Bibliography

The ionospheric response to high-intensity long duration continuous AE activity (HILDCAA) event (13--15 April 2005) over mid-latitude African region

The ionospheric responses to High-Intensity Long Duration Continuous Auroral Electrojet Activity (HILDCAA) event which happened following the CIR-driven storm were studied over the southern hemisphere mid-latitude in the African sector. The 13–15 April 2005 event was analysed to understand some of the mechanisms responsible for the ionospheric changes during HILDCAA event. The ionosonde critical frequency of F2 layer (foF2) and Global Navigation Satellite System (GNSS) Total Electron Content (TEC) were used to analyse the ionospheric responses. The daytime increase in foF2 and TEC values were observed on 13 April 2005. The TEC and foF2 enhancement could be attributed to Large Scale Traveling Ionospheric Disturbances (LSTIDs), increase in thermospheric neutral composition changes, Prompt Penetration Electric Field (PPEF) and an expansion of Equatorial Ionization Anomaly (EIA) to the mid-latitude.

Matamba, Tshimangadzo; Habarulema, John;

Published by: Advances in Space Research      Published on: jan

YEAR: 2021     DOI: 10.1016/j.asr.2020.10.034

CIR; HILDCAA; Ionospheric storm; PPEF; TEC; TIDs

Ionospheric response at conjugate locations during the 7—8 September 2017 geomagnetic storm over the Europe-African longitude sector

This paper focuses on unique aspects of the ionospheric response at conjugate locations over Europe and South Africa during the 7–8 September 2017 geomagnetic storm including

Habarulema, John; Katamzi-Joseph, Zama; a, Dalia; Nndanganeni, Rendani; Matamba, Tshimangadzo; Tshisaphungo, Mpho; Buchert, Stephan; Kosch, Michael; Lotz, Stefan; Cilliers, Pierre; , others;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2020     DOI: 10.1029/2020JA028307

Long-term analysis of ionospheric response during geomagnetic storms in mid, low and equatorial latitudes

Understanding changes in the ionosphere is important for High Frequency (HF) communications and navigation systems. Ionospheric storms are the disturbances in the Earth’s upper

Matamba, Tshimangadzo;

Published by:       Published on:

YEAR: 2017     DOI:

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

This paper presents an investigation of ionospheric response to great (Dst<=\textendash350 nT) geomagnetic storms that occurred during solar cycle 23. The storm periods analyzed are 29 March to 2 April 2001, 27\textendash31 October 2003, 18\textendash23 November 2003, and 6\textendash11 November 2004. Global Navigation Satellite System, total electron content (TEC), and ionosonde critical frequency of F 2 layer (f o F 2 ) data over Southern Hemisphere (African sector) and Northern Hemisphere (European sector) midlatitudes were used to study the ionospheric responses within 15\textdegreeE\textendash40\textdegreeE longitude and \textpm 31\textdegree to \textpm 46\textdegree 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 \textpm 5.

Matamba, Tshimangadzo; Habarulema, John; a, Dalia;

Published by: Space Weather      Published on: 12/2016

YEAR: 2016     DOI: 10.1002/swe.v14.1210.1002/2016SW001516

Assessing ionospheric response during some strong storms in solar cycle 24 using various data sources

We present an analysis of a regional ionospheric response during six strong storms (-200\ nT\ <=Dst<=-100\ nT) that occurred in 2012 for the geographic latitudinal coverage of 10\textdegreeS\textendash40\textdegreeS within a longitude sector of 10\textdegreeE\textendash40\textdegreeE. Although these storms occurred during the same solar activity period and were all coronal mass ejection driven, their impacts and associated features on the ionosphere have been found different due to different contributing factors to their driving mechanisms. With the exception of one case, the rest of the storm periods were characterized by positive storm effects during the main and (or) recovery phases with varying physical mechanisms including low-latitude electrodynamics, neutral composition changes, and traveling ionospheric disturbances (TIDs). The common result to all the analyzed strong storms was the presence of large-scale TIDs during the storm main phases. Using total electron content data derived from the Global Navigational Satellite System (GNSS) observations and radio occultation (RO) electron density data on a regional scale, we have attempted to investigate meridional and vertical propagation of TIDs simultaneously during the strong storms. We have showed that it is possible to identify vertical motion of TIDs using RO data in cases when equatorward TIDs, as revealed by GNSS total electron content data, are present. RO results were compared to ionosonde data, and both data sources gave vertical velocities below 100\ m/s of the associated TIDs.

Habarulema, John; Katamzi, Zama; Sibanda, Patrick; Matamba, Tshimangadzo;

Published by: Journal of Geophysical Research: Space Physics      Published on: 12/2016

YEAR: 2016     DOI: 10.1002/jgra.v122.110.1002/2016JA023066

Statistical analysis of the ionospheric response during geomagnetic storm conditions over South Africa using ionosonde and GPS data

This paper presents a statistical analysis of ionospheric response over ionosonde stations Grahamstown (33.3\textdegreeS, 26.5\textdegreeE, geographic) and Madimbo (22.4\textdegreeS, 30.9\textdegreeE, geographic), South Africa, during geomagnetic storm conditions which occurred during the period 1996\textendash2011. Such a climatological study is important in establishing local ionospheric behavior trend which later forms a basis for accurate modeling and forecasting electron density and critical frequency of the\ F₂\ layer (f_oF₂) useful for high-frequency communication. The analysis was done using\ f_oF₂\ and total electron content (TEC), and to identify the geomagnetically disturbed conditions, the\ Dst\ index with a storm criterion of\ Dst\ <=\ nT was used. Results show a strong solar cycle dependence with negative ionospheric storm effects following the solar cycle and positive ionospheric storm effects occurring most frequently during solar minimum. Seasonally, negative and positive ionospheric storm effects occurred most in summer (63.24\%) and in winter (53.62\%), respectively. An important finding is that only negative ionospheric storms were observed during great geomagnetic storm activity (Dst\ <=\ nT). For periods when both\ f_oF₂\ and TEC data (from colocated ionosonde and GPS receiver stations) were available, a similar response in terms of variational trend was observed. Hence, GPS data can be used to effectively identify the ionospheric response in the absence of ionosonde data.

Matamba, Tshimangadzo; Habarulema, John; McKinnell, Lee-Anne;

Published by: Space Weather      Published on: 09/2015

YEAR: 2015     DOI: 10.1002/swe.v13.910.1002/2015SW001218

Geomagnetic storms; ionospheric storm effects; midlatitude ionosphere

Statistical analysis of the ionospheric response during geomagnetic storm conditions over South Africa using ionosonde and GPS data

Matamba, Tshimangadzo; Habarulema, John; McKinnell, Lee-Anne;

Published by: Space Weather      Published on:

YEAR: 2014     DOI: https://doi.org/10.1002/2015SW001218

ionospheric storm effects; Geomagnetic storms; midlatitude ionosphere