A statistical study of the coronal mass ejection phenomenon

Abstract

The coronal mass ejection (CME) phenomenon represents a major component of the evolution of the solar corona, yet the mechanisms leading to such events remain something of a mystery. To understand the onset phase of these ejecta, many studies have focused on the relationship between CMEs and other, apparently related activity. A typical CME occurs on a very large spatial scale and involves the expulsion of up to 10 12 kg of matter, and the release of up to 10 25 J from the coronal magnetic field. A solar flare is an explosive event at the base of the atmosphere involving the release of up to 10 25 J of energy. Since there is an apparent association between these two phenomena and the time-scale for flares is comparable to that of the acceleration phase of the mass ejections, the questions arise as to what precise relationship exists between the two and what does this indicate about the physics of each. Many earlier studies of this kind were compromised by unfortunate assumptions, poor data coverage or instrumental limitations. This study attempts to identify purely formal correlations between parameters relating to flare and mass ejection observations through the period 1986–1987. In spite of a strong association between flares and CME onsets, we find that no single type of flare shows a preferred association with mass ejections, and the relative locations and timing of the two phenomena show no systematic ordering.