into patches drawn into the polar cap from the dayside storm-enhanced plasma density, and in the auroral oval. In this paper we examine the relation between...

  12. 14C measurement: effect of variations in sample preparation and storage on the counting efficiency for 14C using a carbo-sorb/permafluor E+ liquid scintillation cocktail

    International Nuclear Information System (INIS)

    Kramer, S.J.; Milton, G.M.; Repta, C.J.W.

    1995-06-01

    The effect of variations in sample preparation and storage on the counting efficiency for 14 C using a Carbo-Sorb/PermafluorE+ liquid scintillation cocktail has been studied, and optimum conditions are recommended. (author). 2 refs., 2 tabs., 4 figs

  13. Effects of the leakage magnetic field from an analog meter on the response of scintillation survey meters

    International Nuclear Information System (INIS)

    Abe, Toshiaki; Yamamoto, Hisao; Norimura, Toshiyuki; Katase, Akira

    2003-01-01

    Effects of the weak leakage magnetic field are studied on the response of two kinds of scintillation survey meters: an ordinary type for γ-rays and that optimized for the detection of low-energy photons from 125 I. In the presence of the magnetic field, the response of the optimized survey meter decreases to the photons from 125 I, and increases considerably to the background radiations. On the other hand, the response of the ordinary survey meter decreases slightly to both the γ-rays from 131 I and the background radiations. From analysis of the pulse-height spectra for the radiations, such variations of the response are ascribed to the reduction of the amplification factor of photomultiplier tubes by the magnetic field. (author)

  14. The Effect of the Ionosphere on Radiowave Signals and Systems Performance Based on Ionospheric Effects Symposium Held on 1-3 May 1990

    Science.gov (United States)

    1990-05-03

    extensive computer modeling studies were carried out, as summarized in reports and reviews by Croft, 1972; Testud , 1973; Hines, 1974; Yeh and Liu, 1974...1968) and Testud (1972), as a result of some complicated chemistry changes described by Hooke (1968). if the object of the investigation is to...B)l Testud (1972) showed that in addition to the electron density fluctuation, there are other effects complicating the AGW/TID coupling mechanism His

  15. Comparison of analysis techniques by liquid scintillation and Cerenkov Effect for {sup 40}K quantification in aqueous samples; Comparacion de las tecnicas de analisis por centelleo liquido y efecto Cerenkov para la cuantificacion {sup 40}K en muestras acuosas

    Energy Technology Data Exchange (ETDEWEB)

    Miranda C, L.; Davila R, J. I.; Lopez del R, H.; Mireles G, F., E-mail: lilimica20@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2015-09-15

    In this work the counting by liquid scintillation and Cerenkov Effect to quantify {sup 40}K in aqueous samples was used. The performance of both techniques was studied by comparing the response of three commercial liquid scintillation OptiPhase HiSafe 3, Ultima Gold Ab and OptiPhase TriSafe, the vial type and presentation conditions of the sample for counting. In liquid scintillation, the ability to form homogeneous mixtures depended on the ionic strength of the aqueous solutions. The scintillator OptiPhase HiSafe 3 showed a greater charge capacity for solutions with high ionic strength (<3.4), while the scintillator OptiSafe TriSafe no form homogeneous mixtures for solutions of ionic strength higher than 0.3. Counting efficiencies for different proportions of sample and scintillator near 100% for the scintillators OptiSafe HiSafe 3 and Ultima Gold Ab were obtained. In the counting by Cerenkov Effect, the efficiency and sensitivity depended of the vial type; polyethylene vials were more suitable for counting that the glass vials. The sample volume had not significant effect on counting efficiency, obtaining an average value of 44.8% for polyethylene vials and 37.3% for glass vials. Therefore, the liquid scintillation was more efficient and sensitive for the measurement of {sup 40}K in aqueous solutions. (Author)

  16. Induced radioactivity of a GSO scintillator by secondary fragments in carbon ion therapy and its effects on in-beam OpenPET imaging.

    Science.gov (United States)

    Hirano, Yoshiyuki; Nitta, Munetaka; Nishikido, Fumihiko; Yoshida, Eiji; Inadama, Naoko; Yamaya, Taiga

    2016-07-07

    The accumulation of induced radioactivity within in-beam PET scanner scintillators is of concern for its long-term clinical usage in particle therapy. To estimate the effects on OpenPET which we are developing for in-beam PET based on GSOZ (Zi doped Gd2SiO5), we measured the induced radioactivity of GSO activated by secondary fragments in a water phantom irradiation by a (12)C beam with an energy of 290 MeV u(-1). Radioisotopes of Na, Ce, Eu, Gd, Nd, Pm and Tb including positron emitters were observed in the gamma ray spectra of the activated GSO with a high purity Ge detector and their absolute radioactivities were calculated. We used the Monte Carlo simulation platform, Geant4 in which the observed radioactivity was assigned to the scintillators of a precisely reproduced OpenPET and the single and coincidence rates immediately after one treatment and after one-year usage were estimated for the most severe conditions. Comparing the highest coincidence rate originating from the activated scintillators (background) and the expected coincidence rate from an imaging object (signal), we determined the expected signal-to-noise ratio to be more than 7 within 3 min and more than 10 within 1 min from the scan start time. We concluded the effects of scintillator activation and their accumulation on the OpenPET imaging were small and clinical long-term usage of the OpenPET was feasible.

  17. Remote sensing of the ionosphere using satellite radio beacons

    International Nuclear Information System (INIS)

    Davies, Kenneth

    1991-01-01

    Since the launch of Sputnik I in 1957, satellite radio beacons have been used to measure the total electron content of the ionosphere. A review of the role of satellite beacons in studies of the vertical and spatial structure of the total electron content and on the occurrence of plasma irregularities, both of which affect transionospheric radio signals, is presented. Measurements of Faraday rotation and time of flight give information on the topside of the ionosphere and on the protonosphere. Morphological studies show that the slab thickness of the ionosphere depends on the solar index but is approximately independent of geographical location. Scintillation of amplitude, phase, polarization, and angle provide information on plasma irregularity occurrence in space and time. (author). 23 refs., 16 figs ., 4 tabs

  18. The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes

    Directory of Open Access Journals (Sweden)

    E. D. Tereshchenko

    2006-11-01

    Full Text Available Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF transmitter located near Tromsø (Norway. Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers it has been stressed that in the polar ionosphere the thermal self-focusing on striations during ionospheric modification is the main mechanism resulting in the formation of large-scale (hundreds of meters to kilometers nonlinear structures aligned along the geomagnetic field (magnetic zenith effect. It has also been claimed that the maximum effects caused by small-scale (tens of meters irregularities detected in satellite signals are also observed in the direction parallel to the magnetic field. Contrary to those studies, the present paper shows that the maximum in amplitude scintillations does not correspond strictly to the magnetic zenith direction because high latitude drifts typically cause a considerable anisotropy of small-scale irregularities in a plane perpendicular to the geomagnetic field resulting in a deviation of the amplitude-scintillation peak relative to the minimum angle between the line-of-sight to the satellite and direction of the geomagnetic field lines. The variance of the logarithmic relative amplitude fluctuations is considered here, which is a useful quantity in such studies. The experimental values of the variance are compared with model calculations and good agreement has been found. It is also shown from the experimental data that in most of the satellite passes a variance maximum occurs at a minimum in the phase fluctuations indicating that the artificial excitation of large-scale irregularities is minimum when the excitation of small-scale irregularities is maximum.

  19. An Experiment to Prove the Effect of Low-Level Magnetic Fields Resulting from Ionospheric Changes on Humans

    Directory of Open Access Journals (Sweden)

    Hanzelka M.

    2017-02-01

    Full Text Available The investigation presented in the paper was performed in the laboratories of the Department of Theoretical and Experimental Electrical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, between April 22 and June 26, 2014. We examined a homogeneous sample of male and female participants comprising a total of 49 persons aged 19 to 26. The time required for the measurement of psychophysiological parameters corresponded to 19 minutes, encompassing five stages: Basic (5 mins., Color (2 mins., Rest (5 mins., Math (2 mins., and Rest (5 mins.. All the measuring cycles were carried out using a BioGraph Infiniti device (Thought Technology, Ltd.. Generally, the impact of the environment upon living organisms constitutes a crucial problem examined by today’s science. In this context, the present article describes the results of an investigation focused on ionosphere parameter variation and its role in the basic function of the nervous system. The discussed research concentrates on the measurement and detection of changes in the region of very low electromagnetic field frequencies; the authors introduce and verify related theoretical and experimental procedures to define the effects that influence brain activity and the cardiovascular system.

  20. An Experiment to Prove the Effect of Low-Level Magnetic Fields Resulting from Ionospheric Changes on Humans

    Science.gov (United States)

    Hanzelka, M.; Dan, J.; Šlepecky, M.; Holcner, V.; Dohnal, P.; Kadlec, R.

    2017-02-01

    The investigation presented in the paper was performed in the laboratories of the Department of Theoretical and Experimental Electrical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, between April 22 and June 26, 2014. We examined a homogeneous sample of male and female participants comprising a total of 49 persons aged 19 to 26. The time required for the measurement of psychophysiological parameters corresponded to 19 minutes, encompassing five stages: Basic (5 mins.), Color (2 mins.), Rest (5 mins.), Math (2 mins.), and Rest (5 mins.). All the measuring cycles were carried out using a BioGraph Infiniti device (Thought Technology, Ltd.). Generally, the impact of the environment upon living organisms constitutes a crucial problem examined by today's science. In this context, the present article describes the results of an investigation focused on ionosphere parameter variation and its role in the basic function of the nervous system. The discussed research concentrates on the measurement and detection of changes in the region of very low electromagnetic field frequencies; the authors introduce and verify related theoretical and experimental procedures to define the effects that influence brain activity and the cardiovascular system.

  1. Digital liquid-scintillation counting and effective pulse-shape discrimination with artificial neural networks

    International Nuclear Information System (INIS)

    Langrock, Gert; Wiehl, Norbert; Kling, Hans-Otto; Mendel, Matthias; Naehler, Andrea; Tharun, Udo; Eberhardt, Klaus; Trautmann, Norbert; Kratz, Jens Volker

    2015-01-01

    A typical problem in low-level liquid scintillation (LS) counting is the identification of α particles in the presence of a high background of β and γ particles. Especially the occurrence of β-β and β-γ pile-ups may prevent the unambiguous identification of an α signal by commonly used analog electronics. In this case, pulse-shape discrimination (PSD) and pile-up rejection (PUR) units show an insufficient performance. This problem was also observed in own earlier experiments on the chemical behaviour of transactinide elements using the liquid-liquid extraction system SISAK in combination with LS counting. α-particle signals from the decay of the transactinides could not be unambiguously assigned. However, the availability of instruments for the digital recording of LS pulses changes the situation and provides possibilities for new approaches in the treatment of LS pulse shapes. In a SISAK experiment performed at PSI, Villigen, a fast transient recorder, a PC card with oscilloscope characteristics and a sampling rate of 1 giga samples s -1 (1 ns per point), was used for the first time to record LS signals. It turned out, that the recorded signals were predominantly α β-β and β-γ pile up, and fission events. This paper describes the subsequent development and use of artificial neural networks (ANN) based on the method of 'back-propagation of errors' to automatically distinguish between different pulse shapes. Such networks can 'learn' pulse shapes and classify hitherto unknown pulses correctly after a learning period. The results show that ANN in combination with fast digital recording of pulse shapes can be a powerful tool in LS spectrometry even at high background count rates.

  2. Effects of packaging SrI{sub 2}(Eu) scintillator crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sturm, Benjamin W., E-mail: sturm1@llnl.gov [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Cherepy, Nerine J.; Drury, Owen B.; Thelin, Peter A.; Fisher, Scott E.; Payne, Stephen A. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Burger, Arnold [Fisk University, Nashville, TN 37201 (United States); Boatner, Lynn A.; Ramey, Joanne O. [Oak Ridge National Laboratory, Oak Ridge, TN 37830 (United States); Shah, Kanai S.; Hawrami, Rastgo [Radiation Monitoring Devices, Watertown, MA 02472 (United States)

    2011-10-01

    Recent renewed emphasis placed on gamma-ray detectors for national security purposes has motivated researchers to identify and develop new scintillator materials capable of high energy resolution and growable to large sizes. We have discovered that SrI{sub 2}(Eu) has many desirable properties for gamma-ray detection and spectroscopy, including high light yield of {approx}90,000 photons/MeV and excellent light yield proportionality. We have measured <2.7% FWHM at 662 keV with small detectors (<1 cm{sup 3}) in direct contact with a photomultiplier tube, and {approx}3% resolution at 662 keV is obtained for 1 in.{sup 3} crystals. Due to the hygroscopic nature of SrI{sub 2}(Eu), similar to NaI(Tl), proper packaging is required for field use. This work describes a systematic study performed to determine the key factors in the packaging process to optimize performance. These factors include proper polishing of the surface, the geometry of the crystal, reflector materials and windows. A technique based on use of a collimated {sup 137}Cs source was developed to examine light collection uniformity. Employing this technique, we found that when the crystal is packaged properly, the variation in the pulse height at 662 keV from events near the bottom of the crystal compared to those near the top of the crystal could be reduced to <1%. This paper describes the design and engineering of our detector package in order to improve energy resolution of 1 in.{sup 3}-scale SrI{sub 2}(Eu) crystals.

  3. Digital liquid-scintillation counting and effective pulse-shape discrimination with artificial neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Langrock, Gert; Wiehl, Norbert; Kling, Hans-Otto; Mendel, Matthias; Naehler, Andrea; Tharun, Udo; Eberhardt, Klaus; Trautmann, Norbert; Kratz, Jens Volker [Mainz Univ. (Germany). Inst. fuer Kernchemie; Omtvedt, Jon-Petter [Oslo Univ. (Norway). Dept. of Chemistry; Skarnemark, Gunnar [Chalmers Univ. of Technology, Goeteborg (Sweden)

    2015-05-01

    A typical problem in low-level liquid scintillation (LS) counting is the identification of α particles in the presence of a high background of β and γ particles. Especially the occurrence of β-β and β-γ pile-ups may prevent the unambiguous identification of an α signal by commonly used analog electronics. In this case, pulse-shape discrimination (PSD) and pile-up rejection (PUR) units show an insufficient performance. This problem was also observed in own earlier experiments on the chemical behaviour of transactinide elements using the liquid-liquid extraction system SISAK in combination with LS counting. α-particle signals from the decay of the transactinides could not be unambiguously assigned. However, the availability of instruments for the digital recording of LS pulses changes the situation and provides possibilities for new approaches in the treatment of LS pulse shapes. In a SISAK experiment performed at PSI, Villigen, a fast transient recorder, a PC card with oscilloscope characteristics and a sampling rate of 1 giga samples s{sup -1} (1 ns per point), was used for the first time to record LS signals. It turned out, that the recorded signals were predominantly α β-β and β-γ pile up, and fission events. This paper describes the subsequent development and use of artificial neural networks (ANN) based on the method of 'back-propagation of errors' to automatically distinguish between different pulse shapes. Such networks can 'learn' pulse shapes and classify hitherto unknown pulses correctly after a learning period. The results show that ANN in combination with fast digital recording of pulse shapes can be a powerful tool in LS spectrometry even at high background count rates.

  4. Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

    Directory of Open Access Journals (Sweden)

    R. Sridharan

    Full Text Available The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N, India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii significant increase in h' F immediately following the eclipse and (iii distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.

    Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities

  5. Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

    Directory of Open Access Journals (Sweden)

    R. Sridharan

    2002-12-01

    Full Text Available The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N, India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii significant increase in h' F immediately following the eclipse and (iii distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities

  6. Transient Effects in Atmosphere and Ionosphere preceding the two 2015 M7.8 and M7.3 Earthquakes in Nepal

    Science.gov (United States)

    Ouzounov, D.; Pulinets, S. A.; Hernandez-Pajares, M.; Alberto Garcia Rigo, A. G.; Davidenko, D.; Hatzopoulos, N.; Kafatos, M.

    2015-12-01

    The recent M7.8 Nepal earthquake of April 25, 2015 was the largest recorded earthquake event to hit this nation since 1934. We prospectively and retrospectively analyzed the transient variations of three different physical parameters - outgoing earth radiation (OLR), GPS/TEC and the thermodynamic proprieties in the lower atmosphere. These changes characterize the state of the atmosphere and ionosphere several days before the onset of this earthquake. Our preliminary results show that in mid March 2015 a rapid increase of emitted infrared radiation was observed from the satellite data and an anomaly near the epicenter reached the maximum on April 21-22. The ongoing analysis of satellite radiation revealed another transient anomaly on May 3th, probably associated with the M7.3 of May 12, 2015. The analysis of air temperature form ground stations show similar patterns of rapid increases offset 1-2 days earlier to the satellite transient anomalies.The GPS/TEC data indicate an increase and variation in electron density reaching a maximum value during April 22-24. We found a strong negative TEC anomaly in the crest of EIA (Equatorial Ionospheric Anomaly) on April 21st and strong positive on April 24th, 2015. Our results show strong ionospheric effects not only in the changes of the EIA intensity but also within the latitudinal movements of the crests of EIA.

  7. Characterising the Ionosphere (La caracterisation de l’ionosphere)

    Science.gov (United States)

    2009-01-01

    2003; Valdivia , 2003; Tong et al ., 2004). Tidal motions and planetary waves in the thermosphere have significant influence on ionospheric...such as storms, earthquakes and volcanic explosions may produce F2-layer signatures (Rishbeth, 2006 ). Kazimirovsky et al . (2003) have reviewed such...possible effects. Pulinets et al . ( 2006 ) have published a case study of anomalous variations of the total electron content (TEC) registered over the

  8. Effect of seismic activities on ion temperature in the F{sub 2} region of the ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, D.K.; Rai, J. [Department of Physics, Indian Institute of Technology, Roorkee (India); Chand, R.; Israil, M. [Department of Earth Sciences, Indian Institute of Technology, Roorkee (India)]. E-mail: ramesh20june@yahoo.co.in

    2006-01-15

    Ionospheric anomalies related to the seismic events have been analyzed in the present paper. The ionospheric ion temperature data recorded by the Retarded Potential Analyzer (RPA) payload aboard the Indian SROSS-C2 satellite are used for the period from January 1995 to December 1996. Earthquake events recorded in the region of interest from United State Geological Survey (USGS) were used to define the ionospheric ion temperature anomalies associated with the earthquake preparation, occurrence and relaxation. Ionospheric ion temperature data were analyzed in such a way that the anomalies due to other phenomena will not be masked over the temperature anomalies due to earthquakes. Ion temperature enhancements in the ionosphere were observed during earthquake events and few pre-post days to the events. The seismogenic vertical electric field propagation up to ionospheric height induces the Joule heating that may cause the ion temperature enhancement. [Spanish] En este articulo se analizan anomalias ionosfericas relacionadas con eventos sismicos. Se utilizaron los datos de temperatura ionosferica registrados por el Analizador Potencial Retrasado (RPA) del satelite hindu SROSS-C2 para el periodo de enero de 1995 a diciembre de 1996. Para definir las anomalias de la temperatura ionica de la ionosfera asociadas con la preparacion, ocurrencia y relajacion de los eventos sismicos se utilizaron los datos de estos eventos registrados por el Estudio Geologico de Estado Unido (USGS) para la region de interes. Los datos de temperatura ionica fueron analizados de manera que las anomalias debidas a otros fenomenos no enmascararan aquellas relacionadas con los eventos sismicos. La propagacion del campo electrico vertical sismogenico hacia la ionosfera induce el calentamiento joulico que podria causar el incremento de la temperatura ionica.

  9. Distributed sensing of ionospheric irregularities with a GNSS receiver array

    Science.gov (United States)

    Su, Yang; Datta-Barua, Seebany; Bust, Gary S.; Deshpande, Kshitija B.

    2017-08-01

    We present analysis methods for studying the structuring and motion of ionospheric irregularities at the subkilometer scale sizes that produce L band scintillations. Spaced-receiver methods are used for Global Navigation Satellite System (GNSS) receivers' phase measurements over approximately subkilometer to kilometer length baselines for the first time. The quantities estimated by these techniques are plasma drift velocity, diffraction anisotropy magnitude and orientation, and characteristic velocity. Uncertainties are quantified by ensemble simulation of noise on the phase signals carried through to the observations of the spaced-receiver linear system. These covariances are then propagated through to uncertainties on drifts through linearization about the estimated values of the state. Five receivers of SAGA, the Scintillation Auroral Global Positioning System (GPS) Array, provide 100 Hz power and phase data for each channel at L1 frequency. The array is sited in the auroral zone at Poker Flat Research Range, Alaska. A case study of a single scintillating satellite observed by the array is used to demonstrate the spaced-receiver and uncertainty estimation process. A second case study estimates drifts as measured by multiple scintillating channels. These scintillations are correlated with auroral activity, based on all-sky camera images. Measurements and uncertainty estimates made over a 30 min period are compared to a collocated incoherent scatter radar and show good agreement in horizontal drift speed and direction during periods of scintillation for which the characteristic velocity is less than the drift velocity.

  10. Memory effect, resolution, and efficiency measurements of an Al{sub 2}O{sub 3} coated plastic scintillator used for radioxenon detection

    Energy Technology Data Exchange (ETDEWEB)

    Bläckberg, L., E-mail: lisa.blackberg@physics.uu.se [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Fritioff, T.; Mårtensson, L.; Nielsen, F.; Ringbom, A. [Division of Defence and Security Systems, Swedish Defence Research Agency (FOI), SE-17290 Stockholm (Sweden); Sjöstrand, H.; Klintenberg, M. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden)

    2013-06-21

    A cylindrical plastic scintillator cell, used for radioxenon monitoring within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, has been coated with 425 nm Al{sub 2}O{sub 3} using low temperature Atomic Layer Deposition, and its performance has been evaluated. The motivation is to reduce the memory effect caused by radioxenon diffusing into the plastic scintillator material during measurements, resulting in an elevated detection limit. Measurements with the coated detector show both energy resolution and efficiency comparable to uncoated detectors, and a memory effect reduction of a factor of 1000. Provided that the quality of the detector is maintained for a longer period of time, Al{sub 2}O{sub 3} coatings are believed to be a viable solution to the memory effect problem in question.

  11. Shock-resistant scintillation detector

    International Nuclear Information System (INIS)

    Novak, W.P.

    1979-01-01

    A unique scintillation detector unit is disclosed which employs a special light transfer and reflector means that encases and protects the scintillator crystal against high g forces. The light transfer means comprises a flexible silicon rubber optical material bonded between the crystal and the optical window and having an axial thickness sufficient to allow the scintillator to move axially inside the container under high g forces without destroying the bonds. The reflector means comprises a soft elastic silicone rubber sleeve having a multiplicity of closely arranged tapered protrusions radiating toward and engaging the periphery of the scintillator crystal to cushion shocks effectively and having a reflective material, such as aluminum oxide powder, in the spaces between the protrusions. The reflector means provides improved shock absorption because of the uniform support and cushioning action of the protrusions and also provides the detector with high efficiency. The silicon rubber composition is specially compounded to include a large amount of aluminum oxide which enables the rubber to function effectively as a light reflector

  12. Ionospheric phenomena before strong earthquakes

    Directory of Open Access Journals (Sweden)

    A. S. Silina

    2001-01-01

    Full Text Available A statistical analysis of several ionospheric parameters before earthquakes with magnitude M > 5.5 located less than 500 km from an ionospheric vertical sounding station is performed. Ionospheric effects preceding "deep" (depth h > 33 km and "crust" (h 33 km earthquakes were analysed separately. Data of nighttime measurements of the critical frequencies foF2 and foEs, the frequency fbEs and Es-spread at the middle latitude station Dushanbe were used. The frequencies foF2 and fbEs are proportional to the square root of the ionization density at heights of 300 km and 100 km, respectively. It is shown that two days before the earthquakes the values of foF2 averaged over the morning hours (00:00 LT–06:00 LT and of fbEs averaged over the nighttime hours (18:00 LT–06:00 LT decrease; the effect is stronger for the "deep" earthquakes. Analysing the coefficient of semitransparency which characterizes the degree of small-scale turbulence, it was shown that this value increases 1–4 days before "crust" earthquakes, and it does not change before "deep" earthquakes. Studying Es-spread which manifests itself as diffuse Es track on ionograms and characterizes the degree of large-scale turbulence, it was found that the number of Es-spread observations increases 1–3 days before the earthquakes; for "deep" earthquakes the effect is more intensive. Thus it may be concluded that different mechanisms of energy transfer from the region of earthquake preparation to the ionosphere occur for "deep" and "crust" events.

  13. Effects of sporadic E-layer characteristics on spread-F generation in the nighttime midlatitude ionosphere: A climatological study

    Science.gov (United States)

    Lee, C. C.; Chen, W. S.

    2018-04-01

    The aim of this study is to examine the effects of Es-layer characteristics on spread-F generation in the nighttime midlatitude ionosphere. The Es-layer parameters and spread-F appearance of the 23rd solar cycle (1996-2008) are recorded by the Kokubunji ionosonde. The Es-layer parameters are foEs (critical frequency of Es-layer), fbEs (blanketing frequency of Es-layer), and Δf (≡foEs-fbEs). In order to completely explore the effects, the pre-midnight and post-midnight data are classified by seasons, solar activities, and geomagnetic conditions. Results show that the spread-F occurs more frequently in post-midnight and in summer. And, the occurrence probabilities of spread-F are greater, when the solar activity is lower. For the occurrence probabilities of spread-F versus foEs and Δf under geomagnetic quiet-conditions, the trend is increasing, when the associated probabilities are significant. These indicate that the spread-F occurrence increases with increasing foEs and/or Δf. Further, the increasing trends demonstrate that polarization electric fields generated in Es-layer would be helpful to generate spread-F, through the electrodynamical coupling of Es-layer and F-region. Moreover, this electrodynamical coupling is efficient not only under quiet-conditions but under disturbed-conditions, since the significant increasing trend can also be found under disturbed-conditions. Regarding the occurrence probabilities of spread-F versus fbEs, the evident trends are not in the majority. This implies that fbEs might not be a major factor for the spread-F formation.

  14. Global Ionospheric and Thermospheric Effects of the June 2015 Geomagnetic Disturbances : Multi-Instrumental Observations and Modeling

    NARCIS (Netherlands)

    Astafyeva, E; Zakharenkova, I; Huba, J. D.; Doornbos, E.N.; van den IJssel, J.A.A.

    2017-01-01

    By using data from multiple instruments, we investigate ionospheric/thermospheric behavior during the period from 21 to 23 June 2015, when three interplanetary shocks (IS) of different intensities arrived at Earth. The first IS was registered at 16:45 UT on 21 June and caused ~50 nT increase in

  15. Interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from Cluster EDI observations

    Science.gov (United States)

    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.

  16. Electron collision frequency variations and electric fields in the lower ionosphere

    International Nuclear Information System (INIS)

    Gokov, A.M.; Martynenko, S.I.

    1997-01-01

    Distribution of relative variations of the electron effective collision frequency at the ionosphere lower boundary is determined on the basis of analysis of radio-signals partially reflected from the lower ionosphere. Technique to evaluate the strength of electrical fields at the ionosphere lower boundary using experimentally measured variations of the effective frequency of electron collisions is elaborated. 12 refs., 2 figs

  17. GPS phase scintillation during the geomagnetic storm of March 17, 2015: The relation to auroral electrojet currents

    DEFF Research Database (Denmark)

    Prikryl, Paul; Ghoddousi-Fard, Reza; Connors, Martin

    and magnetometers. GPS phase scintillation index is computed for L1 signal sampled at the rate of 50 Hz by specialized GPS scintillation receivers of the Expanded Canadian High Arctic Ionospheric Network (ECHAIN). To further extend the geographic coverage, the phasescintillation proxy index is obtained from......Ionospheric irregularities cause rapid fluctuations of radio wave amplitude and phase that candegrade GPS positional accuracy and affect performance of radio communication and navigation systems. The ionosphere becomes particularly disturbed during geomagnetic storms caused by impacts of coronal...... mass ejections compounded by high-speed plasma streams from coronal holes. Geomagnetic storm of March 17, 2015 was the largest in the current solar cycle. The high-latitude ionosphere dynamics is studied using arrays of ground-based instruments including GPS receivers, HF radars, ionosondes, riometers...

  18. Comparative ionospheres: Terrestrial and giant planets

    Science.gov (United States)

    Mendillo, Michael; Trovato, Jeffrey; Moore, Luke; Müller-Wodarg, Ingo

    2018-03-01

    The study of planetary ionospheres within our solar system offers a variety of settings to probe mechanisms of photo-ionization, chemical loss, and plasma transport. Ionospheres are a minor component of upper atmospheres, and thus their mix of ions observed depends on the neutral gas composition of their parent atmospheres. The same solar irradiance (x-rays and extreme-ultra-violet vs. wavelength) impinges upon each of these atmospheres, with solar flux magnitudes changed only by the inverse square of distance from the Sun. If all planets had the same neutral atmosphere-with ionospheres governed by photochemical equilibrium (production = loss)-their peak electron densities would decrease as the inverse of distance from the Sun, and any changes in solar output would exhibit coherent effects throughout the solar system. Here we examine the outer planet with the most observations of its ionosphere (Saturn) and compare its patterns of electron density with those at Earth under the same-day solar conditions. We show that, while the average magnitudes of the major layers of molecular ions at Earth and Saturn are approximately in accord with distance effects, only minor correlations exist between solar effects and day-to-day electron densities. This is in marked contrast to the strong correlations found between the ionospheres of Earth and Mars. Moreover, the variability observed for Saturn's ionosphere (maximum electron density and total electron content) is much larger than found at Earth and Mars. With solar irradiance changes far too small to cause such effects, we use model results to explore the roles of other agents. We find that water sources from Enceladus at low latitudes, and 'ring rain' at middle latitudes, contribute substantially to variability via water ion chemistry. Thermospheric winds and electrodynamics generated at auroral latitudes are suggested causes of high latitude ionospheric variability, but remain inconclusive due to the lack of relevant

  19. Sudden Ionospheric Disturbances (SID)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sudden ionospheric disturbances (SID) are caused by solar flare enhanced X-rays in the 1 to 10 angstrom range. Solar flares can produce large increases of ionization...

  20. How Interplanetary Scintillation Data Can Improve Modeling of Coronal Mass Ejection Propagation

    Science.gov (United States)

    Taktakishvili, A.; Mays, M. L.; Manoharan, P. K.; Rastaetter, L.; Kuznetsova, M. M.

    2017-12-01

    Coronal mass ejections (CMEs) can have a significant impact on the Earth's magnetosphere-ionosphere system and cause widespread anomalies for satellites from geosynchronous to low-Earth orbit and produce effects such as geomagnetically induced currents. At the NASA/GSFC Community Coordinated Modeling Center we have been using ensemble modeling of CMEs since 2012. In this presnetation we demonstrate that using of interplanetary scintillation (IPS) observations from the Ooty Radio Telescope facility in India can help to track CME propagaion and improve ensemble forecasting of CMEs. The observations of the solar wind density and velocity using IPS from hundreds of distant sources in ensemble modeling of CMEs can be a game-changing improvement of the current state of the art in CME forecasting.

  1. Effect of Gd substitution on structure and spectroscopic properties of (Lu,Gd)2O3:Eu ceramic scintillator

    Science.gov (United States)

    Cao, Maoqing; Hu, Zewang; Ivanov, Maxim; Dai, Jiawei; Li, Chaoyu; Kou, Huamin; Shi, Yun; Chen, Haohong; Xu, Jiayue; Pan, Yubai; Li, Jiang

    2018-02-01

    In this paper, (Lu1-xGdx)2O3:Eu (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) ceramics were consolidated by the solid-state reaction method combined with vacuum sintering without sintering aids. We investigated the effect of the varying contents of Gd2O3 on the structure and spectroscopic properties of (Lu1-xGdx)2O3:Eu ceramics. X-ray diffraction (XRD) patterns indicate that proper amount of Gd2O3 can incorporate well with Lu2O3 and form Lu2O3-Gd2O3 solid solution. However, excessive Gd3+-doping in Lu2O3 will lead to the cubic phase transforming into monoclinic even hexagonal phase. The Gd3+ substitution no more than 50% of Lu2O3 enhances the radioluminescence, and reduces the fluorescence lifetime. Transmittance, photoluminescence, and radiation damage of the (Lu1-xGdx)2O3:Eu scintillation ceramics were also studied.

  2. Effects of film thickness on scintillation characteristics of columnar CsI:Tl films exposed to high gamma radiation doses

    Energy Technology Data Exchange (ETDEWEB)

    Shinde, Seema; Singh, S.G.; Sen, S.; Gadkari, S.C., E-mail: gadkari@barc.gov.in

    2016-02-21

    Oriented columnar films of Tl doped CsI (CsI:Tl) of varying thicknesses from 50 µm to 1000 µm have been deposited on silica glass substrates by a thermal evaporation technique. The SEM micrographs confirmed the columnar structure of the film while the powder X-ray diffraction pattern recorded for the films revealed a preferred orientation of the grown columns along the <200> direction. Effects of high energy gamma exposure up to 1000 Gy on luminescence properties of the films were investigated. Results of radio-luminescence, photo-luminescence and scintillation studies on the films are compared with those of a CsI:Tl single crystal with similar thickness. A possible correlation between the film thicknesses and radiation damage in films has been observed. - Highlights: • CsI:Tl films of different thicknesses deposited for γ and α detection. • Pulse-height spectra found to degrade with increasing thickness. • Radiation damage is found more in films than single crystal of comparable thickness. • Detection efficiency increases for γ while it is invariant for α beyond 50 µm.

  3. Effects of film thickness on scintillation characteristics of columnar CsI:Tl films exposed to high gamma radiation doses

    International Nuclear Information System (INIS)

    Shinde, Seema; Singh, S.G.; Sen, S.; Gadkari, S.C.

    2016-01-01

    Oriented columnar films of Tl doped CsI (CsI:Tl) of varying thicknesses from 50 µm to 1000 µm have been deposited on silica glass substrates by a thermal evaporation technique. The SEM micrographs confirmed the columnar structure of the film while the powder X-ray diffraction pattern recorded for the films revealed a preferred orientation of the grown columns along the direction. Effects of high energy gamma exposure up to 1000 Gy on luminescence properties of the films were investigated. Results of radio-luminescence, photo-luminescence and scintillation studies on the films are compared with those of a CsI:Tl single crystal with similar thickness. A possible correlation between the film thicknesses and radiation damage in films has been observed. - Highlights: • CsI:Tl films of different thicknesses deposited for γ and α detection. • Pulse-height spectra found to degrade with increasing thickness. • Radiation damage is found more in films than single crystal of comparable thickness. • Detection efficiency increases for γ while it is invariant for α beyond 50 µm.

  4. Measurement methods for several properties of scintillator

    International Nuclear Information System (INIS)

    Luo Fengqun; Ji Changsong

    1998-01-01

    The current paper describes the experimental measurement methods for the relative light output, the relative energy conversion efficiency, the intrinsic amplitude resolution and the detection efficiency of the scintillators and their temperature effects

  5. Magnetic field orientations in Saturn's upper ionosphere inferred from Voyager radio occultations

    Science.gov (United States)

    Hinson, D. P.

    1984-01-01

    The radio scintillations observed during occultations of Voyagers 1 and 2 by Saturn are analyzed to determine the morphology of plasma irregularities and hence the magnetic field orientation in Saturn's upper atmosphere. The measurement techniques, the weak scattering theory, and the method used to relate the observed radio scintillations to physical properties of the ionospheric irregularities are briefly described. Results on the spatial characteristics of the irregularities are presented, and the magnetic field orientation in Saturn's ionosphere is inferred. Although the occultation measurements generally confirm the accuracy of the Saturnian magnetic field model of Connerney et al. (1982), it is found that a small adjustment of the coefficients in that model's zonal harmonic expansion would remove the discrepancy between the model predictions and the measurements. A strategy for obtaining improved measurements of Saturn's magnetic field from radio occultation observations of scintillations and Faraday rotation using an orbiting spacecraft is briefly discussed.

  6. Scintillator material. Szintillatormaterial

    Energy Technology Data Exchange (ETDEWEB)

    Siegmund, M; Bendig, J; Regenstein, W

    1987-11-25

    A scintillator material for detection and quantitative determination of ionizing radiation is discussed consisting of an acridone dissolved in a fluid or solid medium. Solvent mixtures with at least one protogenic component or polymers and copolymers are used. The scintillator material is distinguished by an excellent stability at high energy doses.

  7. Measurement of light emission in scintillation vials

    International Nuclear Information System (INIS)

    Duran Ramiro, M. Teresa; Garcia-Torano, Eduardo

    2005-01-01

    The efficiency and energy resolution of liquid scintillation counting (LSC) systems are strongly dependent on the optical characteristics of scintillators, vials, and reflectors. This article presents the results of measurements of the light-emission profile of scintillation vials. Two measurement techniques, autoradiographs and direct measurements with a photomultiplier tube, have been used to obtain light-emission distribution for standard vials of glass, etched glass and polyethylene. Results obtained with both techniques are in good agreement. For the first time, the effect of the meniscus in terms of light contribution has been numerically estimated. These results can help design LSC systems that are more efficient in terms of light collection

  8. Electrodynamics of the Martian Ionosphere

    Science.gov (United States)

    Ledvina, S. A.; Brecht, S. H.

    2017-12-01

    The presence of the Martian crustal magnetic fields makes a significant modification to the interaction between the solar wind/IMF and the ionosphere of the planet. This paper presents the results of 3-D hybrid simulations of Martian solar wind interaction containing the Martian crustal fields., self-consistent ionospheric chemistry and planetary rotation. It has already been reported that the addition of the crustal fields and planetary rotation makes a significant modification of the ionospheric loss from Mars, Brecht et al., 2016. This paper focuses on two other aspects of the interaction, the electric fields and the current systems created by the solar wind interaction. The results of several simulations will be analyzed and compared. The electric fields around Mars due to its interaction with the solar wind will be examined. Special attention will be paid to the electric field constituents (∇ X B, ∇Pe, ηJ). Regions where the electric field is parallel to the magnetic field will be found and the implications of these regions will be discussed. Current systems for each ion species will be shown. Finally the effects on the electric fields and the current systems due to the rotation of Mars will be examined.

  9. Linear energy transfer effects on time profiles of scintillation of Ce-doped LiCaAlF6 crystals

    International Nuclear Information System (INIS)

    Yanagida, Takayuki; Koshimizu, Masanori; Kurashima, Satoshi; Iwamatsu, Kazuhiro; Kimura, Atsushi; Taguchi, Mitsumasa; Fujimoto, Yutaka; Asai, Keisuke

    2015-01-01

    We measured temporal profiles of the scintillation of Ce-doped LiCaAlF 6 scintillator crystals at different linear energy transfers (LETs). Based on the comparison of high-LET temporal profiles with those at low LET, a fast component was observed only at low LET. The disappearance of the fast component at high LET is tentatively ascribed to the quenching of excited states at crystal defects owing to the interaction between excited states via the Auger process. In addition, the rise and the initial decay behavior were dependent on the LET. This LET-dependent behavior is explained by an acceleration process and a deceleration process in energy transfer at high LET. The LET-dependent temporal profiles provide the basis for a discrimination technique of gamma-ray and neutron detection events using these scintillators based on the nuclear reaction, 6 Li(n,α)t.

  10. Coupled storm-time magnetosphere-ionosphere-thermosphere simulations including microscopic ionospheric turbulence

    Science.gov (United States)

    Merkin, V. G.; Wiltberger, M. J.; Zhang, B.; Liu, J.; Wang, W.; Dimant, Y. S.; Oppenheim, M. M.; Lyon, J.

    2017-12-01

    During geomagnetic storms the magnetosphere-ionosphere-thermosphere system becomes activated in ways that are unique to disturbed conditions. This leads to emergence of physical feedback loops that provide tighter coupling between the system elements, often operating across disparate spatial and temporal scales. One such process that has recently received renewed interest is the generation of microscopic ionospheric turbulence in the electrojet regions (electrojet turbulence, ET) that results from strong convective electric fields imposed by the solar wind-magnetosphere interaction. ET leads to anomalous electron heating and generation of non-linear Pedersen current - both of which result in significant increases in effective ionospheric conductances. This, in turn, provides strong non-linear feedback on the magnetosphere. Recently, our group has published two studies aiming at a comprehensive analysis of the global effects of this microscopic process on the magnetosphere-ionosphere-thermosphere system. In one study, ET physics was incorporated in the TIEGCM model of the ionosphere-thermosphere. In the other study, ad hoc corrections to the ionospheric conductances based on ET theory were incorporated in the conductance module of the Lyon-Fedder-Mobarry (LFM) global magnetosphere model. In this presentation, we make the final step toward the full coupling of the microscopic ET physics within our global coupled model including LFM, the Rice Convection Model (RCM) and TIEGCM. To this end, ET effects are incorporated in the TIEGCM model and propagate throughout the system via thus modified TIEGCM conductances. The March 17, 2013 geomagnetic storm is used as a testbed for these fully coupled simulations, and the results of the model are compared with various ionospheric and magnetospheric observatories, including DMSP, AMPERE, and Van Allen Probes. Via these comparisons, we investigate, in particular, the ET effects on the global magnetosphere indicators such as the

  11. Could ionospheric variations be precursors of a seismic event? A short discussion

    Energy Technology Data Exchange (ETDEWEB)

    Kouris, S.S. [Thessaloniki Univ., Thessaloniki (Greece). Dept. of Electrical and Computer Engineering; Spalla, P. [Consiglio Nazionale delle Ricerche, Istituto di Ricerca Onde Elettromagnetiche, Florence (Italy); Zolesi, B. [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy)

    2001-04-01

    A short review of published papers on the perturbations in the ionosphere due to seismogenic effects is reported. The method to correlate different classes of phenomena as ionospheric variations and subsequent seismic events is discussed. Even if the theoretical attempts to understand or to explain the electromagnetic phenomena in the ionosphere, as precursors of earthquakes are not satisfactory, the reported results encourage further investigations.

  12. Structure of the polar ionosphere and convection of magnetospheric plasma outside the plazmapause

    International Nuclear Information System (INIS)

    Mozhaev, A.M.; Osipov, N.K.; AN SSSR, Moscow. Inst. Zemnogo Magnetizma, Ionosfery i Rasprostraneniya Radiovoln)

    1977-01-01

    The effect of large-scale magnetospheric convection on the space structure of high-latitude ionosphere was investigated. Simple analytical models were used. The continuity equation for the electron concentration at a given rate of transfer is solved. It has been found that the formation of the principal structural forms in the ionosphere is associated with the horizontal convective transfer of ionospheric plasma

  13. Bayesian estimation for ionospheric calibration in radio astronomy

    NARCIS (Netherlands)

    Van der Tol, S.

    2009-01-01

    Radio astronomical observations at low frequencies (< 250 MHz), can be severely distorted by fluctuations in electron density in the ionosphere. The free electrons cause a phase change of electromagnetic waves traveling through the ionosphere. This effect increases for lower frequencies. For this

  14. Effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan

    2001-01-01

    Roč. 26, 6, Part C (2001), s. 381-386 ISSN 1464-1917 R&D Projects: GA AV ČR IBS3012007; GA AV ČR IAA3042102; GA MŠk OC 271.10 Institutional research plan: CEZ:AV0Z3042911 Keywords : planetary wave * gravity wave * lower ionosphere Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.399, year: 2001

  15. Use of IRI to Model the Effect of Ionosphere Emission on Earth Remote Sensing at L-Band

    Science.gov (United States)

    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.

  16. Effects of Na and K co-doping on growth and scintillation properties of Eu:SrI_2 crystals

    International Nuclear Information System (INIS)

    Ito, Tomoki; Yokota, Yuui; Kurosawa, Shunsuke; Kral, Robert; Pejchal, Jan; Ohashi, Yuji; Kamada, Kei; Nikl, Martin; Yoshikawa, Akira

    2016-01-01

    We grew Na and K co-doped Eu:SrI_2 [Na,Eu:SrI_2 and K,Eu:SrI_2] crystals by a modified micro-pulling-down method to reveal the co-doping effects on the crystal growth and scintillation properties. The non-codoped, Na0.5%, Na1.0%, K0.5% and K1.0%,Eu:SrI_2 crystals indicated high transparency while the milky parts were generated in the Na5.0% and K5.0%,Eu:SrI_2 crystals. The light yields of Na,Eu:SrI_2 and K,Eu:SrI_2 crystals under γ-ray irradiation were decreased by the Na and K co-doping. On the other hand, there was a small change within 940–1020 ns in the decay times by the Na and K co-doping. In the light yield proportionality under γ-ray irradiation, the non-proportionality in the low energy region was improved by Na and K co-doping. - Highlights: • Na or K co-doped Eu:SrI_2crystals were grown by the modified μ-PD method. • The milky parts were generated in the Na5.0% and K5.0%,Eu:SrI_2crystals. • The light yield of Eu:SrI_2was decreased by the Na or K co-doping. • The decay times of Eu:SrI_2were almost constant by the Na or K co-doping. • The non-proportionalitywas improved in the low energy region by the K co-doping.

  17. A Study on the Radio Propagation in the Korean Ionosphere

    Directory of Open Access Journals (Sweden)

    Seok-Hee Bae

    1992-06-01

    Full Text Available The effects of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. If ionospheric conditions are suitable, the charged particles can remove energy from radio waves and thus attenuate the signal. Also, a radio wave traveling a path along which the electron density is not constant undergoes changes in direction, position and time of propagation. The present study is based on Korean ionospheric data obtained at the AnYong Radio Research Institute from Jan. 1985 through Oct. 1989. The data are used to simulate the Korean ionosphere following the Chapman law. The effects of the model ionosphere on the radio wave propagation, such as the angle, position error, time delay, and the attenuation, are studies for the various cases of the wave frequency and the altitude.

  18. Variation of saturation effect in the ionospheric F2 critical frequency at low latitude

    Science.gov (United States)

    Ikubanni, S. O.; Adeniyi, J. O.

    2013-08-01

    Saturation in the dependence of foF2 on solar flux is a phenomenon more pronounced in the equatorial ionization anomaly region. The phenomenon was observed in the relationship between the F2 critical frequency (foF2) and any solar indices. Using a two-segmented regression fit on data from an African low latitude station (Geographical Latitude 12.4°N; Geomagnetic latitude 3.5°N), saturation features from the dependence of foF2 on solar radio flux (F10.7) was studied. Diurnal and seasonal variation were studied for the first time in this low latitude region of the African sector. Significant variations were observed, especially in the solstices. It was observed that saturation effect is closely related to the hourly F2 critical frequency and these results were compared with those from Asian, Australian and the American sectors. The diurnal and seasonal variations find their explanations in the photo-ionization process, the fountain effect, and the pre-reversal enhancement while the seasonal variation was attributed to both the ion drift and thermospheric circulation. Future work with larger volume of data is expected to validate the observations from this study.

  19. Toward the Probabilistic Forecasting of High-latitude GPS Phase Scintillation

    Science.gov (United States)

    Prikryl, P.; Jayachandran, P.T.; Mushini, S. C.; Richardson, I. G.

    2012-01-01

    The phase scintillation index was obtained from L1 GPS data collected with the Canadian High Arctic Ionospheric Network (CHAIN) during years of extended solar minimum 2008-2010. Phase scintillation occurs predominantly on the dayside in the cusp and in the nightside auroral oval. We set forth a probabilistic forecast method of phase scintillation in the cusp based on the arrival time of either solar wind corotating interaction regions (CIRs) or interplanetary coronal mass ejections (ICMEs). CIRs on the leading edge of high-speed streams (HSS) from coronal holes are known to cause recurrent geomagnetic and ionospheric disturbances that can be forecast one or several solar rotations in advance. Superposed epoch analysis of phase scintillation occurrence showed a sharp increase in scintillation occurrence just after the arrival of high-speed solar wind and a peak associated with weak to moderate CMEs during the solar minimum. Cumulative probability distribution functions for the phase scintillation occurrence in the cusp are obtained from statistical data for days before and after CIR and ICME arrivals. The probability curves are also specified for low and high (below and above median) values of various solar wind plasma parameters. The initial results are used to demonstrate a forecasting technique on two example periods of CIRs and ICMEs.

  20. Ionospheric Caustics in Solar Radio Observations

    Science.gov (United States)

    Koval, A.; Chen, Y.; Stanislavsky, A.

    2016-12-01

    The Earth ionosphere possesses by natural focusing and defocusing effects on radio waves due to presence of variable ionospheric irregularities which could act like convergent and divergent lenses on incident radiation. In particular, the focusing of emission from the Sun was firstly detected on the Nançay Decameter Array dynamic spectra in the 1980s. On time-frequency spectrograms the intensity variations form specific structures different from well-known solar radio bursts and clearly distinguishing on a background of solar radiation. Such structures have been identified as ionospheric caustics (ICs) and considered to be the result of radio waves refraction on medium scale travelling ionospheric disturbances (MSTIDs). Although nowadays the ICs are registered by different radio observatories due to augmentation of low-frequency radio telescopes, the most recent papers devoted to ICs in solar radio records date back to the 1980s. In this study, we revisit the ICs issue with some new results by conducting a statistical analysis of occurrence rate of ICs in solar dynamic spectra in meter-decameter wavelength range for long continuous period (15 years). The seasonal variations in ICs appearance have been found for the first time. Besides, we report the possible solar cycle dependence of ICs emergence. The radio waves propagation in the ionosphere comprising MSTIDs will be considered. The present research renews the subject of ICs in the low-frequency solar radio astronomy after about 35-year letup.

  1. (Alpha-) quenching temperature dependence in liquid scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen, Arnd; Lozza, Valentina; Krosigk, Belina von; Zuber, Kai [Institut fuer Kern- und Teilchenphysik, TU Dresden (Germany)

    2015-07-01

    Liquid scintillator (LS) is an effective and promising detector material, which is and will be used by many small and large scale experiments. In order to perform correct signal identification and background suppression, a very good knowledge of LS properties is crucial. One of those is the light yield from alpha particles in liquid scintillator. This light output strongly quenched, approx. 10 times compared to that of electrons, and has been precisely studied at room temperature for various LS. Big scintillator experiments, such as SNO+ and maybe future large scale detectors, will operate at different temperatures. While a strong temperature dependence is well known for solid state scintillators, due to the different scintillation process, a quenching temperature dependence in LS is usually assumed negligible. On the other hand, inconsistencies in between measurements are often explained by potential temperature effects. This study investigates LAB based liquid scintillator with an intrinsic, dissolved alpha emitter and its behaviour with temperature change. In a small, cooled and heated setup, a stabilized read-out with two PMTs is realised. First results are presented.

  2. Ionospheric topside sounding.

    Science.gov (United States)

    Calvert, W

    1966-10-14

    Over the past few years, the satellite topside sounders have significantly contributed to the understanding of the upper ionosphere. A great quantity of radio echo data has been accumulated, from which the ionospheric electrondensity distribution can be determined. The topside measurements of electron density essentially agree with similar measurements from the ground, except for an occasional 10-percent discrepancy near the peak of the ionosphere. While horizontal non-uniformity is a likely cause, this discrepancy has not yet been adequately explained. The electron-density scale heights measured at a constant altitude indicate both a higher temperature and a heavier mean ion mass at high latitudes. At low latitudes the topside measurements have shown the detailed latitudinal structure of the equatorial anomaly, demonstrating control by the geomagnetic field. A variety of electron-density irregularities have been studied. Most are greatly elongated along the magnetic field, and produce echoes either by lateral scattering, if they are thin, or by longitudinal ducting, if they are thick. Some of the thick irregularities are continuous between the hemispheres and support conjugate echo propagation. The topside sounders have revealed the complex structure of the ionosphere near the auroral zone and at higher latitudes. At night an east-west trough of greatly reduced electron density occurs equatorward of the auroral zone. At the auroral zone itself the electron density is high and quite variable, both in space and time. The electron density at the polar cap within the auroral zone is often uniform and smooth. Ionospheric irregularities are common in the area of the trough and the auroral zone. Among other satellites, the topside sounders have been used in various plasma studies involving the excitation and propagation of waves. These studies suggest that the ionosphere is an appropriate region for future plasma physics investigations, especially with rocket and

  3. Anti-inflamatory effect and objective evaluation of naproxen in osteoarthritis by computerized scintillation scanning

    International Nuclear Information System (INIS)

    Scheinberg, M.A.; Schainberg, H.; Diniz, R.; Nunes, A.P.; Marone, M.; Hasson, R.; Lewin, S.

    1985-01-01

    The anti-inflammatory effect of naproxen, a non-steroidal anti-inflammatory drug, in osteoarthritis was evaluated through subjective clinical and objective computerized scintigraphic scanning parameters. All patients received 1.0g daily of naproxen administered once a day in the morning during six weeks. Twenty patients were evaluated clinically and the results were favourable in 19 (95%) with complete symptoms disappearance in 9 (45%). Sixteen patients were evaluated through the computerized scintilography, and a significant reduction in the articular flow was observed in 11 patients (68.75%). Side effects were few, mild to moderate, the majority related to G.I. tract, and in none patient was necessary treatment interruption. It is concluded that naproxen is a useful agent in the treatment of osteoarthritis and the correspondent inflamation associated with the basic mechanisms of the disease. (author) [pt

  4. Phosphor scintillator structure

    International Nuclear Information System (INIS)

    Cusano, D.A.; Prener, J.S.

    1980-01-01

    A method of fabricating scintillators is described in which the phosphor is distributed within the structure in such a way as to enhance the escape of the visible wavelength radiation that would otherwise be dissipated within the scintillator body. Two embodiments of the present invention are disclosed: one in which the phosphor is distributed in a layered structure and another in which the phosphor is dispersed throughout a transparent matrix. (U.K.)

  5. Real-time volumetric scintillation dosimetry

    International Nuclear Information System (INIS)

    Beddar, S

    2015-01-01

    The goal of this brief review is to review the current status of real-time 3D scintillation dosimetry and what has been done so far in this area. The basic concept is to use a large volume of a scintillator material (liquid or solid) to measure or image the dose distributions from external radiation therapy (RT) beams in three dimensions. In this configuration, the scintillator material fulfills the dual role of being the detector and the phantom material in which the measurements are being performed. In this case, dose perturbations caused by the introduction of a detector within a phantom will not be at issue. All the detector configurations that have been conceived to date used a Charge-Coupled Device (CCD) camera to measure the light produced within the scintillator. In order to accurately measure the scintillation light, one must correct for various optical artefacts that arise as the light propagates from the scintillating centers through the optical chain to the CCD chip. Quenching, defined in its simplest form as a nonlinear response to high-linear energy transfer (LET) charged particles, is one of the disadvantages when such systems are used to measure the absorbed dose from high-LET particles such protons. However, correction methods that restore the linear dose response through the whole proton range have been proven to be effective for both liquid and plastic scintillators. Volumetric scintillation dosimetry has the potential to provide fast, high-resolution and accurate 3D imaging of RT dose distributions. Further research is warranted to optimize the necessary image reconstruction methods and optical corrections needed to achieve its full potential

  6. Ionosphere Waves Service - A demonstration

    Science.gov (United States)

    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.

  7. Theory of imperfect magnetosphere-ionosphere coupling

    International Nuclear Information System (INIS)

    Kan, J.R.; Lee, L.C.

    1980-01-01

    Atheory of magnetosphere-ionosphere coupling in the presence of field-aligned potential drops is formulated within the framework of magnetohydrodynamic equations. Our formulation allows the magnetosphere as well as the ionosphere to respond self-consistently to the parallel potential drop along auroral field lines. Equipotential contours are distorted into a V-shaped structure near the convection reversal boundary and S-shaped on the equatorward side, each gives rise to an inverted V precipitation band. The loading effect of the imperfect coupling results in a valley in the electric field profile which occurs equatorward of the convection reversal boundary

  8. Scintillating properties of frozen new liquid scintillators

    CERN Document Server

    Britvich, G I; Golovkin, S V; Martellotti, G; Medvedkov, A M; Penso, G; Soloviev, A S; Vasilchenko, V G

    1999-01-01

    The light emission from scintillators which are liquid at room temperature was studied in the interval between $+20$~$^{\\circ}$C and $-120$~$^{\\circ}$C, where the phase transition from liquid to solid takes place. The light yield measured at $-120$~$^{\\circ}$C is about twice as much as that observed at $+20$~$^{\\circ}$C. By cooling the scintillator from $+20$~$^{\\circ}$C to $-120$~$^{\\circ}$C and then heating it from $-120$~$^{\\circ}$C to $+20$~$^{\\circ}$C, the light yield varies in steps at well defined temperatures, which are different for the cooling and heating processes. These hysteresis phenomena appear to be related to the solvent rather than to the dopant. The decay time of scintillation light was measured at $+20$~$^{\\circ}$C and $-120$~$^{\\circ}$C. Whilst at room temperature most of the light is emitted with a decay time of 6--8 ns, at $-120$~$^{\\circ}$C a slower component, with a decay time of 25--35 ns, becomes important.

  9. Ionospheric Impacts on UHF Space Surveillance

    Science.gov (United States)

    Jones, J. C.

    2017-12-01

    Earth's atmosphere contains regions of ionized plasma caused by the interaction of highly energetic solar radiation. This region of ionization is called the ionosphere and varies significantly with altitude, latitude, local solar time, season, and solar cycle. Significant ionization begins at about 100 km (E layer) with a peak in the ionization at about 300 km (F2 layer). Above the F2 layer, the atmosphere is mostly ionized but the ion and electron densities are low due to the unavailability of neutral molecules for ionization so the density decreases exponentially with height to well over 1000 km. The gradients of these variations in the ionosphere play a significant role in radio wave propagation. These gradients induce variations in the index of refraction and cause some radio waves to refract. The amount of refraction depends on the magnitude and direction of the electron density gradient and the frequency of the radio wave. The refraction is significant at HF frequencies (3-30 MHz) with decreasing effects toward the UHF (300-3000 MHz) range. UHF is commonly used for tracking of space objects in low Earth orbit (LEO). While ionospheric refraction is small for UHF frequencies, it can cause errors in range, azimuth angle, and elevation angle estimation by ground-based radars tracking space objects. These errors can cause significant errors in precise orbit determinations. For radio waves transiting the ionosphere, it is important to understand and account for these effects. Using a sophisticated radio wave propagation tool suite and an empirical ionospheric model, we calculate the errors induced by the ionosphere in a simulation of a notional space surveillance radar tracking objects in LEO. These errors are analyzed to determine daily, monthly, annual, and solar cycle trends. Corrections to surveillance radar measurements can be adapted from our simulation capability.

  10. Ionospheric earthquake precursors

    International Nuclear Information System (INIS)

    Bulachenko, A.L.; Oraevskij, V.N.; Pokhotelov, O.A.; Sorokin, V.N.; Strakhov, V.N.; Chmyrev, V.M.

    1996-01-01

    Results of experimental study on ionospheric earthquake precursors, program development on processes in the earthquake focus and physical mechanisms of formation of various type precursors are considered. Composition of experimental cosmic system for earthquake precursors monitoring is determined. 36 refs., 5 figs

  11. Ionosphere and Radio Communication

    Indian Academy of Sciences (India)

    The upperionosphere is used for radio communication and navigationas it reflects long, medium, as well as short radio waves. Sincesolar radiation is the main cause of the existence of ionosphere,any variation in the radiations can affect the entireradio communication system. This article attempts to brieflyintroduce the ...

  12. Influence of coma aberration on aperture averaged scintillations in oceanic turbulence

    Science.gov (United States)

    Luo, Yujuan; Ji, Xiaoling; Yu, Hong

    2018-01-01

    The influence of coma aberration on aperture averaged scintillations in oceanic turbulence is studied in detail by using the numerical simulation method. In general, in weak oceanic turbulence, the aperture averaged scintillation can be effectively suppressed by means of the coma aberration, and the aperture averaged scintillation decreases as the coma aberration coefficient increases. However, in moderate and strong oceanic turbulence the influence of coma aberration on aperture averaged scintillations can be ignored. In addition, the aperture averaged scintillation dominated by salinity-induced turbulence is larger than that dominated by temperature-induced turbulence. In particular, it is shown that for coma-aberrated Gaussian beams, the behavior of aperture averaged scintillation index is quite different from the behavior of point scintillation index, and the aperture averaged scintillation index is more suitable for characterizing scintillations in practice.

  13. Effect of crystal shape, size and reflector type on operation characteristics of gamma-radiation detectors based on CsI(Tl) and CsI(Na) scintillators

    International Nuclear Information System (INIS)

    Globus, M.E.; Grinyov, B.V.; Ratner, M.A.

    1996-01-01

    Operation characteristics of CsI(Tl) and CsI(Na) scintillation detectors, to a large degree connected with light collection in crystals, are calculated for various shapes, sizes and reflecting surface types. Allowance is made for the true light reflection indicatrix which is characterized by the effective mirror constituent of the reflected light, p. Its value , averaged over incidence angle, is used for the classification of reflecting surfaces. Operation characteristics (in particular, spectrometric ones) are found to be essentially dependent on . Tables of operation characteristics, given below, permit one to make inferential conclusions on an optimal combination of the shape, sizes an the reflecting surface version

  14. Spatial irregularities in Jupiter's upper ionosphere observed by Voyager radio occultations

    Science.gov (United States)

    Hinson, D. P.; Tyler, G. L.

    1982-01-01

    Radio scintillations (at 3.6 and 13 cm) produced by scattering from ionospheric irregularities during the Voyager occultations are interpreted using a weak-scattering theory. Least squares solutions for ionospheric parameters derived from the observed fluctuation spectra yield estimates of (1) the axial ratio, (2) angular orientation of the anisotropic irregularities, (3) the power law exponent of the spatial spectrum of irregularities, and (4) the magnitude of the spatial variations in electron density. It is shown that the measured angular orientation of the anisotropic irregularities indicates magnetic field direction and may provide a basis for refining Jovian magnetic field models.

  15. Ionospheric modification and parametric instabilities

    International Nuclear Information System (INIS)

    Fejer, J.A.

    1979-01-01

    Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force are also discussed. Stimulated Brillouin and Raman scattering are weakly excited by existing incoherent backscatter radars. The parametric decay instability is strongly excited in ionospheric heating experiments. Saturation theories of the parametric decay instability are therefore described. After a brief discussion of the purely growing instability the effect of using several pumps is discussed as well as the effects of inhomogenicity. Turning to detailed theories of ionospheric heating, artificial spread F is discussed in terms of a purely growing instability where the nonlinearity is due to dissipation. Field-aligned short-scale striations are explained in terms of dissipation of the parametrically excited Langmuir waves (plasma oscillations): they might be further amplified by an explosive instability (except the magnetic equator). Broadband absorption is probably responsible for the 'overshoot' effect: the initially observed level of parametrically excited Langmuir waves is much higher than the steady state level

  16. Report on radiation exposure of lead-scintillator stack

    International Nuclear Information System (INIS)

    Underwood, D.G.

    1990-01-01

    A stack of lead and scintillator was placed in a neutral beam obtained from targeting 800 GeV protons. Small pieces of film containing radiochromic dye were placed adjacent to the layers of scintillator for the purpose of measuring the radiation dose to the scintillator. Our motivation was to calibrate the radiation dose obtainable in this manner for future tests of scintillator for SSC experiments and to relate dose to flux to check absolute normalization for calculations. We also observed several other radiation effects which should be considered for both damage and compensation in a calorimeter

  17. Influence of Ionospheric Irregularities on GNSS Remote Sensing

    Directory of Open Access Journals (Sweden)

    M. V. Tinin

    2015-01-01

    Full Text Available We have used numerical simulation to study the effects of ionospheric irregularities on accuracy of global navigation satellite system (GNSS measurements, using ionosphere-free (in atmospheric research and geometry-free (in ionospheric research dual-frequency phase combinations. It is known that elimination of these effects from multifrequency GNSS measurements is handi-capped by diffraction effects during signal propagation through turbulent ionospheric plasma with the inner scale being smaller than the Fresnel radius. We demonstrated the possibility of reducing the residual ionospheric error in dual-frequency GNSS remote sensing in ionosphere-free combination by Fresnel inversion. The inversion parameter, the distance to the virtual screen, may be selected from the minimum of amplitude fluctuations. This suggests the possibility of improving the accuracy of GNSS remote sensing in meteorology. In the study of ionospheric disturbances with the aid of geometry-free combination, the Fresnel inversion eliminates only the third-order error. To eliminate the random TEC component which, like the measured average TEC, is the first-order correction, we should use temporal filtering (averaging.

  18. Experimental observations of the spatial structure of wave-like disturbances generated in midlatitude ionosphere by high power radio waves

    Science.gov (United States)

    Kunitsyn, V.; Andreeva, E.; Padokhin, A. M.; Nazarenko, M.; Frolov, V.; Komrakov, G.; Bolotin, I.

    2012-12-01

    We present the results of the experiments carried out in 2009-2012 on the Sura heating facility (Radio Physical Research Institute, N. Novgorod, Russia) on modification of the midlatitude ionosphere by powerful HF radiowaves. The experiments were conducted using O-mode radiowaves at frequencies lower than critical frequency of the ionospheric F2 layer both in daytime and nighttime ionosphere. Various schemes of the radiation of the heating wave were used including square wave modulation of the effective radiated power (ERP) at various frequencies and power stepping. Radio transmissions of the low- (Parus/Tsikada) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. The variations in the slant total electron content (TEC), which are proportional to the reduced phase of navigational signals, were studied for the satellite passes for which ionospheric penetration points crossed the disturbed area during HF heating. The variations in TEC caused by HF heating are identified in a number of examples. It is shown that the GNSS TEC spectra contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. Different behavior of TEC variations was observed during nighttime and daytime heating experiments. In daytime conditions the pump wave switched ON causes the increase of TEC while in the nighttime it causes a decrease in TEC. This can be explained by the different contribution of the processes responsible for the increase and decrease of TEC in daytime in nighttime conditions. In this work we also present the first time radiotomographic reconstructions of the spatial structure of the wave-like disturbances, generated in the ionosphere by high-power radio waves radiated by the Sura heater

  19. Observed and modelled effects of auroral precipitation on the thermal ionospheric plasma: comparing the MICA and Cascades2 sounding rocket events

    Science.gov (United States)

    Lynch, K. A.; Gayetsky, L.; Fernandes, P. A.; Zettergren, M. D.; Lessard, M.; Cohen, I. J.; Hampton, D. L.; Ahrns, J.; Hysell, D. L.; Powell, S.; Miceli, R. J.; Moen, J. I.; Bekkeng, T.

    2012-12-01

    Auroral precipitation can modify the ionospheric thermal plasma through a variety of processes. We examine and compare the events seen by two recent auroral sounding rockets carrying in situ thermal plasma instrumentation. The Cascades2 sounding rocket (March 2009, Poker Flat Research Range) traversed a pre-midnight poleward boundary intensification (PBI) event distinguished by a stationary Alfvenic curtain of field-aligned precipitation. The MICA sounding rocket (February 2012, Poker Flat Research Range) traveled through irregular precipitation following the passage of a strong westward-travelling surge. Previous modelling of the ionospheric effects of auroral precipitation used a one-dimensional model, TRANSCAR, which had a simplified treatment of electric fields and did not have the benefit of in situ thermal plasma data. This new study uses a new two-dimensional model which self-consistently calculates electric fields to explore both spatial and temporal effects, and compares to thermal plasma observations. A rigorous understanding of the ambient thermal plasma parameters and their effects on the local spacecraft sheath and charging, is required for quantitative interpretation of in situ thermal plasma observations. To complement this TRANSCAR analysis we therefore require a reliable means of interpreting in situ thermal plasma observation. This interpretation depends upon a rigorous plasma sheath model since the ambient ion energy is on the order of the spacecraft's sheath energy. A self-consistent PIC model is used to model the spacecraft sheath, and a test-particle approach then predicts the detector response for a given plasma environment. The model parameters are then modified until agreement is found with the in situ data. We find that for some situations, the thermal plasma parameters are strongly driven by the precipitation at the observation time. For other situations, the previous history of the precipitation at that position can have a stronger

  20. Space-polarization Collaborative Suppression Method for Ionospheric Clutter in HFSWR

    Directory of Open Access Journals (Sweden)

    Yang Yunlong

    2016-12-01

    Full Text Available High Frequency Surface Wave Radar (HFSWR is able to receive surface target and low-flying aircraft echoes at a long-distance, but it suffers severely from ionospheric clutter. In this paper, a spacepolarization collaborative-based filter is introduced to mitigate ionospheric clutter. For parameter estimation on ionospheric clutter used for filters, a spatial parameter estimation algorithm based on compressive sensing is introduced to the DOA estimation of ionospheric clutter. In addition, a polarized parameter estimation algorithm based on statistical characteristics is proposed for ionospheric clutter in the range-Doppler spectrum. Higher estimation accuracy is achieved as a result of the range-Doppler spectrum; therefore, these two estimation algorithms enhance the performance of the space-polarization collaborative suppression method for ionospheric clutter. Experimental results of practical dual-polarized HFSWR data show the effectiveness of the two algorithms and the above mentioned filter for ionospheric clutter suppression.

  1. Inorganic liquid scintillator

    International Nuclear Information System (INIS)

    Pavlicek, Z.; Barta, C.; Jursova, L.

    1986-01-01

    An inorganic liquid scintillator is designed which contains 1 to 30 wt.% of an inorganic molecular compound as the basic active component; the compound contains a cation with an atomic number higher than 47 and a halogen anion. The basic inorganic component is dissolved in water or in an organic solvent in form of non-dissociated molecules or self-complexes in which the bond is preserved between the cation and anion components. The light yield from these scintillators ranges between 70 and 150% of the light yield of a standard organic scintillator based on toluene. They are advantageous in that that they allow to increase the water content in the sample to up to 100%. (M.D.)

  2. Physics of scintillation detectors

    International Nuclear Information System (INIS)

    Novotny, R.

    1991-01-01

    The general concept of a radiation detector is based on three fundamental principles: sensitivity of the device to the radiation of interest which requires a large cross-section in the detector material, detector response function to the physical properties of the radiation. As an example, a scintillation detector for charged particles should allow to identify the charge of the particle, its kinetic energy and the time of impact combined with optimum resolutions. Optimum conversion of the detector response (like luminescence of a scintillator) into electronical signals for further processing. The following article will concentrate on the various aspects of the first two listed principles as far as they appear to be relevant for photon and charged particle detection using organic and inorganic scintillation detectors. (orig.)

  3. Scintillator plate calorimetry

    International Nuclear Information System (INIS)

    Price, L.E.

    1990-01-01

    Calorimetry using scintillator plates or tiles alternated with sheets of (usually heavy) passive absorber has been proven over multiple generations of collider detectors. Recent detectors including UA1, CDF, and ZEUS have shown good results from such calorimeters. The advantages offered by scintillator calorimetry for the SSC environment, in particular, are speed (<10 nsec), excellent energy resolution, low noise, and ease of achieving compensation and hence linearity. On the negative side of the ledger can be placed the historical sensitivity of plastic scintillators to radiation damage, the possibility of nonuniform response because of light attenuation, and the presence of cracks for light collection via wavelength shifting plastic (traditionally in sheet form). This approach to calorimetry is being investigated for SSC use by a collaboration of Ames Laboratory/Iowa State University, Argonne National Laboratory, Bicron Corporation, Florida State University, Louisiana State University, University of Mississippi, Oak Ridge National Laboratory, Virginia Polytechnic Institute and State University, Westinghouse Electric Corporation, and University of Wisconsin

  4. Alkali earth co-doping effects on luminescence and scintillation properties of Ce doped Gd.sub.3./sub.Al.sub.2./sub.Ga.sub.3./sub.O.sub.12./sub. scintillator

    Czech Academy of Sciences Publication Activity Database

    Kamada, K.; Nikl, Martin; Kurosawa, S.; Beitlerová, Alena; Nagura, A.; Shoji, Y.; Pejchal, Jan; Ohashi, Y.; Yokota, Y.; Yoshikawa, A.

    2015-01-01

    Roč. 41, Mar SI (2015), s. 63-66 ISSN 0925-3467 R&D Projects: GA MŠk(CZ) LH14266 EU Projects: European Commission(XE) 316906 - LUMINET Institutional support: RVO:68378271 Keywords : scintillator * garnet * single crystal growth Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.183, year: 2015

  5. Study on determination of 90Sr by liquid scintillation spectrometry

    International Nuclear Information System (INIS)

    Zhai Xiufang; Li Weiping; Tian Mei; Zou Ronghu

    2012-01-01

    Both of Liquid scintillation counting and Cerenkov counting can be used to determinate 90 Sr in samples by Liquid scintillation spectrometry. In this work, effects of scintillation vials wit-h different material, Liquid scintillation cocktails, sample volume, Strontium carrier, pH, quenching (chemical quenching and color quenching)are studied, and both counting methods are compared. For Liquid scintillation counting. The results show that the best appropriate volume ratio of sample and liquid scintillation cocktail is 8:12 for OPTIPHASE HISAFE-3 and OPTIPHASE HISAFE-2, stability of solution decreased when sample load exceeds the maximum load for both Liquid scintillation cocktails, and OPTIPHASE HISAFE-3 also show superior performance for high saline solution. The type of scintillation vial haven't clear influence on the MDA of 90 Sr. Chemical quenching and color quenching can decrease the counting efficiency. For Cerenkov counting, the lowest MDA is obtained when polyethylene plastic vial is used and sample volume is 20 ml. Color quenching decreases the counting efficiency, while there isn't chemical quenching for Cerenkov counting. The MDA of 90 Sr is 1.19 and 1.00 Bq/L for Liquid scintillation counting and Cerenkov counting with the optimal labeling condition. (authors)

  6. Scintillation proximity assay

    International Nuclear Information System (INIS)

    Hart, H.

    1980-01-01

    In a method of immunological assay two different classes of particles which interact at short distances to produce characteristic detectable signals are employed in a modification of the usual latex fixation test. In one embodiment an aqueous suspension of antigen coated tritiated latex particles (LH) and antigen coated polystyrene scintillant particles (L*) is employed to assay antibody in the aqueous medium. The amount of (LH) (L*) dimer formation and higher order aggregation induced and therefore the concentration of antibody (or antigen) present which caused the aggregation can be determined by using standard liquid scintillation counting equipment. (author)

  7. Microfluidic Scintillation Detectors

    CERN Multimedia

    Microfluidic scintillation detectors are devices of recent introduction for the detection of high energy particles, developed within the EP-DT group at CERN. Most of the interest for such technology comes from the use of liquid scintillators, which entails the possibility of changing the active material in the detector, leading to an increased radiation resistance. This feature, together with the high spatial resolution and low thickness deriving from the microfabrication techniques used to manufacture such devices, is desirable not only in instrumentation for high energy physics experiments but also in medical detectors such as beam monitors for hadron therapy.

  8. A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

    Directory of Open Access Journals (Sweden)

    A. V. Pavlov

    2006-05-01

    Full Text Available We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2, which were observed in the low-latitude ionosphere simultaneously by the Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders, by the middle and upper atmosphere (MU radar during 17-22 March 1990, and by the Arecibo radar for the time period of 20-22 March 1990. A comparison between the electron and ion temperatures measured by the MU and Arecibo radars and those produced by the model of the ionosphere and plasmasphere is presented. The empirical zonal electric field, the meridional neutral wind taken from the HWM90 wind model, and the NRLMSISE-00 neutral temperature and densities are corrected so that the model results agree reasonably with the ionospheric sounder observations, and the MU and Arecibo radar data. It is proved that the nighttime weakening of the equatorial zonal electric field (in comparison with that produced by the empirical model of Fejer and Scherliess (1997 or Scherliess and Fejer (1999, in combination with the corrected wind-induced plasma drift along magnetic field lines, provides the development of the nighttime enhancements in NmF2 observed over Manila during 17-22 March 1990. As a result, the new physical mechanism of the nighttime NmF2 enhancement formation close to the geomagnetic equator includes the nighttime weakening of the equatorial zonal electric field and equatorward nighttime plasma drift along magnetic field lines caused by neutral wind in the both geomagnetic hemispheres. It is found that the latitudinal positions of the crests depend on the E×B drift velocity and on the neutral wind velocity. The relative role of the main mechanisms of the equatorial anomaly suppression observed during geomagnetic storms is studied for the first time in terms of storm-time variations of the model crest-to-trough ratios of the equatorial anomaly. During most of the studied time period, a total contribution from

  9. Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

    Science.gov (United States)

    Darian, D.; Marholm, S.; Paulsson, J. J. P.; Miyake, Y.; Usui, H.; Mortensen, M.; Miloch, W. J.

    2017-09-01

    The charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numerical particle-in-cell (PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionospheric F2 layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.

  10. Liquid scintillation, counting, and compositions

    International Nuclear Information System (INIS)

    Sena, E.A.; Tolbert, B.M.; Sutula, C.L.

    1975-01-01

    The emissions of radioactive isotopes in both aqueous and organic samples can be measured by liquid scintillation counting in micellar systems. The micellar systems are made up of scintillation solvent, scintillation solute and a mixture of surfactants, preferably at least one of which is relatively oil-soluble water-insoluble and another which is relatively water-soluble oil-insoluble

  11. Scintillating fiber detector performance, detector geometries, trigger, and electronics issues for scintillating fiber tracking

    International Nuclear Information System (INIS)

    Baumbaugh, A.E.

    1994-06-01

    Scintillating Fiber tracking technology has made great advances and has demonstrated great potential for high speed charged particle tracking and triggering. The small detector sizes and fast scintillation fluors available make them very promising for use at high luminosity experiments at today's and tomorrow's colliding and fixed target experiments where high rate capability is essential. This talk will discuss the current state of Scintillating fiber performance and current Visual Light Photon Counter (VLPC) characteristics. The primary topic will be some of the system design and integration issues which should be considered by anyone attempting to design a scintillating fiber tracking system which includes a high speed tracking trigger. Design. constraints placed upon the detector system by the electronics and mechanical sub-systems will be discussed. Seemingly simple and unrelated decisions can have far reaching effects on overall system performance. SDC and DO example system designs will be discussed

  12. An empirical model of L-band scintillation S4 index constructed by using FORMOSAT-3/COSMIC data

    Science.gov (United States)

    Chen, Shih-Ping; Bilitza, Dieter; Liu, Jann-Yenq; Caton, Ronald; Chang, Loren C.; Yeh, Wen-Hao

    2017-09-01

    Modern society relies heavily on the Global Navigation Satellite System (GNSS) technology for applications such as satellite communication, navigation, and positioning on the ground and/or aviation in the troposphere/stratosphere. However, ionospheric scintillations can severely impact GNSS systems and their related applications. In this study, a global empirical ionospheric scintillation model is constructed with S4-index data obtained by the FORMOSAT-3/COSMIC (F3/C) satellites during 2007-2014 (hereafter referred to as the F3CGS4 model). This model describes the S4-index as a function of local time, day of year, dip-latitude, and solar activity using the index PF10.7. The model reproduces the F3/C S4-index observations well, and yields good agreement with ground-based reception of satellite signals. This confirms that the constructed model can be used to forecast global L-band scintillations on the ground and in the near surface atmosphere.

  13. A clear link connecting the troposphere and ionosphere: ionospheric reponses to the 2015 Typhoon Dujuan

    Science.gov (United States)

    Kong, Jian; Yao, Yibin; Xu, Yahui; Kuo, Chungyen; Zhang, Liang; Liu, Lei; Zhai, Changzhi

    2017-09-01

    The global navigation satellite system (GNSS) total electron content (TEC) sequences were used to capture the arrival time and location of the ionosphere disturbances in response to the 2015 Typhoon Dujuan. After removing the de-trended TEC variation, the clear ionosphere disturbances on the typhoon landing day could be distinguished, and these disturbances disappeared from the TEC sequences before and after the typhoon landing day. The foF2 data observed by Xiamen ionosonde station also show ionosphere disturbances. Based on the advantages of GNSS multi-point observations, the disturbances horizontal velocity in the ionosphere were estimated according to the linear theory for a dispersion relation of acoustic gravity waves (AGWs) in an isothermal atmosphere. The average horizontal velocity (˜ 240 m/s) and the radial velocity (˜ 287 m/s) were used in the two-dimensional grid search for the origin point on the Earth's surface. The origin area was determined to be on the eastern side of Taiwan. Lastly, a possible physical mechanism is discussed in this study. When typhoons land on Taiwan, the severe convective storms and the drag effect from the Central Mountains create an ideal location for development of AGWs. Topographic conditions, like the high lapse rate, contribute to the formation of AGWs, which then propagates into the ionosphere altitude.

  14. Performance Analysis of Different NeQuick Ionospheric Model Parameters

    Directory of Open Access Journals (Sweden)

    WANG Ningbo

    2017-04-01

    Full Text Available Galileo adopts NeQuick model for single-frequency ionospheric delay corrections. For the standard operation of Galileo, NeQuick model is driven by the effective ionization level parameter Az instead of the solar activity level index, and the three broadcast ionospheric coefficients are determined by a second-polynomial through fitting the Az values estimated from globally distributed Galileo Sensor Stations (GSS. In this study, the processing strategies for the estimation of NeQuick ionospheric coefficients are discussed and the characteristics of the NeQuick coefficients are also analyzed. The accuracy of Global Position System (GPS broadcast Klobuchar, original NeQuick2 and fitted NeQuickC as well as Galileo broadcast NeQuickG models is evaluated over the continental and oceanic regions, respectively, in comparison with the ionospheric total electron content (TEC provided by global ionospheric maps (GIM, GPS test stations and JASON-2 altimeter. The results show that NeQuickG can mitigate ionospheric delay by 54.2%~65.8% on a global scale, and NeQuickC can correct for 71.1%~74.2% of the ionospheric delay. NeQuick2 performs at the same level with NeQuickG, which is a bit better than that of GPS broadcast Klobuchar model.

  15. Scintillation properties of acrylate based plastic scintillator by photoploymerization method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Hwan [Dept. of Radiological Science, Cheongju University, Cheongju (Korea, Republic of); Lee, Joo Il [Dept. of of Radiology, Daegu Health College, Daegu (Korea, Republic of)

    2016-12-15

    In this study, we prepared and characterized a acrylate based UV-curable plastic scintillator. It was used co-polymers TMPTA, DHPA and Ultima GoldTM LLT organic scintillator. The emission spectrum of the plastic scintillator was located in the range of 380⁓520 nm, peaking at 423 nm. And the scintillator is more than 50% transparent in the range of 400⁓ 800 nm. The emission spectrum is well match to the quantum efficiency of photo-multiplier tube and the fast decay time of the scintillation is 12 ns, approximately. This scintillation material provides the possibility of combining 3D printing technology, and then the applications of the plastic scintillator may be expected in human dosimetry etc.

  16. Ionospheric error analysis in gps measurements

    Directory of Open Access Journals (Sweden)

    G. Pugliano

    2008-06-01

    Full Text Available The results of an experiment aimed at evaluating the effects of the ionosphere on GPS positioning applications are presented in this paper. Specifically, the study, based upon a differential approach, was conducted utilizing GPS measurements acquired by various receivers located at increasing inter-distances. The experimental research was developed upon the basis of two groups of baselines: the first group is comprised of "short" baselines (less than 10 km; the second group is characterized by greater distances (up to 90 km. The obtained results were compared either upon the basis of the geometric characteristics, for six different baseline lengths, using 24 hours of data, or upon temporal variations, by examining two periods of varying intensity in ionospheric activity respectively coinciding with the maximum of the 23 solar cycle and in conditions of low ionospheric activity. The analysis revealed variations in terms of inter-distance as well as different performances primarily owing to temporal modifications in the state of the ionosphere.

  17. The First Use of Coordinated Ionospheric Radio and Optical Observations Over Italy: Convergence of High-and Low-Latitude Storm-Induced Effects

    Science.gov (United States)

    Cesaroni, C.; Alfonsi, L.; Pezzopane, M.; Martinis, C.; Baumgardner, J.; Wroten, J.; Mendillo, M.; Musicò, E.; Lazzarin, M.; Umbriaco, G.

    2017-11-01

    Ionospheric storm effects at midlatitudes were analyzed using different ground-based instruments distributed in Italy during the 13-15 November 2012 geomagnetic storm. These included an all-sky imager (ASI) in Asiago (45.8°N, 11.5°E), a network of dual-frequeny Global Navigation Satellite Systems receivers (Rete Integrata Nazionale GPS network), and ionosondes in Rome (41.8°N, 12.5°E) and San Vito (40.6°N, 17.8°E). GPS measurements showed an unusual enhancement of total electron content (TEC) in southern Italy, during the nights of 14 and 15 November. The ASI observed colocated enhancements of 630 nm airglow at the same time, as did variations in NmF2 measured by the ionosondes. Moreover, wave-like perturbations were identified propagating from the north. The Ensemble Empirical Mode Decomposition, applied to TEC values revealed the presence of traveling ionospheric disturbances (TIDs) propagating southward between 01:30 UT and 03:00 UT on 15 November. These TIDs were characterized by weak TEC oscillations ( ±0.5 TEC unit), period of 45 min, and velocity of 500 m/s typical of large-scale TIDs. Optical images showed enhanced airglow entering the field of view of the ASI from the N-NE at 02:00 UT and propagating to the S-SW, reaching the region covered by the GPS stations after 03:00 UT, when TEC fluctuations are very small ( ±0.2 TEC unit). The enhancement of TEC and airglow observed in southern Italy could be a consequence of a poleward expansion of the northern crest of the equatorial ionization anomaly. The enhanced airglow propagating from the north and the TEC waves resulted from energy injected at auroral latitudes as confirmed by magnetometer observations in Scandinavia.

  18. Polysiloxane scintillator composition

    Science.gov (United States)

    Walker, J.K.

    1992-05-05

    A plastic scintillator useful for detecting ionizing radiation comprising a matrix which comprises an optically transparent polysiloxane having incorporated therein at least one ionizing radiation-hard fluor capable of converting electromagnetic energy produced in the polysiloxane upon absorption of ionizing radiation to detectable light.

  19. WORKSHOP: Scintillating crystals

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1992-12-15

    Scintillating crystals are one of the big spinoff success stories of particle physics, and from 22-26 September an international workshop in Chamonix in the French Alps looked at the increasing role of these materials in pure and applied science and in industry.

  20. Radiopharmaceuticals for bone scintillators

    International Nuclear Information System (INIS)

    Rey, A.M.

    1994-01-01

    One of the diagnostic techniques used in nuclear medicine is the bone scintiscanning with labelled compounds for obtain skeletal images. The main sections in this work are: (1) bone composition and anatomy;(2)skeletal radiopharmaceutical development;(3)physical properties of radionuclides;(4)biological behaviour and chemical structures;(5)radiopharmaceuticals production for skeletal scintillation;(6)kits;(7)dosimetry and toxicity.tabs

  1. WORKSHOP: Scintillating crystals

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Scintillating crystals are one of the big spinoff success stories of particle physics, and from 22-26 September an international workshop in Chamonix in the French Alps looked at the increasing role of these materials in pure and applied science and in industry

  2. Economical stabilized scintillation detector

    International Nuclear Information System (INIS)

    Anshakov, O.M.; Chudakov, V.A.; Gurinovich, V.I.

    1983-01-01

    An economical scintillation detector with the stabilization system of an integral type is described. Power consumed by the photomultiplier high-voltage power source is 40 mW, energy resolution is not worse than 9%. The given detector is used in a reference detector of a digital radioisotope densimeter for light media which is successfully operating for several years

  3. Uranium-scintillator device

    International Nuclear Information System (INIS)

    Smith, S.D.

    1979-01-01

    The calorimeter subgroup of the 1977 ISABELLE Summer Workshop strongly recommended investigation of the uranium-scintillator device because of its several attractive features: (1) increased resolution for hadronic energy, (2) fast time response, (3) high density (i.e., 16 cm of calorimeter per interaction length), and, in comparison with uranium--liquid argon detectors, (4) ease of construction, (5) simple electronics, and (6) lower cost. The AFM group at the CERN ISR became interested in such a calorimeter for substantially the same reasons, and in the fall of 1977 carried out tests on a uranium-scintillator (U-Sc) calorimeter with the same uranium plates used in their 1974 studies of the uranium--liquid argon (U-LA) calorimeter. The chief disadvantage of the scintillator test was that the uranium plates were too small to fully contain the hadronic showers. However, since the scintillator and liquid argon tests were made with the plates, direct comparison of the two types of devices could be made

  4. Scintillation properties of polycrystalline LaxY1-xO3 ceramic

    Science.gov (United States)

    Sahi, Sunil; Chen, Wei; Kenarangui, Rasool

    2015-03-01

    Scintillators are the material that absorbs the high-energy photons and emits visible photons. Scintillators are commonly used in radiation detector for security, medical imaging, industrial applications and high energy physics research. Two main types of scintillators are inorganic single crystals and organic (plastic or liquid) scintillators. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, some efficient inorganic scintillator such as NaI and CsI are not environmental friendly. But on the other hand, organic scintillators have low density and hence poor energy resolution which limits their use in gamma spectroscopy. Polycrystalline ceramic can be a cost effective alternative to expensive inorganic single crystal scintillators. Here we have fabricated La0.2Y1.8O3 ceramic scintillator and studied their luminescence and scintillation properties. Ceramic scintillators were fabricated by vacuum sintering of La0.2Y1.8O3 nanoparticles at temperature below the melting point. La0.2Y1.8O3 ceramic were characterized structurally using XRD and TEM. Photoluminescence and radioluminescence studies were done using UV and X-ray as an excitation source. We have used gamma isotopes with different energy to studies the scintillation properties of La0.2Y1.8O3 scintillator. Preliminary studies of La0.2Y1.8O3 scintillator shows promising result with energy resolution comparable to that of NaI and CsI.

  5. Analysis of low-intensity scintillation spectra

    International Nuclear Information System (INIS)

    Muravsky, V.; Tolstov, S.A.

    2002-01-01

    The maximum likelihood algorithms for nuclides activities estimation from low intensity scintillation γ-ray spectra have been created. The algorithms treat full energy peaks and Compton parts of spectra, and they are more effective than least squares estimators. The factors that could lead to the bias of activity estimates are taken into account. Theoretical analysis of the problem of choosing the optimal set of initial spectra for the spectrum model to minimize errors of the activities estimation has been carried out for the general case of the N-components with Gaussian or Poisson statistics. The obtained criterion allows to exclude superfluous initial spectra of nuclides from the model. A special calibration procedure for scintillation γ-spectrometers has been developed. This procedure is required for application of the maximum likelihood activity estimators processing all the channels of the scintillation γ-spectrum, including the Compton part. It allows one to take into account the influence of the sample mass density variation. The algorithm for testing the spectrum model adequacy to the processed scintillation spectrum has been developed. The algorithms are realized in Borland Pascal 7 as a library of procedures and functions. The developed library is compatible with Delphi 1.0 and higher versions. It can be used as the algorithmic basis for analysis of highly sensitive scintillation γ- and β-spectrometric devices. (author)

  6. Present situation of researches on polar ionosphere by C.C.I.R

    International Nuclear Information System (INIS)

    Ishikawa, Saburo

    1974-01-01

    Various subjects of studies made by the sixth research committee of C.C.I.R. (International Radio Consultative Committee) are reported. The C.C.I.R. has not any definite study programme and question concerning polar ionosphere, because it studies and delivers opinion on the techniques and operation of radio communication especially in developing countries. The subjects of study programme by the sixth research committee are as follows: estimation of the intensity and transmission loss of space wave electric field in a zone between 1.5 and 40 MHz, observation of the ionosphere of oblique entrance, scattering propagation of ionosphere, back scattering, fading of signal transmitted through ionosphere, transmission of space waves in the zone between 150 and 1,500 kHz, and effect of ionosphere on space communication. In addition, the following fourteen reports are cited: confirmation of prodromal phenomena of ionosphere disturbances, observation of the ionosphere of oblique entrance, remote propagation with supermode, basic information on forecast, back scattering, side scattering from the ground surface and ionosphere, Esub(s) propagation, scattering propagation, Esub(s) forecast, fading, effect of ionosphere on the transmission between the earth and space, radio noise produced in and above ionosphere, and propagation of standard broadcast wave. (Iwakiri, K.)

  7. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    Science.gov (United States)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  8. Scintillation camera with improved output means

    International Nuclear Information System (INIS)

    Lange, K.; Wiesen, E.J.; Woronowicz, E.M.

    1978-01-01

    In a scintillation camera system, the output pulse signals from an array of photomultiplier tubes are coupled to the inputs of individual preamplifiers. The preamplifier output signals are coupled to circuitry for computing the x and y coordinates of the scintillations. A cathode ray oscilloscope is used to form an image corresponding with the pattern in which radiation is emitted by a body. Means for improving the uniformity and resolution of the scintillations are provided. The means comprise biasing means coupled to the outputs of selected preamplifiers so that output signals below a predetermined amplitude are not suppressed and signals falling within increasing ranges of amplitudes are increasingly suppressed. In effect, the biasing means make the preamplifiers non-linear for selected signal levels

  9. Scintillation counting: an extrapolation into the future

    International Nuclear Information System (INIS)

    Ross, H.H.

    1983-01-01

    Progress in scintillation counting is intimately related to advances in a variety of other disciplines such as photochemistry, photophysics, and instrumentation. And while there is steady progress in the understanding of luminescent phenomena, there is a virtual explosion in the application of semiconductor technology to detectors, counting systems, and data processing. The exponential growth of this technology has had, and will continue to have, a profound effect on the art of scintillation spectroscopy. This paper will review key events in technology that have had an impact on the development of scintillation science (solid and liquid) and will attempt to extrapolate future directions based on existing and projected capability in associated fields. Along the way there have been occasional pitfalls and several false starts; these too will be discussed as a reminder that if you want the future to be different than the past, study the past

  10. Radiocarbon dating methods using benzene liquid scintillation

    International Nuclear Information System (INIS)

    Togashi, Shigeko; Matsumoto, Eiji

    1983-01-01

    The radiocarbon dating method using benzene liquid scintillation is reported in detail. The results of measurement of NBS oxalic acid agree with the recommended value, indicating that isotopic fractionation during benzene synthesis can be negligible. Ten samples which have been already measured by gas counter are dated by benzene liquid scintillation. There is no significant difference in age for the same sample between benzene liquid scintillation and gas counters. It is shown that quenching has to be corrected for the young sample. Memory effect in stainless steel reaction vessel can be removed by using an exchangeable inner vessel and by baking it in the air. Using this method, the oldest age that can be measured with 2.3 g carbon is 40,000 years B.P. (author)

  11. Further analysis of scintillation index for a laser beam propagating through moderate-to-strong non-Kolmogorov turbulence based on generalized effective atmospheric spectral model

    Science.gov (United States)

    Ma, Jing; Fu, Yu-Long; Yu, Si-Yuan; Xie, Xiao-Long; Tan, Li-Ying

    2018-03-01

    A new expression of the scintillation index (SI) for a Gaussian-beam wave propagating through moderate-to-strong non-Kolmogorov turbulence is derived, using a generalized effective atmospheric spectrum and the extended Rytov approximation theory. Finite inner and outer scale parameters and high wave number “bump” are considered in the spectrum with a generalized spectral power law in the range of 3–4, instead of the fixed classical Kolmogorov power law of 11/3. The obtained SI expression is then used to analyze the effects of the spectral power law and the inner scale and outer scale on SI under various non-Kolmogorov fluctuation conditions. These results will be useful in future investigations of optical wave propagation through atmospheric turbulence.

  12. Correlations between Strong Range Spread-F and GPS L-Band Scintillations Observed in Hainan in 2004

    International Nuclear Information System (INIS)

    Guo-Jun, Wang; Jian-Kui, Shi; She-Ping, Shang; Xiao, Wang

    2009-01-01

    Data from the DPS-4 digisonde and the GPS L-band ionospheric scintillation monitor are employed to study the correlations between strong range spread-F (SSF) and GPS L-band scintillations observed in the ionosphere over Hainan Island, China (19.5°N, 109.1°E geogr., dip lat. 9°N) in 2004. The SSF in the ionogram is different from the general range spread-F because it extends in frequency well beyond FoF2 and makes FoF2 difficult to be determined. The observations show that the SSF phenomenon is frequently accompanied by the occurrence of GPS L-band scintillations. The SSF and GPS L-band scintillations occur frequently in the equinoctial months (March, April, September, and October), but rarely in the winter (January, February, November, and December) and summer (May–August); especially, occurrence variations of the SSF and GPS L-band scintillations nearly have a same trend. The SSF and scintillations may be associated with the occurrence of topside plasma bubbles and could be explained by the generalized Rayleigh–Taylor instability

  13. Superimposed disturbance in the ionosphere triggered by spacecraft launches in China

    OpenAIRE

    L. M. He; L. X. Wu; L. X. Wu; S. J. Liu; S. N. Liu

    2015-01-01

    Using GPS dual-frequency observations collected by continuously operating GPS tracking stations in China, superimposed disturbances caused by the integrated action of spacecraft's physical effect and chemical effect on ionosphere during the launches of the spacecrafts Tiangong-1 and Shenzhou-8 in China were firstly determined. The results show that the superimposed disturbance was composed of remarkable ionospheric waves and significant ionospheric depletion emerged after bo...

  14. Temporal and Spatial Characterization of GPS Fading From Ionospheric Irregularities Under Low latitude

    Science.gov (United States)

    De Paula, E. R.; Moraes, A. D. O.; Vani, B. C.; Sobral, J. H. A.; Abdu, M. A.; Galera Monico, J. F.

    2017-12-01

    The ionosphere over the peak of the anomaly represents a treat for navigation systems based on GNSS. Brazilian territory is mostly under this harsh layer for satellite communication in general and in particular for navigation, like GPS users, where their receivers tracking performance are damaged under scintillation conditions. Ionospheric scintillation is responsible for significant degradation in the accuracy of navigation and positioning. Phase shifts accompanied by amplitude fades significantly degrades the signal-to-noise ratio of the received signal disrupting the channel and loosing navigation performance. The stronger the scintillations are, more difficulty will be for the GNSS receiver tracking loops to recover the phase and code replicas. These phenomena under specific geophysical conditions may severely affect the system availability and positioning. In this work the temporal characteristics of amplitude scintillation will be analyzed at the three available GPS frequencies, L1, L2C and L5. Aspect like fading duration and depth will be evaluated and compared among the three available frequencies for the current solar cycle. This work will use GPS scintillation data recorded during six months of data during 2014 to 2015 at three stations under Brazilian territory located near the southern crest of the equatorial ionization anomaly. The analysis will be performed focusing on the fading profile of the three frequencies comparing how the fading of those signals behave statistically between them. Aspects like loss of lock, spatial orientation between the signal across the ionospheric irregularity will also be discussed showing how much more susceptible the new frequencies might be in comparison to the widely used and studied L1 frequency.

  15. High Resolution Reconstruction of the Ionosphere for SAR Applications

    Science.gov (United States)

    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

  16. Ionospheric Remote Sensing using GPS Radio Occultation and Ultraviolet Photometry aboard the ISS

    Science.gov (United States)

    Budzien, S. A.; Powell, S. P.; O'Hanlon, B.; Humphreys, T.; Bishop, R. L.; Stephan, A. W.; Gross, J.; Chakrabarti, S.

    2017-12-01

    The GPS Radio Occultation and Ultraviolet Photometer Co-located (GROUP-C) experiment launched to the International Space Station (ISS) on February 19, 2017 as part of the Space Test Program Houston #5 payload (STP-H5). After early orbit testing, GROUP-C began routine science operations in late April. GROUP-C includes a high-sensitivity far-ultraviolet photometer measuring horizontal nighttime ionospheric gradients and an advanced software-defined GPS receiver providing ionospheric electron density profiles, scintillation measurements, and lower atmosphere profiles. GROUP-C and a companion experiment, the Limb-Imaging Ionospheric and Thermospheric Extreme-Ultraviolet Spectrograph (LITES), offer a unique capability to study spatial and temporal variability of the thermosphere and ionosphere using multi-sensor approaches, including ionospheric tomography. Data are collected continuously across low- and mid-latitudes as the ISS orbit precesses through all local times every 60 days. The GROUP-C GPS sensor routinely collects dual-frequency GPS occultations, makes targeted raw signal captures of GPS and Galileo occultations, and includes multiple antennas to characterize multipath in the ISS environment. The UV photometer measures the 135.6 nm ionospheric recombination airglow emision along the nightside orbital track. We present the first analysis of ionospheric observations, discuss the challenges and opportunities of remote sensing from the ISS platform, and explore how these new data help address questions regarding the complex and dynamic features of the low and middle latitude ionosphere-thermosphere relevant to the upcoming GOLD and ICON missions.

  17. Global scale ionospheric irregularities associated with thunderstorm activity

    International Nuclear Information System (INIS)

    Pulinets, Sergey A.; Depuev, Victor H.

    2003-01-01

    The potential difference near 280 kV exists between ground and ionosphere. This potential difference is generated by thunderstorm discharges all over the world, and return current closes the circuit in the areas of fair weather (so-called fair weather current). The model calculations and experimental measurements clearly demonstrate non-uniform latitude-longitude distribution of electric field within the atmosphere. The recent calculations show that the strong large scale vertical atmospheric electric field can penetrate into the ionosphere and create large scale irregularities of the electron concentration. To check this the global distributions of thunderstorm activity obtained with the satellite monitoring for different seasons were compared with the global distributions of ionosphere critical frequency (which is equivalent to peak electron concentration) obtained with the help of satellite topside sounding. The similarity of the obtained global distributions clearly demonstrates the effects of thunderstorm electric fields onto the Earth's ionosphere. (author)

  18. The use of energy information in plastic scintillator materia

    International Nuclear Information System (INIS)

    Ely, J.; Anderson, K.; Bates, D.; Kouzes, R.; Lo Presti, C.; Runkle, R.; Siciliano, E.; Weier, D.

    2008-01-01

    Plastic scintillator material is often used for gamma-ray detection in many applications due to its relatively good sensitivity and cost-effectiveness compared to other detection materials. However, due to the dominant Compton scattering interaction mechanism, full energy peaks are not observed in plastic scintillator spectra and isotopic identification is impossible. Typically plastic scintillator detectors are solely gross count detectors. In some safeguards and security applications, such as radiation portal monitors for vehicle screening, naturally-occurring radioactive material (NORM) often triggers radiation alarms and results in innocent or nuisance alarms. The limited energy information from plastic scintillator material can be used to discriminate the NORM from targeted materials and reduce the nuisance alarm rate. An overview of the utilization of the energy information from plastic scintillator material will be presented, with emphasis on the detection capabilities and potential limitations for safeguards and security applications. (author)

  19. Alpha scintillation radon counting

    International Nuclear Information System (INIS)

    Lucas, H.F. Jr.

    1977-01-01

    Radon counting chambers which utilize the alpha-scintillation properties of silver activated zinc sulfide are simple to construct, have a high efficiency, and, with proper design, may be relatively insensitive to variations in the pressure or purity of the counter filling. Chambers which were constructed from glass, metal, or plastic in a wide variety of shapes and sizes were evaluated for the accuracy and the precision of the radon counting. The principles affecting the alpha-scintillation radon counting chamber design and an analytic system suitable for a large scale study of the 222 Rn and 226 Ra content of either air or other environmental samples are described. Particular note is taken of those factors which affect the accuracy and the precision of the method for monitoring radioactivity around uranium mines

  20. Scintillator detector array

    International Nuclear Information System (INIS)

    Cusano, D.A.; Dibianca, F.A.

    1981-01-01

    This patent application relates to a scintillator detector array for use in computerized tomography and comprises a housing including a plurality of chambers, the said housing having a front wall transmissive to x-rays and side walls opaque to x-rays, such as of tungsten and tantalum, a liquid scintillation medium including a soluble fluor, the solvent for the fluor being disposed in the chambers. The solvent comprises either an intrinsically high Z solvent or a solvent which has dissolved therein a high Z compound e.g. iodo or bromonaphthalene; or toluene, xylene or trimethylbenzene with a lead or tin alkyl dissolved therein. Also disposed about the chambers are a plurality of photoelectric devices. (author)

  1. DETECTORS: scintillating fibres

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    In the continual search for improved detection techniques, new materials are continually proving profitable. A good example is scintillating plastic fibres - tiny transparent threads sometimes finer than a human hair which transmit light. The narrowness and flexibility of these fibres was a major breakthrough for endoscopy - non-invasive techniques for viewing the otherwise inaccessible in surgery or machine inspection. In a more sophisticated form, these fibres find ready application in communications technology, where the goal is to transmit information rather than electrical power, replacing conventional and unwieldy current-carrying wire conductors. In particle physics, fibres have long been used to take the tiny scintillations produced when high energy particles hit fluorescent materials and 'conduct' them to photosensitive detectors some distance away

  2. Study of colour quenching effects in the calibration of liquid scintillation counters: the case of sup 2 sup 1 sup 0 Pb

    CERN Document Server

    Villa, M; Manjon, G

    2003-01-01

    In this work a rigorous method for the calibration of a liquid scintillation counter for sup 2 sup 1 sup 0 Pb activity determination is proposed. The variation of the PSA threshold level for alpha/beta discrimination with the colour quenching is analysed for different beta energies. Also the changes in some parameters of the detector response, as the muon-peak, the channel ratio and the centroid of the spectrum, due to colour quenching are studied. The relationship between such parameters and the counting efficiency is described in such a way that the effects of colour in the efficiency are established. sup 9 sup 9 Tc is proposed as a good standard to calibrate the counter for sup 2 sup 1 sup 0 Pb determination in real samples.

  3. A gamma scintillation spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Symbalisty, S

    1952-07-01

    A scintillation type gamma ray spectrometer employing coincidence counting, designed and built at the Physics Department of the University of Western Ontario is described. The spectrometer is composed of two anthracene and photomultiplier radiation detectors, two pulse analyzing channels, a coincidence stage, three scalers and a high voltage stabilized supply. A preliminary experiment to test the operation of the spectrometer was performed and the results of this test are presented. (author)

  4. System and method of liquid scintillation counting

    International Nuclear Information System (INIS)

    Rapkin, E.

    1977-01-01

    A method of liquid scintillation counting utilizing a combustion step to overcome quenching effects comprises novel features of automatic sequential introduction of samples into a combustion zone and automatic sequential collection and delivery of combustion products into a counting zone. 37 claims, 13 figures

  5. Modular scintillation camera

    International Nuclear Information System (INIS)

    Barrett, H. H.

    1985-01-01

    Improved optical coupling modules to be used in coded-aperture-type radiographic imaging systems. In a first system, a rotating slit coded-aperture is employed between the radioactive object and the module. The module consists of one pair of side-by-side photomultipliers receiving light rays from a scintillation crystal exposed to the object via the coded-aperture. The light rays are guided to the photomultipliers by a mask having a central transverse transparent window, or by a cylindrical lens, the mask or lens being mounted in a light-conveying quartz block assembly providing internal reflections at opposite faces of the assembly. This generates output signals from the photomultipliers which can be utilized to compute one-dimensional coordinate values for restoring the image of the radioactive object on a display screen. In another form of optical coupling module, usable with other types of coded-apertures, four square photomultipliers form a substantially square block and receive light rays from scintillations from a scintillation crystal exposed to the radioactive object via the coded-aperture. The light rays are guided to the photomultipliers by a square mask or a centrally transparent square lens configuration mounted in a light-conveying assembly formed by internally reflecting quartz blocks, the optical rays being directed to the respective photomultipliers so as to generate resultant output signals which can be utilized to compute image coordinate values for two-dimensional representation of the radioactive object being examined

  6. A study on multifrequency scintillations near the EIA crest of the Indian zone

    Science.gov (United States)

    Chakraborty, S. K.; Chatterjee, S.; Jana, Debasis

    2017-10-01

    Occurrence features of ionospheric scintillations at S band (2492.028 MHz) are reported for the first time. The same have been explored in the context of scintillations at VHF (250.650 MHz) and L5 (1176.45 MHz) bands. Observations were carried out during the period April-December, 2015 at Raja Peary Mohan College Centre (RPMC: 22.66° N, 88.4° E), located near the equatorial ionization anomaly (EIA) crest of the Indian longitude zone. Mostly weak (<10 dB), short duration, slow fading rate with shallower slope power spectra characterize the S band scintillations compared to VHF and L5 band. In the severe scintillation conditions of VHF frequent loss of lock in L5 channel is reflected. Fade depth of 4.2 ± 1.3 dB and fade rate ∼9 fades/minute at S band mostly precede the loss of lock at L5 channel. A good correspondence between fade rates at multi frequency band is reflected irrespective of phases of scintillation. Spectral analysis reveals weak scattering is the dominating mechanism for scintillation at S band while VHF and L5 band scintillations are mostly attributed to multiple scattering. The estimated threshold coherence length of <23 m at VHF may be suggested to be a good indicator for occurrence of L5 and S band scintillations. Occurrence of simultaneous multi-satellite multi-frequency scintillations leads to speculation over the failsafe navigation using available IRNSS constellation. The results are discussed in terms of existing theory of evolution, structure and dynamics of electron density irregularities in the low latitude region.

  7. Effects of the midnight temperature maximum observed in the thermosphere-ionosphere over the northeast of Brazil

    Science.gov (United States)

    Figueiredo, Cosme Alexandre O. B.; Buriti, Ricardo A.; Paulino, Igo; Meriwether, John W.; Makela, Jonathan J.; Batista, Inez S.; Barros, Diego; Medeiros, Amauri F.

    2017-08-01

    The midnight temperature maximum (MTM) has been observed in the lower thermosphere by two Fabry-Pérot interferometers (FPIs) at São João do Cariri (7.4° S, 36.5° W) and Cajazeiras (6.9° S, 38.6° W) during 2011, when the solar activity was moderate and the solar flux was between 90 and 155 SFU (1 SFU = 10-22 W m-2 Hz-1). The MTM is studied in detail using measurements of neutral temperature, wind and airglow relative intensity of OI630.0 nm (referred to as OI6300), and ionospheric parameters, such as virtual height (h'F), the peak height of the F2 region (hmF2), and critical frequency of the F region (foF2), which were measured by a Digisonde instrument (DPS) at Eusébio (3.9° S, 38.4° W; geomagnetic coordinates 7.31° S, 32.40° E for 2011). The MTM peak was observed mostly along the year, except in May, June, and August. The amplitudes of the MTM varied from 64 ± 46 K in April up to 144 ± 48 K in October. The monthly temperature average showed a phase shift in the MTM peak around 0.25 h in September to 2.5 h in December before midnight. On the other hand, in February, March, and April the MTM peak occurred around midnight. International Reference Ionosphere 2012 (IRI-2012) model was compared to the neutral temperature observations and the IRI-2012 model failed in reproducing the MTM peaks. The zonal component of neutral wind flowed eastward the whole night; regardless of the month and the magnitude of the zonal wind, it was typically within the range of 50 to 150 m s-1 during the early evening. The meridional component of the neutral wind changed its direction over the months: from November to February, the meridional wind in the early evening flowed equatorward with a magnitude between 25 and 100 m s-1; in contrast, during the winter months, the meridional wind flowed to the pole within the range of 0 to -50 m s-1. Our results indicate that the reversal (changes in equator to poleward flow) or abatement of the meridional winds is an important factor in

  8. Equatorial plasma bubbles in the ionosphere over Eritrea: occurrence and drift speed

    Directory of Open Access Journals (Sweden)

    R. H. Wiens

    2006-07-01

    Full Text Available An all-sky imager was installed in Asmara, Eritrea (15.4° N, 38.9° E, 7° N dip and used to monitor the OI 630-nm nightglow. Nine months of data were studied between September 2001 and May 2002, a time including the recent maximum in the solar activity cycle. Equatorial plasma bubbles (EPBs were recorded on 63% of nights with adequate viewing conditions. The station location within view of the equatorial ionization anomaly and with a magnetic declination near zero makes it an excellent test case for comparison with satellite studies of the seasonal variation of EPBs with longitude. The imager was accompanied by two Cornell GPS scintillation monitors, and the amplitude scintillation data are compared to the all-sky data. GPS scintillations indicate the beginning of EPBs, but die out sooner in the post-midnight period than the larger scale EPBs. Both phenomena exhibit clear occurrence maxima around the equinoxes. Ionospheric zonal drift speeds have been deduced from EPB and GPS scintillation pattern movement. Average near-midnight EPB drift speeds are between 100 and 120 m/s most months, with the GPS scintillation speeds being about the same. A winter drift speed maximum is evident in both EPB and GPS scintillation monthly means.

  9. Liquid scintillation counting of chlorophyll

    International Nuclear Information System (INIS)

    Fric, F.; Horickova, B.; Haspel-Horvatovic, E.

    1975-01-01

    A precise and reproducible method of liquid scintillation counting was worked out for measuring the radioactivity of 14 C-labelled chlorophyll a and chlorophyll b solutions without previous bleaching. The spurious count rate caused by luminescence of the scintillant-chlorophyll system is eliminated by using a suitable scintillant and by measuring the radioactivity at 4 to 8 0 C after an appropriate time of dark adaptation. Bleaching of the chlorophyll solutions is necessary only for measuring of very low radioactivity. (author)

  10. Scintillation measurements at Bahir Dar during the high solar activity phase of solar cycle 24

    Energy Technology Data Exchange (ETDEWEB)

    Kriegel, Martin; Jakowski, Norbert; Berdermann, Jens; Sato, Hiroatsu [German Aerospace Center (DLR), Neustrelitz (Germany). Inst. of Communications and Navigation; Mersha, Mogese Wassaie [Bahir Dar Univ. (Ethiopia). Washera Geospace and Radar Science Lab.

    2017-04-01

    Small-scale ionospheric disturbances may cause severe radio scintillations of signals transmitted from global navigation satellite systems (GNSSs). Consequently, smallscale plasma irregularities may heavily degrade the performance of current GNSSs such as GPS, GLONASS or Galileo. This paper presents analysis results obtained primarily from two high-rate GNSS receiver stations designed and operated by the German Aerospace Center (DLR) in cooperation with Bahir Dar University (BDU) at 11.6 N, 37.4 E. Both receivers collect raw data sampled at up to 50 Hz, from which characteristic scintillation parameters such as the S4 index are deduced. This paper gives a first overview of the measurement setup and the observed scintillation events over Bahir Dar in 2015. Both stations are located close to one another and aligned in an east-west, direction which allows us to estimate the zonal drift velocity and spatial dimension of equatorial ionospheric plasma irregularities. Therefore, the lag times of moving electron density irregularities and scintillation patterns are derived by applying cross-correlation analysis to high-rate measurements of the slant total electron content (sTEC) along radio links between a GPS satellite and both receivers and to the associated signal power, respectively. Finally, the drift velocity is derived from the estimated lag time, taking into account the geometric constellation of both receiving antennas and the observed GPS satellites.

  11. VLF/LF Radio Sounding of Ionospheric Perturbations Associated with Earthquakes

    Directory of Open Access Journals (Sweden)

    Masashi Hayakawa

    2007-07-01

    Full Text Available It is recently recognized that the ionosphere is very sensitive to seismic effects,and the detection of ionospheric perturbations associated with earthquakes, seems to bevery promising for short-term earthquake prediction. We have proposed a possible use ofVLF/LF (very low frequency (3-30 kHz /low frequency (30-300 kHz radio sounding ofthe seismo-ionospheric perturbations. A brief history of the use of subionospheric VLF/LFpropagation for the short-term earthquake prediction is given, followed by a significantfinding of ionospheric perturbation for the Kobe earthquake in 1995. After showingprevious VLF/LF results, we present the latest VLF/LF findings; One is the statisticalcorrelation of the ionospheric perturbation with earthquakes and the second is a case studyfor the Sumatra earthquake in December, 2004, indicating the spatical scale and dynamicsof ionospheric perturbation for this earthquake.

  12. Kriging with Unknown Variance Components for Regional Ionospheric Reconstruction

    Directory of Open Access Journals (Sweden)

    Ling Huang

    2017-02-01

    Full Text Available Ionospheric delay effect is a critical issue that limits the accuracy of precise Global Navigation Satellite System (GNSS positioning and navigation for single-frequency users, especially in mid- and low-latitude regions where variations in the ionosphere are larger. Kriging spatial interpolation techniques have been recently introduced to model the spatial correlation and variability of ionosphere, which intrinsically assume that the ionosphere field is stochastically stationary but does not take the random observational errors into account. In this paper, by treating the spatial statistical information on ionosphere as prior knowledge and based on Total Electron Content (TEC semivariogram analysis, we use Kriging techniques to spatially interpolate TEC values. By assuming that the stochastic models of both the ionospheric signals and measurement errors are only known up to some unknown factors, we propose a new Kriging spatial interpolation method with unknown variance components for both the signals of ionosphere and TEC measurements. Variance component estimation has been integrated with Kriging to reconstruct regional ionospheric delays. The method has been applied to data from the Crustal Movement Observation Network of China (CMONOC and compared with the ordinary Kriging and polynomial interpolations with spherical cap harmonic functions, polynomial functions and low-degree spherical harmonic functions. The statistics of results indicate that the daily ionospheric variations during the experimental period characterized by the proposed approach have good agreement with the other methods, ranging from 10 to 80 TEC Unit (TECU, 1 TECU = 1 × 1016 electrons/m2 with an overall mean of 28.2 TECU. The proposed method can produce more appropriate estimations whose general TEC level is as smooth as the ordinary Kriging but with a smaller standard deviation around 3 TECU than others. The residual results show that the interpolation precision of the

  13. Ionosphere research with a HF/MF cubesat radio instrument

    Science.gov (United States)

    Kallio, Esa; Aikio, Anita; Alho, Markku; Fontell, Mathias; Harri, Ari-Matti; Kauristie, Kirsti; Kestilä, Antti; Koskimaa, Petri; Mäkelä, Jakke; Mäkelä, Miika; Turunen, Esa; Vanhamäki, Heikki; Verronen, Pekka

    2017-04-01

    New technology provides new possibilities to study geospace and 3D ionosphere by using spacecraft and computer simulations. A type of nanosatellites, CubeSats, provide a cost effective possibility to provide in-situ measurements in the ionosphere. Moreover, combined CubeSat observations with ground-based observations gives a new view on auroras and associated electromagnetic phenomena. Especially joint and active CubeSat - ground based observation campaigns enable the possibility of studying the 3D structure of the ionosphere. Furthermore using several CubeSats to form satellite constellations enables much higher temporal resolution. At the same time, increasing computation capacity has made it possible to perform simulations where properties of the ionosphere, such as propagation of the electromagnetic waves in the medium frequency, MF (0.3-3 MHz) and high frequency, HF (3-30 MHz), ranges is based on a 3D ionospheric model and on first-principles modelling. Electromagnetic waves at those frequencies are strongly affected by ionospheric electrons and, consequently, those frequencies can be used for studying the plasma. On the other hand, even if the ionosphere originally enables long-range telecommunication at MF and HF frequencies, the frequent occurrence of spatiotemporal variations in the ionosphere disturbs communication channels, especially at high latitudes. Therefore, study of the MF and HF waves in the ionosphere has both a strong science and technology interests. We introduce recently developed simulation models as well as measuring principles and techniques to investigate the arctic ionosphere by a polar orbiting CubeSat whose novel AM radio instrument measures HF and MF waves. The cubesat, which contains also a white light aurora camera, is planned to be launched in late 2017 (http://www.suomi100satelliitti.fi/eng). The new models are (1) a 3D ray tracing model and (2) a 3D full kinetic electromagnetic simulation. We also introduce how combining of the

  14. First light from a kilometer-baseline Scintillation Auroral GPS Array.

    Science.gov (United States)

    Datta-Barua, S; Su, Y; Deshpande, K; Miladinovich, D; Bust, G S; Hampton, D; Crowley, G

    2015-05-28

    We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100-1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed.

  15. Neutron crosstalk between liquid scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Verbeke, J.M., E-mail: verbeke2@llnl.gov; Prasad, M.K., E-mail: prasad1@llnl.gov; Snyderman, N.J., E-mail: snyderman1@llnl.gov

    2015-09-11

    A method is proposed to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators was modeled to illustrate the improvement of the mass reconstruction.

  16. Neutron crosstalk between liquid scintillators

    International Nuclear Information System (INIS)

    Verbeke, J.M.; Prasad, M.K.; Snyderman, N.J.

    2015-01-01

    A method is proposed to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators was modeled to illustrate the improvement of the mass reconstruction

  17. New Method for Solving Inductive Electric Fields in the Ionosphere

    Science.gov (United States)

    Vanhamäki, H.

    2005-12-01

    We present a new method for calculating inductive electric fields in the ionosphere. It is well established that on large scales the ionospheric electric field is a potential field. This is understandable, since the temporal variations of large scale current systems are generally quite slow, in the timescales of several minutes, so inductive effects should be small. However, studies of Alfven wave reflection have indicated that in some situations inductive phenomena could well play a significant role in the reflection process, and thus modify the nature of ionosphere-magnetosphere coupling. The input to our calculation method are the time series of the potential part of the ionospheric electric field together with the Hall and Pedersen conductances. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfven wave reflection from uniformly conducting ionosphere.

  18. Ionospheric plasma by VHF waves

    Indian Academy of Sciences (India)

    The amplitude scintillations of very high frequency electromagnetic wave ... Scintillations at low latitude are known to occur in discrete patches [5,6] and are part .... weakly ionized plasma with a density gradient and a relative drift of ions and ...

  19. Radio techniques for probing the terrestrial ionosphere.

    Science.gov (United States)

    Hunsucker, R. D.

    The subject of the book is a description of the basic principles of operation, plus the capabilities and limitations of all generic radio techniques employed to investigate the terrestrial ionosphere. The purpose of this book is to present to the reader a balanced treatment of each technique so they can understand how to interpret ionospheric data and decide which techniques are most effective for studying specific phenomena. The first two chapters outline the basic theory underlying the techniques, and each following chapter discusses a separate technique. This monograph is entirely devoted to techniques in aeronomy and space physics. The approach is unique in its presentation of the principles, capabilities and limitations of the most important presently used radio techniques. Typical examples of data are shown for the various techniques, and a brief historical account of the technique development is presented. An extended annotated bibliography of the salient papers in the field is included.

  20. The Optimum Condition For Determination Of Radioactivity Of Pest Insects Labelled with P-32 By Using Liquid scintillation Counter

    International Nuclear Information System (INIS)

    Yarianto, S.; Susilo, Budi; Sutrisno, Singgih

    2002-01-01

    Tracer technique is needed in the control programe of pest insects especially for determining of its direction and dispersal. Radioisotopes of P-32 is frecuently used for labeling of pest insects. Liquid Scintillation Counter can be used effectively for measuring radioactivity of pest insects labelled by P-32. Optilnization of liquid compositions that consist of solvents. primary scintillation PPO and secondary scintillation POPOP were determined by examination of their compositions. Based on the research result obtained, composition of scintillator which had the highest efficiency. consists of P-Xylene solvent. primary scintillation PPO (5 g/l ) and secondary scintillation POPOP (0.5 g/l)

  1. Cerium doped lanthanum halides: fast scintillators for medical imaging

    International Nuclear Information System (INIS)

    Selles, O.

    2006-12-01

    This work is dedicated to two recently discovered scintillating crystals: cerium doped lanthanum halides (LaCl 3 :Ce 3+ and LaBr 3 :Ce 3+ ).These scintillators exhibit interesting properties for gamma detection, more particularly in the field of medical imaging: a short decay time, a high light yield and an excellent energy resolution. The strong hygroscopicity of these materials requires adapting the usual experimental methods for determining physico-chemical properties. Once determined, these can be used for the development of the industrial manufacturing process of the crystals. A proper comprehension of the scintillation mechanism and of the effect of defects within the material lead to new possible ways for optimizing the scintillator performance. Therefore, different techniques are used (EPR, radioluminescence, laser excitation, thermally stimulated luminescence). Alongside Ce 3+ ions, self-trapped excitons are involved in the scintillation mechanism. Their nature and their role are detailed. The knowledge of the different processes involved in the scintillation mechanism leads to the prediction of the effect of temperature and doping level on the performance of the scintillator. A mechanism is proposed to explain the thermally stimulated luminescence processes that cause slow components in the light emission and a loss of light yield. Eventually the study of afterglow reveals a charge transfer to deep traps involved in the high temperature thermally stimulated luminescence. (author)

  2. Effects of the midnight temperature maximum observed in the thermosphere–ionosphere over the northeast of Brazil

    Directory of Open Access Journals (Sweden)

    C. A. O. B. Figueiredo

    2017-08-01

    Full Text Available The midnight temperature maximum (MTM has been observed in the lower thermosphere by two Fabry–Pérot interferometers (FPIs at São João do Cariri (7.4° S, 36.5° W and Cajazeiras (6.9° S, 38.6° W during 2011, when the solar activity was moderate and the solar flux was between 90 and 155 SFU (1 SFU  =  10−22 W m−2 Hz−1. The MTM is studied in detail using measurements of neutral temperature, wind and airglow relative intensity of OI630.0 nm (referred to as OI6300, and ionospheric parameters, such as virtual height (h′F, the peak height of the F2 region (hmF2, and critical frequency of the F region (foF2, which were measured by a Digisonde instrument (DPS at Eusébio (3.9° S, 38.4° W; geomagnetic coordinates 7.31° S, 32.40° E for 2011. The MTM peak was observed mostly along the year, except in May, June, and August. The amplitudes of the MTM varied from 64 ± 46 K in April up to 144 ± 48 K in October. The monthly temperature average showed a phase shift in the MTM peak around 0.25 h in September to 2.5 h in December before midnight. On the other hand, in February, March, and April the MTM peak occurred around midnight. International Reference Ionosphere 2012 (IRI-2012 model was compared to the neutral temperature observations and the IRI-2012 model failed in reproducing the MTM peaks. The zonal component of neutral wind flowed eastward the whole night; regardless of the month and the magnitude of the zonal wind, it was typically within the range of 50 to 150 m s−1 during the early evening. The meridional component of the neutral wind changed its direction over the months: from November to February, the meridional wind in the early evening flowed equatorward with a magnitude between 25 and 100 m s−1; in contrast, during the winter months, the meridional wind flowed to the pole within the range of 0 to −50 m s−1. Our results indicate that the reversal (changes

  3. Sounding rockets explore the ionosphere

    International Nuclear Information System (INIS)

    Mendillo, M.

    1990-01-01

    It is suggested that small, expendable, solid-fuel rockets used to explore ionospheric plasma can offer insight into all the processes and complexities common to space plasma. NASA's sounding rocket program for ionospheric research focuses on the flight of instruments to measure parameters governing the natural state of the ionosphere. Parameters include input functions, such as photons, particles, and composition of the neutral atmosphere; resultant structures, such as electron and ion densities, temperatures and drifts; and emerging signals such as photons and electric and magnetic fields. Systematic study of the aurora is also conducted by these rockets, allowing sampling at relatively high spatial and temporal rates as well as investigation of parameters, such as energetic particle fluxes, not accessible to ground based systems. Recent active experiments in the ionosphere are discussed, and future sounding rocket missions are cited

  4. Scintillating-fibre calorimetry

    International Nuclear Information System (INIS)

    Livan, M.; Vercesi, V.; Wigmans, R.

    1995-01-01

    In the past decade, calorimetry based on scintillating plastic fibres as active elements was developed from a conceptual idea to a mature detector technology, which is nowadays widely applied in particle physics experiments. This development and the performance characteristics of representative calorimeters, both for the detection of electromagnetic and hadronic showers, are reviewed. We also discuss new information on shower development processes in dense matter and its application to calorimetric principles that has emerged from some very thorough studies that were performed in the framework of this development. (orig.)

  5. Martian Ionospheric Observation and Modeling

    Science.gov (United States)

    González-Galindo, Francisco

    2018-02-01

    The Martian ionosphere is a plasma embedded within the neutral upper atmosphere of the planet. Its main source is the ionization of the CO2-dominated Martian mesosphere and thermosphere by the energetic EUV solar radiation. The ionosphere of Mars is subject to an important variability induced by changes in its forcing mechanisms (e.g., the UV solar flux) and by variations in the neutral atmosphere (e.g., the presence of global dust storms, atmospheric waves and tides, changes in atmospheric composition, etc.). Its vertical structure is dominated by a maximum in the electron concentration placed at about 120–140 km of altitude, coincident with the peak of the ionization rate. Below, a secondary peak produced by solar X-rays and photoelectron-impact ionization is observed. A sporadic third layer, possibly of meteoric origin, has been also detected below. The most abundant ion in the Martian ionosphere is O2+, although O+ can become more abundant in the upper ionospheric layers. While below about 180–200 km the Martian ionosphere is dominated by photochemical processes, above those altitudes the dynamics of the plasma become more important. The ionosphere is also an important source of escaping particles via processes such as dissociative recombination of ions or ion pickup. So, characterization of the ionosphere provides or can provide information about such disparate systems and processes as the solar radiation getting to the planet, the neutral atmosphere, the meteoric influx, the atmospheric escape to space, or the interaction of the planet with the solar wind. It is thus not surprising that the interest about this region dates from the beginning of the space era. From the first measurements provided by the Mariner 4 mission in the 1960s to the contemporaneous observations, still ongoing, by the Mars Express and MAVEN orbiters, our current knowledge of this atmospheric region is the consequence of the accumulation of more than 50 years of discontinuous

  6. Hybrid scintillators for neutron discrimination

    Science.gov (United States)

    Feng, Patrick L; Cordaro, Joseph G; Anstey, Mitchell R; Morales, Alfredo M

    2015-05-12

    A composition capable of producing a unique scintillation response to neutrons and gamma rays, comprising (i) at least one surfactant; (ii) a polar hydrogen-bonding solvent; and (iii) at least one luminophore. A method including combining at least one surfactant, a polar hydrogen-bonding solvent and at least one luminophore in a scintillation cell under vacuum or an inert atmosphere.

  7. Liquid scintillation in medical diagnosis

    International Nuclear Information System (INIS)

    Painter, K.

    1976-01-01

    With the tremendous increase in the application of radioassay, particularly radioimmunoassay, in the clinical laboratory liquid scintillation counting became an indispensable tool in diagnostic medicine. Few publications, however, have concerned themselves with problem areas which occur with the method in the clinical laboratory. The purpose of this presentation is to summarize our experiences with the liquid scintillation technique in the clinical situation

  8. A user's guide to scintillation

    International Nuclear Information System (INIS)

    Hewish, A.

    1989-01-01

    During the past four decades scintillation methods have been used for remote-sensing distant plasmas and for providing high angular resolution in radioastronomy. This brief review illustrates some of the techniques employed and explains the underlying theory in simple physical terms; it is not intended to be a complete survey of all applications of scintillation. (author)

  9. Laser Beam Scintillation with Applications

    CERN Document Server

    Andrews, Larry C; Young, Cynthia

    2001-01-01

    Renewed interest in laser communication systems has sparked development of useful new analytic models. This book discusses optical scintillation and its impact on system performance in free-space optical communication and laser radar applications, with a detailed look at propagation phenomena and the role of scintillation on system behavior. Intended for practicing engineers, scientists, and students.

  10. Scintillation light transport and detection

    International Nuclear Information System (INIS)

    Gabriel, T.A.; Lillie, R.A.

    1986-08-01

    The MORSE neutron gamma-ray transport code has been modified to allow for the transport of scintillation light. This modified code is used to analyze the light collection characteristics of a large liquid scintillator module (18 x 18 x 350 cm 3 )

  11. Extruding plastic scintillator at Fermilab

    International Nuclear Information System (INIS)

    Pla-Dalmau, Anna; Bross, Alain D.; Rykalin, Viktor V.

    2003-01-01

    An understanding of the costs involved in the production of plastic scintillators and the development of a less expensive material have become necessary with the prospects of building very large plastic scintillation detectors. Several factors contribute to the high cost of plastic scintillating sheets, but the principal reason is the labor-intensive nature of the manufacturing process. In order to significantly lower the costs, the current casting procedures had to be abandoned. Since polystyrene is widely used in the consumer industry, the logical path was to investigate the extrusion of commercial-grade polystyrene pellets with dopants to yield high quality plastic scintillator. This concept was tested and high quality extruded plastic scintillator was produced. The D0 and MINOS experiments are already using extruded scintillator strips in their detectors. An extrusion line has recently been installed at Fermilab in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new facility will serve to further develop and improve extruded plastic scintillator. This paper will discuss the characteristics of extruded plastic scintillator and its raw materials, the different manufacturing techniques and the current R andD program at Fermilab

  12. Quenching the scintillation in CF4 Cherenkov gas radiator

    International Nuclear Information System (INIS)

    Blake, T.; D'Ambrosio, C.; Easo, S.; Eisenhardt, S.; Fitzpatrick, C.; Forty, R.; Frei, C.; Gibson, V.; Gys, T.; Harnew, N.; Hunt, P.; Jones, C.R.; Lambert, R.W.; Matteuzzi, C.; Muheim, F.; Papanestis, A.; Perego, D.L.; Piedigrossi, D.; Plackett, R.; Powell, A.

    2015-01-01

    CF 4 is used as a Cherenkov gas radiator in one of the Ring Imaging Cherenkov detectors at the LHCb experiment at the CERN Large Hadron Collider. CF 4 is well known to have a high scintillation photon yield in the near and far VUV, UV and in the visible wavelength range. A large flux of scintillation photons in our photon detection acceptance between 200 and 800 nm could compromise the particle identification efficiency. We will show that this scintillation photon emission system can be effectively quenched, consistent with radiationless transitions, with no significant impact on the photons resulting from Cherenkov radiation

  13. Trigger and electronics issues for scintillating fiber tracking

    International Nuclear Information System (INIS)

    Baumbaugh, A.E.

    1994-01-01

    Scintillating Fiber technology has made great advances and has demonstrated great promise for high speed charged particle tracking and triggering. The small detector sizes and fast scintillation floors available, make them very promising for use at high luminosity experiments at today's and tomorrow's colliding and fixed target experiments where high rate capability is essential. This paper will discuss some of the system aspects which should be considered by anyone attempting to design a scintillating fiber tracking system and high speed tracking trigger. As the reader will see, seemingly simple decisions can have far reaching effects on overall system performance

  14. Scintillation trigger system of the liquid argon neutrino detector

    International Nuclear Information System (INIS)

    Belikov, S.V.; Gurzhiev, S.N.; Gutnikov, Yu.E.; Denisov, A.G.; Kochetkov, V.I.; Matveev, M.Yu.; Mel'nikov, E.A.; Usachev, A.P.

    1994-01-01

    This paper presents the organization of the Scintillation Trigger System (STS) for the Liquid Argon Neutrino Detector of the Tagged Neutrino Facility. STS is aimed at the effective registration of the needed neutrino interaction type and production of a fast trigger signal with high time resolution. The fast analysis system of analog signal from the trigger scintillation planes for rejection of the trigger signals from background processes is described. Real scintillation trigger planes characteristics obtained on the basis of the presented data acquisition system are shown. 10 refs., 12 figs., 3 tabs

  15. Liquid scintillation spectrometer survey 155Eu liquid activity

    International Nuclear Information System (INIS)

    Zhang Zuhua

    2002-01-01

    In the countrywide contrasting survey of 155 Eu activity, 155 Eu liquid activity was determined for the first time through using liquid scintillation spectrometer survey 155 Eu β ray. In survey total uncertainty, determining activity accord with determining activity average value of all a wide variety of survey instrument entering into contrasting survey. But using liquid scintillation spectrometer survey, it is simple and save time, is beyond compare for other survey method. It indicate liquid scintillation spectrometer survey β-γ nuclide activity is effective as well

  16. Development of scintillation materials for medical imaging and other applications

    International Nuclear Information System (INIS)

    Melcher, C. L.

    2013-01-01

    Scintillation materials that produce pulses of visible light in response to the absorption of energetic photons, neutrons, and charged particles, are widely used in various applications that require the detection of radiation. The discovery and development of new scintillators has accelerated in recent years, due in large part to their importance in medical imaging as well as in security and high energy physics applications. Better understanding of fundamental scintillation mechanisms as well as the roles played by defects and impurities have aided the development of new high performance scintillators for both gamma-ray and neutron detection. Although single crystals continue to dominate gamma-ray based imaging techniques, composite materials and transparent optical ceramics potentially offer advantages in terms of both synthesis processes and scintillation performance. A number of promising scintillator candidates have been identified during the last few years, and several are currently being actively developed for commercial production. Purification and control of raw materials and cost effective crystal growth processes can present significant challenges to the development of practical new scintillation materials.

  17. A snapshot of the polar ionosphere

    International Nuclear Information System (INIS)

    Whitteker, J.H.

    1976-01-01

    This paper presents a picture of the north polar F layer and topside ionosphere obtained primarily from three satellites (Alouette 2, ISIS 1, ISIS 2), that passed over the region within a time interval of ca. 50 min on 25 April 1971, a magnetically quiet day. The horizontal distribution of electron densities at the peak of the F layer is found to be similar to synoptic results from the IGY. Energetic particle and ionospheric plasma data are also presented, and the F layer data are discussed in terms of these measurements, and also in terms of electric field and neutral N 2 density measurements made by other satellites on other occasions. The major features observed are as follows: A tongue of F region ionization extends from the dayside across the polar cap, which is accounted for by antisunward drift due to magnetospheric convection. In the F layer and topside ionosphere, the main effect of auroral precipitation appears to be heating and expansion of the topside. A region of low F layer density appears on the morning side of the polar cap, which may be due to convection and possibly also to enhanced N 2 densities. (author)

  18. Scintillation properties of GSO

    International Nuclear Information System (INIS)

    Melcher, C.L.; Schweitzer, J.S.; Utsu, T.; Akiyama, S.

    1990-01-01

    The timing properties of Gd 2 SiO 5 :Ce (GSO) single crystal scintillators have previously been evaluated for positron emission tomography applications. The measured time resolution, however, was worse than expected from calculations based on photoelectron yield and a 60 nanosecond exponential decay constant, leading us to further investigate GSO's basic properties. With a time-correlated-single-photon technique, the authors have found two decay components, one of 56 ns and one of 600 ns, the latter containing 10--15% of the total scintillation output. This may explain the difference between the experimental and theoretical time resolutions and confirms a previous hypothesis of a long decay component. In addition, the authors have found that each component's decay constant strongly depends on the cerium concentration. The primary component varies from ∼ 20 ns to ∼ 190 ns and the secondary component varies from ∼ 70 ns to ∼ 1200 ns as the cerium concentration is varied from 5.0 mol% to 0.1 mol%

  19. The Role of Ionospheric Outflow Preconditioning in Determining Storm Geoeffectiveness

    Science.gov (United States)

    Welling, D. T.; Liemohn, M. W.; Ridley, A. J.

    2012-12-01

    It is now well accepted that ionospheric outflow plays an important role in the development of the plasma sheet and ring current during geomagnetic storms. Furthermore, even during quiet times, ionospheric plasma populates the magnetospheric lobes, producing a reservoir of hydrogen and oxygen ions. When the Interplanetary Magnetic Field (IMF) turns southward, this reservoir is connected to the plasma sheet and ring current through magnetospheric convection. Hence, the conditions of the ionosphere and magnetospheric lobes leading up to magnetospheric storm onset have important implications for storm development. Despite this, there has been little research on this preconditioning; most global simulations begin just before storm onset, neglecting preconditioning altogether. This work explores the role of preconditioning in determining the geoeffectiveness of storms using a coupled global model system. A model of ionospheric outflow (the Polar Wind Outflow Model, PWOM) is two-way coupled to a global magnetohydrodynamic model (the Block-Adaptive Tree Solar wind Roe-type Upwind Scheme, BATS-R-US), which in turn drives a ring current model (the Ring current Atmosphere interactions Model, RAM). This unique setup is used to simulate an idealized storm. The model is started at many different times, from 1 hour before storm onset to 12 hours before. The effects of storm preconditioning are examined by investigating the total ionospheric plasma content in the lobes just before onset, the total ionospheric contribution in the ring current just after onset, and the effects on Dst, magnetic elevation angle at geosynchronous, and total ring current energy density. This experiment is repeated for different solar activity levels as set by F10.7 flux. Finally, a synthetic double-dip storm is constructed to see how two closely spaced storms affect each other by changing the preconditioning environment. It is found that preconditioning of the magnetospheric lobes via ionospheric

  20. Assessments of higher-order ionospheric effects on GPS coordinate time series: A case study of CMONOC with longer time series

    Science.gov (United States)

    Jiang, Weiping; Deng, Liansheng; Zhou, Xiaohui; Ma, Yifang

    2014-05-01

    Higher-order ionospheric (HIO) corrections are proposed to become a standard part for precise GPS data analysis. For this study, we deeply investigate the impacts of the HIO corrections on the coordinate time series by implementing re-processing of the GPS data from Crustal Movement Observation Network of China (CMONOC). Nearly 13 year data are used in our three processing runs: (a) run NO, without HOI corrections, (b) run IG, both second- and third-order corrections are modeled using the International Geomagnetic Reference Field 11 (IGRF11) to model the magnetic field, (c) run ID, the same with IG but dipole magnetic model are applied. Both spectral analysis and noise analysis are adopted to investigate these effects. Results show that for CMONOC stations, HIO corrections are found to have brought an overall improvement. After the corrections are applied, the noise amplitudes decrease, with the white noise amplitudes showing a more remarkable variation. Low-latitude sites are more affected. For different coordinate components, the impacts vary. The results of an analysis of stacked periodograms show that there is a good match between the seasonal amplitudes and the HOI corrections, and the observed variations in the coordinate time series are related to HOI effects. HOI delays partially explain the seasonal amplitudes in the coordinate time series, especially for the U component. The annual amplitudes for all components are decreased for over one-half of the selected CMONOC sites. Additionally, the semi-annual amplitudes for the sites are much more strongly affected by the corrections. However, when diplole model is used, the results are not as optimistic as IGRF model. Analysis of dipole model indicate that HIO delay lead to the increase of noise amplitudes, and that HIO delays with dipole model can generate false periodic signals. When dipole model are used in modeling HIO terms, larger residual and noise are brought in rather than the effective improvements.

  1. The topside ionospheric effective scale heights (HT) derived with ROCSAT-1 and ground-based Ionosonde observations at equatorial and mid-latitude stations

    Science.gov (United States)

    Ram Sudarsanam, Tulasi; Su, Shin-Yi; Liu, C. H.; Reinisch, Bodo

    In this study, we propose the assimilation of topside in situ electron density data from ROCSAT-1 satellite along with the ionosonde measurements for accurate determination of topside iono-spheric effective scale heights (HT) using -Chapman function. The reconstructed topside elec-tron density profiles using these scale heights exhibit an excellent similitude with Jicamarca Incoherent Scatter Radar (ISR) profiles, and are much better representations than the existing methods of Reinisch-Huang method and/or the empirical IRI-2007 model. The main advan-tage with this method is that it allows the precise determination of the effective scale height (HT) and the topside electron density profiles at a dense network of ionosonde/digisonde sta-tions where no ISR facilities are available. The demonstration of the method is applied by investigating the diurnal, seasonal and solar activity variations of HT over the dip-equatorial station Jicamarca and the mid-latitude station Grahamstown. The diurnal variation of scale heights over Jicamarca consistently exhibits a morning time descent followed by a minimum around 0700-0800 LT and a pronounced maximum at noon during all the seasons of both high and moderate solar activity periods. Further, the scale heights exhibit a secondary maximum during the post-sunset hours of equinoctial and summer months, whereas the post-sunset peak is absent during the winter months. These typical features are further investigated using the topside ion properties obtained by ROCSAT-1 as well as SAMI2 model simulations. The re-sults consistently indicate that the diurnal variation of the effective scale height (HT) does not closely follow the plasma temperature variation and at equatorial latitudes is largely controlled by the vertical ExB drift.

  2. VHF and L-band scintillation characteristics over an Indian low latitude station, Waltair (17.7° N, 83.3° E

    Directory of Open Access Journals (Sweden)

    P. V. S. Rama Rao

    2005-10-01

    Full Text Available Characteristics of simultaneous VHF (244 MHz and L-band (1.5 GHz scintillations recorded at a low-latitude station, Waltair (17.7° N, 83.3° E, during the low sunspot activity year of March 2004 to March 2005, suggest that the occurrence of scintillations is mainly due to two types, namely the Plasma Bubble Induced (PBI, which maximizes during the post sunset hours of winter and equinoctial months, and the Bottom Side Sinusoidal (BSS type, which maximizes during the post-midnight hours of the summer solstice months. A detailed study on the spectral characteristics of the scintillations at both the frequencies show that the post-sunset scintillations are strong with fast fading (≈40 fad/min and are multiple in nature in scattering, giving rise to steep spectral slopes, whereas the post-midnight scintillations, which occur mostly on the VHF signal with low fading rate (≈4 fad/min, are of the BSS type, often showing typical Fresnel oscillations with reduced roll off spectral slopes, indicating that the type of irregularity resembles a thin screen structure giving rise to weak scattering. Using the onset times of several similar scintillation patches across the two satellite (FLEETSAT 73° E, INMARSAT 65° E ray paths (sub-ionospheric points are separated by 82 km, the East ward movement of the irregularity patches is found to vary from 150 to 250 m/s during the post sunset hours and decrease slowly during the post midnight hours. Further, the east-west extent of the PBI type of irregularities is found to vary from 100 to 500 km, while that of the BSS type extend up to a few thousand kilometers. Keywords. Ionosphere (Ionospheric irregularities; Auroral ionosphere; Electric fields and currents

  3. Multi-Instrument Observations of Geomagnetic Storms in the Arctic Ionosphere

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Komjathy, Attila; Verkhoglyadova, Olga

    from the solar corona on 16 February and the second one on 18 February. We focus on effects of such solar-originated geomagnetic disturbances on the high latitude ionosphere because our present understanding of the fundamental ionospheric processes – particularly during perturbed times – in this region...... is still incomplete....

  4. Ionospheric F-region response to the 26 September 2011 geomagnetic storm in the Antarctica American and Australian sectors

    Directory of Open Access Journals (Sweden)

    E. Correia

    2017-10-01

    Full Text Available The ionospheric response at middle and high latitudes in the Antarctica American and Australian sectors to the 26–27 September 2011 moderately intense geomagnetic storm was investigated using instruments including an ionosonde, riometer, and GNSS receivers. The multi-instrument observations permitted us to characterize the ionospheric storm-enhanced density (SED and tongues of ionization (TOIs as a function of storm time and location, considering the effect of prompt penetration electric fields (PPEFs. During the main phase of the geomagnetic storm, dayside SEDs were observed at middle latitudes, and in the nightside only density depletions were observed from middle to high latitudes. Both the increase and decrease in ionospheric density at middle latitudes can be attributed to a combination of processes, including the PPEF effect just after the storm onset, dominated by disturbance dynamo processes during the evolution of the main phase. Two SEDs–TOIs were identified in the Southern Hemisphere, but only the first episode had a counterpart in the Northern Hemisphere. This difference can be explained by the interhemispheric asymmetry caused by the high-latitude coupling between solar wind and the magnetosphere, which drives the dawn-to-dusk component of the interplanetary magnetic field. The formation of polar TOI is a function of the SED plume location that might be near the dayside cusp from which it can enter the polar cap, which was the case in the Southern Hemisphere. Strong GNSS scintillations were observed at stations collocated with SED plumes at middle latitudes and cusp on the dayside and at polar cap TOIs on the nightside.

  5. Electric fields in the ionosphere

    International Nuclear Information System (INIS)

    Kirchhoff, V.W.J.H.

    1975-01-01

    F-region drift velocities, measured by incoherent-scatter radar, were analyzed in terms of diurnal, seasonal, magnetic-activity, and solar-cycle effects. A comprehensive electric field model was developed that includes the effects of the E and F-region dynamos, magnetospheric sources, and ionospheric conductivities, for both the local and conjugate regions. The E-region dynamo dominates during the day, but at night the F-region and convection are more important. This model provides much better agreement with observations of the F-region drifts than previous models. Results indicate that larger magnitudes occur at night, and that daily variation is dominated by the diurnal mode. Seasonal variations in conductivities and thermospheric winds indicate a reversal in direction in the early morning during winter from south to northward. On magnetic perturbed days the drifts deviate rather strongly from the quiet days average, especially around 13 L.T. for the northward and 18 L.T. for the westward component

  6. Scintillating plate calorimeter optical design

    International Nuclear Information System (INIS)

    McNeil, R.; Fazely, A.; Gunasingha, R.; Imlay, R.; Lim, J.

    1990-01-01

    A major technical challenge facing the builder of a general purpose detector for the SSC is to achieve an optimum design for the calorimeter. Because of its fast response and good energy resolution, scintillating plate sampling calorimeters should be considered as a possible technology option. The work of the Scintillating Plate Calorimeter Collaboration is focused on compensating plate calorimeters. Based on experimental and simulation studies, it is expected that a sampling calorimeter with alternating layers of high-Z absorber (Pb, W, DU, etc.) and plastic scintillator can be made compensating (e/h = 1.00) by suitable choice of the ratio of absorber/scintillator thickness. Two conceptual designs have been pursued by this subsystem collaboration. One is based on lead as the absorber, with read/out of the scintillator plates via wavelength shifter fibers. The other design is based on depleted uranium as the absorber with wavelength shifter (WLS) plate readout. Progress on designs for the optical readout of a compensating scintillator plate calorimeter are presented. These designs include readout of the scintillator plates via wavelength shifter plates or fiber readout. Results from radiation damage studies of the optical components are presented

  7. Radiation damage studies on new liquid scintillators and liquid-core scintillating fibers

    International Nuclear Information System (INIS)

    Golovkin, S.V.

    1994-01-01

    The radiation resistant of some new liquid scintillation and capillaries filled with liquid scintillators has been presented. It was found that scintillation efficiency of the scintillator based on 1-methyl naphthalene with a new R39 only by 10% at the dose of 190 Mrad and the radiation resistance of thin liquid-core scintillating was decreased fibers exceeded 60 Mrad. 35 refs

  8. On the mapping of ionospheric convection into the magnetosphere

    International Nuclear Information System (INIS)

    Hesse, M.; Birn, J.; Hoffman, R.A.

    1997-01-01

    Under steady state conditions and in the absence of parallel electric fields, ionospheric convection is a direct map of plasma and magnetic flux convection in the magnetosphere, and quantitative estimates can be obtained from the mapping along magnetic field lines of electrostatic ionospheric electric fields. The resulting magnetospheric electrostatic potential distribution then provides the convection electric field in various magnetospheric regions. We present a quantitative framework for the investigation of the applicability and limitations of this approach based on an analytical theory derived from first principles. Particular emphasis is on the role of parallel electric field regions and on inductive effects, such as expected during the growth and expansive phases of magnetospheric substorms. We derive quantitative estimates for the limits in which either effect leads to a significant decoupling between ionospheric and magnetospheric convection and provide an interpretation of ionospheric convection which is independent of the presence of inductive electric fields elsewhere in the magnetosphere. Finally, we present a study of the relation between average and instantaneous convection, using two periodic dynamical models. The models demonstrate and quantify the potential mismatch between the average electric fields in the ionosphere and the magnetosphere in strongly time-dependent cases that may exist even when they are governed entirely by ideal MHD

  9. Influence of Ionospheric Weather on GNSS Radio Occultation Signals

    Science.gov (United States)

    Yue, X.; Schreiner, W. S.; Pedatella, N. M.; Kuo, Y. H.

    2016-12-01

    Transient loss of lock (LOL) is one of the key space weather effects on the Global Navigation Satellite System (GNSS). Based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System (GPS) radio occultation (RO) observations during 2007-2011, we have analyzed the signal cycle slip (CS) occurrence comprehensively and its correlation to the ionospheric weather phenomena such as sporadic E (Es), equatorial F region irregularity (EFI), and the ionospheric equatorial ionization anomaly (EIA). The high vertical resolution of RO observations enables us to distinguish the CS resulting from different ionospheric layers clearly on a global scale. In the E layer, the CS is dominated by the Es occurrence, while in the F layer, the CS is mainly related to the EIA and EFI at low and equatorial latitudes. In the polar region, the CS is primarily related to polar cap electron density gradients. The overall average CS (> 6 cycles) occurrence is 23% per occultation, with the E (50-150 km) and F (150-600 km) layers contributing 8.3% and 14.7%, respectively. Awareness of the effect of the ionospheric weather on the CS of the low-Earth-orbit (LEO)-based GNSS signal could be beneficial to a variety of applications, including the LEO-based GNSS data processing and the corresponding hardware/firmware design.

  10. Scintillation 1024-channel hodoscope

    International Nuclear Information System (INIS)

    Kotov, I.V.; Krasnokutskij, R.N.; Kurbakov, V.I.; Shchukin, A.V.

    1993-01-01

    Flow diagram of voltage divider for photomultiplier used in scintillation multichannel hodoscope is described. The suggested diagram of the divider allows to optimize potential distribution at the innput chamber (photocathode - modulator - first dynode) and in the tail segment of the divider (the nineth dynode-anode). Adjustment of high voltage is conducted using multirotational potentiometer switched in series with the divider. Amplifier-limiter with 80 mkA threshold set at voltage comparator is placed at divide plate. Threshold of its sensitivity constitutes 80 mkA. Hodoscope supply system consists of supply sources of comparators (+-6V) four sources of auxiliary supply sources of the last dynodes of photomultipliers and high-voltage source. Current consumption constitutes 25 A by - 6V, 23 A by + 6 V for the whole hodoscope and up to 200 mA from high-voltage source for one plane. Additional charging sources have constant consumption equal to ∼ 20 mA

  11. Encapsulated scintillation detector

    International Nuclear Information System (INIS)

    Toepke, I.L.

    1982-01-01

    A scintillation detector crystal is encapsulated in a hermetically sealed housing having a glass window. The window may be mounted in a ring by a compression seal formed during cooling of the ring and window after heating. The window may be chemically bonded to the ring with or without a compression seal. The ring is welded to the housing along thin weld flanges to reduce the amount of weld heat which must be applied. A thin section is provided to resist the flow of welding heat to the seal between the ring and the window thereby forming a thermal barrier. The thin section may be provided by a groove cut partially through the wall of the ring. A layer of PTFE between the tubular body and the crystal minimizes friction created by thermal expansion. Spring washers urge the crystal towards the window. (author)

  12. Scintillation counter, segmented shield

    International Nuclear Information System (INIS)

    Olson, R.E.; Thumim, A.D.

    1975-01-01

    A scintillation counter, particularly for counting gamma ray photons, includes a massive lead radiation shield surrounding a sample-receiving zone. The shield is disassembleable into a plurality of segments to allow facile installation and removal of a photomultiplier tube assembly, the segments being so constructed as to prevent straight-line access of external radiation through the shield into radiation-responsive areas. Provisions are made for accurately aligning the photomultiplier tube with respect to one or more sample-transmitting bores extending through the shield to the sample receiving zone. A sample elevator, used in transporting samples into the zone, is designed to provide a maximum gamma-receiving aspect to maximize the gamma detecting efficiency. (U.S.)

  13. Properties of scintillator solutes

    International Nuclear Information System (INIS)

    Fluornoy, J.M.

    1998-06-01

    This special report summarizes measurements of the spectroscopic and other properties of the solutes that were used in the preparation of several new liquid scintillators developed at EG and G/Energy Measurements/Santa Barbara Operations (the precursor to Bechtel Nevada/Special Technologies Laboratory) on the radiation-to-light converter program. The data on the individual compounds are presented in a form similar to that used by Prof. Isadore Berlman in his classic handbook of fluorescence spectra. The temporal properties and relative efficiencies of the new scintillators are presented in Table 1, and the efficiencies as a function of wavelength are presented graphically in Figure 1. In addition, there is a descriptive glossary of the abbreviations used herein. Figure 2 illustrates the basic structures of some of the compounds and of the four solvents reported in this summary. The emission spectra generally exhibit more structure than the absorption spectra, with the result that the peak emission wavelength for a given compound may lie several nm away from the wavelength, λ avg , at the geometric center of the emission spectrum. Therefore, the author has chosen to list absorption peaks, λ max , and emission λ avg values in Figures 3--30, as being most illustrative of the differences between the compounds. The compounds, BHTP, BTPB, ADBT, and DPTPB were all developed on this program. P-terphenyl, PBD, and TPB are commercially available blue emitters. C-480 and the other longer-wavelength emitters are laser dyes available commercially from Exciton Corporation. 1 ref., 30 figs

  14. Analysis of ionospheric structure influences on residual ionospheric errors in GNSS radio occultation bending angles based on ray tracing simulations

    Science.gov (United States)

    Liu, Congliang; Kirchengast, Gottfried; Sun, Yueqiang; Zhang, Kefei; Norman, Robert; Schwaerz, Marc; Bai, Weihua; Du, Qifei; Li, Ying

    2018-04-01

    The Global Navigation Satellite System (GNSS) radio occultation (RO) technique is widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source to RO at upper stratospheric altitudes, and a linear dual-frequency bending angle correction is commonly used to remove the first-order ionospheric effect. However, the higher-order residual ionospheric error (RIE) can still be significant, so it needs to be further mitigated for high-accuracy applications, especially from 35 km altitude upward, where the RIE is most relevant compared to the decreasing magnitude of the atmospheric bending angle. In a previous study we quantified RIEs using an ensemble of about 700 quasi-realistic end-to-end simulated RO events, finding typical RIEs at the 0.1 to 0.5 µrad noise level, but were left with 26 exceptional events with anomalous RIEs at the 1 to 10 µrad level that remained unexplained. In this study, we focused on investigating the causes of the high RIE of these exceptional events, employing detailed along-ray-path analyses of atmospheric and ionospheric refractivities, impact parameter changes, and bending angles and RIEs under asymmetric and symmetric ionospheric structures. We found that the main causes of the high RIEs are a combination of physics-based effects - where asymmetric ionospheric conditions play the primary role, more than the ionization level driven by solar activity - and technical ray tracer effects due to occasions of imperfect smoothness in ionospheric refractivity model derivatives. We also found that along-ray impact parameter variations of more than 10 to 20 m are possible due to ionospheric asymmetries and, depending on prevailing horizontal refractivity gradients, are positive or negative relative to the initial impact parameter at the GNSS transmitter. Furthermore, mesospheric RIEs are found generally higher than upper-stratospheric ones, likely due to

  15. Radiation damage in plastic scintillators

    International Nuclear Information System (INIS)

    Majewski, S.

    1990-01-01

    Results of radiation damage studies in plastic scintillators are reviewed and critically analyzed from the point of view of applications of plastic scintillators in calorimetric detectors for the SSC. Damage to transmission and to fluorescent yield in different conditions is discussed. New directions in R ampersand D are outlined. Several examples are given of the most recent data on the new scintillating materials made with old and new plastics and fluors, which are exhibiting significantly improved radiation resistance. With a present rate of a vigorous R D programme, the survival limits in the vicinity of 100 MRad seem to be feasible within a couple of years

  16. Applications of liquid scintillation tubes

    International Nuclear Information System (INIS)

    Broga, D.W.

    1977-01-01

    A new cocktail containing device for liquid scintillation counting, the scintillation tube, consists of a two-layered plastic bag which is heatsealed after the cocktail and sample have been placed in it. It is then placed in a carrying vial and counted in a conventional liquid scintillation counter. These tubes have proved to be a practical and economical alternative to vials. Some of their advantages are elimination of absorption problems, transparency, lower background and higher counting efficiency, low breakage danger and savings in waste disposal costs. Two applications for which the tubes are particularly suitable are the counting of laboratory swipes and urine analysis. (author)

  17. Average energy expended per ion pair, exciton enhanced ionization (Jesse effect), electron drift velocity, average electron energy and scintillation in rare gas liquids

    International Nuclear Information System (INIS)

    Doke, T.; Hitachi, A.; Hoshi, Y.; Masuda, K.; Hamada, T.

    1977-01-01

    Precise measurements of W-values, the average energy expended per electron-hole pair in liquid Ar and Xe, were made by the electron-pulse method, and that in liquid Kr by the steady conduction current method. The results showed that the W-values were clearly smaller than those in gaseous Ar, Xe and Kr as predicted by Doke. The results can be explained by the conduction bands which exist in these rare gas liquids as well as in the solid state. The enhanced ionization yield was observed for Xe-doped liquid Ar, and it was attributed to the ionizing excitation transfer process from Ar excitons to doped Xe. This is very similar to the Jesse effect in the gas phase. The saturated value of the enhanced ionization was in good agreement with the theoretical value, and it provides strong evidence for the existence of the exciton states in liquid Ar. Fano factors in liquid Ar, Kr, Xe and Xe-doped liquid Ar have been estimated from the Fano Formula, and they were smaller than those in the gas phase. The drift velocity of electrons in liquid Ar, liquid Ar-gas mixtures and liquid Xe have been measured with gridded ionization chambers. The average electron energy in liquid Ar has been measured. The electron-induced scintillations of liquid Xe and Ar have been studied. (Kato, T.)

  18. Use of pliable bags in liquid scintillation counting

    International Nuclear Information System (INIS)

    Simonnet, G.; Jacquet, M.A.; Sharif, A.; Engler, R.

    1981-01-01

    Pliable plastic bags have been used to replace glass or plastic vials for liquid scintillation counting. The two major advantages of this method are the lower cost of the plastic bags and the fact that, per sample, the radioactive waste is significantly reduced. The following parameters have been checked: the impermeability of the bags to various scintillator mixtures and the fact that neither the irregular shape of the bags nor their position in the counting chamber had any effect on the results of the counting. The latter was also constant with time, at least over a period of 10 days. The technique has been used to count the radioactivity of 3 H-DNA precipitates prepared from bacteria and lymphocytes and deposited on filters impregnated with only 200 μl scintillator. It is a method that can be applied to the counting of any samples deposited on filters and insoluble in scintillator. (author)

  19. Gamma spectrometry and plastic-scintillator inherent background

    International Nuclear Information System (INIS)

    Pomerantsev, V.V.; Gagauz, I.B.; Mitsai, L.I.; Pilipenko, V.S.; Solomonov, V.M.; Chernikov, V.V.; Tsirlin, Y.A.

    1988-01-01

    The authors measured the energy resolution for a linear dependence of light yield on gamma radiation energy of gamma spectrometers based on plastic scintillation detectors for several plastic scintillators. If there were several gamma lines from the source the line with the highest energy was used to eliminate distortion due to overlap from the Compton background from gamma radiation of higher energy. Attenuation lengths were calculated. The tests were based on three modes of interaction between the gamma radiation and the scintillator: Compton scattering, the photoelectric effect, and pair formation. The contribution from light collection was also considered. The scintillators tested included polystyrene, polymethyl methacrylate, cesium iodide, and sodium iodide. Gamma sources included cesium 137, sodium 22, potassium 40, yttrium 88, thorium 232, and plutonium-beryllium

  20. LET dependence of scintillation yields in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Doke, Tadayoshi; Hitachi, Akira; Kikuchi, Jun; Crawford, H J; Lindstrom, P J; Masuda, Kimiaki; Shibamura, Eido; Takahashi, Tan

    1988-06-01

    Scintillation yields (scintillation intensity per unit absorbed energy) in liquid argon for ionizing particles are reviewed as a function of LET for the particles. The maximum scintillation yield, which is obtained for relativistic heavy ions from Ne to La, is about 1.2 times larger than that for gamma rays in NaI(Tl) crystal. In the low LET region, the scintillation yields for relativistic electrons, protons and He ions are 10-20% lower than the maximum yield. This tendency can be explained by taking into account the existence of the electrons which have escaped from their parent ions. In the high LET region, a quenching effect due to high ionization density is observed for alpha particles, fission fragments and relativistic Au ions.

  1. Superimposed disturbance in the ionosphere triggered by spacecraft launches in China

    Science.gov (United States)

    He, L. M.; Wu, L. X.; Liu, S. J.; Liu, S. N.

    2015-11-01

    Using GPS dual-frequency observations collected by continuously operating GPS tracking stations in China, superimposed disturbances caused by the integrated action of spacecraft's physical effect and chemical effect on ionosphere during the launches of the spacecrafts Tiangong-1 and Shenzhou-8 in China were firstly determined. The results show that the superimposed disturbance was composed of remarkable ionospheric waves and significant ionospheric depletion emerged after both launches. Meanwhile, we found for the first time that the ionospheric waves were made up of two periods of wave by wavelet analysis. The first period of ∼ 4 min shows one event in the near stations and two sub-events in the few far stations. The second period of ∼ 9 min shows only one event in all the observed stations. Finally, the time characteristics for ionospheric waves and depletions were examined.

  2. Superimposed disturbance in the ionosphere triggered by spacecraft launches in China

    Directory of Open Access Journals (Sweden)

    L. M. He

    2015-11-01

    Full Text Available Using GPS dual-frequency observations collected by continuously operating GPS tracking stations in China, superimposed disturbances caused by the integrated action of spacecraft's physical effect and chemical effect on ionosphere during the launches of the spacecrafts Tiangong-1 and Shenzhou-8 in China were firstly determined. The results show that the superimposed disturbance was composed of remarkable ionospheric waves and significant ionospheric depletion emerged after both launches. Meanwhile, we found for the first time that the ionospheric waves were made up of two periods of wave by wavelet analysis. The first period of ∼ 4 min shows one event in the near stations and two sub-events in the few far stations. The second period of ∼ 9 min shows only one event in all the observed stations. Finally, the time characteristics for ionospheric waves and depletions were examined.

  3. Application of TaiWan Ionosphere Model to Single-Frequency Ionospheric Delay Correction for GPS Static Position Positioning

    Science.gov (United States)

    Macalalad, E. P.; Tsai, L.; Wu, J.

    2011-12-01

    Ionospheric delay is one of the major sources of error in GPS positioning and navigation. This error in both pseudorange and phase ranges can vary depending on the location of observation, local time, season, solar cycle and geomagnetic activity. This effect can be practically removed using dual-frequency receivers. However, these types of receivers are very expensive and thus, impractical for most users. Therefore, for single-frequency receivers, ionosphere is usually modeled to attempt to remove this effect analytically. Numerous ionosphere models have been introduced in the past. Some of which are the Klobuchar (or broadcast) model and the global ionosphere map (GIM) provided by the International GNSS Service (IGS). In this paper, another model, called the TaiWan Ionosphere Model (TWIM) was used to correct this effect. TWIM is a three dimensional ionospheric electron (ne) density model derived from FormoSat3/COSMIC GPS Radio Occultation measurements, was used to calculate ionospheric delay for GPS single-frequency positioning. The ne profiles were used to calculate the slant TEC (STEC) between a receiver and each GPS satellite and correct the pseudorange single-frequency observations. The corrected pseudorange for every epoch was used to calculate the position of the receiver. Observations were made in a low-latitude location near one of the peaks of the equatorial anomaly. It was shown that TEC maps generated using TWIM exhibited detailed structure of the ionosphere, whereas Klobuchar and GIM only provided the basic diurnal and geographic features of the ionosphere. Also, it was shown that for static point positioning TWIM provides more accurate and more precise positioning than the Klobuchar and GIM models. That is, on the average, the horizontal accuracy, represented by the circular error probable (CEP), distance RMS (DRMS) and twice the DRMS (2DRMS), were better by 15-18% as compared with the CEP, DRMS and 2DRMS of uncorrected, Klobuchar and GIM. Moreover

  4. First demonstration of HF-driven ionospheric currents

    Science.gov (United States)

    Papadopoulos, K.; Chang, C.-L.; Labenski, J.; Wallace, T.

    2011-10-01

    The first experimental demonstration of HF driven currents in the ionosphere at low ELF/ULF frequencies without relying in the presence of electrojets is presented. The effect was predicted by theoretical/computational means in a recent letter and given the name Ionospheric Current Drive (ICD). The effect relies on modulated F-region HF heating to generate Magneto-Sonic (MS) waves that drive Hall currents when they reach the E-region. The Hall currents inject ELF waves into the Earth-Ionosphere waveguide and helicon and Shear Alfven (SA) waves in the magnetosphere. The proof-of-concept experiments were conducted using the HAARP heater in Alaska under the BRIOCHE program. Waves between 0.1-70 Hz were measured at both near and far sites. The letter discusses the differences between ICD generated waves and those relying on modulation of electrojets.

  5. L-band nighttime scintillations at the northern edge of the EIA along 95°E during the ascending half of the solar cycle 24

    Science.gov (United States)

    Dutta, Barsha; Kalita, Bitap Raj; Bhuyan, Pradip Kumar

    2018-04-01

    The characteristics of nighttime ionospheric scintillations measured at the L-band frequency of 1.575 GHz over Dibrugarh (27.5°N, 95°E, MLAT ∼ 17°N, 43° dip) during the ascending half of the solar cycle 24 from 2010 to 2014 have been investigated and the results are presented in this paper. The measurement location is within or outside the zone of influence of the equatorial ionization anomaly depending on solar and geomagnetic activity. Maximum scintillation is observed in the equinoxes irrespective of solar activity with clear asymmetry between March and September. The occurrence frequency in the solstices shifts from minimum in the June solstice in low solar activity to a minimum in the December solstice in high solar activity years. A significant positive correlation of occurrence of scintillations in the June solstice with solar activity has been observed. However, earlier reports from the Indian zone (∼75°E) indicate negative or no correlation of scintillation in June solstice with solar activity. Scintillations activity/occurrence in solstices indicates a clear positive correlation with Es recorded simultaneously by a collocated Ionosonde. In equinoxes, maximum scintillations occur in the pre-midnight hours while in solstices the occurrence frequency peaks just after sunset. The incidence of strong scintillations (S4 ≥ 0.4) increases with increase in solar activity. Strong (S4 ≥ 0.4) ionospheric scintillations accompanied by TEC depletions in the pre-midnight period is attributed to equatorial irregularities whereas the dusk period scintillations are related to the sporadic-E activity. Present results thus indicate that the current location at the northern edge of the EIA behaves as low as well as mid-latitude location.

  6. A method to identify aperiodic disturbances in the ionosphere

    Science.gov (United States)

    Wang, J.-S.; Chen, Z.; Huang, C.-M.

    2014-05-01

    In this paper, variations in the ionospheric F2 layer's critical frequency are decomposed into their periodic and aperiodic components. The latter include disturbances caused both by geophysical impacts on the ionosphere and random noise. The spectral whitening method (SWM), a signal-processing technique used in statistical estimation and/or detection, was used to identify aperiodic components in the ionosphere. The whitening algorithm adopted herein is used to divide the Fourier transform of the observed data series by a real envelope function. As a result, periodic components are suppressed and aperiodic components emerge as the dominant contributors. Application to a synthetic data set based on significant simulated periodic features of ionospheric observations containing artificial (and, hence, controllable) disturbances was used to validate the SWM for identification of aperiodic components. Although the random noise was somewhat enhanced by post-processing, the artificial disturbances could still be clearly identified. The SWM was then applied to real ionospheric observations. It was found to be more sensitive than the often-used monthly median method to identify geomagnetic effects. In addition, disturbances detected by the SWM were characterized by a Gaussian-type probability density function over all timescales, which further simplifies statistical analysis and suggests that the disturbances thus identified can be compared regardless of timescale.

  7. Identification of scintillation signatures on GPS signals originating from plasma structures detected with EISCAT incoherent scatter radar along the same line of sight.

    Science.gov (United States)

    Forte, Biagio; Coleman, Chris; Skone, Susan; Häggström, Ingemar; Mitchell, Cathryn; Da Dalt, Federico; Panicciari, Tommaso; Kinrade, Joe; Bust, Gary

    2017-01-01

    Ionospheric scintillation originates from the scattering of electromagnetic waves through spatial gradients in the plasma density distribution, drifting across a given propagation direction. Ionospheric scintillation represents a disruptive manifestation of adverse space weather conditions through degradation of the reliability and continuity of satellite telecommunication and navigation systems and services (e.g., European Geostationary Navigation Overlay Service, EGNOS). The purpose of the experiment presented here was to determine the contribution of auroral ionization structures to GPS scintillation. European Incoherent Scatter (EISCAT) measurements were obtained along the same line of sight of a given GPS satellite observed from Tromso and followed by means of the EISCAT UHF radar to causally identify plasma structures that give rise to scintillation on the co-aligned GPS radio link. Large-scale structures associated with the poleward edge of the ionospheric trough, with auroral arcs in the nightside auroral oval and with particle precipitation at the onset of a substorm were indeed identified as responsible for enhanced phase scintillation at L band. For the first time it was observed that the observed large-scale structures did not cascade into smaller-scale structures, leading to enhanced phase scintillation without amplitude scintillation. More measurements and theory are necessary to understand the mechanism responsible for the inhibition of large-scale to small-scale energy cascade and to reproduce the observations. This aspect is fundamental to model the scattering of radio waves propagating through these ionization structures. New insights from this experiment allow a better characterization of the impact that space weather can have on satellite telecommunications and navigation services.

  8. Light Collection in the High Energy X-ray Detector with the Pixelated CdWO4 Scintillator using Monte Carlo Method

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Chang Hwy; Moon, Myung-Kook; Lee, Suhyun; Kim, Jongyul; Kim, Jeongho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Jong Won [Korea Research Institute of Ships and Ocean Engineering, Daejeon (Korea, Republic of)

    2015-05-15

    The performance of indirect detectors, which use the scintillator as CdWO{sub 4}, BGO, CsI, NaI, etc., are effected by optical properties of scintillator and geometrical condition of scintillator. Some of generated lights by interaction between x-ray photons and scintillator are collected at the photo-sensor and others are absorbed in scintillator or escape out of detector. In order to make the high performance image detector, detector should be able to gather the generated lights as much as possible. To minimize the loss of generated lights, thickness of scintillator is to be chosen appropriately. Therefore, the quality of the image detector using the pixelated scintillator is determined by scintillator size, reflectance of scintillator surface, electric noise, etc. In this study, we carried out a study the correlation between the number of collected light and the change of thickness of scintillator using Monte Carlo method. As shown in results, the optimal thickness of a scintillator should be properly selected depending on the incident x-ray energy. In case of without reflector, the scintillator thickness range for x-ray detection is thinner than other cases (with reflector). In the case of a scintillator with reflector, number of collected light and the optima thickness of a scintillator is higher and thicker than scintillator without reflector.

  9. Linear energy transfer effects on time profiles of scintillation of Ce-doped LiCaAlF{sub 6} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yanagida, Takayuki [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-Cho, Ikoma, Nara 630-0192 (Japan); Koshimizu, Masanori [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Kurashima, Satoshi [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Iwamatsu, Kazuhiro [Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Kimura, Atsushi; Taguchi, Mitsumasa [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Fujimoto, Yutaka; Asai, Keisuke [Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2015-12-15

    We measured temporal profiles of the scintillation of Ce-doped LiCaAlF{sub 6} scintillator crystals at different linear energy transfers (LETs). Based on the comparison of high-LET temporal profiles with those at low LET, a fast component was observed only at low LET. The disappearance of the fast component at high LET is tentatively ascribed to the quenching of excited states at crystal defects owing to the interaction between excited states via the Auger process. In addition, the rise and the initial decay behavior were dependent on the LET. This LET-dependent behavior is explained by an acceleration process and a deceleration process in energy transfer at high LET. The LET-dependent temporal profiles provide the basis for a discrimination technique of gamma-ray and neutron detection events using these scintillators based on the nuclear reaction, {sup 6}Li(n,α)t.

  10. Photon statistics in scintillation crystals

    Science.gov (United States)

    Bora, Vaibhav Joga Singh

    Scintillation based gamma-ray detectors are widely used in medical imaging, high-energy physics, astronomy and national security. Scintillation gamma-ray detectors are eld-tested, relatively inexpensive, and have good detection eciency. Semi-conductor detectors are gaining popularity because of their superior capability to resolve gamma-ray energies. However, they are relatively hard to manufacture and therefore, at this time, not available in as large formats and much more expensive than scintillation gamma-ray detectors. Scintillation gamma-ray detectors consist of: a scintillator, a material that emits optical (scintillation) photons when it interacts with ionization radiation, and an optical detector that detects the emitted scintillation photons and converts them into an electrical signal. Compared to semiconductor gamma-ray detectors, scintillation gamma-ray detectors have relatively poor capability to resolve gamma-ray energies. This is in large part attributed to the "statistical limit" on the number of scintillation photons. The origin of this statistical limit is the assumption that scintillation photons are either Poisson distributed or super-Poisson distributed. This statistical limit is often dened by the Fano factor. The Fano factor of an integer-valued random process is dened as the ratio of its variance to its mean. Therefore, a Poisson process has a Fano factor of one. The classical theory of light limits the Fano factor of the number of photons to a value greater than or equal to one (Poisson case). However, the quantum theory of light allows for Fano factors to be less than one. We used two methods to look at the correlations between two detectors looking at same scintillation pulse to estimate the Fano factor of the scintillation photons. The relationship between the Fano factor and the correlation between the integral of the two signals detected was analytically derived, and the Fano factor was estimated using the measurements for SrI2:Eu, YAP

  11. Analysis of pre-earthquake ionospheric anomalies before the global M = 7.0+ earthquakes in 2010

    Directory of Open Access Journals (Sweden)

    W. F. Peng

    2012-03-01

    Full Text Available The pre-earthquake ionospheric anomalies that occurred before the global M = 7.0+ earthquakes in 2010 are investigated using the total electron content (TEC from the global ionosphere map (GIM. We analyze the possible causes of the ionospheric anomalies based on the space environment and magnetic field status. Results show that some anomalies are related to the earthquakes. By analyzing the time of occurrence, duration, and spatial distribution of these ionospheric anomalies, a number of new conclusions are drawn, as follows: earthquake-related ionospheric anomalies are not bound to appear; both positive and negative anomalies are likely to occur; and the earthquake-related ionospheric anomalies discussed in the current study occurred 0–2 days before the associated earthquakes and in the afternoon to sunset (i.e. between 12:00 and 20:00 local time. Pre-earthquake ionospheric anomalies occur mainly in areas near the epicenter. However, the maximum affected area in the ionosphere does not coincide with the vertical projection of the epicenter of the subsequent earthquake. The directions deviating from the epicenters do not follow a fixed rule. The corresponding ionospheric effects can also be observed in the magnetically conjugated region. However, the probability of the anomalies appearance and extent of the anomalies in the magnetically conjugated region are smaller than the anomalies near the epicenter. Deep-focus earthquakes may also exhibit very significant pre-earthquake ionospheric anomalies.

  12. AATR an ionospheric activity indicator specifically based on GNSS measurements

    Science.gov (United States)

    Juan, José Miguel; Sanz, Jaume; Rovira-Garcia, Adrià; González-Casado, Guillermo; Ibáñez, D.; Perez, R. Orus

    2018-03-01

    This work reviews an ionospheric activity indicator useful for identifying disturbed periods affecting the performance of Global Navigation Satellite System (GNSS). This index is based in the Along Arc TEC Rate (AATR) and can be easily computed from dual-frequency GNSS measurements. The AATR indicator has been assessed over more than one Solar Cycle (2002-2017) involving about 140 receivers distributed world-wide. Results show that it is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity (i.e. DST or Ap), it is sensitive to the regional behaviour of the ionosphere and identifies specific effects on GNSS users. Moreover, from a devoted analysis of different Satellite Based Augmentation System (SBAS) performances in different ionospheric conditions, it follows that the AATR indicator is a very suitable mean to reveal whether SBAS service availability anomalies are linked to the ionosphere. On this account, the AATR indicator has been selected as the metric to characterise the ionosphere operational conditions in the frame of the European Space Agency activities on the European Geostationary Navigation Overlay System (EGNOS). The AATR index has been adopted as a standard tool by the International Civil Aviation Organization (ICAO) for joint ionospheric studies in SBAS. In this work we explain how the AATR is computed, paying special attention to the cycle-slip detection, which is one of the key issues in the AATR computation, not fully addressed in other indicators such as the Rate Of change of the TEC Index (ROTI). After this explanation we present some of the main conclusions about the ionospheric activity that can extracted from the AATR values during the above mentioned long-term study. These conclusions are: (a) the different spatial correlation related with the MOdified DIP (MODIP) which allows to clearly separate high, mid and low latitude regions, (b) the large spatial correlation in mid

  13. Metrology and ionospheric observation standards

    Science.gov (United States)

    Panshin, Evgeniy; Minligareev, Vladimir; Pronin, Anton

    Accuracy and ionospheric observation validity are urgent trends nowadays. WMO, URSI and national metrological and standardisation services bring forward requirements and descriptions of the ionospheric observation means. Researches in the sphere of metrological and standardisation observation moved to the next level in the Russian Federation. Fedorov Institute of Applied Geophysics (IAG) is in charge of ionospheric observation in the Russian Federation and the National Technical Committee, TC-101 , which was set up on the base of IAG- of the standardisation in the sphere. TC-101 can be the platform for initiation of the core international committee in the network of ISO The new type of the ionosounde “Parus-A” is engineered, which is up to the national requirements. “Parus-A” calibration and test were conducted by National metrological Institute (NMI) -D.I. Mendeleyev Institute for Metrology (VNIIM), signed CIMP MRA in 1991. VNIIM is a basic NMI in the sphere of Space weather (including ionospheric observations), the founder of which was celebrated chemist and metrologist Dmitriy I. Mendeleyev. Tests and calibration were carried out for the 1st time throughout 50-year-history of ionosonde exploitation in Russia. The following metrological characteristics were tested: -measurement range of radiofrequency time delay 0.5-10 ms; -time measurement inaccuracy of radio- frequency pulse ±12mcs; -frequency range of radio impulse 1-20 MHz ; -measurement inaccuracy of radio impulse carrier frequency± 5KHz. For example, the sound impulse simulator that was built-in in the ionosounde was used for measurement range of radiofrequency time delay testing. The number of standards on different levels is developed. - “Ionospheric observation guidance”; - “The Earth ionosphere. Terms and definitions”.

  14. Alkali metal hafnium oxide scintillators

    Science.gov (United States)

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Taylor, Scott Edward

    2018-05-08

    The present invention provides for a composition comprising an inorganic scintillator comprising an alkali metal hafnate, optionally cerium-doped, having the formula A2HfO3:Ce; wherein A is an alkali metal having a valence of 1, such as Li or Na; and the molar percent of cerium is 0% to 100%. The alkali metal hafnate are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  15. Observations of the Ionospheric Response to a Weak Substorm Onset

    Science.gov (United States)

    Chartier, A.; Gjerloev, J. W.; Ohtani, S.; Nikoukar, R.; Forte, B.

    2015-12-01

    We present observations of substorm onset at Tromsø, Norway. This event was unusually well observed by ground magnetometers, incoherent scatter radar, satellites, an allsky camera and a scintillation monitor in the vicinity of the onset location. At onset, ground magnetometer observations indicate the formation of a westward electrojet above Tromsø and, at the same location, allsky camera images show an arc brightening and moving poleward. Satellite observations are consistent with an onset location at Tromsø, followed by a westward surge of dipolarization. Two features of the ionospheric response are observed by the incoherent scatter radar at Tromsø: 1) At onset, ion drift velocities reduce sharply from 100-400 m/s to roughly zero, consistent with a field-aligned potential drop shielding the ionosphere from magnetospheric convection. 2) There is a two-stage enhancement of the westward electrojet, with each stage directly preceded by an increase of ionization. Both these features are consistent with the theory that the inner magnetosphere acts neither as a current nor a voltage generator during substorm onset. Figure shows EISCAT observations of line-of-sight ion drifts, electron and ion temperatures. There is a transition from ExB drift, indicated by a decrease in ion velocity in panel (a), to electron precipitation indicated by increased electron temperatures in panel (b). Substorm onset occurs at the transition time, around 20:02:30 UT.

  16. Multifrequency techniques for studying interplanetary scintillations

    International Nuclear Information System (INIS)

    Woo, R.

    1975-01-01

    Rytov's approximation or the method of smooth perturbations is utilized to derive the temporal frequency spectra of the amplitude and phase fluctuations of multifrequency plane and spherical waves propagating in the interplanetary medium and solar corona. It is shown that multifrequency observations of interplanetary scintillations using either compact radio stars or spacecraft radio signals are desirable because the correlation of the multifrequency waves yields additional independent measurements of the solar wind and turbulence. Measurements of phase fluctuations are also desirable because, unlike amplitude fluctuations, they provide information on the full range of scale sizes for the electron density fluctuations. It is shown that a coherent dual-frequency radio system is particularly useful in making such measurements. In addition to providing a means for interpreting observations of multifrequency interplanetary scintillations, the analysis is also essential for estimating the effects of solar corona turbulence on the communications and navigation of a spacecraft whose line-of-sight path passes close to the Sun

  17. CARINA Satellite Mission to Investigate the Upper Atmosphere below the F-Layer Ionosphere

    Science.gov (United States)

    Siefring, C. L.; Bernhardt, P. A.; Briczinski, S. J., Jr.; Huba, J.; Montgomery, J. A., Jr.

    2017-12-01

    A new satellite design permits broad science measurements from the ocean to the ionosphere by flying below the F-Layer. The satellite called CARINA for Coastal-Ocean, Assimilation, Radio, Ionosphere, Neutral-Drag, and Atmospherics. The unique system capabilities are long duration orbits below the ionosphere and a HF receiver to measure broadband signals. The CARINA science products include recording the ocean surface properties, data for assimilation into global ionosphere models, radio wave propagation measurements, in-situ observations of ionospheric structures, validating neutral drag models and theory, and broadband atmospheric lightning characterization. CARINA will also measure nonlinear wave-generation using ionospheric modification sites in Alaska, Norway, Puerto Rico, and Russia and collaborate with geophysics HF radars (such as Super-DARN) for system calibration. CARINA is a linear 6-U CubeSat with a long antenna extended in the wake direction. The CARINA science mission is supported by three instruments. First, the Electric Field Instrument (EFI) is a radio receiver covering the 2 to 18 MHz range. The receiver can capture both narrow and wide bandwidths for up to 10 minutes. EFI is designed to provide HF signal strength and phase, radar Doppler shift and group delay, and electron plasma density from photoelectron excited plasma waves. Second a Ram Langmuir Probe (RLP) measures high-resolution ion currents at a 10 kHz rate. These measurements yield electron and ion density at the spacecraft. Finally, the Orbiting GPS Receiver (OGR) provides dual frequency GPS position with ionosphere correction. OGR also measures total electron content above the spacecraft and L-Band scintillations. CARINA will be the lowest satellite in orbit at 250 km altitude, <0.01 eccentricity, and up to 4-month lifetime. The design supports unique capabilities with broad applications to the geosciences. Remote sensing of the ocean will sample the HF signals scattered from the rough

  18. Rayleigh-Taylor and wind-driven instabilities of the nighttime equatorial ionosphere

    International Nuclear Information System (INIS)

    Chiu, Y.T.; Straus, J.M.

    1979-01-01

    We have made a thorough re-examination of the Rayleigh-Taylor instability in the nighttime equatorial ionosphere from approx.100 km to the bottomside F region. We have taken into account explicitly the following effects which have been ignored by other workers in various combinations: (1) The eastward drift of the ionosphere caused by the nighttime polarization electric field, (2) the eastward nighttime neutral wind, and (3) recombination in the F and E regions. We found that, well below the bottomside F region, the Rayleigh-Taylor mode can be unstable and is driven by an eastward neutral wind rather than by gravitational drift. Formation of ionospheric bubbles below the bottomside F region is consistent with the observation of lower ionospheric ions in F region ionospheric holes; furthermore, seasonal and shorter term variations in spread-F occurrence may be associated with variations in the neutral wind and polarization electric field

  19. Generation of Unbiased Ionospheric Corrections in Brazilian Region for GNSS positioning based on SSR concept

    Science.gov (United States)

    Monico, J. F. G.; De Oliveira, P. S., Jr.; Morel, L.; Fund, F.; Durand, S.; Durand, F.

    2017-12-01

    Mitigation of ionospheric effects on GNSS (Global Navigation Satellite System) signals is very challenging, especially for GNSS positioning applications based on SSR (State Space Representation) concept, which requires the knowledge of spatial correlated errors with considerable accuracy level (centimeter). The presence of satellite and receiver hardware biases on GNSS measurements difficult the proper estimation of ionospheric corrections, reducing their physical meaning. This problematic can lead to ionospheric corrections biased of several meters and often presenting negative values, which is physically not possible. In this contribution, we discuss a strategy to obtain SSR ionospheric corrections based on GNSS measurements from CORS (Continuous Operation Reference Stations) Networks with minimal presence of hardware biases and consequently physical meaning. Preliminary results are presented on generation and application of such corrections for simulated users located in Brazilian region under high level of ionospheric activity.

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

    Science.gov (United States)

    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.

  1. Response of the ionosphere to natural and man-made acoustic sources

    Directory of Open Access Journals (Sweden)

    O. A. Pokhotelov

    Full Text Available A review is presented of the effects influencing the ionosphere which are caused by acoustic emission from different sources (chemical and nuclear explosions, bolides, meteorites, earthquakes, volcanic eruptions, hurricanes, launches of spacecrafts and flights of supersonic jets. A terse statement is given of the basic theoretical principles and simplified theoretical models underlying the physics of propagation of infrasonic pulses and gravity waves in the upper atmosphere. The observations of "quick" response by the ionosphere are pointed out. The problem of magnetic disturbances and magnetohydrodynamic (MHD wave generation in the ionosphere is investigated. In particular, the supersonic propagation of ionospheric disturbances, and the conversion of the acoustic energy into the so-called gyrotropic waves in the ionospheric E-layer are considered.

  2. New Model for Ionospheric Irregularities at Mars

    Science.gov (United States)

    Keskinen, M. J.

    2018-03-01

    A new model for ionospheric irregularities at Mars is presented. It is shown that wind-driven currents in the dynamo region of the Martian ionosphere can be unstable to the electromagnetic gradient drift instability. This plasma instability can generate ionospheric density and magnetic field irregularities with scale sizes of approximately 15-20 km down to a few kilometers. We show that the instability-driven magnetic field fluctuation amplitudes relative to background are correlated with the ionospheric density fluctuation amplitudes relative to background. Our results can explain recent observations made by the Mars Atmosphere and Volatile EvolutioN spacecraft in the Martian ionosphere dynamo region.

  3. Global scale ionospheric irregularities associated with thunderstorm activity

    CERN Document Server

    Pulinets, S A

    2002-01-01

    The potential difference near 280 kV exists between ground and ionosphere. This potential difference is generated by thunderstorm discharges all over the world, and return current closes the circuit in the areas of fair weather (so-called fair weather current). The model calculations and experimental measurements clearly demonstrate non-uniform latitude-longitude distribution of electric field within the atmosphere. The recent calculations show that the strong large scale vertical atmospheric electric field can penetrate into the ionosphere and create large scale irregularities of the electron concentration. To check this the global distributions of thunderstorm activity obtained with the satellite monitoring for different seasons were compared with the global distributions of ionosphere critical frequency (which is equivalent to peak electron concentration) obtained with the help of satellite topside sounding. The similarity of the obtained global distributions clearly demonstrates the effects of thunderstor...

  4. Plasma bubbles near the dawn terminator in the topside ionosphere

    International Nuclear Information System (INIS)

    Burke, W.J.

    1979-01-01

    The physical properties of plasma bubbles in the topside ionosphere near the dawn terminator are investigated. It is assumed that the bubbles result from either a Rayleigh-Taylor or an E X B instability on the bottom side of the F-layer. While the E-region is in darkness, the top and bottomsides of the ionospheres are electrically decoupled and the motion of the bubbles can be described by non-linear, two-dimensional theory. After sunrise, electric fields within the bubbles discharge through the conducting lower ionosphere. The upward drift of the bubbles is effectively halted. To achieve a dayside state of diffusive equilibrium the bubbles slowly begin to collapse from the bottom. (author)

  5. Role of parametric decay instabilities in generating ionospheric irregularities

    International Nuclear Information System (INIS)

    Kuo, S.P.; Cheo, B.R.; Lee, M.C.

    1983-01-01

    We show that purely growing instabilities driven by the saturation spectrum of parametric decay instabilities can produce a broad spectrum of ionospheric irregularities. The threshold field Vertical BarE/sub th/Vertical Bar of the instabilities decreases with the scale lengths lambda of the ionospheric irregularities as Vertical BarE/sub th/Vertical Barproportionallambda -2 in the small-scale range ( -2 with scale lengths larger than a few kilometers. The excitation of kilometer-scale irregularities is strictly restricted by the instabilities themselves and by the spatial inhomogeneity of the medium. These results are drawn from the analyses of four-wave interaction. Ion-neutral collisions impose no net effect on the instabilities when the excited ionospheric irregularities have a field-aligned nature

  6. Troposphere - ionosphere interaction during tropospheric MCC events

    International Nuclear Information System (INIS)

    Manzano, J.R.; Zossi Artigas, M.M. de; Filippi Manzano, A.N. de; Cosio Ragone, A.H. de

    1995-09-01

    The present paper describes the investigation of possible effects of the type of large meteorological events known as Mesoscale Convective Complexes (MCC) on the F-region of the ionosphere over Argentina. These warm-season weather systems of huge size are present in the United States (Maddox, 1980) and in South Americal (Velasco and Fritsch, 1987). Their extension can be as large as 1,300,000 Km 2 and they tend to move in different directions over the earth surface. It is expected that these meteorological events should leave its signature in the upper region of the atmosphere. 13 refs, 12 figs, 1 tab

  7. Multi-Instrument Observations of a Geomagnetic Storm and its Effects on the Arctic Ionosphere: A Case Study of the 19 February 2014 Storm

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Komjathy, Attila; Verkhoglyadova, Olga

    2017-01-01

    We present a multi-instrumented approach for the analysis of the Arctic ionosphere during the 19 February 2014 highly complex, multiphase geomagnetic storm, which had the largest impact on the disturbance storm-time (Dst) index that year. The geomagnetic storm was the result of two powerful Earth......-directed coronal mass ejections (CMEs). It produced a strong long lasting negative storm phase over Greenland with a dominant energy input in the polar-cap. We employed GNSS networks, geomagnetic observatories, and a specific ionosonde station in Greenland. We complemented the approach with spaceborne measurements...... specifically found that, (1) Thermospheric O/N2 measurements demonstrated significantly lower values over the Greenland sector than prior to the storm-time. (2) An increased ion flow in the topside ionosphere was observed during the negative storm phase. (3) Negative storm phase was a direct consequence...

  8. Scintillation counter based radiation dosimeter

    International Nuclear Information System (INIS)

    Shin, Jeong Hyun

    2009-02-01

    The average human exposure per year is about 240mrem which is come from Radon and human body and terrestrial and cosmic radiation and man-made source. Specially radiation exposure through air from environmental radiation sources is 80mrem/yr(= 0.01mR/hr) which come from Terrestrial and cosmic radiation. Radiation dose is defined as energy deposit/mass. There are two major methods to detect radiation. First method is the energy integration using Air equivalent material like GM counter wall material. Second method is the spectrum to dose conversion method using NaI(Tl), HPGe. These two methods are using generally to detect radiation. But these methods are expensive. So we need new radiation detection method. The research purpose is the development of economical environmental radiation dosimeter. This system consists of Plastic/Inorganic scintillator and Si photo-diode based detector and counting based circuitry. So count rate(cps) can be convert to air exposure rate(R/hr). There are three major advantages in this system. First advantages is no high voltage power supply like GM counter. Second advantage is simple electronics. Simple electronics system can be achieved by Air-equivalent scintillation detector with Al filter for the same detection efficiency vs E curve. From former two advantages, we can know the most important advantages of the this system. Third advantage is economical system. The price of typical GM counter is about $1000. But the price of our system is below $100 because of plastic scintillator and simple electronics. The role of scintillation material is emitting scintillation which is the flash of light produced in certain materials when they absorb ionizing radiation. Plastic scintillator is organic scintillator which is kind of hydrocarbons. The special point are cheap price, large size production(∼ton), moderate light output, fast light emission(ns). And the role of Al filter is equalizing counting efficiency of air and scintillator for

  9. Generation of a severe convective ionospheric storm under stable Rayleigh–Taylor conditions: triggering by meteors?

    Directory of Open Access Journals (Sweden)

    M. C. Kelley

    2016-02-01

    Full Text Available Here we report on four events detected using the Jicamarca Radio Observatory (JRO over an 18-year period, in which huge convective ionospheric storms (CISs occur in a stable ionosphere. We argue that these rare events could be initiated by meteor-induced electric fields. The meteor-induced electric fields map to the bottomside of the F region, causing radar echoes and a localized CIS. If and when a localized disturbance reaches 500 km, we argue that it becomes two-dimensionally turbulent and cascades structure to both large and small scales. This leads to long-lasting structure and, almost certainly, to scintillations over a huge range of latitudes some ±15° wide and to 3 m irregularities, which backscatter the VHF radar waves. These structures located at high altitudes are supported by vortices shed by the upwelling bubble in a vortex street.

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

    Czech Academy of Sciences Publication Activity Database

    Yigit, E.; Koucká Knížová, Petra; Georgieva, K.; Ward, W.

    2016-01-01

    Roč. 141, April (2016), s. 1-12 ISSN 1364-6826 R&D Projects: GA ČR(CZ) GA15-24688S; GA MŠk(CZ) LG13042 Institutional support: RVO:68378289 Keywords : atmosphere–ionosphere * vertical coupling * gravity waves * tides * space weather * solar activity Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.326, year: 2016 http://www.sciencedirect.com/science/article/pii/S1364682616300426

  11. Effects of Na and K co-doping on growth and scintillation properties of Eu:SrI.sub.2./sub. crystals\

    Czech Academy of Sciences Publication Activity Database

    Ito, T.; Yokota, Y.; Kurosawa, S.; Král, Robert; Pejchal, Jan; Ohashi, Y.; Kamada, K.; Nikl, Martin; Yoshikawa, A.

    2016-01-01

    Roč. 90, Jul (2016), 157-161 ISSN 1350-4487 R&D Projects: GA MŠk(CZ) LH14266 Institutional support: RVO:68378271 Keywords : Eu:SrI 2 * scintillator * single crystal * alkali metal * light yield * non-proportionality Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.442, year: 2016

  12. Temperature quenching in LAB based liquid scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen, A.; Zuber, K. [Technische Universitaet Dresden, Institute for Nuclear- and Particle Physics, Dresden (Germany); Hans, S.; Yeh, M. [Brookhaven National Laboratory, Chemistry Devision, Upton, NY (United States); Junghans, A.R.; Koegler, T.; Wagner, A. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Krosigk, B. v. [Technische Universitaet Dresden, Institute for Nuclear- and Particle Physics, Dresden (Germany); University of British Columbia, Department of Physics and Astronomy, Vancouver, BC (Canada); Lozza, V. [Technische Universitaet Dresden, Institute for Nuclear- and Particle Physics, Dresden (Germany); Laboratorio de Instrumentacao e Fisica Experimental de Particulas, Lisboa (Portugal)

    2018-01-15

    The effect of temperature changes on the light output of LAB based liquid scintillator is investigated in a range from -5 to 30 C with α-particles and electrons in a small scale setup. Two PMTs observe the scintillator liquid inside a cylindrically shaped aluminum cuvette that is heated or cooled and the temperature dependent PMT sensitivity is monitored and corrected. The α-emitting isotopes in dissolved radon gas and in natural Samarium (bound to a LAB solution) excite the liquid scintillator mixtures and changes in light output with temperature variation are observed by fitting light output spectra. Furthermore, also changes in light output by compton electrons, which are generated from external calibration γ-ray sources, is analysed with varying temperature. Assuming a linear behaviour, a combined negative temperature coefficient of (-0.29 ± 0.01)%/ C is found. Considering hints for a particle type dependency, electrons show (-0.17 ± 0.02)%/ C, whereas the temperature dependency seems stronger for α-particles, with (-0.35 ± 0.03)%/ C. Due to a high sampling rate, a pulse shape analysis can be performed and shows an enhanced slow decay component at lower temperatures, pointing to reduced non-radiative triplet state de-excitations. (orig.)

  13. Development of TOF-PET using Compton scattering by plastic scintillators

    International Nuclear Information System (INIS)

    Kuramoto, M.; Nakamori, T.; Kimura, S.; Gunji, S.; Takakura, M.; Kataoka, J.

    2017-01-01

    We propose a time-of-flight (TOF) technique using plastic scintillators which have fast decay time of a few ns for positron emission tomography (PET). While the photoelectric absorption probability of the plastic for 511 keV gamma rays are extremely low due to its small density and effective atomic number, the cross section of Compton scattering is comparable to that of absorption by conventional inorganic scintillators. We thus propose TOF-PET using Compton scattering with plastic scintillators (Compton-PET), and performed fundamental experiments towards exploration of the Compton-PET capability. We demonstrated that the plastic scintillators achieved the better time resolution in comparison to LYSO(Ce) and GAGG(Ce) scintillators. In addition we evaluated the depth-of-interaction resolving capability with the plastic scintillators.

  14. Development of TOF-PET using Compton scattering by plastic scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Kuramoto, M., E-mail: kuramoto@maxwell.kj.yamagata-u.ac.jp [Yamagata University, Kojirakawa 1-4-12, Yamagata 990-8560 (Japan); Nakamori, T., E-mail: nakamori@maxwell.kj.yamagata-u.ac.jp [Yamagata University, Kojirakawa 1-4-12, Yamagata 990-8560 (Japan); Kimura, S.; Gunji, S.; Takakura, M. [Yamagata University, Kojirakawa 1-4-12, Yamagata 990-8560 (Japan); Kataoka, J. [Waseda University, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan)

    2017-02-11

    We propose a time-of-flight (TOF) technique using plastic scintillators which have fast decay time of a few ns for positron emission tomography (PET). While the photoelectric absorption probability of the plastic for 511 keV gamma rays are extremely low due to its small density and effective atomic number, the cross section of Compton scattering is comparable to that of absorption by conventional inorganic scintillators. We thus propose TOF-PET using Compton scattering with plastic scintillators (Compton-PET), and performed fundamental experiments towards exploration of the Compton-PET capability. We demonstrated that the plastic scintillators achieved the better time resolution in comparison to LYSO(Ce) and GAGG(Ce) scintillators. In addition we evaluated the depth-of-interaction resolving capability with the plastic scintillators.

  15. Development of TOF-PET using Compton scattering by plastic scintillators

    Science.gov (United States)

    Kuramoto, M.; Nakamori, T.; Kimura, S.; Gunji, S.; Takakura, M.; Kataoka, J.

    2017-02-01

    We propose a time-of-flight (TOF) technique using plastic scintillators which have fast decay time of a few ns for positron emission tomography (PET). While the photoelectric absorption probability of the plastic for 511 keV gamma rays are extremely low due to its small density and effective atomic number, the cross section of Compton scattering is comparable to that of absorption by conventional inorganic scintillators. We thus propose TOF-PET using Compton scattering with plastic scintillators (Compton-PET), and performed fundamental experiments towards exploration of the Compton-PET capability. We demonstrated that the plastic scintillators achieved the better time resolution in comparison to LYSO(Ce) and GAGG(Ce) scintillators. In addition we evaluated the depth-of-interaction resolving capability with the plastic scintillators.

  16. Using LEDs to stimulate the recovery of radiation damage to plastic scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Wetzel, J., E-mail: james-wetzel@uiowa.edu [The University of Iowa, Iowa City, IA (United States); Tiras, E. [The University of Iowa, Iowa City, IA (United States); Bilki, B. [The University of Iowa, Iowa City, IA (United States); Beykent University, Istanbul (Turkey); Onel, Y. [The University of Iowa, Iowa City, IA (United States); Winn, D. [Fairfield University, Fairfield, CT (United States)

    2017-03-15

    In this study, we consider using LEDs to stimulate the recovery of scintillators damaged from radiation in high radiation environments. We irradiated scintillating tiles of polyethylene naphthalate (PEN), Eljen brand EJ-260 (EJN), an overdoped EJ-260 (EJ2P), and a lab-produced elastomer scintillator (ES) composed of p-terphenyl (ptp) in epoxy. Two different high-dose irradiations took place, with PEN dosed to 100 kGy, and the others to 78 kGy. We found that the ‘blue’ scintillators (PEN and ES) recovered faster and maximally higher with LEDs than without. Conversely exposing the ‘green’ scintillators (EJ-260) to LED light had a nearly negligible effect on the recovery. We hypothesize that the ‘green’ scintillators require wavelengths that match their absorption and emission spectra for LED stimulated recovery.

  17. Multiscale Modeling of Ionospheric Irregularities

    Science.gov (United States)

    2014-10-22

    numerical simulations of ionospheric plasma density structures associated with nonlinear evolution of the Rayleigh-Taylor (RT) instabilities in...model was developed to resolve the transport pat- terns of plasma density coupled with neutral atmospheric dynamics. Inclusion of neutral dynamics in...trapping electromagnetic (EM) waves in parabolic cavities, which are created by the refractive index gradients along the propagation paths. Keywords

  18. Interplanetary phenomenon, geomagnetic and ionospheric ...

    African Journals Online (AJOL)

    The analysis of the D(foF2) plots appear to show that the storm event is characterized by (i) the occurrence of positive ionospheric storm at the high latitudes and mid latitude stations of Khabarovsk, Yamagawa and Okinawa stations before the beginning of the storm event (ii) Presence of strong negative phase at Manila, ...

  19. The ionospheric eclipse factor method (IEFM) and its application to determining the ionospheric delay for GPS

    DEFF Research Database (Denmark)

    Yuan, Y.; Tscherning, C.C.; Knudsen, Per

    2006-01-01

    A new method for modeling the ionospheric delay using global positioning system (GPS) data is proposed, called the ionospheric eclipse factor method (IEFM). It is based on establishing a concept referred to as the ionospheric eclipse factor (IEF) lambda of the ionospheric pierce point (IPP....... The IEFM-based ionospheric delay estimates are validated by combining an absolute positioning mode with several ionospheric delay correction models or algorithms, using GPS data at an international Global Navigation Satellite System (GNSS) service (IGS) station (WTZR). Our results indicate that the IEFM...

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

    Science.gov (United States)

    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.