Variation of ionosonde foE and its comparison with IRI-2016 & a local model over Pakistan longitude sector during solar cycle 22

Abstract

The study presents the variation of ionospheric critical frequency of E-layer (f oE), its comparison with International Reference Ionosphere (IRI-2016) over Pakistan, and suggests an artificial neural network (ANN) based algorithm to predict noontime daily hourly values. The ionosonde measurements of Karachi (Geog. Coord: 24.95
N, 67.13
E, dip latitude = 17.0
N), Multan (30.18
N, 71.48
E, 21.8
N), and Islamabad (33.75
N, 73.13
E, 25.2
N) have been used for the purpose. The observed f oE values have been analyzed during the high, moderate and low solar activity years 1989, 1992, and 1996, respectively. Results show a strong correlation between f oE and solar activity which was expected because the E-layer is essentially solar controlled. It is found that f oE peaks around noon with higher values during summer. The annual relative percentage deviation between data and IRI-2016 modeled values remains less than 6% for all locations and years under study. The ANN-based algorithm predicts daily noontime f oE values with a goodness of fit of 78%, compared to the IRI-2016 prediction, which has a goodness of fit of 71%. It is noted that the performance of IRI-2016 in predicting monthly hourly median values of f oE improves with decreasing solar activity. The study confirms the data authenticity of f oE over Pakistan and suggests an ANN-based algorithm in predicting noontime values with no immediate updates to IRI-2016 for this Asian longitude sector.