Coexistence of a planar magnetic structure and an Alfven wave in the shock-sheath of an interplanetary coronal mass ejection

Abstract

The excess speed of coronal mass ejection over the ambient solar wind in interplanetary space generates a highly compressed, heated and turbulent shock-sheath. Here, for the first time, we present in situ observations of a unique and distinct feature of the shock-sheath, which exhibits the characteristics of a planar magnetic structure (PMS) and an Alfv´en wave simultaneously. We have used standard techniques to confirm the presence of the PMS as described in Shaikh et al. We have employed the minimum variance analysis technique to estimate the properties of the PMS. The Wal´en test is used to confirm the presence of the Alfv´en wave. Our study unambiguously proves the coexistence of the Alfv´en wave and the PMS in the shock-sheath region. Further studies are essential to investigate the origin of such a peculiar shock-sheath and its effect on our view of solar-terrestrial physics.