Comment on angeo-2021-13

When wireless electromagnetic waves pass through the earth's atmosphere, they are affected by ionospheric irregularities, and their amplitude and phase will jitter rapidly in a short period of time, which is called ionospheric scintillation. With the human exploration of outer space and the demand for space communication, the study of ionospheric scintillation characteristics and its influence on electromagnetic communication has become increasingly important. This paper used the observation data received by GPS scintillation/TEC receivers in the Chengdu (104.07° N, 30.67° E) area of China from January 2018 to September 2020, and a data processing program was developed for the received GPS/BDS/GAL. The satellite data at multiple frequency points were processed to extract key data such as S4, azimuth angle, and elevation angle, and then the annual changes in ionospheric scintillation in the Chengdu region and the characteristics of local time changes were statistically analysed. The results show that the frequency and intensity of ionospheric scintillation events have obvious half-year changes. The scintillation intensity and frequency in spring and autumn are higher and more frequent than those in summer and winter; and scintillation events mainly occur at night. but they also occur during the day, mostly in the afternoon; and their occurrence is related to the airspace and is further closely related to the elevation and azimuth angles of the observation point. The overall scintillation events from 2018 to 2020 were in a gradual downward trend. At the end of May 2018, a scintillation event with a longer duration occurred. Further analysis showed that the occurrence of scintillation events increased with the rapid changes in solar activity and the geomagnetic environment. There is a certain positive correlation between the changes.

Ionospheric irregularities during a substorm event: Observations of ULF pulsations and GPS scintillations

The statistic characteristics of ionospheric scintillation occurrence over Vietnam region have been studied using the continuous data from three GSV4004 receivers at Hanoi, Hue and Ho Chi Minh city during 2009-2012 period. The local time variation, seasonal variation and directional variation of scintillation occurrences in each stations were considered. The obtained results showed that the ionospheric scintillation over Vietnam region, mainly occurred at night time between 20 to 24 local time. The occurrence of ionospheric scintillation depend on the season and solar activity, with the maximum occurrence frequency on the equinox months (March, April and September, October) and significant enhancements on the strong active solar years (2011-2012). Over Vietnam region, ionospheric scintillation occurs concentratively on the equatorial ionisation anomaly crest, from the 13oN to 21oN geographic latitude with maximum at about 15oN. The ionospheric scintillation occurs mainly within the elevation angle smaller 40o and concentrate on some deterministic azimuth angles at each station.ReferencesAarons J.,1982: Global morphology of ionospheric scintillations, Proc. IEEE, 70, 360-378.Abadi P., Saito S., and Srigutomo W., 2014: Low-latitude scintillation occurrences around the equatorial anomaly crest over Indonesia, Annales Geophys., 32, 7-17.Basu, S., S. Basu, J. Aarons, J.P. McClure, and M.D. Cousins, 1978: On the coexistence of kilometer- and meter-scale irregularities in the nighttime equatorial F region, Journal of Geophysical Research, 83 (A9), pp. 4219 - 4226.Basu S., E. Kudeki, S. Basu, C. E. Valladares and E. J. Weber, 1996: Scintillation, plasma drifts, and neutral winds in the equatorial ionosphere after sunset, Journal of Geophysical Research, Vol. 101, N.A12, 26795-26809.Beniguel Y., and Adam JP, 2007: Ionosphere Scintillation and their Effect on the Positioning Errors, IEEA, proccesding, France.Cervera M. A. and R. M. Thomas, 2006: Latitudinal and temporal variation of equatorial ionospheric irregularities determined from GPS scintillation observations, Ann.Geophys.,N.24, 3329-3341.Dierendonck V., A.J, John Klobuchar, Quyen Hua, 1993: Ionospheric Scintillation monitoring using commercial single frequency C/A code receivers, Proceedings of ION GPS-93.Kintner P. M., Ledvina B. M., and Paula E. R, 2007: GPS and ionospheric scintillations, Space weather, Vol.5, S09003, doi:10.1029/2007W000260.Trần Thị Lan, Lê Huy Minh, R. Fleury, P. Lassudrie Duchesne, A. Bourdillon, 2009: Bước đầu nghiên cứu nồng độ điện tử tổng cộng và nhấp nháy điện ly sử dụng số liệu các trạm thu GPS liên tuc ở Việt Nam, Tạp chí Các khoa học về Trái Đất. T. 31, 3, 212-223.Trần Thị Lan, Lê Huy Minh, 2011: Biến thiên theo thời gian của nồng độ điện tử tổng cộng và nhấp nháy điện ly theo số liệu GPS liên tuc ở Việt Nam, Tạp chí Các khoa học về Trái Đất. T. 33, N4, 681-689.Le Huy Minh, Amory-Mazaudier C.,Fleury R., Bourdillon A., Lassudrie-Duchesne P., L. Tran Thi, T. Nguyen Chien and T. Nguyen Ha, P. Vila, 2014 : Time variations of the total electron content in the Southeast Asian equatorial ionization anomaly for the period 2006-2011, Advances in Space Research, 54, 355-368.Rama Rao, P. V. S., Gopi Krishna, S., Niranjan, and Prasad, D. S. V. V. D, 2006: Study of spatial and temporal characteristics of L-band scintillation over the Indian low latitude region and their possible effects on GPS navigation, Ann. Geophys., 24, 1567-1580.Saito S., Maruyama T., Ishii M., Kubota M., Ma G., Chen Y., Li J., Duyen C. H., Truong T. L., 2008: Observation of small to large scale ionospheric irregularities associated with plasma bubbles with a transequatorial HF propagation experiment and spaced GPS receivers, Journal of Geophysical research, V.113, A12313.Valladares C. E., Villalobos J., Sheehan R., and Hagan M.P., 2004: Latitudinal extension of low laititude scintillations measured with a network of GPS receivers, Ann. Geophys., 22, 3155-3175.GSV GPS Silicon Valley, 2005: GSV4004/GSV4004A - GPS Ionospheric Scintillation & TEC Monitor, USER’S MANUAL.

The Global Positioning System (GPS) is one of the most important and useful technologies developed for information and communication technology. Propagated wireless signals along the GPS link are affected by the ionospheric irregularities, therefore the GPS signals may experience ionospheric scintillation. In this study, GPS L-band amplitude scintillations observed at a low latitude station. Data from the Global Navigation Satellite System (GNSS) Ionospheric Scintillation and Total Electron Content (TEC) monitor (GISTM) receiver installed at the Space Science Centre (ANGKASA), Institute of Climate Change, UniversitiKebangsaan Malaysia, UKM (2.92°N, 101.78°E) were used for this study. Of the 460 scintillation (by neglecting S4<0.15) events recorded during February 2014, 55% were weak (0.15≤S4<0.25), 32% were moderate (0.25≤S4 <0.35) and 13% were strong (S4 ≥0.35). For February 2014, the amplitude scintillations were most pronounced in the post-sunset time to pre-midnight time. Finally, these analysed data are used to study the variability of scintillation with solar activities.

Signals recorded by two stations in the Brazilian region: [Fortaleza (3.74°S, 38.57°W) and Inconfidentes (22.31°S, 46.32°W)], receiving L1 transmissions from different geostationary satellites, were used to evaluate the amplitude scintillation index S4 and several characteristics of scintillation events (continuous record with S4 &gt; 0.2) during nighttime hours (18:00 LT–02:00 LT) in the years 2014–2016. The effects from solar activity, season, and local time on the number of scintillation events per night, maximum scintillation, scintillation event duration, and spacing between consecutive events will be discussed. The results indicate that: (a) scintillation occurs from September to March in both links; (b) the most likely numbers of observed scintillation events per night were two or three, particularly during the first 2 years; (c) on average, the first scintillation event usually had larger maximum S4 values when compared to those of the later ones along the night; (d) the first scintillation event had a longer mean duration than the succeeding ones in a given night; (e) the durations of scintillation events, regardless of their numbers per night and the location, decreased with local time; (f) the opposite dependence of spacings between consecutive events on local time was observed; (g) the cumulative distribution functions of the scintillation onset time indicated a strong dependence on the dip latitude of the station; and (h) early occurrences of onset times are directly related to the increased probability of the occurrence of multiple scintillation events.

Satellite-based communications, navigation systems and many scientific instruments rely on observations of trans-ionospheric signals. The quality of these signals can be deteriorated by ionospheric scintillation which can have detrimental effects on the mentioned applications. Therefore, monitoring of ionospheric scintillation and quantifying its effect on the ground are of significant interest. In this work, we develop a methodology which estimates the scintillation-induced ionospheric uncertainties in the sky and translates their impact to the end users on the ground. First, by using the risk concept from decision theory and by exploiting the intensity and duration of scintillation events (as measured by the S_4 index), we estimate ionospheric risk maps that could readily give an initial impression on the effects of scintillation on the satellite-receiver communication. However, to better understand the influence of scintillation on the positioning accuracy on the ground, we formulate a new weighted dilution of precision (WPDOP) measure that incorporates the ionospheric scintillation risks as weighting factors for the given satellite-receiver constellations. These weights depend implicitly on scintillation intensity and duration thresholds which can be specified by the end user based on the sensitivity of the application, for example. We demonstrate our methodology by using scintillation data from South America and produce ionospheric risk maps which illustrate broad scintillation activity, especially at the equatorial anomaly. Moreover, we construct ground maps of WPDOP over a grid of hypothetical receivers which reveal that ionospheric scintillation can also affect such regions of the continent that are not exactly under the observed ionospheric scintillation structures. Particularly, this is evident in cases when only the global positioning system is available.

Ionospheric scintillation has a great impact on radio propagation and electronic system performance, thus is extensively studied currently. The influence of scintillation on Global Navigation Satellite System (GNSS) is particularly evident, making GNSS an effective medium to study characteristics of scintillation. Ionospheric scintillation varies greatly in relation with temporal and spatial distribution. In this paper, both temporal and spatial characteristics of scintillation are investigated based on Macquarie Island’s GNSS scintillation data collected from 2011 to 2015. Experiments demonstrate that occurrence rates of amplitude scintillation have a close relationship with solar activity, while phase scintillation is more likely to be generated by geomagnetic activity. In addition, scintillation distribution behaviors related to elevation and azimuth angles are statistically analyzed for both amplitude and phase scintillation. The proposed work is valuable for a deeper understanding of theoretical mechanisms of ionospheric scintillation in this region, and provides a reference for GNSS applications in certain regions around sub-Antarctica.

Results are presented of twenty-four-hour interplanetary and ionosphere scintillation monitoring obtained in Pushchino Radioastronomy Observatory during three observation series: between 18 November and 30 December 2006; between 11 June and 18 June 2007; between 20 October and 4 November 2008. Observations were carried out simultaneously in 16 beams of the radio telescope BSA LPI (Big Scanning Array of Lebedev Physical Institute) at the frequency 111 MHz. All the sources with scintillating flux greater than 0.2 Jy were recorded in the range of declination from +3° to +12°40 by observations in the years 2006, 2008 and from 21° to 28° in the year 2007. The values of radio source flux fluctuation temporal structure functions were measured at the temporal lags of 0.1 s, 1 s and 10 s, which characterize noise, interplanetary scintillations and ionosphere scintillations, respectively. About 1000 scintillating radio sources were observed every day. The number of sources N (σ IPS≥σ IPS,0) with scintillating flux σ IPS greater than the given value σ IPS,0 in the sky area with sizes 8° in declination and 0.5 hours in right ascension was used as the parameter describing turbulent interplanetary plasma. This parameter is shown to be proportional to the mean scintillation index of the radio source statistical ensemble in the given sky area. Similarly, the parameter N (σ IONS≥σ IONS,0) was introduced for a description of the turbulent ionosphere. The mean twenty-four-hour temporal dependence of the scintillation index is found. Weak day-to-day variations of the scintillation index were observed. In general, interplanetary plasma, as well as the ionosphere, was in a quiet state during the observation periods. Unusually a weak dependence of scintillation index on the position of the sources relative to the Sun was observed in the year 2008 at very deep solar activity minimum. Such a weak dependence is explained by a strong elongation of the turbulence level spatial distribution along the solar equatorial plane during a very deep minimum of solar activity.

Solar and magnetic activity effects on VHF night-time ionospheric scintillations recorded during three and half year at Bhopal, a station near the northern crest of the equatorial anomaly in the Indian region have been presented. The night time diurnal scintillation occurrence decreases with decrease in solar activity. Monthly mean scintillation occurrence changes according to solar activity during E- and D- months but not so during J-months. The magnetic activity shows seasonal effect on scintillations and, in general, inhibits the scintillation occurrence in pre-midnight period and enhances little in post-midnight period especially after 03h IST. For most of the severe magnetic storms in which D st goes below −125 nT and recovery phase starts in post-midnight — dawn local time sector, strong post-midnight scintillations which sometimes extend for several hours beyond the local sunrise, are observed.

Ionospheric irregularities can affect satellite communication and navigation by causing scintillations of radio signals. The scintillations are routinely measured using ground-based networks of receivers. This study presents observations of ionospheric irregularities by Langmuir probes on the Swarm satellites. They are compared with amplitude scintillation events recorded by the Global Positioning System-Scintillation Network and Decision Aid (GPS-SCINDA) receiver installed in Mbarara (Lat: 0.6^{circ }hbox {S}, Lon: 30.8^{circ }hbox {E} , Mag. lat: 10.2^{circ }hbox {S}). The study covers the years from 2014 to 2018 when both data sets were available. It was found that the ground-based amplitude scintillations were enhanced when Swarm registered ionospheric irregularities for a large number of passes. The number of matching observations was greater for Swarm A and C which orbited at lower altitudes compared to Swarm B. However, some counterexamples, i.e., cases when in situ electron density fluctuations were not associated with any observed L-band amplitude scintillation and vice versa, were also found. Therefore, mismatches between observed irregularity structures and scintillations can occur just over a few minutes and within distances of a few tens of kilometers. The amplitude scintillation strength, characterized by the S4 index was estimated from the electron density data using the well-known phase screen model for weak scattering. The derived amplitude scintillation was on average lower for Swarm B than for A and C and less in accordance with the observed range. Irregularities at an altitude of about 450 km contribute strongly to scintillations in the L-band, while irregularities at about 510-km altitude contribute significantly less. We infer that in situ density fluctuations observed on passes over or near Mbarara may be used to indicate the risk that ionospheric radio wave scintillations occur at that site.

The starting times of mass spontaneous social movements have been compared with temporal changes in solar activity (Wolf numbers) and in the Aa index of geomagnetic activity. It is shown that relatively high values of solar and, hence, geomagnetic activity are typical (on average) of a set of years when social cataclysms began. In addition, the relationship between social activity and geomagnetic activity is expressed somewhat more strongly than with solar activity. Heliogeomagnetic activity itself is not, however, the cause of social conflicts, as is evidenced by the weakness of the statistical relationship and the fact that the time intervals of an extremely large number of social conflicts (the decades of the 1800s, 1910s, and 1990s) occur during periods of a reduced mean level of solar and geomagnetic activity. From an averaged statistical model of the solar-geomagnetic influence on social activity and the current status and forecast of the 24th solar cycle, we can assume that heliogeomagnetic factors will contribute to an increased level of sociopolitical activity at least until the end of 2014 and, possibly, a little longer.

Ionospheric scintillation causes major impairments to Global Navigation Satellite System (GNSS) in low-latitude regions. In severe scenarios, this event can lead to complete loss of lock, thus making GNSS measurements unusable for navigation. In this paper, we derive a cooperative localization algorithm where a set of partially connected aircraft exchange messages with neighboring nodes on the network to improve their own position estimates. We consider the scintillation events as abrupt changes in the measurement variance, which are modeled by a discrete-valued Markov process at the nodes which have access to GNSS measurements. Simulation results show that Markovian modeling and cooperation via factor graph message passing reduce the average 3D root mean square localization error and yield an average vertical position error that meets civil aviation standards for approach and landing.

Ionospheric scintillation is a pressing issue in space weather studies due to its diverse effects on positioning, navigation, and timing (PNT) systems. Developing an accurate and timely prediction model for this event is crucial. In this work, we developed two machine learning models for the prediction of ionospheric scintillation events at the equatorial anomaly during the maximum and minimum phases of solar cycle 24. The models developed in this study are the Random Forest (RF) algorithm and the eXtreme Gradient Boosting (XGBoost) algorithm. The models take inputs based on the solar wind parameters obtained from the OMNI Web database from the years 2010–2017 and Pc5 wave power obtained from the Bear Island (BJN) magnetometer station. We retrieved data from the Scintillation Network and Decision Aid (SCINDA) receiver in Egypt from which the S4 index was computed to quantify amplitude scintillations that were utilized as the target in the model development. Out-of-sample model testing was performed to evaluate the prediction accuracy of the models on unseen data after training. The similarity between the observed and predicted scintillation events, quantified by the R2 score, was 0.66 and 0.74 for the RF and XGBoost models, respectively. The corresponding Root Mean Square Errors (RMSEs) associated with the models were 0.01 and 0.01 for the RF and XGBoost models, respectively. The similarity in error shows that the XGBoost model is a good and preferred choice for the prediction of ionospheric scintillation events at the equatorial anomaly. With these results, we recommend the use of ensemble learning techniques for the study of the ionospheric scintillation phenomenon.

This work examines the change in the activity of the Sun based on the reconstruction of the heliospheric modulation potential in the time interval 8000 - 1000 BC. Reconstructions of this potential were obtained using radiocarbon data, taking into account the influence of changes in the Earth’s climate. A comparison is made of the variations in the activity of the Sun with the global surface temperature. It is shown that variations in global temperature during this period could be the result of changes in solar activity. So high solar activity could lead to recorded temperature maximums around 7000 and 5300 BC. The drop in temperature in the range 3000-1000BC could be the result of low solar activity.

Investigation of ionospheric scintillation at UKM station, Malaysia during low solar activity