North-South asymmetry of equatorial ionospheric anomaly computed from the IRI model

Abstract

Using the electron density from the IRI-2016 model and processed results of the in-situ measurements (GRACE and CHAMP) in Xiong et al. (2013), the morphological features of the equatorial ionization anomaly (EIA) such as its magnitude and inter-hemispheric asymmetry have been studied during 2001-2009. The effect of solar activity on ability of the IRI-2016 model to predict the EIA parameters is studied and the results are compared with in-situ measurements from GRACE and CHAMP during high and low solar activity phases. The IRI-2016 generally follows the same latitudinal asymmetry (ACL - Asymmetry of Crest Latitude) at 400 km (the same trend of ACL as for CHAMP) while it tends to be asymmetric towards the North at 480 km (GRACE) (Positive ACL). In addition, during June solstice the IRI-2016 model shows larger departure from observation after 19:00 UT with a larger difference during high solar activity than that during the low solar activity. Also the IRI-2016 model failed to predict significantly North-South asymmetry (southern crest disappears) in the electron density for high solar activity period. This is probably the reason for larger discrepancy of observations and the IRI-2016 model particularly during the summer solstice of the high solar activity period. This suggests that data input in the IRI model particularly in the equatorial- and low-latitude regions are required so that it could better predict the location of EIA crests.