Characterization of ionospheric irregularities over the equatorial and low latitude Nigeria region

Ogwala, Aghogho; Oyedokun, Oluwole John; Akala, A. O.; Amaechi, P. O.; Simi, K. G.; Panda, Sampad Kumar; Ogabi, Cornelius; Somoye, E.O.

doi:10.1007/s10509-022-04110-0

Cited by 10 publications

(5 citation statements)

References 75 publications

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“…Geomagnetic storm can either trigger or inhibit the postsunset ESF and initiate the postmidnight ESF. (Abdu, 1997, Ogwala et al, 2022 indicated that disturbance winds and electric fields triggering or inhibiting of ESF depend on the phase of the geomagnetic storm. This study also found that the DDEFs limits the rise of the 2 m hF during the post-sunset thus reduces the ESF probability.…”

Section: Discussionmentioning

confidence: 99%

Solar Radiation and Geomagnetic Contribution of Consecutive 27-Day Recurrent Geomagnetic Storms to Variations of Equatorial Ionospheric Parameters and Spread F

YEERAM

2024

Preprint

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This study investigates solar radiation and geomagnetic effects of consecutive 27-day recurrent geomagnetic storms (RGSs) during 2007 on the variabilities in the equatorial ionospheric F-region in American Peruvian sector. Results show correspondence of quasi-periodic variations between geomagnetic activities and ionospheric responses in the F-region. In High-Intensity Long-Duration Continuous (AE) Activity (HILDCAA) events, the ionospheric responses are more variable than in non-HILDCAA. The critical frequency and peak heights of the F-layer tend to increase during storm-time in summer months, but decrease in response to enhanced equatorial electrojets. A new classification of daily variations in the virtual height of the F-layer (h′F) is proposed: (mode A) mixing of great height before noon and low height before midnight, (mode B) moderate height before midnight, and (mode C) mixing of low height before noon and great height before midnight. These (h′F) modes efficiently characterize ionospheric variabilities and processes. The great uplifts of (h′F) during night-time coincide with the presence of strong disturbance dynamo electric fields and disturbed neutral winds generated by intensified Joule heating in the summer months. The solar EUV plays a role in the uplifts during daytime. Zonal electric field disturbances and perturbations in neutral meridional winds critically contribute to the equatorial ionospheric responses and ESF variability. Most of inhibited/suppressed ESF occurred in mode A and in overshielding conditions. The inhibited ESF in the recovery phase is mainly contributed by a cooling state after great uplifts by daytime thermospheric winds.

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Section: Discussionmentioning

confidence: 99%

Solar Radiation and Geomagnetic Contribution of Consecutive 27-Day Recurrent Geomagnetic Storms to Variations of Equatorial Ionospheric Parameters and Spread F

YEERAM

2024

Preprint

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“…Their results show that usually, the occurrence of scintillations is felt between the local dusk and midnight at the equatorial and its nearby regions in the low latitudes. The changes in the occurrence characteristics of plasma irregularities from one day to the other during quiet and disturbed geomagnetic periods have been discussed in earlier literature [3,9,10]. At the equatorial regions, the zonal wind velocity variation poses a pivotal role in the generation of plasma bubbles which are the primary cause of low-latitude scintillation effects [11].…”

Section: Introductionmentioning

confidence: 99%

Seasonal Characteristics of Phase Scintillation Observed at UKM Station in Malaysia

Seif,

Panda

2023

J. Phys.: Conf. Ser.

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We present a statistical comparison of the seasonal occurrence of ionospheric phase scintillation in the GPS signals at an equatorial region in Malaysia using the ground-based ionospheric monitoring GPS receiver and space-based radio occultation (RO) measurements. The observations were recorded at UKM (2.55°N, 101.461°E) in Malaysia during 2010 using GPS based scintillation and TEC Monitoring setup (GISTM). The space-based measurements were recorded by the FORMOSAT_3/COSMIC (F_3/C) satellites in 2010. The GPS limb-viewing radio occultation technique is an innovative technique that provides ideal geometry to observe vertical ionospheric structures to detect Equatorial Plasma bubbles (EPBs) and Sporadic E layers (Es). Radio waves throughout the irregular equatorial ionosphere are studied to characterize phase scintillations at the L1 frequency in different seasons. Seasonal characteristics of the GPS phase scintillation show it mainly occurs in the equinox months, particularly during March. The results show similar values as the Radio Occultation (RO) observations over UKM station, which demonstrates that March equinox has the maximum occurrence of scintillations with the appearance of EPBs and during June corresponding to the appearance of the Es layer in the ionosphere. We found seasonal characteristics of phase scintillations obtained from the Ground-based station are consistent with seasonal characteristics of amplitude scintillation that occurred from the space-based measurements. Nevertheless, F3/C RO provided an opportunity for concurrent sounding of EPBs and Es characteristic structures across the globe, unlike other traditional ground-based measurements.

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“…They concluded that the electric field induces a downward movement of the equatorial F-region at dusk, inhibiting the RTI. A recent study by Ogwala et al (2022) about the ionospheric irregularity characteristics over Nigeria shows that the enhancement or suppression of ionospheric irregularities during a geomagnetic storm is influenced by the local time of the sudden storm commencement (SSC), determining when electric fields penetrate equatorial/low latitudes. Furthermore, Abdu et al (2009) observed two different effects of geomagnetic storms on EPBs in the Brazilian sector, which are as follows: 1) EPB suppression due to the westward PPEF and 2) EPB intensification when the polarity of the electric field is eastward, improving the pre-reversal enhancement (PRE) conditions.…”

Section: Introductionmentioning

confidence: 99%

Equatorial plasma bubbles features over the Brazilian sector according to the solar cycle and geomagnetic activity level

Carmo,

Dai,

Denardini

et al. 2023

Front. Astron. Space Sci.

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Equatorial plasma bubbles (EPBs) can lead to signal degradation, affecting the measurement accuracy. Studying EPBs and their characteristics has gained increasing importance. The characteristics of EPBs were investigated using the rate of total electron content (TEC) index (ROTI) maps under different solar and magnetic activity conditions during two periods: July 2014–July 2015 (solar maximum activity with F10.7: 145.9 × 10−22 W⋅m−2⋅Hz−1) and July 2019–July 2020 (solar minimum activity with F10.7: 69.7 × 10−22 W⋅m−2⋅Hz−1). We also divided this analysis according to the magnetic activity levels based on Kp and Dst (disturbance storm time) indices, classified as follows: quiet+ (Kp ≤3 and Dst >−30 nT), quiet− (Kp ≤3 and Dst <−30 nT), disturbed weak (−50 nT <Dst ≤−30 nT), moderate (−100 nT <Dst ≤−50 nT), and intense (Dst ≤−100 nT). The ROTI is calculated using the slant TEC with the carrier phase, and its keograms are used to extract the zonal velocity and distance. Our statistical investigation shows the occurrence rate, duration, zonal drift velocity, and inter-bubble zonal distance of EPBs over the Brazilian sector. The latitudinal extension and zonal drift velocity of EPBs are higher during the solar maximum than those in the solar minimum. In addition, EPBs are found with unusually long durations, remaining until the morning (∼12 UT), and 10% of EPB observations occurred on the winter solstice.

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Characterization of ionospheric irregularities over the equatorial and low latitude Nigeria region

Cited by 10 publications

References 75 publications

Solar Radiation and Geomagnetic Contribution of Consecutive 27-Day Recurrent Geomagnetic Storms to Variations of Equatorial Ionospheric Parameters and Spread F

Solar Radiation and Geomagnetic Contribution of Consecutive 27-Day Recurrent Geomagnetic Storms to Variations of Equatorial Ionospheric Parameters and Spread F

Seasonal Characteristics of Phase Scintillation Observed at UKM Station in Malaysia

Equatorial plasma bubbles features over the Brazilian sector according to the solar cycle and geomagnetic activity level

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