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.  
Highlights
Coronal mass ejections (CMEs) are huge explosions of solar materials from the sun that are released into space
Influence of the phases solar activity cycle 23 on Coronal Mass Ejections (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
CMEs data with initial speed ≥ 900 kms-1 associated with intense geomagnetic storm obtained from Large Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO) during solar cycle 23 were used
Summary
Coronal mass ejections (CMEs) are huge explosions of solar materials (clouds of plasma and magnetic fields) from the sun that are released into space. There are several space weather phenomena which tend to be associated with or are caused by geomagnetic storm. These include: Solar Energetic Particles (SEP) events (hazardous to Humans), Geomagnetically Induced Currents (GIC) which cause damages to satellites and electricity grid, ionospheric disturbances which may lead to radio and radar scintillation, disruption of navigation by magnetic compass and aurora displays at much lower latitudes than normal (Baker and John, 2008). Kim et al (2007) asserted that CMEs tend to tag along with solar activity cycle having its highest occurrence in solar maximum and its lowest during solar minimum Scientists are more interested in the solar cycle maximum and its minimum because they mark the peak and the least of the solar activity. Tripathi and Mishra (2005) observed that the occurrence frequency of CMEs generally follow the phase of solar cycle. Carol and Dale (2007) established that the occurrence rate of CMEs increases with increasing solar activity, its peak occurs during solar maximum, and CMEs can occur at any time during the solar cycle. Kim et al (2007) asserted that CMEs tend to tag along with solar activity cycle having its highest occurrence in solar maximum and its lowest during solar minimum
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