Seasonal and solar cycle effects on TEC at 95°E in the ascending half (2009–2014) of the subdued solar cycle 24: Consistent underestimation by IRI 2012

Kakoti, Geetashree; Bhuyan, Pradip Kumar; Hazarika, Rumajyoti

doi:10.1016/j.asr.2016.09.002

Cited by 11 publications

(5 citation statements)

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“…Therefore, the vertical TEC

italicVTEC = ((), italicSTEC - ((), b_{R} + b_{s})) / S ((), E),

where E is the elevation angle of the satellite in degrees, S ( E ) is the obliquity factor with zenith angle at the ionospheric piece point (IPP), and VTEC is the vertical TEC at the IPP. Other details of VTEC retrievals for DBRG are given in Kakoti et al (2017, 2018). In the present study, the hourly average VTEC is calculated as the average of VTEC (hereinafter TEC) obtained from all the passes received in each hour for respective GPS receiver stations with elevation cutoff 50°.…”

Section: Methodsmentioning

confidence: 99%

Longitudinal and Interhemispheric Ionospheric Response to 2009 and 2013 SSW Events in the African‐European and Indian‐East Asian Sectors

et al. 2020

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The ionospheric response to two sudden stratospheric warming (SSW) events that occurred during low (2009) and moderate solar activity (2013) around 10°E (±10°) African-European and 95°E (±10°) Indian-East Asian sectors is investigated. The total electron content (TEC) obtained from a meridional chain of stations in the two sectors are used to understand the interlongitudinal and interhemispheric response to these SSW events. Significant depletion of daytime TEC was observed after the onset of 2009 SSW around the equatorial ionization anomaly (EIA) crest followed by an increase during the decaying phase of SSW. The formation of an early peak in the daytime TEC and semidiurnal variation in the response of TEC in the form of morning enhancement and afternoon depletion was observed at low latitudes. The morning enhancement is prominent at northern low latitudes while afternoon depletion is more at southern low latitudes. The conspicuous TEC perturbations characterized by semidiurnal variation in mid-January of 2013 override the sudden increase in solar activity after the onset of the SSW. SSW impacted semidiurnal perturbations in F2 layer peak electron density (NmF2) and height (hmF2) noticed at Cocos Island, the southern hemisphere low latitude station. Longitudinal and interhemispheric differences in the magnitude and evolution of TEC perturbations were noticed. The longitudinal differences in SSW modulation of TEC might be attributed to the differential impact of the nonmigrating tides and differences in the geomagnetic field elements between the two sectors. The meridional wind in the mesosphere and lower thermosphere region contribute to the TEC enhancement.

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“…Therefore, the vertical TEC

italicVTEC = ((), italicSTEC - ((), b_{R} + b_{s})) / S ((), E),

Section: Methodsmentioning

confidence: 99%

Longitudinal and Interhemispheric Ionospheric Response to 2009 and 2013 SSW Events in the African‐European and Indian‐East Asian Sectors

et al. 2020

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“…Almost equal levels of saturation effects were observed during the June solstice for MSA and HSA. Liu et al [58] and Kakoti et al [59] suggested that changes in solar EUV, thermospheric neutral wind composition and ion pressure were also important factors that may give rise to the saturation effect during different epochs of the solar cycle. Hence, the reason behind the generation of the saturation effect should be further investigated to understand its effects on satellite launch processes and satellite Radio communication devices.…”

Section: Discussionmentioning

confidence: 99%

Variations in the Maximum Electron Density of the F2 Layer (NmF2) over the Middle Latitude Station of Grahamstown, South Africa, during Solar Cycle 23

Ogwala¹,

Onori²,

Ogabi³

et al. 2022

Adv Environ Eng Res

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Ultraviolet (UV) and X-ray radiation are the primary causes of ionization that produce electron density in sufficient quantities to promote the propagation of satellite radio signals in the ionosphere. The electron densities suffer from spatio-temporal variations, and this poses different degrees of threats to satellite radio signals propagating through the ionosphere. We aimed to characterize the maximum electron density of the F2 layer (NmF2) in the middle-latitude ionosphere over Grahamstown, South Africa (Geographic latitude: 33.30°S, Geographic longitude: 26.50°E; Geomagnetic Latitude: 33.92°S, Geomagnetic Longitude: 89.37°E). The mean NmF2 data for solar cycle 23 (1998–2008) were used for the studies. The data were grouped into the high solar activity (HSA: 2000–2002), moderate solar activity (MSA: 1998–1999, 2003–2005), and low solar activity (LSA: 2006–2008) years. NmF2 variations were characterized based on the diurnal, seasonal, monthly, and annual data. Also, the correlation between NmF2 and the sunspot number was investigated. Results on diurnal and seasonal variations revealed that noontime bite-out of NmF2 was observed during the June solstice every year. However, it was not observed in the other three seasons. Equinoctial asymmetry is observed to show insignificant annual and solar cycle variations. The seasonal and annual variations of NmF2 with sunspot number were linear (exception: June solstice for MSA, the year 1999; HSA, years 2000–2001). The results reveal that the correlation between NmF2 and the sunspot number was insignificant under conditions of the annual, solar cycle, and latitudinal variations (exception: MSA, the year 2005; negative correlation (0.64)).

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“…From these figures, it is perceived that descending orbits present much higher FRA and higher dynamic ranges than ascending ones. In the afternoon local time, the surviving amount of VTEC generated by sunlight during the preceding hours is higher than in the morning local time [19] and because SMOS is in a 6 am-6 pm sun-synchronous orbit, the resulting FRA range is large. Consequently, in the first stage, the analysis was focused on descending orbits.…”

Section: Faraday Rotationmentioning

confidence: 96%

“…It is known that the VTEC and therefore the FRA vary with solar activity, which can be assessed using sunspot numbers [18], and in a geographical and temporal way [7,19]. SMOS data is here It is known that the VTEC and therefore the FRA vary with solar activity, which can be assessed using sunspot numbers [18], and in a geographical and temporal way [7,19]. SMOS data is here considered within the 24th sun cycle, which started on January 4th, 2008, with each cycle lasting about 11 years.…”

Section: Faraday Rotationmentioning

confidence: 99%

“…SMOS data is here considered within the 24th sun cycle, which started on January 4th, 2008, with each cycle lasting about 11 years. The sun's peak activity during this cycle was reached on March 2014 [18,19]. It is also important to note that the value of the FRA reaches its highest point during the year in the March equinox due to the sun's illumination geometry over the earth during that season.…”

Section: Faraday Rotationmentioning

confidence: 99%

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Deriving VTEC Maps from SMOS Radiometric Data

et al. 2020

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In this work, a new methodology is proposed in order to derive vertical total electron content (VTEC) maps from the radiometric measurements of the Soil Moisture and Ocean Salinity (SMOS) mission as an alternative approach to those based on external databases and models. This approach uses spatiotemporal filtering techniques with optimized filters to be robust against the thermal noise and image reconstruction artifacts present in SMOS images. It is also possible to retrieve the Faraday rotation angle from the recovered VTEC maps in order to correct the effect that it causes in the SMOS brightness temperatures.

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Seasonal and solar cycle effects on TEC at 95°E in the ascending half (2009–2014) of the subdued solar cycle 24: Consistent underestimation by IRI 2012

Cited by 11 publications

References 58 publications

Longitudinal and Interhemispheric Ionospheric Response to 2009 and 2013 SSW Events in the African‐European and Indian‐East Asian Sectors

Longitudinal and Interhemispheric Ionospheric Response to 2009 and 2013 SSW Events in the African‐European and Indian‐East Asian Sectors

Variations in the Maximum Electron Density of the F<sub>2</sub> Layer (NmF<sub>2</sub>) over the Middle Latitude Station of Grahamstown, South Africa, during Solar Cycle 23

Deriving VTEC Maps from SMOS Radiometric Data

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