Abstract
A Coronal Mass Ejection (CME) is an inhomogeneous structure consisting of different features which evolve differently with the propagation of the CME. Simultaneous heliospheric tracking of different observed features of a CME can improve our understanding about relative forces acting on them. It also helps to estimate accurately their arrival times at the Earth and identify them in in-situ data. This also enables finding any association between remotely observed features and in-situ observations near the Earth. In this paper, we attempt to continuously track two density enhanced features in the CME of 6 October 2010, one at the front and another at the rear edge. This is achieved by using time-elongation maps constructed from STEREO /SECCHI observations. We derive the kinematics of the tracked features using various reconstruction methods. The estimated kinematics are used as inputs in the Drag Based Model (DBM) to estimate the arrival time of the tracked features of the CME at L1. On comparing the estimated kinematics as well as the arrival times of the remotely observed features with in-situ observations by Advanced Composition Explorer (ACE ) and Wind , we find that the tracked bright feature at the rear edge of 6 October 2010 CME corresponds most probably to the enhanced density structure after the magnetic cloud detected by ACE and Wind . In-situ plasma and compositional parameters provide evidence that the rear edge density structure may correspond to a filament associated with the CME while the density enhancement at the front corresponds to the leading edge of the CME. Based on this single event study, we discuss the relevance and significance of Heliospheric Imager (HI) observations in identification of the three-part structure of the CME.
Highlights
A Coronal Mass Ejection (CME) is huge magnetized plasma eruption from the Sun into the heliosphere and can be observed due to Thomson scattering of photospheric light off free electrons in the corona (Billings 1966; Howard & Tappin 2009)
On comparing the estimated kinematics as well as the arrival times of the remotely observed features with in-situ observations by Advanced Composition Explorer (ACE) and Wind, we find that the tracked bright feature at the rear edge of 6 October 2010 CME corresponds most probably to the enhanced density structure after the magnetic cloud detected by ACE and Wind
We have shown that stereoscopic methods which take into account the spherical geometry of a CME are superior to single-spacecraft reconstruction methods and single-spacecraft fitting methods
Summary
A CME is huge magnetized plasma eruption from the Sun into the heliosphere and can be observed due to Thomson scattering of photospheric light off free electrons in the corona (Billings 1966; Howard & Tappin 2009). The heliospheric tracking of CMEs has been successfully attempted using J-map, which is an elongation versus time plot at a certain position angle constructed from a sequence of stacked images (Sheeley et al 1999; Davies et al 2009) Such attempts have mostly dealt with tracking of a CME front and associated it with the sheath observed prior to the leading edge in in-situ data (Davis et al 2009; Liu et al 2010a, 2011; Möstl et al 2011; Mishra & Srivastava 2013). In a rare attempt, Howard & DeForest (2012) tracked a cavity like feature (in coronagraph images) of a classical CME using HI images which could be associated with a magnetic cloud identified in in-situ data near the Earth.
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