Coronal mass ejections and the associated activities on the solar disk observed on October 26, 2003

¹ National Astronomical Observatories of China, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: xbao@bao.ac.cn
² Yunnan Astronomical Observatory, National Astronomical Observatories of China, Chinese Academy of Sciences, Kunming, Yunnan 650011, PR China
³ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁴ Department of Physics, Catholic University of America, 620 Michigan Avenue, Washington, DC 20064, USA

Received: 21 April 2006
Accepted: 6 September 2006

Abstract

Aims.Coronal mass ejections (CMEs) are usually considered fast (slow) if their velocities are greater (less) than 500 km s^-1. It is generally believed that fast CMEs are well associated with activity manifested on the solar disk, such as solar flares, and that slow CMEs are often associated with filament eruptions out of active regions and can hardly leave any signature on the solar disk. However, this may not be totally true for the cases we are studying in the present work, where we have explored more explicitly than in previous studies the relationship between different types of CMEs and the associated on-disk activities.

Methods.We analyzed four CMEs that happen to take off near the west limb of the Sun on October 26, 2003. Their maximum speeds varied from 300 to 1800 km s^-1, with average accelerations from about 6 m s^-2 up to 330 m s^-2. They span over almost the full range of speeds of typical CMEs, from slow to fast. The evolution and kinematical properties of each CME at their early stages as well as the corresponding processes on the solar disk are examined.

Results.Three out of the four events analyzed, including slow and fast ones, exhibited apparent acceleration during their early development and a likely association with solar disk activity as manifested by ribbon flares and post-event loops. The fourth event (the CME that did not show any clear association with solar disk activity) was not the slowest one: it had a median speed (≤400 km s^-1). This suggests that some existing conclusions about the CME-flare correlation need to be re-investigated. In addition, the correlation of the coronal mass ejection angular widths to their speeds is also discussed.