Scintillation Level Research Articles

Relative sensitivity of plastic scintillator: A comparative analysis with 60Co gamma rays, deuterium-deuterium, and deuterium-tritium neutrons.

A plastic scintillator has found extensive application in the realm of high-energy physics and national security science. Many applications in those fields often involve the simultaneous production of photons, neutrons, and charged particles, which makes the relative sensitivity information for these different radiation types important. In this study, we have adopted a multi-head detector comprised of a plastic scintillator and high gain phototubes, which provides a large dynamic range and linearity. A comparative study on the relative sensitivities of plastic scintillators was facilitated by adopting three distinct radiation calibration sources (i.e., 60Co γ rays, DD neutrons, and DT neutrons). Neutrons from a DD source generate a comparable level of scintillation to gamma rays emitted by 60Co (i.e., 60Co-γ/DD-n = 0.92 ± 16%). DT neutrons induce ∼3.5 times the scintillation observed with DD neutrons (i.e., DT-n/DD-n = 3.5 ± 28%). In addition, the Geant4 simulation granted us valuable insights into the relative sensitivity of the scintillator. This comparative study will provide a useful database for users in diverse applications.

Occurrence characteristics of ionospheric scintillations in the civilian GPS signals (L1, L2, and L5) through a dedicated scintillation monitoring receiver at a low-latitude location in India during the 25th solar cycle

Abstract The ionospheric post-sunset irregularities are responsible for the discrepancies in the received global navigation satellite system (GNSS) signals to fluctuate the phase and amplitude resulting in scintillations in the respective components. Ionospheric scintillations reduce the signal quality and alter the signal reception time inducing position errors which is not preferable for the precise position applications. The level of ionospheric amplitude scintillation, quantified by the amplitude scintillation index (S4), is analyzed during the year 2022, which accentuates the ascending phase of solar cycle 25. For this, we analyzed scintillation intensity and occurrence percentage at a low latitude Indian location in India by employing all the available frequencies of the global positioning system (GPS) constellation. The scintillation distribution for each month is also observed which reveals that the autumn equinox seasons has high scintillation occurrence compared to the vernal equinox seasons. The impact of the scintillation on the three civilian signals (L1, L2 and L5) of the GPS constellation is also observed in terms of the scintillation intensity distribution. The cross-correlation of the S4 index for these three signals reveals a strong correlation existing among them during strong scintillations whereas L2 and L5 signals portray a high correlation irrespective of signal intensities. In brief, the strong scintillation occurrence percentage is higher in the L5 signal compared to the L1 and L2 in contrast with weak scintillation, which is high in L1, followed by L2 and L5. Further, the analysis shows that the autumnal equinox has the highest percentage occurrence of strong scintillations (less than 10 % of the scintillation cases) compared to the vernal equinox whereas among solstice seasons June solstice presented the least scintillation occurrence at the location. The outcomes of this study instigate further analysis of scintillation occurrences from diverse GNSS frequencies covering diverse solar activity conditions for complementing the development of robust scintillation mitigation strategies across the low latitudes during the diverse scintillation conditions.

Scintillation Level of Scattered Radio Waves in the Equatorial Ionosphere

Scintillation effects of propagating and scattered radio waves (RWs) are considered analytically and numerically in the equatorial terrestrial ionosphere applying the statistical characteristics. Analytical calculations of the second-order statistical moments of the phase fluctuations of the ordinary and extraordinary RWs in the conductive collision ionospheric magnetoplasma (COCOIMA) are carried out for the first time using the Wentzel-Kramers-Brilluen method and the modified smooth perturbation method in consideration of the diffraction effects. Polarization coefficients of these waves in the equatorial ionosphere have been derived for the first time. The scintillation level includes the variance and the correlation functions of scattered RWs. Statistical moments contain complex refractive index, anisotropy coefficient characterizing irregular plasmonic structures, tilt angle of prolate irregularities concerning to the external magnetic field, permittivity components of the equatorial ionosphere, Hall's, Pedersen and longitudinal conductivities. A new feature of the "Fountain Effect" has been discovered in the equatorial ionosphere at weak and moderate scintillations caused due to anisotropy parameters of electron density fluctuations. Anisotropy parameters of electron density inhomogeneities influence the scintillation index of both the ordinary and extraordinary radio waves shifting maximums of the curves in the opposite directions at weak and moderate scintillations. Numerical calculations are carried out using the hybrid anisotropic correlation function of electron density fluctuations containing both exponential and power-law spectral functions having arbitrary spectral index, applying the experimental data.

Scintillation analysis of gaussian beams in anisotropic and uniaxial media

Scintillation of Gaussian beams both in anisotropic and uniaxial media is examined numerically utilizing the split step approach. Both the point-like and the power scintillation indices of Gaussian beams that propagate for a 5 Km in anisotropic and uniaxial media are investigated. The effect of turbulence strength on the scintillation level is also studied. In this regard, the scintillation level of the three components of Gaussian beam both the anisotropic and the uniaxial are analysed and compared with the scintillation of the fundamental Gaussian beam. The provided results show that the x-component of the Gaussian beam as propagate in both the anisotropic and the uniaxial media has the lowest scintillation. In addition, in uniaxial medium, the three components of the Gaussian beam have a power scintillation level less than the fundamental Gaussian.

Analysis of finite energy fresnel bessel beams scintillation level in turbulent communication links

Scintillation indices of Finite Energy Fresnel-Bessel Beams (FEFBBs) propagating for 6 Km in a turbulent atmosphere are analyzed. In this context, the effects of beam order and Gaussian beam waist on the reduction of scintillation level are evaluated. Both the point-like scintillation and the power scintillation indices are examined. The obtained results show that beam order does not have a significant impact on the scintillation levels. FEFBBs are able to reduce the power scintillation levels, then improve the system performance better than fundamental Gaussian beams. Thus, the provided results are significant for not only the performance improvement of the free-space optical (FSO) communication systems but also for the applications that require line of sight alignment namely directed infrared countermeasure (DIRCM).

Photon Induced Scintillation Amplifier — The PISA concept

Photoelectron signal amplification in gas photomultipliers (GPMs) is achieved through charge avalanche development in the holes of a cascade of hole-type microperforated foils. When a voltage difference is applied between the metal film electrodes that are deposited on both surfaces of those foils, an electric field with a high intensity is established inside the holes. As a consequence, each electron entering those holes produces an electron avalanche that emerges from the other side of the holes. A cascade of few foils is necessary for a single primary electron to produce a final avalanche intense enough to be read out, in the anode electrode, above the electronic noise. We propose the Photon Induced Scintillation Amplifier (PISA), where the photoelectron signal amplification is obtained by reading out the photon scintillation produced in the charge avalanches of solely one Micro-Hole-and-Strip-Plate-type microstructure with SiPMs. The optical readout has the advantage of having the extra gain from the photosensor and is less sensitive to electronic noise. A large photosensor gain produces large output signals that can travel over long distances without significant degradation. This allows for the readout electronics to be placed away from the photosensor and, thus, from the detector sensitive volume. The scintillation readout plane can be made of a 2D-array of SiPMs, with size and pitch in accordance with the needed scintillation level and position resolution. A first basic prototype was assembled to present a proof-of-principle of the PISA concept.

Scintillation modeling with random phase gradient screens

Multiple studies of scintillation phenomena have shown that, in certain situations, the intense phase fluctuations of trans-ionospheric radio signals are associated with the scattering on strong electron density gradients. The present study provides a theoretical framework for modeling such types of phase fluctuation events. Using the geometrical-optics approximation and retaining the second-order smallness correction in the expansion of the eikonal function, we relate the phase of the transmitted wave not only to the total electron content (TEC) of the ionosphere but also to the spatial gradient of the TEC. The considered correction term is related to the random refraction of signal rays on large-scale ionospheric structures, an effect, that becomes significant in the presence of strong electron density gradients. To conveniently simulate the wave propagation under such conditions, we propose the random phase gradient screen algorithm. For this purpose, we use the novel spatial electron density gradient product (NeGIX) based on in-situ observations of the Swarm Langmuir probe and ground-based TEC and TEC gradient observations. To illustrate the performance of the algorithm, we apply it to simulate a scintillation event over Europe and in the low-latitude region and compare the simulation results with scintillation indices, measured from GNSS ground observations. We show that in regions of the ionosphere where spatial ionospheric gradients are large, the phase gradient method shows better agreement with the observed scintillation levels than the conventional phase screen approach.

Temporal characterization of pre-midnight fading events over low latitudes

Several works investigated aspects of amplitude scintillation over low-latitude regions. Some of these studies also addressed characteristics and consequences of fading events in receivers and systems relying on information from satellites. It is now known that amplitude scintillation severity in transionospheric signals is stronger around the region of the Equatorial Ionization Anomaly and depends on the signal propagation path. However, a temporal characterization of the occurrence of amplitude scintillation and fading events over distinct latitudes is still needed. In this work this temporal analysis was done by using data from 4 ground-based scintillation monitor stations with distinct dip latitudes over the southern hemisphere (Brazilian region). The period of observation covers 5 months during the peak of the last solar cycle, and the hours considered are from 19:00 LT up to 23:30 LT for every station. The analyses revealed that the occurrence of scintillation for all the stations peaks at 21:00 LT, with weaker/stronger scintillation levels for stations closer to the dip equator/Equatorial Ionization Anomaly, respectively. More importantly, the results demonstrated that deep fading events are concentrated in the early hours of the night for all levels of scintillation. The probabilities of deep fading events peaks at 21:00 LT, decaying considerably for later hours. The results also revealed that the deepest fading experienced occurs in the earlier hours and that the depth of the fading decreases as later hours are considered. The probabilities of a given depth for the deepest fading also decay after peaking at 21:00 LT. All these findings provide a temporal characterization that can be insightful to users of information from satellites whose links are susceptible to problems such as cycle slips and loss-of-lock, especially in the earlier hours of the night.

Resolving Moving Heliospheric Structures Using Interplanetary Scintillation Observations With the Murchison Widefield Array

AbstractWe have conducted a blind search in 49 consecutive days of interplanetary scintillation observations made by the Murchison Widefield Array from mid‐2019, with overlapping daily observations approximately East and South‐East of the Sun at an elongation of ∼30° and a field of view of 30°. These observations detect an unprecedented density of sources. In spite of these observations being taken at sunspot minimum, this search has revealed several interesting transitory features characterized by elevated scintillation levels. One solar wind enhancement is captured in two observations several hours apart, allowing its radial movement away from the Sun to be measured. We present here a methodology for measuring the plane‐of‐sky velocity for the moving heliospheric structure. The plane‐of‐sky velocity was inferred as 0.66 ± 0.147 hr−1, or 480 ± 106 kms−1 assuming a distance of 1AU. After cross‐referencing our observed structure with multiple catalogs of heliospheric events, we propose that the likely source of our observed structure is a stream‐interaction region originating from a low‐latitude coronal hole. This work demonstrates the power of widefield interplanetary scintillation observations to capture detailed features in the heliosphere which are otherwise unresolvable and go undetected.

Performance of hollow hyperbolic sinusoidal Gaussian beam in weak turbulent optical communication links

The performance of hollow hyperbolic sinusoidal Gaussian beam (HHsGB) propagating in weak turbulent optical communication link is examined by analysing the beam scintillation indices. System parameters’ effect on point-like and aperture-averaged scintillation index values is investigated. The obtained results show that HHsGBs with small source sizes improve the link performance by reducing the scintillation level. In communication systems with a big receiver aperture radius, HHsGBs with high orders significantly minimize the scintillation level. Thus, the provided results will have significant potential in improving free-space optical communication performance in a wide range of applications.

Corotating Disturbances of the Solar Wind in the Monitoring Data of Interplanetary Scintillations: Simulation and Observation

A simple model has been proposed for the leading part of an interaction region between solar wind streams of different speeds. The model describes an increased plasma concentration as a spiral jet with a rectangular cross-section. Using this model, two-dimensional dynamic maps of interplanetary scintillation level distribution were calculated, which were specifically adapted to the configuration of the BSA LPI radio telescope. The model calculations were compared with the data from a series of observations of interplanetary scintillation during four geomagnetic storms in 2022 and 2023, caused by corotating disturbances. The calculations and observational data exhibit a qualitative correspondence. It has been shown that corotating disturbances manifest as scintillation enhancement three days before a geomagnetic storm, occurring at around 15:00–16:00 Moscow time. Over the next two days, the scintillation enhancement zone shifts to a later time, while there is no enhancement in the morning sector. During the actual geomagnetic storm period, there is an increase in night scintillations. This sequence of scintillation enhancement indicates that the disturbance approaches Earth from the eastern side while rotating with the Sun. The qualitative differences between the observational data for corotating and propagating large-scale disturbances are discussed.

Probing the Plasma Tail of Interstellar Comet 2I/Borisov

We present an occultation study of compact radio sources by the plasma tail of interstellar comet 2I/Borisov (C/2019 Q4) both pre- and near-perihelion using the Arecibo and Green Bank radio telescopes. The interplanetary scintillation technique was used to probe the plasma tail at the P band (302–352 MHz), 820 MHz, and the L band (1120–1730 MHz). The presence and absence of scintillation at different perpendicular distances from the central axis of the plasma tail suggests a narrow tail of less than 6′ at a distance of ∼10′ (∼106 km) from the comet nucleus. Data recorded during the occultation of B1019+083 on 2019 October 31 with the Arecibo Telescope covered the width of the plasma tail from its outer region to the central axis. The systematic increase in scintillation during the occultation provides the plasma properties associated with the tail when the comet was at its pre-perihelion phase. The excess level of L-band scintillation indicates a plasma density enhancement of ∼15–20 times that of the background solar wind. The evolving shape of the observed scintillation power spectra across the tail from its edge to the central axis suggests a density spectrum flatter than Kolmogorov and that the plasma density irregularity scales present in the tail range between 10 and 700 km. The discovery of a high-frequency spectral excess corresponding to irregularity scales much smaller than the Fresnel scale suggests the presence of small-scale density structures in the plasma tail, likely caused by interaction between the solar wind and the plasma environment formed by the comet.

On Correlation of the Interplanetary Scintillation Level and Solar Wind Speed

On Correlation of the Interplanetary Scintillation Level and Solar Wind Speed

Orbital angular momentum for turbulence mitigation in long free-space optical communication links

The ability of laser beams carrying orbital angular momentum to reduce the scintillation level of Gaussian beam propagating in atmospheric turbulence is numerically investigated. The effect of topological charge, beam waist, operating wavelength and also the receiver radius on the scintillation indices is examined in detail. It is shown that the Gaussian beam carrying orbital angular momentum has a priority over a fundamental Gaussian beam in communication links longer than 2.5 Km. It is clear that Gaussian beams carrying orbital angular momentum in the cases when having a small beam waist and operating at a high wavelength are able seriously to reduce the scintillation index. Accordingly, the presented results will be significant for designing optical communication links that use laser beams carrying orbital angular momentum.

Emulating atmospheric turbulence effects on a micro-mirror array: assessing the DMD for use with free-space-to-fibre optical connections

Emulated atmospheric turbulence effects constructed from a set of 22 Zernike modes have been written upon a DMD micromirror array operating as a binary amplitude spatial light modulator. Sequences of aberrated frames with controlled amounts of turbulence have been produced and can be operated at controlled rates that can exceed 1 kHz rates which can be seen in strong turbulence. In this case 400 Hz was chosen and the scintillation levels observed for the same turbulence sequence with single, few and multi-mode fibres at a receiver. Resulting scintillation levels are consistent with standard turbulence models. Increased received intensity and reduced scintillation was observed with larger core fibres and related to aberration-induced focal spot size. Correlation between the received intensity variation and the amplitude variations for individual Zernike modes demonstrates specifically the effect of atmospheric induced beam wander when focusing into a receive fibre. The DMD is thus shown to be able to generate both the necessary frequency content and range of scintillation required for atmospheric emulation.

Effects of 15th January 2010 Annular Solar Eclipse on Traveling Ionospheric Disturbances and Equatorial Plasma Bubbles over Low Latitude Regions of East Africa

The influence of the 15th January 2010 annular solar eclipse on traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) is studied using data from six global navigation and satellite system (GNSS) receivers spread across the path of annularity over the low latitude region of East Africa. The GNSS receivers are stationed at Nairobi (RCMN), Malindi (MAL2), and Eldoret (MOIU) in Kenya; Mbarara (MBAR) in Uganda; Kigali (NURK) in Rwanda; and Mtwara (MTWA) in Tanzania. The study period ranges from 12th to 18th January 2010, three days before and after the 15th January 2010 annular solar eclipse. The year 2010 marked the beginning phase of solar cycle 24, evidently observed in low total electron content (TEC) values and the disturbed storm time index (Dst). The eclipse started at 7 : 06 LT and ended at 10 : 14 LT, with MOIU and RCMN experiencing eclipse magnitudes of 0.946 and 0.93, respectively. The maximum obscuration occurred between 8 : 21 LT and 8 : 34 LT across most of the stations. A detrending on vertical TEC (VTEC) derived from GNSS receivers across or close to the path of totality revealed a reduction of ∼2-3 TECU during the maximum phase of the eclipse. The level of reduction was highly close to the totality path and decreased smoothly away from the totality path. Using a background polynomial fitting technique on diurnal TEC, we analyzed TIDs along NURK-MBAR-MOIU and MOIU-RCMN-MAL2 GPS arrays. The results revealed a wavelike perturbation with a virtual horizontal velocity of 830m/s and ∼1 TECU amplitude propagating eastward along the MOIU-RCMN-MAL2 GPS array. The study reports a moderate scintillation activity of 0.5 ≤ ROTI ≤ 0.9 values, demonstrating the presence of few EPBs over the region. The results show a latitudinal variation in GPS-TEC scintillation activities and suggest a possible influence of the eclipse on the observed increase in average scintillation levels across East Africa.

Application of novel interplanetary scintillation visualisations using LOFAR: A case study of merged CMEs from September 2017

Observations of interplanetary scintillation (IPS – the scintillation of compact radio sources due to density variations in the solar wind) enable the velocity of the solar wind to be determined, and its bulk density to be estimated, throughout the inner heliosphere. A series of observations using the Low Frequency Array (LOFAR - a radio telescope centred on the Netherlands with stations across Europe) were undertaken using this technique to observe the passage of an ultra-fast CME which launched from the Sun following the X-class flare of 10 September 2017. LOFAR observed the strong radio source 3C147 at an elongation of 82 degrees from the Sun over a period of more than 30 h and observed a strong increase in speed to 900kms−1 followed two hours later by a strong increase in the level of scintillation, interpreted as a strong increase in density. Both speed and density remained enhanced for a period of more than seven hours, to beyond the period of observation. Further analysis of these data demonstrates a view of magnetic-field rotation due to the passage of the CME, using advanced IPS techniques only available to a unique instrument such as LOFAR.

Performance Analysis of Satellite Navigation Positioning Service under Ionospheric Scintillation

Abstract Satellite navigation signals may be affected by ionospheric anomalies such as ionospheric scintillation and ionospheric storms. These anomalies will lead to fluctuations and delays of signals, and thus affecting the performance of satellite navigation service. How to evaluate the performance of satellite navigation service under the influence of ionospheric anomaly is one of the key issues to ensure the safety of satellite navigation aviation service. To solve this problem, the simulation of satellite navigation signals under scintillation and the performance evaluation of positioning service are studied in this paper. Firstly, the scintillation sequence is simulated based on Cornell model. Then, the influence of scintillation on satellite signal parameters is modeled and a generation approach of intermediate frequency satellite navigation signals under scintillation is proposed. Finally, the performance indicators of normal signal and scintillating signal are quantitatively analyzed by solving the navigation parameters and evaluating the performance indicators of the receiver. Simulation results show that the ionospheric scintillation affects the satellite navigation service performance, with reference to the standard specification requirements. Performance of satellite navigation positioning service is severely affected even only one satellite signal is affected by a common moderate scintillation level.

Variations in the Radial Dependence of the Interplanetary Scintillation Level in the Descending Phase of Solar Cycle 24

Variations in the Radial Dependence of the Interplanetary Scintillation Level in the Descending Phase of Solar Cycle 24

Assessment of GPS positioning performance using different signals in the context of ionospheric scintillation: a month-long case study on São José dos Campos, Brazil

The ionospheric scintillation associated to small-scale irregularities in the ionospheric layer can lead to performance degradation of Global Navigation Satellite Systems (GNSS) signals, and the reduction of positioning accuracy. The influence of the ionospheric layer on the GNSS systems is expected to be different for each signal since it is transmitted on different carrier frequencies. This paper presents the results of a quantitative analysis of the scintillation amplitude of GPS (Global Positioning System) signals at L1, L2 and L5 frequencies, aiming to evaluate the impact of the ionospheric scintillation effects on the GPS frequencies. As the ionospheric scintillation may impact positioning accuracy, we also present an assessment of GPS point positioning using those frequencies. The GPS sample data were collected for 30 days between November and December 2014 at SJCE station located in São José dos Campos (SP), Brazil. Such a region is subjected to the equatorial anomaly effects being characterized by the occurrence of strong ionosphere scintillation. Considering the quantitative analysis, during the different levels of ionospheric scintillation presented a similar behavior, the magnitude of scintillations is small for the L1 signal and larger for L5. In general, the results confirmed that lower frequencies (L2 and L5) suffer more impact from intense scintillation than L1. Regarding the positioning assessment, the multi-frequency positioning was more accurate than single frequency. Considering dual-frequency positioning, results with L1-L2 were more accurate than those with L1-L5 signals. With single-frequency positioning, the L1 signal was more accurate compared to the L2 frequency.