Multi-station observation of ionospheric irregularities over South Africa during strong geomagnetic storms

Amabayo, Emirant B.; Cilliers, Pierre J.

doi:10.1016/j.asr.2012.10.015

Cited by 8 publications

(7 citation statements)

References 18 publications

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“…Ionosonde data in Figures c and d are in agreement with TEC observations and show a negative ionospheric storm effect almost 5 h after the SI+ in the Northern (JR055 and RO041) and Southern (GR13L) Hemispheres for about 10 h (06:00 UT to 16:00 UT) and 9 hours (06:00 UT to 15:00 UT), respectively. Similar results over South Africa have been reported for 31 March to 2 April 2001 [ Amabayo and Pierre , ]. The negative ionospheric response is usually associated with neutral composition changes.…”

Section: Discussionsupporting

confidence: 86%

“…Borries et al [] reported large‐scale TIDs in Europe (at latitude 30°N–70°N and longitude 10°W–30°E) on 31 March 2001 at 07:00 UT with the phase speed of 497 ± 39 m/s. Large‐scale TIDs have also been reported over Southern Africa midlatitude using TEC and ionosonde data on 31 March 2001 [ Amabayo and Pierre , ]. TIDs lead to increased electron densities resulting from plasma motion to F region heights [ Prölss and Jung , ; Prölss , ].…”

Section: Discussionmentioning

confidence: 99%

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Midlatitude ionospheric changes to four great geomagnetic storms of solar cycle 23 in Southern and Northern Hemispheres

2016

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This paper presents an investigation of ionospheric response to great (Dst ≤−350 nT) geomagnetic storms that occurred during solar cycle 23. The storm periods analyzed are 29 March to 2 April 2001, 27–31 October 2003, 18–23 November 2003, and 6–11 November 2004. Global Navigation Satellite System, total electron content (TEC), and ionosonde critical frequency of F2 layer (foF2) data over Southern Hemisphere (African sector) and Northern Hemisphere (European sector) midlatitudes were used to study the ionospheric responses within 15°E–40°E longitude and ±31° to ±46° geomagnetic latitude. Midlatitude regions within the same longitude sector in both hemispheres were selected in order to assess the contribution of the low‐latitude changes especially the expansion of equatorial ionization anomaly (EIA) also called the dayside ionospheric superfountain effect during these storms. In all storm periods, both negative and positive ionospheric responses were observed in both hemispheres. Negative ionospheric responses were mainly due to changes in neutral composition, while the expansion of the EIA led to pronounced positive storm effects at midlatitudes for some storm periods. In other cases (e.g., 29 October 2003), penetration electric fields, EIA expansion, and large‐scale traveling ionospheric disturbances were found to be present during the positive storm effect at midlatitudes in both hemispheres. An increase in TEC on the 28 October 2003 was because of the large solar flare with previously determined intensity of X45 ±5.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Midlatitude ionospheric changes to four great geomagnetic storms of solar cycle 23 in Southern and Northern Hemispheres

2016

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“…They associated these structures with equatorward meridional winds. Habarulema et al (2013), Ngwira et al (2012) and Amabayo and Cilliers (2012) highlighted that there are still unresolved issues in the understanding of the response of ionosphere to geomagnetic storms over the South African region. More studies of this nature are important for South Africa to meet its mandate as the Regional Space Weather Warning Center for Africa, especially in its frequency prediction duties.…”

Section: Introductionmentioning

confidence: 98%

“…Using South African ground based GPS and ionosonde measurements for mid latitudes, they observed that a traveling atmospheric disturbance could be responsible for short duration electron density enhancements and the upwelling of the ionospheric F region. Amabayo and Cilliers (2012) studied the response of South African mid latitude ionosphere to the strong geomagnetic storms of 31 March -2 April 2001 and 7-9 September 2002 using ground based GPS, ionosonde, solar wind from ACE and ground based magnetometer measurements. They found that the storms had both negative and positive ionospheric effects over South Africa and observed TEC perturbations and spread F phenomenon which they associated with storm induced TIDs.…”

Section: Introductionmentioning

confidence: 99%

Traveling ionospheric disturbances observed at South African midlatitudes during the 29–31 October 2003 geomagnetically disturbed period

Katamzi

Habarulema

2014

Advances in Space Research

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“…These authors estimated the apparent velocity of the TIDs and pointed out that further analysis was required to determine other properties such as periods and wavelengths. Very recently, Amabayo and Cilliers [] did an analysis of storm‐induced perturbations in the ionospheric electron concentration using ionosonde and GPS data over Southern Africa and pointed out the storm‐induced TIDs as one of the irregularity sources. Reconstruction of electron density profiles using computerized ionospheric tomography (CIT) and a network of South African GPS receivers also showed a profound increase in electron densities for the 15 May 2005 storm over the entire Southern Africa region [ Yao et al , ].…”

Section: Introductionmentioning

confidence: 99%

Estimating the propagation characteristics of large‐scale traveling ionospheric disturbances using ground‐based and satellite data

2013

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In this article, the propagation characteristics of large‐scale traveling ionospheric disturbances (LS TIDs) are estimated during the geomagnetic storm periods of 14–16 May 2005 and 25–27 September 2011 over South Africa. One and two GPS arrays have been independently considered for the storms of 15 May 2005 and 26 September 2011, respectively. The average periods of dominant modes (≈ 2.5–3.5h) in the time series data were determined by applying wavelet analysis on both ionosonde and GPS data. The consideration of diurnal GPS total electron content (TEC) variability from receivers along three different longitude sectors showed a time shift in TEC enhancement with increasing latitude, the first indication of equatorward motion of the traveling ionospheric disturbances (TIDs). The statistical method (based on GPS radio interferometry) employed shows that these TIDs were mostly propagating nearly equatorward (for both storm periods), which is consistent with the existing literature about storm‐induced TIDs. On storm days, TID horizontal velocities have been determined in the range of ≈200–500m/s. The analysis of diurnal TEC response from different stations confirmed that the positive storm effect observed on 15 May 2005 was a result of the large‐scale TIDs of wavelength ≈4000 km. On the other hand, the estimated wavelengths of LS TIDs on 26 September 2011 were ≈2400–3400km between 10 and 17 UT. A time lag is observed between the times at which enhancements in TEC, ionosonde foF2, and hmF2 data are revealed, and this has been attributed to the passage of the TID.

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Multi-station observation of ionospheric irregularities over South Africa during strong geomagnetic storms

Cited by 8 publications

References 18 publications

Midlatitude ionospheric changes to four great geomagnetic storms of solar cycle 23 in Southern and Northern Hemispheres

Midlatitude ionospheric changes to four great geomagnetic storms of solar cycle 23 in Southern and Northern Hemispheres

Traveling ionospheric disturbances observed at South African midlatitudes during the 29–31 October 2003 geomagnetically disturbed period

Estimating the propagation characteristics of large‐scale traveling ionospheric disturbances using ground‐based and satellite data

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