Investigation of Effects of Coronal Mass Ejections on Ionospheric Total Electron Content over Nsukka, South Eastern Nigeria

Abstract. In this work, we attempted to investigate the contributions and effects of coronal mass ejections (CMEs) on total electron content (TEC) in the ionosphere of an equatorial station, Nsukka (Lat. 6.86N; Long 7.38E) located in South Eastern Nigeria. Using TEC data recorded by the Global Positioning System (GPS) of the Air Force Research Laboratory, USA, and CME data obtained from the USA owned Solar and Heliospheric Observatory (SOHO) satellite, we calculated the variation of TEC in the solar maximum year 2012, and observed regular, Gaussian distribution of TEC during geomagnetic solar quiet (Sq) days. On days associated with CME events, TEC variations assumed very sporadic patterns; maximized quite early during geomagnetic disturbed days and peaked at later hours during quiet days. The ionospheric electron contents are generally very low at both pre-noon and nighttime hours but quite high at noon and post-noon hours. This pattern of TEC variation is due to fluctuation in solar radiations incident on earth’s equatorial ionosphere. During quiet periods the number of free electrons generated is smaller in comparison to that generated during disturbed times, which shows a positive contribution of CMEs to TEC profile. TEC profiles for days categorized as neither disturbed nor quiet are synonymous to TEC curves on quiet days. There is significant time-variance in peak-time of TEC between disturbed and quiet days. TEC maximized quit earlier on disturbed days, implying increased influx of charged particles into the ionosphere due to the prevailing CME events. These results can contribute as input to the ionospheric monitoring and forecasting for the equatorial region of South Eastern Nigeria.