Dependence of the F-region peak electron density (foF2) on solar activity observed in the equatorial ionospheric anomaly region in the Brazilian sector

Cardoso, Felipe Antonio; Sahai, Y.; Guarnieri, F. L.; Fagundes, P. R.; Pillat, V. G.; Silva, J.V.P.R. da

doi:10.1016/j.asr.2011.04.016

Cited by 4 publications

(2 citation statements)

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“…) at different longitudes. Solar activity variations of daily averaged noontime NmF2 or NmF2 for multiple stations (Liu et al 2006) or single station (Cardoso et al 2011) have also been reported. Chen and Liu (2010) found that the rate of linear increase of monthly mean NmF2 with F 10.7 cm solar flux shows remarkable dependency on latitude, season, and local time at low solar activity levels.…”

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confidence: 98%

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

2015

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The characteristics of the F2 layer parameters NmF2 and hmF2 over Dibrugarh (27.5°N, 95°E, 17°N geomagnetic, 43°dip) measured by a Canadian Advanced Digital Ionosonde (CADI) for the period of August 2010 to July 2014 are reported for the first time from this low mid-latitude station lying within the daytime peak of the longitudinal wave number 4 structure of equatorial anomaly (EIA) around the northern edge of anomaly crest. Equinoctial asymmetry is clearly observed at all solar activity levels whereas the midday winter anomaly is observed only during high solar activity years and disappears during the temporary dip in solar activity in 2013 but forenoon winter anomaly can be observed even at moderate solar activity. The NmF2/hmF2 variations over Dibrugarh are compared with that of Okinawa (26.5°N, 127°E, 17°N geomagnetic), and the eastward propagation speed of the wave number 4 longitudinal structure from 95°E to 127°E is estimated. The speed is found to be close to the theoretical speed of the wave number 4 (WN4) structure. The correlation of daily NmF2 over Dibrugarh and Okinawa with solar activity exhibits diurnal and seasonal variations. The highest correlation in daytime is observed during the forenoon hours in equinox. The correlation of daily NmF2 (linear or non-linear) with solar activity exhibits diurnal variation. A tendency for amplification with solar activity is observed in the forenoon and late evening period of March equinox and the postsunset period of December solstice. NmF2 saturation effect is observed only in the midday period of equinox. Non-linear variation of neutral composition at higher altitudes and variation of recombination rates with solar activity via temperature dependence may be related to the non-linear trend. The noon time maximum NmF2 over Dibrugarh exhibits better correlation with equatorial electrojet (EEJ) than with solar activity and, therefore, new low-latitude NmF2 index is proposed taking both solar activity and EEJ strength into account.

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confidence: 98%

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

2015

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“…At Brazilian longitudes, a current flowing westward, called counter electrojet (CEJ), is also present during the morning and the afternoon (Rastogi, 2007). Climatologically, the intensity of the EEJ and the consequent morphology of the EIA crests are modulated by the season, the solar flux, and the occurrence of migrating and nonmigrating tides (Fejer, 1991(Fejer, , 2005Cardoso et al, 2011;Yamazaki & Maute, 2017). Under equinoctial and high solar activity conditions, the expected position of the southern crest of the EIA reaches the most poleward latitudinal sector, that is, in the southern hemisphere up to −20° off magnetic equator (see, e.g., Cesaroni et al, 2015;Muella et al, 2017).…”

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Ionospheric Response Over Brazil to the August 2018 Geomagnetic Storm as Probed by CSES‐01 and Swarm Satellites and by Local Ground‐Based Observations

et al. 2021

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The geomagnetic storm that occurred on 25 August 25 2018, that is, during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo‐Electromagnetic Satellite (CSES‐01). By integrating the in situ measurements provided by CSES‐01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca., 460 km) with ground‐based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower‐ and mid‐latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the equatorial electrojet (EEJ). Our proposed multisensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between prompt penetrating electric fields and disturbance dynamo electric fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES‐01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter‐EEJ during both 25 and 26 August at Braziliian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES‐01/Swarm altitudes integrated with the ground‐based observation recorded signatures of equatorial ionospheric anomaly crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude.

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Pattern of F2-layer peak electron density across African Ionosonde locations and response to solar activity

Adebesin¹,

Ikubanni²,

Adebiyi³

et al. 2023

Advances in Space Research

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Dependence of the F-region peak electron density (foF2) on solar activity observed in the equatorial ionospheric anomaly region in the Brazilian sector

Cited by 4 publications

References 13 publications

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

Ionospheric Response Over Brazil to the August 2018 Geomagnetic Storm as Probed by CSES‐01 and Swarm Satellites and by Local Ground‐Based Observations

Pattern of F2-layer peak electron density across African Ionosonde locations and response to solar activity

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