Abstract
Coronal Mass Ejections (CMEs) are highly dynamic events originating in the solar atmosphere, that show a wide range of kinematic properties and are the major drivers of the space weather. The angular width of the CMEs is a crucial parameter in the study of their kinematics. The fact that whether slow and fast CMEs (as based on their relative speed to the average solar wind speed) are associated with different processes at the location of their ejection is still debatable. Thus, in this study, we investigate their angular width to understand the differences between the slow and fast CMEs. We study the width distribution of slow and fast CMEs and find that they follow different power law distributions, with a power law indices (α) of –1.1 and –3.7 for fast and slow CMEs respectively. To reduce the projection effects, we further restrict our analysis to only limb events as derived from manual catalog and we find similar results. We then associate the slow and fast CMEs to their source regions, and classified the sources as Active Regions (ARs) and Prominence Eruptions. We find that slow and fast CMEs coming from ARs and PEs, also follow different power laws in their width distributions. This clearly hints toward a possibility that different mechanisms might be involved in the width expansion of slow and fast CMEs coming from different sources.These results are also crucial from the space weather perspective since the width of the CME is an important factor in that aspect.
Highlights
Coronal mass ejections (CMEs) consist of plasma and magnetic field that are expelled from the solar atmosphere into the heliosphere at speeds which can range from 100 to 3,000 km s−1 (Gopalswamy, 2004; Gopalswamy, 2010; Manoharan and Mujiber Rahman, 2011; Yashiro et al, 2004; Manoharan and Mujiber Rahman, 2011; Webb and Howard, 2012)
In this work, we study the width distribution of CMEs that occurred during different phases of solar cycle 23 and 24
We investigate if the source regions have any imprint on the width distribution of these slow and fast CMEs
Summary
Coronal mass ejections (CMEs) consist of plasma and magnetic field that are expelled from the solar atmosphere into the heliosphere at speeds which can range from 100 to 3,000 km s−1 (Gopalswamy, 2004; Gopalswamy, 2010; Manoharan and Mujiber Rahman, 2011; Yashiro et al, 2004; Manoharan and Mujiber Rahman, 2011; Webb and Howard, 2012). CMEs during their radial propagation, have been known to follow a three phase kinematic profile (Zhang et al, 2001; Zhang and Dere, 2006; Webb and Howard, 2012) During their propagation, they interact with the ambient solar wind and experience a drag, which leads to a decreasing or constant speed in the later stages of their propagation (Webb and Howard, 2012). Sheeley et al (1999) used the data from LASCO and confirmed this classification by suggesting that there are two dynamical classes of CMEs, which are gradual and impulsive CMEs The former are slower and are preferentially associated with eruptive prominences, whereas, the latter CMEs are faster and are mostly associated with flares and active regions. The most intriguing question in this context is whether there are two physically different processes that are involved in the launch of these slow and fast CMEs or whether they belong to a dynamical continuum with a single unified process, the answer to which is still not clear ( see Webb and Howard, 2012)
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