Weighted Dilution of Precision (WPDOP) with Consideration of the Range Errors and Elevation of GNSS Satellites During the High Ionospheric Activity Period for the Equatorial Region

Evaluating the Performance of IRI-2016 Using GPS-TEC Measurements over the Equatorial Region

Atmosphere ◽

10.3390/atmos12101243 ◽

2021 ◽

Vol 12 (10) ◽

pp. 1243

Author(s):

Nouf Abd Elmunim ◽

Mardina Abdullah ◽

Siti Aminah Bahari

Keyword(s):

Solar Activity ◽

Early Morning ◽

Equatorial Region ◽

Activity Period ◽

High Solar Activity ◽

Electron Content ◽

Dual Frequency ◽

Iri Model ◽

Total Electron ◽

Solar Activity Period

Total electron content (TEC) is an important parameter in the ionosphere that is extensively used to study the variability of the ionosphere as it significantly affects radio wave propagations, causing delays on GPS signals. Therefore, evaluating the performance of ionospheric models is crucial to reveal the variety of ionospheric behaviour in different solar activity periods during geomagnetically quiet and disturbed periods for further improvements of the IRI model performance over the equatorial region. This research aimed to investigate the variations of ionospheric VTEC and observe the improvement in the performance of the IRI-2016 (IRI-2001, IRI01-corr, and NeQuick). The IRI-2016 was evaluated with the IRI-2012 using NeQuick, IRI-2001, and IRI01-corr topside electron density options. The data were obtained using a dual-frequency GPS receiver installed at the Universiti Utara Malaysia Kedah (UUMK) (geographic coordinates 4.62° N–103.21° E, geomagnetic coordinates 5.64° N–174.98° E), Mukhtafibillah (MUKH) (geographic coordinates 6.46° N–100.50° E, geomagnetic coordinates 3.32° S–172.99° E), and Tanjung Pengerang (TGPG) (geographic coordinates 1.36° N–104.10°E, geomagnetic coordinates 8.43° S–176.53° E) stations, during ascending to high solar activity at the geomagnetically quiet and disturbed periods in October 2011, March 2012, and March 2013. The maximum hourly ionospheric VTEC was observed during the post-noon time, while the minimum was during the early morning time. The ionospheric VTEC modelled by IRI-2016 had a slight improvement from the IRI-2012. However, the differences were observed during the post-noon and night-time, while the modelled VTEC from both IRI models were almost similar during the early morning time. Regarding the daily quiet and disturbed period’s prediction capability of the IRI-2016 and IRI-2012, IRI-2016 gave better agreement with the measured VTEC. The overall results showed that the model’s prediction performance during the high solar activity period in 2013 was better than the one during the ascending solar activity period. The results of the comparison between IRI-2016 and IRI-2012 in high solar activity exhibited that during quiet periods, all the IRI models showed better agreement with the measured VTEC compared to the disturbed periods.

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

International Journal of Advanced Astronomy ◽

10.14419/ijaa.v8i1.30232 ◽

2020 ◽

Vol 8 (1) ◽

pp. 1

Author(s):

Uluma Edward ◽

Ndinya Boniface ◽

Omondi George

Keyword(s):

Total Electron Content ◽

Equatorial Region ◽

Activity Period ◽

High Solar Activity ◽

Electron Content ◽

Vertical Total Electron Content ◽

Gps Receiver ◽

Total Electron ◽

Solar Intensity ◽

Using Data

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.

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A study of the equatorial -region during evening twilight using a Langmuir probe

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/s0021-9169(68)90744-7 ◽

1968 ◽

Vol 30 (6) ◽

pp. 1193-1202

Author(s):

S PRAKASH ◽

B SUBBARAYA ◽

S GUPTA

Keyword(s):

Langmuir Probe ◽

Equatorial Region

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The Excavation of a Settlement of the Later Bronze Age and Iron Age at Myrehead, Falkirk District

Glasgow Archaeological Journal ◽

10.3366/gas.1983.10.10.41 ◽

1983 ◽

Vol 10 (1) ◽

pp. 41-71 ◽

Cited By ~ 8

Author(s):

G J Barclay

Keyword(s):

Bronze Age ◽

Iron Age ◽

Farming System ◽

Activity Period ◽

Limited Evidence ◽

Ring Groove ◽

Domestic Activity ◽

First Millennium ◽

First Millennium Bc ◽

Actual Settlement

SUMMARY Myrehead has revealed the eroded remnants of activity from the Beaker period (Period A) onwards, with actual settlement evinced only from about the early first millennium be. The three houses and the cooking pits of Period B may have been constructed and used sequentially. This open settlement was probably replaced during the mid first millennium bc, possibly without a break, by a palisaded enclosure (Period C), which may have contained a ring-groove house and a four-post structure. Continued domestic activity (Period D) was suggested by a single pit outside the enclosure, dated to the late first millennium bc/early first millennium ad. The limited evidence of the economy of the settlements suggests a mixed farming system.

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