Modelling the probability of ionospheric irregularity occurrence over African low latitude region

Mungufeni, Patrick; Jurua, Edward; Habarulema, John Bosco; Katrini, Simon Anguma

doi:10.1016/j.jastp.2015.03.010

Cited by 16 publications

(10 citation statements)

References 22 publications

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Section: Discussionmentioning

confidence: 99%

“…The inadequate number of days in some cases used to derive monthly ROTI which in turn were used in model development might be another limitation of the current models. For practical applications, the models developed in the current study will be combined in future with the geomagnetically quiet time model [Mungufeni et al, 2015]. P. Mungufeni acknowledges the South African National Space Agency (SANSA) for hosting him at the Space science directorate during April-June 2015, where the idea of the study was conceived.…”

Section: Discussionmentioning

confidence: 99%

“…The ionospheric irregularity strength (hourly ROTI) as a function of LT ( t ), month ( m ), solar flux ( F ), and storm effect ( E ) was expressed as a tensor product as follows [ Abdu et al , ; Iyer et al , ; Mungufeni et al , ]:

P (t, m, F, E) = \sum_{i = 1}^{12} \sum_{j = 1}^{12} \sum_{k = 1}^{2} \sum_{l = 1}^{3} a_{i, j, k, l} N_{i, 4} (t) N_{j, 2} (m) N_{k, 2} (F) N_{l, 2} (E),

where N i ,4 ( t ) is a cubic B‐spline of order four applied to LT dependence ( t ). The N j ,2 ( m ), N k ,2 ( F ) , and N l ,2 ( E ) are cubic B‐splines of order two applied to monthly or seasonal ( m ), solar flux ( F ), and storm effect ( E ) dependencies, respectively.…”

Section: The Modelmentioning

confidence: 99%

“…The ionospheric irregularity strength (hourly ROTI) as a function of LT (t), month (m), solar flux (F), and storm effect (E) was expressed as a tensor product as follows [Abdu et al, 2003;Iyer et al, 2006;Mungufeni et al, 2015]:…”

Section: The Modelmentioning

confidence: 99%

“…The coefficients a i,j,k,l were determined by the weighted least squares fit to the binned data (Figures 3c and 3d). The various nodes were determined in a similar way as in Scherliess and Fejer [1999], Abdu et al [2003], Iyer et al [2006], and Mungufeni et al [2015]. For a day, 12 local time nodes were used and distributed between 18:00 and 06:00.…”

Section: The Modelmentioning

confidence: 99%

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Modeling of ionospheric irregularities during geomagnetically disturbed conditions over African low-latitude region

2016

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In this study, station‐specific models of ionospheric irregularities over low‐latitude African region during geomagnetically disturbed days (Dst≤−50 nT) have been developed. Global Navigation Satellite Systems (GNSS)‐derived ionospheric total electron content (TEC) data during 1998–2014 were used. Ionospheric irregularities were represented with the rate of change of TEC index (ROTI). The inputs for the models are the local time, solar flux index, day number of the year, auroral electrojet, and the disturbance storm time indices, while the output is the hourly median ROTI during these given conditions. To develop the models, the ROTI index values were binned based on the input parameters and cubic B splines were then fitted to the binned data. Developed models were validated with independent data over stations within 680 km radius. The models reproduced fairly well the inhibitions and the occurrences of ionospheric irregularities during geomagnetically disturbed days. The models even emulated these patterns in the various seasons, during medium and high solar activity conditions. During validations of the models, the percentages of the number of errors (difference between the observed and the modeled ROTI) <0.05 total electron content unit, 1TECU = 1016 el m−2 (TECU)/Min at all the stations were all >70% and the root‐mean‐square error were mostly < 0.1 TECU/Min. Furthermore, the correlation coefficients ranged from 0.47 to 0.76.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

P (t, m, F, E) = \sum_{i = 1}^{12} \sum_{j = 1}^{12} \sum_{k = 1}^{2} \sum_{l = 1}^{3} a_{i, j, k, l} N_{i, 4} (t) N_{j, 2} (m) N_{k, 2} (F) N_{l, 2} (E),

Section: The Modelmentioning

confidence: 99%

“…The ionospheric irregularity strength (hourly ROTI) as a function of LT (t), month (m), solar flux (F), and storm effect (E) was expressed as a tensor product as follows [Abdu et al, 2003;Iyer et al, 2006;Mungufeni et al, 2015]:…”

Section: The Modelmentioning

confidence: 99%