Large-scale ionospheric irregularities occurrence at Ilorin, Nigeria

Oladipo, O.A.; Adeniyi, J.O.; Olawepo, A.O.; Doherty, Patricia H.

doi:10.1002/2013sw000991

Cited by 30 publications

(24 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The ROT is computed for every 30‐s time interval and then converted to TECU/min unit. The small‐scale density irregularities can then be characterized using the standard deviation of ROT index (ROTI) which is estimated for every 5‐min time interval (i.e.,

italicROTI = \sqrt{(〈〉, {italicROT}^{2}) - {〈italicROT〉}^{2}}

) (Amaechi et al, ; Oladipo et al, ; Pi et al, ). Figure shows the ROTI (bottom panel) comparison with an independently measured S 4 index from high‐resolution GNSS receiver (middle panel) and VHF receiver (top panel).…”

Section: Longitudinal Dependence Of Ionospheric Density Irregularity/mentioning

confidence: 99%

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

Yizengaw

Groves

2018

Space Weather

View full text Add to dashboard Cite

Over the past decades significant progresses have been done to understand the origin of seeding mechanisms of ionospheric irregularities. However, characterization of the global ionospheric irregularities as a function of local time, longitude, and season is still a challenge for the modeling community. In this review paper, using multiinstrument observations, we investigated the global irregularity distribution and its possible drivers that control the longitudinal and seasonal dependences. We demonstrated that forcing from lower thermosphere, like the localized tropospheric gravity waves seeding, may be responsible for the formation of strong longitudinal dependence of irregularity distribution. The location of Intertropical Convergence Zone that generate forceful thunderstorms and become favorable location for the launch of localized gravity waves may play an important role in the longitudinal dependence of irregularity distribution. Hence, incorporating the Intertropical Convergence Zone location into density irregularity modeling effort may provide important information to understand and characterize the longitudinal variability of irregularity distributions.Plain Language Summary The two major coupling processes, namely, (1) the vertical coupling that involves upward propagating atmospheric waves (forcing from below) and (2) magnetosphere-ionosphere coupling (forcing from above), cause for the initiation and development of ionospheric density irregularities that create favorable conditions for the creation of rapid amplitude and phase fluctuations of radio signals. On the other hand, application of radio wave is essential for our communication and navigation systems, either transmitted through the ionosphere for satellite communication and navigation or reflected off the ionosphere for HF and radar applications. This indicates that ionospheric density irregularities are as much an engineering concern as they are a scientific quest. The ionospheric irregularities, which are also not uniform globally, affect the integrity and performance of navigation and communication systems with different magnitudes at different longitudes. Hence, understanding the physics behind the longitudinal variability of equatorial ionospheric irregularities is essential to characterize and develop a model that can accurately capture the global distribution of ionospheric irregularities and its driving mechanisms.

show abstract

italicROTI = \sqrt{(〈〉, {italicROT}^{2}) - {〈italicROT〉}^{2}}

Section: Longitudinal Dependence Of Ionospheric Density Irregularity/mentioning

confidence: 99%

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

Yizengaw

Groves

2018

Space Weather

View full text Add to dashboard Cite

show abstract

“…Numerical and observational studies of the variability of ionospheric features in the middle and low latitudes have been conducted over the years; however, there are limited studies focused exclusively on longitudinal variability due to the univeral time (UT) onset time in the low latitudes. Explorations of the longitude sector differences of equatorial spread F have been conducted by several groups[ Aarons , ; Fejer et al , ; Abdu et al , ; Oladipo et al , ], and several studies have found an impact of longitudinal effects on the equatorial electroject (EEJ) [ England et al , ; Klimenko and Klimenko , ; Yizengaw et al , ; Phani Chandrasekhar et al , ]. It has also been recognized that the neutral atmosphere plays a critical role through nonmigrating tidal influences [ Immel et al , ; Forbes et al , ; Maute et al , ] and longitudinally dependent thermospheric winds [ Fuller‐Rowell et al , ; Sojka et al , ] in the distribution of plasma.…”

Section: Introductionmentioning

confidence: 99%

On the variation in the ionospheric response to geomagnetic storms with time of onset

2017

View full text Add to dashboard Cite

Recent observations from Immel and Mannucci (2013) have indicated that geomagnetic storms cause larger enhancements in the ionospheric plasma density and total electron content (TEC) in the American sector than anywhere else on the planet. This suggests that the presence of a UT storm onset effect is important for correctly understanding the impact, longitudinal structure, and timing of geomagnetic storms. Using the Global Ionosphere‐Thermosphere Model (GITM), we conduct a modeling experiment of the August 2011 geomagnetic storm by modifying the storm arrival time (UT) in Earth's daily rotation and examining the subsequent system response. We find that the simulations reflect the recent studies indicating that the strongest enhancements of TEC are in the American and Pacific longitude sectors of storms with onsets between 1600 UT and 2400 UT. The underlying mechanisms of the strong TEC increases during storm times in these longitude sectors are also examined. Some of the resulting TEC structures may be explained by changes in the [O]/[N2] ratio (especially in the high latitudes), but it is unable to explain all of the variability in the equatorial regions. Storm time neutral winds and vertical ion motions coupled to Earth's asymmetrical geomagnetic topology appear to be driving the longitude sector variability due to UT storm onset times.

show abstract

“…ESF not only remains to be a matter of scientific quest but also poses as a technological challenge in the field of satellite‐based navigation and communication [ Shume et al ., ; Bagiya et al ., ; Oladipo et al ., ]. Several investigations in the recent times have highlighted the day‐to‐day variability in the ionospheric irregularities [e.g., Whalen , ] and its impact on the satellite‐based navigation through L band scintillation [e.g., de Lima et al ., ; Zhang et al ., ; Sreeja et al ., , ; Aquino and Sreeja , ].…”

Section: Introductionmentioning

confidence: 99%

“…ESF not only remains to be a matter of scientific quest but also poses as a technological challenge in the field of satellite-based navigation and communication [Shume et al, 2013;Bagiya et al, 2013;Oladipo et al, 2014]. Several investigations in the recent times have highlighted the day-to-day variability in the ionospheric JOSHI ET AL.…”

Section: Introductionmentioning

confidence: 99%

Investigation onFlayer height rise and equatorial spreadFonset time: Signature of standing large-scale wave

et al. 2015

View full text Add to dashboard Cite

Equatorial spread F observations have been categorized into three categories based on ionograms recorded over Sriharikota. First category comprised cases where the onset of equatorial spread F (ESF) was concurrent with the peak h′F time. Second and third categories comprised cases where the onset of ESF happened with a delay of 30 min and more than 30 min, respectively, with reference to the peak h′F time. Average peak h′F in the first category was more than 35 km higher than that in the second and third categories. Also, the peak vertical (upward) plasma drift was higher in the first category. Assuming the genesis of F region irregularity to have happened at or before the time of F layer attaining the peak height, late onset of ESF indicates the genesis of irregularities to have happened westward of Sriharikota. The fact that the peak h′F values were remarkably different in the three categories indicates a zonal variation of eastward electric field and postsunset height rise of F layer. The relative magnitude of the F layer height rise in the three different categories over Sriharikota has also been found to be significantly different than that over Thumba, an equatorial (magnetic) station located~360 km westward of Sriharikota longitude. This scenario points toward the existence of a large-scale zonal standing wave in the F layer and its important role in F region instability process. Results presented in the manuscript have been discussed in the light of current understanding on the large-scale wave structure.

show abstract

Large-scale ionospheric irregularities occurrence at Ilorin, Nigeria

Cited by 30 publications

References 21 publications

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

On the variation in the ionospheric response to geomagnetic storms with time of onset

Investigation onFlayer height rise and equatorial spreadFonset time: Signature of standing large-scale wave

Contact Info

Product

Resources

About