Relationship between eruptions of active-region filaments and associated flares and coronal mass ejections

Abstract

To better understand the dynamical process of active-region filament eruptions and associated flares and coronal mass ejections (CMEs), we carried out a statistical study of 120 events observed by Big Bear Solar Observatory (BBSO), Transition Region and Coronal Explorer (TRACE) and the Extreme-ultraviolet Imaging Telescope (EIT) on board Solar and Heliospheric Observatory (SOHO) from 1998 to 2007. We combined filament observations with the NOAA's flare reports, Michelson Doppler Imager (MDI) magnetograms and Large Angle and Spectrometric Coronagraph (LASCO) data, to investigate the relationship between active-region filament eruptions and other solar activities. We found that 115 out of 120 (about 96 per cent) filament eruptions are associated with flares. 56 out of 105 (about 53 per cent) filament eruptions are found to be associated with CMEs except for 15 events without corresponding LASCO data. We note the limitation of coronagraphs duo to geometry or sensitivity, leading to many smaller CMEs that are Earth-directed or well out of the plane of sky not being detected by near-Earth spacecraft. Excluding those without corresponding LASCO data, the CME association rate of active-region filament eruptions clearly increases with X-ray flare class from about 32 per cent for C-class flares to 100 per cent for X-class flares. We also found that the eruptions of active-region filaments associated with halo CMEs are often accompanied by large flares (18 out of 20 events; ≥M1.0). About 92 per cent events (11 out of 12) associated with X-class flare are associated with halo CMEs. Such a result is due to the fact that the Earth-directed CMEs detected as halo CMEs are often the larger CMEs and many of the smaller ones are not detected because of the geometry and low intensity. The average speed of the associated CMEs of filament eruptions increases with X-ray flare size from 563.7 kms-1 for C-class flares to 1506.6 kms-1 for X-class flares. Excluding the active region located in the area more than 50° from the solar centre and five without corresponding MDI data, the β magnetic field configuration (about 47 per cent; 36 out of 77) is more likely to form eruptive filaments than the other ones and there are 33 filament eruptions associated with magnetic flux cancellation, 42 events associated with magnetic flux emergence and two events without variation of magnetic field. The average area of emergence regions is 855.9 arcsec2. These findings may be instructive not only in respect to the modelling of active-region filament eruptions but also in predicting flares and CMEs. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.