Scintillation Occurrence Research Articles

Investigating Ionospheric Scintillation Effects on Multifrequency GPS Signals

Over the last 15 years, the satellite constellation of the global positioning system (GPS) has been modernized for more precise applications, with the introduction of the L2C and L5 signals. However, among other effects, they are susceptible to severe ionospheric effects, particularly in the equatorial and low-latitude regions. Equatorial plasma bubbles, resulting from the combination of the ionospheric electrodynamics with plasma instability mechanisms and thermospheric coupling, may generate irregularity structures with scale sizes ranging from hundreds of kilometers to a few meters (or less). Ionospheric irregularities may cause deep amplitude fades and phase shifts to transionospheric signals. That is, they are responsible for amplitude and phase scintillation, which degrade receiver operations and may cause failures and unavailability to positioning and navigation services under extreme conditions. The objective of the present work is to analyze ionospheric scintillation effects on the L2C and L5 GPS signals, to compare their vulnerabilities with those of the L1 signal. The data used in this analysis were collected between November 2014 and March 2015, during the maximum solar activity of cycle 24 (a period of great scintillation incidence), by scintillation monitors deployed at four different sites in the Brazilian territory: Fortaleza, Presidente Prudente, Sao Jose dos Campos, and Porto Alegre. Intensity fades will be analyzed, considering different thresholds, to reveal their empirical probability distributions of scintillation occurrence, average fading occurrences and durations. The results will show that greater probabilities of strong scintillation occurrences are present in the modernized signals, reaching up to five times more events in the L5 signal in comparison with those in the legacy L1 signal. It will be shown that the L5 average fade duration is distinctly longer than the corresponding ones for the other frequencies, considering the same site, threshold, and L1 amplitude scintillation level. The results will also show that the average fade duration decreases according to the average ratio 0.6 s/3 dB within the threshold range from − 6 to − 15 dB, considering the same amplitude scintillation level and location.

Instantaneous Ionospheric Scintillation Mapping over the East African Region by use of GPS Derived Amplitude Scintillation Proxy

Ionospheric scintillation activity over the East African region is often monitored using measurements from the SCIntillation Network Decision Aid (SCINDA) receivers. Many of the SCINDA receivers over East Africa are currently not archiving data and therefore a large part of the region remain un sampled. We investigated the possibility to use dual frequency receivers of the Global Navigation Satellite System (GNSS) network for scintillation mapping. A proxy for amplitude scintillation was first derived by scaling the rate of change of total electron content index (ROTI). The proxy was validated against S4 derived from nearly collocated SCINDA receivers over the region. A good correlation was observed between the proxy and S4. The proxy was then used to map the occurrence of amplitude scintillation over East Africa based on semivariogram modeling and Kriging interpolation technique. The results indicate that the S4 values had a good positive correlation with *Corresponding author: E-mail: emirant.amabayo@gmail.com; Amabayo et al.; AJR2P, 4(2): 6-20, 2021; Article no.AJR2P.66815 the simulated S4p from the Kriging interpolation. This observation suggests that data from the dual frequency receivers of GNSS may be used to map scintillation over East Africa. These maps can in turn be used to study the evolution of ionospheric scintillation patterns over the region.

COSMIC observation of stratospheric gravity wave and ionospheric scintillation correlation

A correlation study is performed to investigate possible connections between the stratospheric gravity waves and the ionospheric plasma bubble induced GPS signal scintillations. Using the COSMIC 1 neutral temperature data (10–30 km), we extract gravity wave amplitudes with vertical wavelengths from 2.5 to 10 km within the latitudinal range from 37.5S to 37.5N. We then calculated the occurrence of high GPS L1 amplitude scintillation (S4 > 0.2) in the equatorial region (25S and 25N). The high S4 values showed consistent higher correlations with gravity waves at the equator than those away from the equator for all vertical wavelengths between 2010 and 2013. While the peak correlation is only ~0.2, the consistency over different wavelengths and years suggests a possible link, which could be through seeding of plasma bubbles and/or modulation of the neutral wind dynamo by gravity waves. We see the need for further study based on statistics of simultaneous observations of gravity waves, ionospheric scintillations, and other ionospheric and thermospheric parameters, which can lead to a better understanding of the plasma bubble formation mechanism.

Impact of Geomagnetic Storms on Ionosphere Variability and Precise Point Positioning Application in High Latitudes of the Northern Hemisphere

Based on the ionospheric scintillation data of the Canadian High Arctic Ionospheric Network (CHAIN), the variation characteristics of ionospheric Total Electric Content (TEC), phase scintillation and Rate of TEC Index (ROTI) were analyzed during the 26 August 2018 geomagnetic storm period. Results show that the TEC anomalies reach 20 TECU on global scale and 6 TECU over Canadian regions, respectively. The occurrence of phase scintillations is about 12.6% during the selected stormy day, which is only around 1% during geomagnetic quiet period. The occurrence of ROTI exhibits high correlation with that of phase scintillations during stormy geomagnetic conditions. The impact of ionospheric scintillations on positioning performance was analyzed by means of GPS Precise Point Positioning (PPP). It is proved that the 3D positioning root mean square errors are within 0.4 m for all test stations during the quiet geomagnetic condition. When it comes to the high geomagnetic condition, the magnitude of positioning errors significantly increase, which reaches 0.9 and 1.7 m in horizontal and vertical directions, respectively.

English

The Global Navigation Satellite System (GNSS) technologies have made significant contribution to seismology studies. Some processing strategies are well known, like real time PPP and DGPS techniques. These two methods have been widely used for GNSS based seismic activities monitoring. The first method requires accurate models of GNSS measurement errors to achieve accuracy in centimeter (cm) and need convergence time in order of minutes to hours. The second method need relative short distance of reference stations to reduce significantly measurement errors. To overcome disadvantages of such two methods, the variometric method was used to attain accuracy, but the method needs to be tested in the high ionospheric disturbance of equatorial region. During occurrences of plasma bubble, the radio signals from satellite passing through the ionosphere sometimes show rapid amplitude and phase variations called ionospheric scintillation. The occurrences of ionospheric scintillation could degrade the performance of systems and generate errors in received messages. In this study, variometric measurements are performed during the equinoctial month (March 2012) when the occurrence of scintillation was more intense. Results showed degradation of measurement accuracy during strong scintillation occurrences. The errors reached more than 1 m/s, especially for up-down measurement. Key words: Equinox, GISTM, ionospheric scintillation, variometric.

Statistical models to provide meaningful information to GNSS users in the presence of ionospheric scintillation

Ionospheric scintillation is one of the most challenging problems in Global Navigation Satellite Systems (GNSS) positioning and navigation. Scintillation occurrence can not only lead to an increase in the probability of losing the GNSS signal lock but also reduce the precision of the pseudorange and carrier phase measurements, thus leading to positioning accuracy degradation. Statistical models developed to estimate the probability of loss of lock and Geometric Dilution of Precision normalized 3D positioning errors as a function of scintillation levels are presented. The models were developed following the statistical approach of nonlinear regression on data recorded by Ionospheric Scintillation Monitoring Receivers operational at high and low latitudes. The validation of the probability of loss of lock models indicated average correlation coefficient values above 0.7 and average Root Mean Squared Error (RMSE) values below 0.35. The validation of the positioning error models indicated average RMSE values below 10 cm. The good performance of the developed models indicates that these can provide GNSS users with information on the satellite loss of lock probability and the error in the 3D position under scintillation.

Multi-Scale Ionospheric Anomalies Monitoring and Spatio-Temporal Analysis during Intense Storm

The ionosphere is a significant component of the geospace environment. Storm-induced ionospheric anomalies severely affect the performance of Global Navigation Satellite System (GNSS) Positioning, Navigation, and Timing (PNT) and human space activities, e.g., the Earth observation, deep space exploration, and space weather monitoring and prediction. In this study, we present and discuss the multi-scale ionospheric anomalies monitoring over China using the GNSS observations from the Crustal Movement Observation Network of China (CMONOC) during the 2015 St. Patrick’s Day storm. Total Electron Content (TEC), Ionospheric Electron Density (IED), and the ionospheric disturbance index are used to monitor the storm-induced ionospheric anomalies. This study finally reveals the occurrence of the large-scale ionospheric storms and small-scale ionospheric scintillation during the storm. The results show that this magnetic storm was accompanied by a positive phase and a negative phase ionospheric storm. At the beginning of the main phase of the magnetic storm, both TEC and IED were significantly enhanced. There was long-duration depletion in the topside ionospheric TEC during the recovery phase of the storm. This study also reveals the response and variations in regional ionosphere scintillation. The Rate of the TEC Index (ROTI) was exploited to investigate the ionospheric scintillation and compared with the temporal dynamics of vertical TEC. The analysis of the ROTI proved these storm-induced TEC depletions, which suppressed the occurrence of the ionospheric scintillation. To improve the spatial resolution for ionospheric anomalies monitoring, the regional Three-Dimensional (3D) ionospheric model is reconstructed by the Computerized Ionospheric Tomography (CIT) technique. The spatial-temporal dynamics of ionospheric anomalies during the severe geomagnetic storm was reflected in detail. The IED varied with latitude and altitude dramatically; the maximum IED decreased, and the area where IEDs were maximum moved southward.

A measure of ionospheric irregularities: zonal velocity and its implications for L-band scintillation at low-latitudes

We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along the magnetic parallel passing in Presidente Prudente (Brazil, magnetic latitude 12.8°S). The investigated ionospheric sector is ideal to study small-scale irregularities, being located close to the expected position of the southern crest of the equatorial ionospheric anomaly. The measurement campaign took place between September 2013 and February 2014, i.e. equinox and summer solstice seasons under solar maximum, during which the probability of formation of small-scale irregularities is expected to maximize. We found that the hourly average of the velocity increases up to 135 m/s right after the local sunset at ionospheric altitudes and then smoothly decreases in the next hours. Such measurements are in agreement with independent estimations of the velocity made by the Incoherent Scatter Radar located at the Jicamarca Radio Observatory (magnetic latitude 0.1°N), by the Boa Vista Ionosonde (magnetic latitude 12.0°N), and by applying a recently-developed empirical regional short-term forecasting model. Additionally, we investigated the relationship with the percentage occurrence of amplitude scintillation; we report that it is exponentially dependent on the zonal velocity of the irregularities that cause it.

Daytime GNSS scintillation due to Es over Arabian Peninsula during low solar activity

A constant presence of daytime GNSS phase (σϕ) and amplitude (S4) scintillation during the times sporadic-E (Es) was observed, is reported. The most favorable local time (LT) of the day for the occurrences are the morning (08:00 to 12:00) and the late afternoon (16:00 to 18:00) hours. Es and σϕ/S4 are found to be in very good correlation. Low occurrences of post-sunset scintillation suggest that the main driver of the ionospheric scintillation over Arabian Peninsula during the low solar activity period is the presence of Es.

GPS derived amplitude scintillation proxy model: A case over a low latitude station in East Africa

Ionospheric scintillation is quite a common phenomenon over the low latitude regions and in East Africa it is often monitored using measurements from the SCIntillation Network Decision Aid (SCINDA) receivers. The SCINDA receivers over East Africa are characterized by long base lines and data paucity thus offering a huge challenge in the long term scintillation characterization over the region. To alleviate this challenge, we implemented the use of data from the dual frequency GPS receivers of the IGS network in combination with data from the SCINDA receiver at Nairobi, Kenya to model amplitude scintillation. The data from the SCINDA (geographic coordinates 36.808oE, −1.274oN) and GPS (geographic coordinates 36.893oE, −1.221oN) receivers were used to derive S4 index and its proxy respectively. Comparison of the S4 and its proxy revealed a high correlation coefficient between the two datasets. Scintillation occurrence was observed to peak during the equinox months of March–April and September–October. The vernal equinox was observed to have less frequent scintillation events than the autumnal equinox. The local time (LT) scintillation occurrence shows a peak between 20:00 LT and 23:00 LT. An empirical hybrid amplitude scintillation occurrence probability model was then developed. The results show that the model predicted values were in good agreement with the observed amplitude scintillation occurrence probabilities from the SCINDA receiver. This observation suggests that the model is a useful tool for approximating amplitude scintillation occurrence probabilities at L-band frequencies at African equatorial latitudes.

New observations of the total electron content and ionospheric scintillations over Ho Chi Minh City

In January 2018, a Trimble NetR9 GNSS receiver was installed at International University - Vietnam National University (IU-VNU), which is located at 10°52'N, 106°48'E in Ho Chi Minh City (HCMC). The GNSS signals recorded from the receiver are useful for studying the ionospheric variations over this station as well as the magnetosphere-ionosphere coupling effects, therefore, we aim to preliminarily process and evaluate data recorded from this new station. Based on the data obtained with this GNSS receiver, we first estimated the total electron content (TEC) using the carrier-phase method which is a combination of code and phase measurements. We then calculated the rate of change of TEC index (ROTI) with respect to time and investigated its day-to-day variations. Our results show some typical features in the diurnal and seasonal TEC and ionospheric scintillation variations during 2018-2019. The distributions of ROTI over these two years of solar minimum show significant occurrences of scintillation, which are caused by small-scale ionospheric irregularities in the equatorial ionosphere. In addition, we found a significant increase of TEC in the latest strong geomagnetic storm in August 2018. The disturbance dynamo appears to have suppressed plasma bubbles after sunset and enhanced their formation at midnight. Thus, the disturbance dynamo effectively caused a delay of ionospheric scintillations. The TEC observed in HCMC also contributes to the data of ground-based observational receiver systems along 105o E longitude for studying ionospheric variations in low-latitude and equatorial regions. Our preliminary results indicate that the GNSS data collected at IU-VNU station is a valuable reference dataset for further research of the ionosphere.

Challenges to Equatorial Plasma Bubble and Ionospheric Scintillation Short-Term Forecasting and Future Aspects in East and Southeast Asia

Equatorial plasma bubbles (EPBs) can cause rapid fluctuations in amplitude and phase of radio signals traversing the ionosphere and in turn produce serious ionospheric scintillations and disrupt satellite-based communication links. Whereas numerous studies on the generation and evolution of EPBs have been performed, the prediction of EPB and ionospheric scintillation occurrences still remains unresolved. The generalized Rayleigh–Taylor (R–T) instability has been widely accepted as the physical mechanism responsible for the generation of EPBs. But how the factors, which seed the development of R–T instability and control the dynamics of EPBs and resultant ionospheric scintillations, change on a short-term basis are not clear. In the East and Southeast Asia, there exist significant differences in the generation rates of EPBs at closely located stations, for example, Kototabang (0.2°S, 100.3°E) and Sanya (18.3°N, 109.6°E), indicating that the decorrelation distance of EPB generation is small (hundreds of kilometers) in longitude. In contrast, after the initial generation of EPBs at one longitude, they can drift zonally more than 2000 km and extend from the magnetic equator to middle latitudes of 40° or higher under some conditions. These features make it difficult to identify the possible seeding sources for the EPBs and to accurately predict their occurrence, especially when the onset locations of EPBs are far outside the observation sector. This paper presents a review on the current knowledge of EPBs and ionospheric scintillations in the East and Southeast Asia, including their generation mechanism and occurrence morphology, and discusses some unresolved issues related to their short-term forecasting, including (1) what factors control the generation of EPBs, its day-to-day variability and storm-time behavior, (2) what factors control the evolution and lifetime of EPBs, and (3) how to accurately determine ionospheric scintillation from EPB measurements. Special focus is given to the whole process of the EPB generation, development and disruption. The current observing capabilities, future new facilities and campaign observations in the East and Southeast Asia in helping to better understand the short-term variability of EPBs and ionospheric scintillations are outlined.

Ionospheric F Layer Scintillation Weakening as Observed by COSMIC/FORMOSAT‐3 During the Major Sudden Stratospheric Warming in January 2013

AbstractSudden stratospheric warming (SSW) events in Northern Hemisphere winter atmosphere play a significant effect on large ionospheric disturbances. Nevertheless, the SSW effects on small‐scale structure in ionosphere, that is, the ionospheric F layer irregularities, are generally lack of understanding. This work carefully studied the equatorial F layer scintillation during the SSW event extending from 4 January to 5 February in 2013 by using the data of COSMIC/FORMOSAT‐3 (a Constellation Observing System for Meteorology, Ionosphere, and Climate mission). The occurrence rate of ionospheric F layer scintillation was found to be apparently decreased by about 30% during the SSW period. This phenomenon was obviously seen in American sector (90°W–0°) and African sector (0°–90°E). Another prominent feature was the ~0.5 local time hour delay of maximum scintillation occurrence rate associated with the suppression of equatorial F layer irregularities in the first 2 hr after the sunset during the SSW event in January 2013.

A Statistical Analysis of Global Ionospheric E‐Layer Scintillation During 2007–2014

AbstractThis paper presents the global three‐dimensional morphology and seasonal variation of the scintillation index at E‐layer altitudes varying from 70 to 140 km. An attempt is conducted to analyze the scintillation distribution in different latitude bins and to explore solar and geomagnetic activity‐dependent characteristic of E‐layer scintillations. The scintillation index is derived from the signal‐to‐noise ratio intensity fluctuations of L1 channels in GPS radio occultation (RO) using the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) during 2007–2014. The results show that the summer scintillation index has the greatest values, followed by the winter, autumn, and spring months. The summer scintillation is in close connection with the solar radiation intensity and sunshine duration, but it exhibits seasonal asymmetry whereby the summer scintillation in the northern hemisphere is more intense than in the southern hemisphere. Meanwhile, the scintillation in the autumn hemisphere is slightly more intense than in the spring hemisphere in approximately midlatitude regions during most daytimes. The conspicuous scintillation activity in the middle and low latitudes starts post‐sunrise and often persists until post‐midnight. Some observed results show that the greatest scintillation occurrence rate of the latitude profile occurs at approximately sunset and at an altitude range of 100–120 km in the middle‐low latitudes. Additionally, the enhanced solar activity possibly can result in the slight decrease of scintillation occurrence, and geomagnetic activity has slight effect on E‐layer scintillation in most cases.

Degradation of Satellite‐Based Navigation Performance Observed From an Anomaly Crest Location in the Indian Longitude Sector

AbstractGPS amplitude and phase scintillations in terms of the index S4 and σϕ and the corresponding losses of lock in signal have been studied with consequent errors in receiver positions for the whole month of March 2014 from Calcutta situated near the northern crest of the equatorial ionization anomaly (EIA). The impact of phase and amplitude scintillations is found to be different on GPS satellites in terms of intensities and duration. There are 42 and 59 cases of loss of lock in C/NO and phase, respectively, all occurring during 13–18 UT (LT = UT + 06:00). For all the cases, duration of amplitude loss of lock is longer than that of phase loss of lock. Associated with such signal perturbations, deviations in receiver positions are found to occur having maximum values of 31.72 m for latitude and 85.2 m for longitude during 15–16 UT. Though 9.5% of the cases start when amplitude scintillation was moderate (0.4 < S4 ≤ 0.6), 32.2% of the cases occurred when phase scintillation was moderate (0.2 < σϕ ≤ 0.7). The percentage of occurrences of moderate amplitude scintillation is 5.07% during 19:00–20:00 UT and does not occur thereafter, whereas the percentage of occurrences of moderate phase scintillations are found to be 18% even during 21:00–22:00 UT. The percentage of occurrences of weak phase scintillations was also higher (49.25%) compared to 1.98% corresponding to amplitude scintillations even at 23:00 UT. Occurrence of phase scintillations on GPS links has not been frequently reported from this longitude sector before, mainly due to nonavailability of appropriate transmissions.

Solar Cycle Variations of GPS Amplitude Scintillation for the Polar Region

AbstractGlobal Positioning System (GPS) L1 amplitude data, obtained using the Canadian High Arctic Ionospheric Network (CHAIN) during the period 2008–2018, is used to study the seasonal and solar cycle dependence of high‐latitude amplitude scintillation. The occurrence of amplitude scintillation is predominantly confined to the 10–18 magnetic local time (MLT) and 72–87° Altitude‐Adjusted Corrected Geomagnetic (AACGM) sector and is a winter and equinoctial phenomenon. The occurrence of amplitude scintillation shows a clear seasonal and solar cycle dependence with a maximum value of ∼11% during the high solar activity early winter periods, and a secondary maximum in equinoctial months, and almost no occurrence during summer months. This pattern in occurrence suggests that amplitude scintillation is a phenomenon that is closely associated with the presence of patches and particle precipitation events.

Low-latitude GNSS ionospheric scintillation dependence on magnetic field orientation and impacts on positioning

Ionospheric scintillation often occurs in equatorial and low-latitudes regions between ± 20° geomagnetic latitude and impacts GNSS performance on geodetic applications. In equatorial and low latitude regions, scintillation on the GNSS signal occurs mainly due to small-scale irregularities inside plasma bubbles that are magnetic field-aligned structures. We derived the propagation angle between GNSS ray paths and magnetic field lines to quantify scintillation occurrences of multi-constellation GNSS signals in relation to magnetic field orientation. Precise point positioning (PPP) solutions are obtained to assess the field-aligned scintillation signal impacts on positioning. A case study based on observations in Hong Kong is conducted to characterize a typical low-latitude region near the northern equatorial anomaly crest. Measurements from multiple GNSS constellations, i.e., GPS, GLONASS, Galileo and BDS are used. Results suggest that the GNSS scintillation intensity is enhanced in the local southern sky within the azimuth range of 150°–240° with peak at ~ 180°, where the signal paths closely align with the magnetic field lines. Analysis of the data show that up to five GPS satellites may have their signal paths aligned closely with magnetic field lines simultaneously. This can result in an increase in the kinematic PPP errors from several centimetres to tens of meters. The relationship between the scintillation occurrence and magnetic field orientation could be exploited in the future to mitigate scintillation effects on GNSS applications.

SCINDA-GPS derived TEC depletions and amplitude scintillations over Kisumu, Kenya during selected quiet and storm days of 2013 and 2014

Total Electron Content (TEC) depletion and amplitude scintillation (S4) can be derived from, SCINDA-GPS receivers situated in various parts of the equatorial region. In this paper we present results of characterization of TEC depletions and amplitude scintillations over Kisumu, Kenya (Geomagnetic coordinates: 9.64o S, 108.59o E; Geographic coordinates: 0.02o S, 34.6o E) for both selected geomagnetically quiet and geomagnetically disturbed conditions between 1st January 2013 and 31st December 2014 using data derived from the Kisumu NovAtel GSV4004B SCINDA-GPS receiver situated at Maseno University. TEC depletions and amplitude scintillations affect Global Positioning System (GPS) signals in the ionosphere as they propagate from the satellite to the receiver. This study aims to investigate day to day variability of TEC depletions and amplitude scintillations over Kisumu, Kenya during both geomagnetically quiet and geomagnetically disturbed days of 2013 and 2014 which was a high solar activity period for Solar Cycle 24. Seasonal variability of TEC depletions and S4 index is also presented. The Receiver Independent Exchange (RINEX) data for the years 2013 and 2014 was retrieved from the Kisumu SCINDA-GPS receiver, processed to obtain Vertical Total Electron Content (VTEC), S4 and Universal Time (UT) and fed into MATLAB to generate VTEC and S4 plots against UT for each selected quiet and storm day within the 2013 and 2014 period. The obtained results showed a diurnal variation of TEC where TEC was minimum at pre-sunrise, maximum during daytime and minimum during nighttime. The minimum TEC during pre-sunrise and nighttime was attributed to reduced solar intensity while maximum TEC during daytime is attributed to increased solar intensity. Most of the selected quiet and storm days of the years 2013 and 2014 showed TEC depletions and TEC enhancements corresponding with enhanced amplitude scintillations between 1800UT and 20:00UT. This might be attributed to the rapid rise of the F-layer and the increase in the vertical E x B plasma drift due to the Pre-reversal Enhancement (PRE) of the eastward electric field. Post-midnight TEC depletions and amplitude scintillations were observed for some days and this was attributed to the effect of zonal winds which brought post-midnight enhancement of the E x B drift. The percentage occurrence of amplitude scintillations for the selected quiet and storm days exhibited a seasonal dependence with equinoctial months having higher occurrences than the solstitial months. The higher average S4 index during equinoctial months might be attributed to increased solar intensity resulting from the close alignment of the solar terminator and the geomagnetic meridian. Â

Scintillation and Luminescence Properties of the Zinc Oxide (ZnO) Doped Frit Crystal Under Gamma Radiation

The main objective of this study is to determine the characteristics of the scintillation and luminescent for Zinc Oxide (ZnO). Two groups of ZnO were prepared: pure (P338) and doped (P338Frit). This study investigates the scintillation and luminescent properties of the prepared ZnO in both powder and crystal forms. The NaI(Tl) scintillator is used as a tool for the control scintillator. It is a crystal that is commercially utilized in many radiation detecting fields. The P338 and P338Frit were used as the scintillator in the experimental setup. The P338 and P338Frit were bombarded with gamma photons of 241Am and 137Cs. The set up was connected to Multichannel Analyzer (MCA) to analyse its gamma spectrum. The scintillation occurrence is followed by the occurrence of luminescence in order for photon interactions to be detected by the MCA system. The photons detected are called count. However, self-absorption of the light is common which prevail the count from being recorded even though the scintillation occurs. The Compton continuum and photoelectric peak of the interaction were not distinguished. In conclusion, the characteristics of the luminescence and scintillation for the prepared ZnO were observed, however, the gamma spectrum peaks recorded were inconclusive.

A comparative study between two percentage of occurrence methodologies for computing ionospheric scintillation statistics

This study presents a detailed comparative analysis of the two widely used percentage of occurrence methodologies used to compute the statistics of ionospheric scintillation activity based on the data of a Global Positioning System (GPS) Ionospheric Scintillation and (TEC) Total Electron Content Monitor (GISTM) receiver located at the northern Equatorial Ionization Anomaly (EIA) crest region Agartala (23.76°N, 91.26°E) of the Indian subcontinent, during 2012–2015 of the rising, peak and declining solar activity periods of solar cycle-24. Both the methodologies, one based on the number of scintillation event days and another based on the number of scintillation events, provide the correct and similar scintillation statistics qualitatively. But a rigorous comparative study shows significant quantitative differences between the statistics obtained by the two methodologies. The variation of scintillation occurrence obtained by the two methodologies with solar and geomagnetic activity shows that the methodology based on the number of scintillation events provides more accurate and physically acceptable results. Though this fact may be familiar to some researchers but still the scientific community has been using both the methodologies in parallel to compute scintillation statistics. So, from this comparative analysis future researchers can get a clear scenario of the advantages and disadvantages of these methodologies over one another before adopting any one of those for computing scintillation statistics. We also want to highlight the issue to the scientific community to come to a common platform by adopting the percentage of occurrence methodology based on the number of scintillation events for future studies.