Use of the East Asia GPS receiving network to observe ionospheric VTEC variations, scintillation and EIA features during the Solar Cycle 24 (original) (raw)
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2001
Morphological studies have qualitatively revealed the regular and seasonal variations of scintillation activity and their dependence on helio-geophysical parameters. There are significant seasonal maxima associated with the equinoxes. Scintillation is severe during the solar activity maximum conditions. In the years of high solar activity, trans-ionospheric propagation through polar and equatorial regions experiences deep fades at frequencies ranging from 54 MHz to 4 GHz. Although scintillation at middle latitudes is generally not as intense as at equatorial and high latitudes, weak to moderate levels of scintillation occur. Calculations showed that the ionospheric scintillation can have some important impacts on Global Positioning System (GPS) satellites, and mobile phone satellite (as "Iridium") systems at solar maximum years 2001-2002 of the current Solar Cycle 23, particularly severe, in the equatorial anomaly region. Scintillation morphology was developed to model ionospheric scintillation effects and to provide both planners and system operators with a tool for assessing the impact of these scintillations on their systems.
The European'GPS Ionospheric Scintillation and TEC Monitor'network: monitoring and database
Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS satellites occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation on GNSS system performance, including integrity, accuracy and availability. The two indices internationally adopted to characterize ionospheric scintillations are: the amplitude scintillation index, S 4 , which is the standard deviation of the received power normalized by its mean value, and the phase scintillation index, σ Φ , which is the standard deviation of the de-trended carrier phase. At low latitudes scintillations occur very frequently and can be intense. This is because the low latitudes show a characteristic feature of the plasma density, known as the equatorial anomaly, EA, for which a plasma density enhancement is produced and seen as crests on either side of the magnetic equator. It is a region in which the electron density is considerably high and inhomogeneous, producing ionospheric irregularities causing scintillations. The upcoming solar maximum, which is expected to reach its peak around May 2013, occurs at a time when our reliance on high-precision GNSS (such as GPS, GLONASS and the forthcoming GALILEO) has reached unprecedented proportions. Understanding and monitoring of scintillations are essential, so that warnings and forecast information can be made available to GNSS end users, either for global system or local augmentation network administrators in order to guarantee the necessary levels of accuracy, integrity and availability of high precision and/or safety-of-life applications. Especially when facing severe geospatial perturbations, receiver-level mitigations are also needed to minimize adverse effects on satellite signals tracking availability and accuracy. In this context, the challenge of the CIGALA (Concept for Ionospheric scintillation mitiGAtion for professional GNSS in Latin America) project, cofunded by the European GNSS Agency (GSA) through the European 7th Framework Program, is to understand the causes of ionospheric disturbances and model their effects in order to develop novel countermeasure techniques to be implemented in professional multifrequency GNSS receivers. This paper describes the scientific advancements made within the project to understand and characterize ionospheric scintillation in Brazil by means of historical and new datasets.
The increase of the ionospheric activity as measured by GPS
Earth, planets and space, 2000
The paper outlines a method allowing to compute the TEC with a precision of about 2-3 TECU and to detect Travelling Ionospheric Disturbances using GPS measurements. We describe the solar cycle dependance of the TEC and TIDs. Since the beginning of 1998, we have observed a stronger ionospheric activity due to the increasing solar activity. This ionospheric activity is characterized by larger TEC values which are regularly reaching the level of 60 TECU and by a larger number of Travelling Ionospheric Disturbances. During the winter 1999-2000, the mean daily TEC was above 45 TECU; at solar minimum the mean daily TEC is ranging from 4 TECU to 12 TECU. In January 2000 (close to solar maximum) more than 1300 events due to TID's were detected: it is 6.5 more than in January 1996 (at solar minimum).
Ionospheric Research Using Satellites
1982
Onset and cessation time Magnetic activit Equatorial scintillation on the 257MHz signals from Marisat. 1 satellite0-11ig 1980 is reported. Scintillation Index and depth of fade are the two par&-Tt-3-s used in the analysis. Seasonal variation pf scintillation and the correla-View~ between scintillation and geomagnetic activity were examined. The results cajqflm earlier observations on the 136 MHz signals made at Legon (Koster, 1972)... bi(cept for a few differences, these results are similar to observations on 1.5 G0q;-. ,de at Huancayo. Apart from May-Ai~gust, scintillatiu.s are negatively correlated %Vt geomagnetic activity in the remaining part of the annual cycl
A Study Of Ionospheric GPS Scintillation During Solar Maximum at UTeM Station
Wireless signals propagated along global positioning system (GPS) channel are affected by ionospheric electron density irregularities such that GPS signals may experience amplitude and phase fluctuations. The global navigation satellite system (GNSS), ionospheric scintillation, and total electron content (TEC) monitor (GISTM) receiver has been installed at UTeM, Malaysia (2.3139°N, 102.3183°E) for monitoring ionospheric scintillation at several frequencies. In this paper, the GPS ionospheric scintillations are concerned for the dual frequency L1 (fL1 = 1.57542 GHz) and L2C (fL2= 1.2276 GHz). Ionospheric scintillation data has been collected during solar maximum cycle 2013-2014 for six months October 2013-March 2014. Solar activities significantly impact the ionospheric GPS scintillation, especially in the equatorial region where Malaysia is located. The GPS link is analyzed to investigate how the scintillation increases during the solar maximum cycle. When the sun flux is maximum, the total of electrons is increased in the ionospheric layer and the scintillation values gradually become high. The ionospheric amplitude/phase scintillation, carrier-to-noise (C/No) ratio, and availability of GPS satellites are reported in the proposed experimental GPS model. Consequently, for Malaysia, typical threshold received C/No ratio is 43 dB-Hz, implying that C/No ratio should be greater than 43 dB-Hz to receive good signals at the GPS receiver.
arXiv: Atmospheric and Oceanic Physics, 2009
Ionospheric scintillation is the rapid change in the phase and/or the amplitude of a radio signal as it passes through small scale plasma density irregularities in the ionosphere. These scintillations not only can reduce the accuracy of GPS/Satellite Based Augmentation System (SBAS) receiver pseudo-range and carrier phase measurement but also can result in a complete loss of lock on a satellite. Scintillation in the ionosphere varies as the sun spot number (SSN), Geomagnetic index (o < Kp < 9), time of year, time of day, geographical position. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. Typically delay locked loop/phase locked loop designs of GPS/SBAS receivers enable them to handle moderate amount if scintillations. Consequently, any attempt to determine the effects of scintillations on GPS/SBAS must consider both predictions of scintillation activity in the ionosphere and residual effect of this activity after processing b...
Observation of GPS ionospheric scintillation at UKM, Malaysia
2011
Ionospheric scintillation can cause serious effects on communication systems, therefore the study of ionospheric scintillation is very crucial especially in the equatorial region where scintillation activity is maximum. The paper presents the month-to-month variations of amplitude and phase scintillations over Malaysia for a period of nine months from January to September 2010. The scintillation parameters are measured by the GPS ionospheric scintillation and TEC monitor (GISTM) using a dual-frequency GPS receiver at UKM, Malaysia (2.55°N, 101.46°E). The observations during the solar minimum show daytime amplitude scintillations were observed in the months of January and February with maximum value of S4 index between 0.2 and 0.3, from 10:00-14:00 LT, while phase scintillations were rarely observed. Nighttime amplitude scintillations were observed in March and August with maximum value of S4 index in the range of 0.2-0.4 at 22:00-24:00 LT and usually occurred with phase scintillations. It was found that amplitude scintillations rarely occurred at daytime but occurred frequently during nighttime.
GPS and ionospheric scintillations
Space Weather, 2007
1] Ionospheric scintillations are one of the earliest known effects of space weather. Caused by ionization density irregularities, scintillating signals change phase unexpectedly and vary rapidly in amplitude. GPS signals are vulnerable to ionospheric irregularities and scintillate with amplitude variations exceeding 20 dB. GPS is a weak signal system and scintillations can interrupt or degrade GPS receiver operation. For individual signals, interruption is caused by fading of the in-phase and quadrature signals, making the determination of phase by a tracking loop impossible. Degradation occurs when phase scintillations introduce ranging errors or when loss of tracking and failure to acquire signals increases the dilution of precision. GPS scintillations occur most often near the magnetic equator during solar maximum, but they can occur anywhere on Earth during any phase of the solar cycle. In this article we review the subject of GPS and ionospheric scintillations for scientists interested in space weather and engineers interested in the impact of scintillations on GPS receiver design and use.
The present paper reports the occurrence of ionospheric scintillation (S4 > 0.2) measured using GPS receiver (GISTM) at Surat, (21.160N, 72.780E) located near the northern crest of equatorial anomaly in India. The results are presented for data collected during di�erent levels of solar activity from Jan-2009 to Dec-2011. These long time observations phenomenon, which covers low to moderate solar activity period, have shown features such as, diurnal, monthly, seasonal, magnetic activity and solar cycle variation in scintillation occurrence. It was observed that the diurnal variation of the amplitude scintillation predominately occurred after sunset time (18:00 to 06:00 LT). Our observation shows that the duration of scintillation occurrence is found to be maximum during moderate solar activity and least during low solar activity. The seasonal variation shows that the occurrence of scintillation is observed to be maximum for equinox months, less in winter months and least in summer...
GPS BASED IONOSPHERIC SCINTILLATION MONITORING
2000
Under normal circumstances, errors due to GPS signals travelling through the ionosphere can be modelled by measurement on two (or more) frequencies. However, during periods of disturbances such as scintillations, this can be impractical and receiver performance can be severely degraded. Ionospheric scintillations are most likely to occur during solar maximum, particularly affecting equatorial and auroral regions. Although isolated efforts have been reported, systematic analyses of the effects on positioning systems have not been performed. Auroral disturbances affect Northern Europe and North-South gradients can lead to effects at mid-latitudes. This paper presents initial results of a study on ionospheric scintillation. A state-of-the-art GPS Ionospheric Scintillation Monitor (GISM), which extracts scintillation parameters from GPS measurements, is being used. A network of GISMs has been co-located with permanently tracking dual-frequency receivers for long term data collection (2001)(2002)(2003). Correlating scintillation parameters with TEC (Total Electron Content) is one of the main aims of the project.