The response of African equatorial GPS-TEC to intense geomagnetic storms during the ascending phase of solar cycle 24

Akala, A. O.; Rabiu, Babatunde; Somoye, E.O.; Oyeyemi, E. O.; Adeloye, A. B.

doi:10.1016/j.jastp.2013.02.006

Cited by 27 publications

(24 citation statements)

References 56 publications

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“…Modeling studies have also shown a longitude effect on enhanced TEC related to high‐latitude electric fields and thermospheric winds [ Sojka et al ., ]. As well, the global regional perspective that analyses of the IGS TEC maps afford provides a broad context for interpreting observation at individual sites, such as reported, for example, for storms in equatorial Africa [ Akala et al ., ]. The negative phases of the ionospheric storms in solar cycle 24 exhibit TEC decreases peaking about a day after the arrival of the CME at Earth (see Figure ), but the negative phases are far more regionally and temporally diverse.…”

Section: Discussionmentioning

confidence: 99%

Comparative ionospheric impacts and solar origins of nine strong geomagnetic storms in 2010–2015

et al. 2016

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For nine of the strongest geomagnetic storms in solar cycle 24 we characterize, quantify, and compare the impacts on ionospheric total electron content (TEC) and the U.S. Wide Area Augmentation System (WAAS) with the heliospheric morphology and kinematics of the responsible coronal mass ejections (CMEs) and their solar source regions. Regional TEC responses to the events are similar in many respects, especially in the initial positive phase. For the subsequent negative phase, Dst is a better indicator than ap of the magnitude of the TEC decrease. The five events that arrive between 13:00 UT and 21:00 UT (local daytime in the U.S.) produce large WAAS degradations, and the four events that arrive outside this time of day produce lesser or no WAAS degradation. Our sample of geoeffective events includes CMEs with only modestly fast speeds, ones that only provided glancing impacts on Earth by their shock sheaths and ones not associated with any significant flare. While all of the CMEs traveled faster than the solar wind, they nevertheless have a wide range of velocities and produced a range of Bz values; neither speed nor Bz correlates significantly with ionospheric impact. Comparison with the locations of surface activity leads to estimates of deflection for the CMEs, with the average deflection being 19°. At least a few events may have missed Earth entirely in the absence of coronal deflection.

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Section: Discussionmentioning

confidence: 99%

Comparative ionospheric impacts and solar origins of nine strong geomagnetic storms in 2010–2015

et al. 2016

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“…In 2011, there have been nine geomagnetic storms, whereas, in 2015, there are 13 storms as given in Table . Some of these storms are well documented in the literature such as 24–26 October 2011 (Akala et al, ; Blanch et al, ; D'ujanga et al, ) and St. Patrick Day storm (Astafyeva et al, ; Nava et al, ; Nayak et al, ; Wu et al, ).…”

Section: Description Of Data and Comparison Methodsmentioning

confidence: 97%

“…In 2011, there have been nine geomagnetic storms, whereas, in 2015, there are 13 storms as given in Table 2. Some of these storms are well documented in the literature such as 24-26 October 2011 (Akala et al, 2013;Blanch et al, 2013;D'ujanga et al, 2013) For each available ionosonde and for each data sample date and time, IRI-2016 is run. The foF2 values are obtained for every option of CCIR or URSI foF2/NmF2; STORM option ON or OFF.…”

Section: Description Of Data and Comparison Methodsmentioning

confidence: 99%

Comparison of IRI‐2016 F2 Layer Model Parameters with Ionosonde Measurements

2019

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International Reference Ionosphere (IRI) is the international standard ionospheric climatic model. Since the original formation of the international task force in 1970s, the IRI model has been continuously improved by ingesting developments in research in ionosphere. The most current version, namely, IRI‐2016, is offered with International Radio Consultative Committee (CCIR) and International Union of Radio Science (URSI) model choices with “STORM” option for the F2 layer critical plasma frequency (foF2) and BSE‐1979, AMTB‐2013, and SHU‐2015 options for maximum ionization height, hmF2. Since these two parameters are the determining values for the other model outputs, the evaluation of the options offered by IRI‐2016 is critical for various applications. In this study, all foF2 and hmF2 model options offered online at http://irimodel.org are computed for winter and summer solstice and equinox seasons of 2011 and 2015 at the locations of all available ionosondes and for all measurement intervals. The ionosondes are grouped into northern and southern midlatitude, northern and southern high‐latitude and equatorial regions. Individual, regional and global model output foF2 and hmF2 values are compared with those of ionosondes in both root‐mean‐square (RMS) and normalized RMS (NRMS) senses. For foF2, “STORM ON” can be used any time and in any region. Equatorial and high‐latitude regions have larger RMS values due to the sparse ionosondes. In northern midlatitude and high‐latitude regions URSI, in all other regions CCIR is the better option. For hmF2, SHU‐2015 and BSE‐1979 options provide a better fit for all regions, seasons, and years.

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“…The ionospheric parameter that has an overbearing influence on GPS-based communication and navigation systems is the total electron content (TEC) (Akala et al, 2013). TEC is the number of electrons in the column of 1 m 2 cross section that extends from a GPS satellite to a GPS receiver.…”

Section: Introductionmentioning

confidence: 99%

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

et al. 2017

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Abstract. The study of diurnal and seasonal variations in total electron content (TEC) over Nigeria has been prompted by the recent increase in the number of GPS continuously operating reference stations (CORSs) across Nigeria as well as the reduced costs of microcomputing. The GPS data engaged in this study were recorded in the year 2012 at nine stations in Nigeria located between geomagnetic latitudes -4.33 and 0.72 • N. The GPS data were used to derive GPS TEC, which was analysed for diurnal and seasonal variations. The results obtained were used to produce local GPS TEC maps and bar charts. The derived GPS TEC across all the stations demonstrates consistent minimum diurnal variations during the pre-sunrise hours 04:00 to 06:00 LT, increases with sharp gradient during the sunrise period (∼ 07:00 to 09:00 LT), attains postnoon maximum at about 14:00 LT, and then falls to a minimum just before sunset. Generally, daytime variations are found to be greater than nighttime variations, which range between 0 and 5 TECU. The seasonal variation depicts a semi-annual distribution with higher values (∼ 25-30 TECU) around equinoxes and lower values (∼ 20-25 TECU) around solstices. The December Solstice magnitude is slightly higher than the June Solstice magnitude at all stations, while March Equinox magnitude is also slightly higher than September Equinox magnitude at all stations. Thus, the seasonal variation shows an asymmetry in equinoxes and solstices, with the month of October displaying the highest values of GPS TEC across the latitudes.

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The response of African equatorial GPS-TEC to intense geomagnetic storms during the ascending phase of solar cycle 24

Cited by 27 publications

References 56 publications

Comparative ionospheric impacts and solar origins of nine strong geomagnetic storms in 2010–2015

Comparative ionospheric impacts and solar origins of nine strong geomagnetic storms in 2010–2015

Comparison of IRI‐2016 F2 Layer Model Parameters with Ionosonde Measurements

Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

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