Abstract

It has been established that Coronal Mass Ejections (CMEs) follow the phase of solar activity cycle. CMEs are known to be the major cause of geomagnetic storms which have devastating effects on earth atmosphere. Predicting their arrival times has been a major issue in space weather forecast. Influence of the phases solar activity cycle 23 on CMEs transit time were investigated using fast CMEs data with initial speed ≥ 900 kms-1 that were associated with intense geomagnetic storm obtained from Large Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO) for solar cycle 23. Empirical Coronal Mass Ejections Arrival (ECA) model equations of Ojih-Okeke modified model, Gopalswamy 2000 model (G2000), Gopalswamy 2001 model (G2001), and Vrsnak and Gopalswamy 2002 model (VG2002) were applied to the data points. Scatter plots of CMEs transit time as function of CMEs initial speed and solar wind speed were generated. Linear correlation coefficients were obtained. The significance of the correlation was tested at 0.05 level of significant. Linear correlation coefficients obtained for solar maximum period of solar cycle 23 for Ojih-Okeke model, VG2002 model, G2001 model and G2000 model were -0.63, -0.82, -0.78 and -0.79 respectively and those obtained for declining phase of solar cycle 23 were -0.93, -0.80, -0.80 and -0.86 respectively. There is no significant difference between the correlations obtained for solar maximum phase and the declining phase of solar cycle 23. The findings depict that phases of solar activity cycle has no significant influence on CMEs transit time.

Key words: Coronal mass ejections, solar activity cycle, transit time, phase, geomagnetic storm.