Radio, visible, and X ray emission preceding and following a coronal mass ejection

Abstract

This study uses both disk and limb observations to examine the changing conditions of the low solar corona, below 1.5 Rs, preceding and following a coronal mass ejection observed on the west limb on April 12, 1993. The disk observations comprise 90 cm (333 MHz) radio and daily Yohkoh soft X ray measurements, while the limb observations include measurements of emission from X rays, Fe X 637.4 nm and Fe XIV 530.3 nm coronal lines, and broadband Thomson‐scattered white light. The analysis of the disk and limb observations shows that throughout the 3 days of consecutive observations, the occurrence and persistence of nonthermal emission at 90 cm, also known as type I noise storm emission, were associated with large‐scale magnetic structures where the coronal mass ejection eventually occurred. Other than a subsequent flare observed in X rays at the limb, the changes in the coronal emission preceding and following the event were not markedly different from changes in other neighboring structures. The analysis of this novel combination of data supports the current view that coronal mass ejections are a cause rather than a consequence of the “classical” solar activity in the low corona. The radio observations, on the other hand, suggest that a connection between a noise storm and a coronal mass ejection exists. However, they do not necessarily imply that the noise storm actually initiates the event.