Statistical study of coronal mass ejection source locations: Understanding CMEs viewed in coronagraphs

Abstract

How to properly understand coronal mass ejections (CMEs) viewed in white light coronagraphs is crucial to many relative researches in solar and space physics. The issue is now particularly addressed in this paper through studying the source locations of all the 1078 Large Angle and Spectrometric Coronagraph (LASCO) CMEs listed in Coordinated Data Analysis Workshop (CDAW) CME catalog during 1997–1998 and their correlation with CMEs' apparent parameters. By manually checking LASCO and Extreme Ultraviolet Imaging Telescope (EIT) movies of these CMEs, we find that, except 231 CMEs whose source locations cannot be identified due to poor data, there are 288 CMEs with location identified on the frontside solar disk, 234 CMEs appearing above solar limb, and 325 CMEs without evident eruptive signatures in the field of view of EIT. On the basis of the statistical results of CMEs' source locations, there are four physical issues: (1) the missing rate of CMEs by SOHO LASCO and EIT, (2) the mass of CMEs, (3) the causes of halo CMEs, and (4) the deflections of CMEs in the corona, are exhaustively analyzed. It is found that (1) about 32% frontside CMEs cannot be recognized by SOHO, (2) the brightness of a CME at any heliocentric distance is roughly positively correlated with its speed, and the CME mass derived from the brightness is probably overestimated, (3) both projection effect and violent eruption are the major causes of halo CMEs, and especially for limb halo CMEs the latter is the primary one, and (4) most CMEs deflected toward equator near the solar minimum; these deflections can be classified into three types: the asymmetrical expansion, the nonradial ejection, and the deflected propagation.

The Physical Processes of CME/ICME Evolution

“…For example, Xie et al (2009) showed that during solar minimum slow CMEs deflected toward the ecliptic and the streamer belt by strong polar magnetic fields, while fast CMEs are deflected less, sometimes also away from the streamer belt away from the streamer belt, confirming earlier results by MacQueen et al (1986). Similarly Wang et al (2011) found 62% of CMEs deflected towards equator with an average deflection angle of 22…”

Are There Different Populations of Flux Ropes in the Solar Wind?

“…However, CMEs are not all moving out radially and moreover some are deflected by nearby coronal holes, especially towards the Equator during solar minimum Cremades, Bothmer, and Tripathi, 2006;Wang et al, 2011). It implies that the distribution of source regions is only an approximation of the distribution of the CME propagation directions.…”

Global Energetics of Solar Flares. VI. Refined Energetics of Coronal Mass Ejections

“…Most CME studies focus on a single or on a small number of events, while statistical studies are rare. We identified about 60 studies that contain large statistics (≈ 10 2 − 10 5 events) of observed and physical CME parameters, such as the sizes and locations of CMEs (Hundhausen 1993;Bewsher et al 2008;Wang et al 2011), the CME speed, acceleration, mass, and energy (Moon et al 2002;Yurchyshyn et al 2005;Zhang and Dere 2006;Cheng et al 2010;Bein et al 2011;Joshi and Srivastava 2011;Gao et al 2011), and the associated flare hard X-ray fluxes, fluences, and durations (Yashiro et al 2006;Aarnio et al 2011). The most extensive statistics of CME parameters is provided in on-line catalogs of CME events detected with the white-light method, mostly from the Large- Angle and Spectrometric Coronagraph Experiment (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) (Brueckner et al 1995), such as the CDAW, Cactus, SEEDS, and CORIMP catalogs of CME events, but also from STEREO/COR2 (see web links in Section 4.1).…”