Relation between solar flares and halo coronal mass ejections

Solar flares and coronal mass ejections (CMEs) are two very important active events from Sun. Inspite of several theoretical and statistical analyses, the relation between solar flares and CMEs is so far not well established, and strong opinions and arguments still continue. Statistical approaches use a lot of data available from many measurements by space and ground instruments. They try to map the measured parameters of one event to that of another event and try to establish the relation between them. Halo CMEs are a kind of special CMEs in the sense that they are directed towards Earth and hence can influence Earth’s atmosphere. For a scientist interested in Sun–Earth interactions and the effect on Earth’s atmosphere, study of Halo CMEs is extremely important. In this paper the relation between solar flares and Halo CMEs is studied. The data sets used are for the period from October 2006 to March 2017. For the first time, the Halo CMEs are categorized into four different groups based on the relative time of occurrence with respect to the flares and the relation between the flare and Halo CME parameters is studied. It is shown that: (a) there is a good correlation between certain flare parameters (like flare flux and peak intensity) and CME parameters (like kinetic energy, linear speed, and mass) especially when the Halo CME occurs during the flare; (b) For the same set of CMEs, the correlation is poor with flare duration; and (c) For CMEs before or after the flare, the correlation is lesser than the CMEs occurring during the flare.