Variability of the bottomside B0 and B1 parameters of ionospheric electron density profile over Cyprus and comparison with IRI-2012 model

摘要

The bottomside profile thickness (B0) and shape (B1) parameters are investigated for the first time over a lower mid-latitude European digisonde station in Nicosia, Cyprus (Station id. NI135; Geographic 35°N, 33°E), with a set of manually scaled ionograms during the period 2009-2014. We performed a comparative analysis of the digisonde observed B0 and B1 parameters with the predictions of International Reference Ionosphere (IRI-2012), using all bottomside modeling options, during different seasons under low and high solar activity conditions. Observations show significant day-to-day variations in their magnitudes manifesting relatively higher B0 (lower B1) from summer to lower B0 (higher B1) in winter, through the moderate B0 and B1 values during the equinox, the degree of which further depend on the level of solar activity. Considerable discrepancy in the model predictions are noticed with (a) Bil-2000 demonstrating almost no diurnal variability in B0 though the B1 is estimated appreciably, (b) Gul-1987 following the observed diurnal pattern of B0 to manifesting the characteristic pre-sunrise enhancement in spite of its relatively higher magnitudes with its constant B1 replaced by the B1 from Bil-2000 option, and (c) ABT-2009 overestimating observed B0 in all seasons except summer and the estimated B1 following a quasi-similar diurnal pattern to that of observed B1, but with relatively flattened slope of the curves in their diurnal plots in all seasons. It is evident from the present analysis that none of the options in the present version of IRI shows adequate agreement with observed B0 and B1 parameters over Cyprus, which in turn necessitates the inclusion of these datasets in IRI model for better lower mid-latitude predictions. The important extracts from this study may support the international efforts for a comprehensive global climatological representation of the IRI model.