Coronal and Chromospheric Dimmings during a Halo-Type CME Event

Abstract

We present complementary solar observations of a filament eruption occurring in association with a halo-type coronal mass ejection (CME) on 2006 July 6 in AR 10898. This eruption was followed by an M2.5 flare and has led to the formation of a pair of dimmings, observed in Hα, over network patterns in regions of opposite magnetic polarities located near the ends of the eruptive filament. These dimmings, also clearly visible in He I 10830 Å, EUV, and soft X-rays, were preceded by distinct Hα and EUV brightenings that first mark the dimming sites during the rise phase of the flare and then form bright edges, observable in EUV, around the growing dim regions. These dimmings have been attributed to a magnetic flux rope that is considered the origin of the CME as proposed in recent theories. The brightenings reported here are a new aspect of the CME hydromagnetic process that has not been included in existing theories. The roles and implications of the network patterns, brightenings, and sharp edges in the dimming evolutions are discussed.