Study of Low-latitude Ionospheric Scintillation using NavIC (original) (raw)
Related papers
2022
Ionospheric irregularity studies are important aspects for understanding ionospheric physics and related processes, especially near the low-latitude regions. However, simultaneous measurements (utilizing the L-band signals of NavIC and GPS) of irregularity scale sizes over the Indian longitude sector, has not been addressed extensively. To address this problem, the paper presents simultaneous characterization of low-latitude ionospheric irregularities over a location near the northern EIA crest (Indore: 22.52$^\circ$N, 75.92$^\circ$E geographic and magnetic dip of 32.23$^\circ$N) and a location (Hyderabad: 17.41$^\circ$N, 78.55$^\circ$E geographic and magnetic dip of 21.69$^\circ$N) between the crest and the magnetic equator, utilizing the Indian navigation system, NavIC and GPS L5 signal C/N$_o$ variations to determine the range of the ionospheric irregularity scale sizes using Power Spectral Density (PSD) analysis. The study period spans from September 2017- September 2019, covering both disturbed and quiet-time conditions in the declining phase of solar cycle 24. Observations show that the irregularity scale size ranges from about 500 m to 6 km. This study for the first time, shows the nature of the temporal PSD for ionospheric scintillation during varying solar and geophysical conditions, by measuring the irregularity scale sizes utilizing simultaneous observations from NavIC and GPS from locations near the northern crest of the EIA and in between crest and the magnetic equator, ensuring proper characterization of ionosphere over the geosensitive Indian subcontinent.
International Journal of Innovative Technology and Exploring Engineering, 2019
Soon Indian’s mobile phones and cars are to be installed with new and indigenous satellite technology, i.e. Navigation with Indian Constellation (NavIC) developed by ISRO. After successful completion of NavIC, India has become fifth nation in the sequence of countries with independent navigation technology/system. The NavIC technology will be used mainly for terrestrial, aerial and marine navigation along with tracking and disaster management. Here we are proposing the application of NavIC signals for measuring and montoring ionosphere layer behaviour leading accuracy degradation of satellite based navigation and communication systems. This paper presents the computation of ionosphere parameters such as TEC, ROTI and scintillation index (S4) using pseudo range and Carrier to Noise density ratio (C/No) measurements of NavIC L5 and S-band signals. ROTI and S4 results revealed that the impact of ionosphere irregularity is more on L5 than that of S-band signals.
Performance of NavIC for studying the ionosphere at an EIA region in India
Advances in Space Research
This paper emphasizes on NavIC's performance in ionospheric studies over the Indian subcontinent region. The study is performed using data of one year (2017-18) at IIT Indore, a location near the northern crest of Equatorial Ionization Anomaly (EIA). It has been observed that even without the individual error corrections, the results are within ±20% of NavIC VTEC estimates observed over the 1 • x 1 • grid of IPP surrounding the GPS VTEC estimates for most of the time.. Additionally, ionospheric response during two distinct geomagnetic storms (September 08 and 28, 2017) at the same location and other IGS stations covering the Indian subcontinent using both GPS and NavIC has also been presented. This analysis revealed similar
Ionospheric scintillations by sporadic-E irregularities over low latitude
2007
The observations of daytime ionospheric scintillation are attributed to E-region irregularities at high and equatorial latitudes. In this paper, VHF amplitude scintillations recorded during the daytime period from 1991 to 1999 at low latitude station Varanasi (geomag. lat. = 14 • 55 N, long. = 154 0 E) are analyzed to study the behaviour of sporadic-E irregularities during the active solar and magnetic periods. The daytime digital scintillation data have been analyzed to study some important parameters of scintillation producing sporadic-E irregularities like auto-correlation function, power spectral densities, signal de-correlation time etc. We report the behaviour of these parameters under weak and strong scintillation conditions. The results are also discussed in the light of recent works.
INDIAN JOURNAL OF …, 2006
Scintillation of VHF (250 MHz) signals from FLEETSAT (73 o E) was recorded at the equatorial anomaly crest location, Rajkot, in India during 1991-93. The irregularity parameters: S 4 index, and fade rate and spectral parameters: spectral slope and upper roll off frequency, f u are derived and their variation with time of night and with solar activity studied. S 4 index and fade rate increase with solar activity. The spectral slope does not show any systematic dependence on solar activity but f u increases with solar activity. These results, when interpreted in terms of Fresnel size, indicate a shifting of irregularity spectrum towards longer scales in low solar activity period. The temporal variation of these parameters, after the irregularity generation phase, also indicate preponderence of large (kilometer) scale irregularities around midnight-post-midnight period, consistent with earlier simultaneous radar and scintillation observations at Jicamarca. The solar activity dependence of S 4 index is interpreted as due to the variation of background F-region plasma density variations. The results suggest that when strong scattering causes strong scintillations, f u is not representative of the Fresnel scale.
Earth, Planets and Space
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}0.6∘S,Lon:0 . 6 ∘ S , Lon:0.6∘S,Lon:30.8^{\circ }\hbox {E}30.8∘E,Mag.lat:30 . 8 ∘ E , Mag. lat:30.8∘E,Mag.lat:10.2^{\circ }\hbox {S}$$ 10 . 2 ∘ 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...
Ionospheric scintillation theory--A mini-review
IEEE Transactions on Antennas and Propagation, 1976
In this paper we briefly review the theories that are used to interpret ionospheric scintillation data. We have emphasized the full structure of the complex signal, because it is now being directly measured with a number of satellites that carry multifrequency phasecoherent beacons. The data that have been analyzed to date clearly show that large phase variations (greater than one radian) are an omnipresent feature of transionospheric signals.
Frequency dependence of equatorial ionospheric scintillations
Proceedings / Indian Academy of Sciences, 1978
Simultaneous observations of amplitude scintillations at 40 MHz, 140 MHz and 360 MHz radiated from ATS-6 satelIite at 34°E longitude were made at Ootacamund near the magnetic equator in India. It has been found that the frequency variation of scintillation index (S.) is S. ce r:». with n being about 1•2 only for weak scintillations, i.e., so long as the scintillation index does not exceed 0•6 at the lower frequency. For strong scintillations (S. > 0'6) where multiple scattering may be present, the exponent n itself is a function of the intensity of scintillation, the scintillation indices at two frequencies are related by: Slfl)=S.(f2) exp [1'3 log (f21/1) (l-S.(f2)j so long as hll l S 3. Thus knowing scintillation index at a given frequency one can estimate the scintillation index at another frequency. This will be of significant importance for communication problems. Evidence is also shown for the reversal of the frequency law in cases of intense scintillations.
Data Analysis for Ionospheric Divergence and Glittering by Using NavIC Receiver
2017
The Indian Regional Navigational Satellite System (IRNSS) renamed as NavIC is used in both the military and civilian communities for navigation, surveying, remote sensing, asset management and precise timing. A number of environmental factors are known to affect the performance of NavIC including electromagnetic interference, multipath, foliage attenuation, atmospheric delays and ionospheric effects. In this paper, the effects of the ionosphere on NavIC will be examined. Ionospheric effects are the most significant disturbance that can affect NavIC users during high sunspot activity. In the presence of glittering, ionospheric modeling can be rendered impractical and receiver performance can be severely degraded. The influence of the ionosphere and a strategy to isolate its effect are a major concern for NavIC positioning and navigation applications. It is also stronger from local sunset until just after midnight, and during periods of high solar activity. If sufficiently intense, th...
Ionospheric scintillation calculations based on in situ irregularity spectra
Radio Science, 1977
Recent results from rocket, satellite, and radar experiments have greatly increased our understanding of equatorial spread-F and its effects upon communication systems. In situ measurements have shown that the typical irregularity spectrum is a power law with a one-dimensional index of -2. Previous applications of scintillation theory to such irregularities have utilized an anisotropic power law, in an effort to model elongation of irregularities along the magnetic field, and have found approximate solutions for the scintillation index S 4, the rms phase deviation, and the characteristic scale size of the scintillation spectrum. We present here rigorous closed-form solutions for these quantities which are valid to the extent that weak scattering thin screen theory allows. In addition we introduce a second "hybrid" form for irregularity spectra which is gaussian along the magnetic field and a power law in the perpendicular plane. The index is chosen in such a way that a one-dimensional spectrum obtained on a spacecraft whose velocity •s makes a reasonable angle to the magnetic field and varies as k -2. Such a spectrum is introduced since it seems likely that at least at long wavelengths equatorial spread-F is an interchange instability and that the density variation along /• is that of the zero-order density variation. One-dimensional spectra for small angles between •s and/• would hence be steeper than k -2 at intermediate k values, a result consistent with some in situ measurements. If particle precipitation is responsible for high latitude irregularities at long wavelengths, the hybrid spectrum might also be more appropriate for their characterization.