[Paper Review] The Kinematics and Morphology of Solar Coronal Mass Ejections

Jason P. Byrne|arXiv (Cornell University)|Feb 17, 2012

Solar and Space Plasma Dynamics153 references3 citations

TL;DR

This PhD thesis develops advanced multiscale image processing and 3D reconstruction techniques to precisely track coronal mass ejections (CMEs) using STEREO's dual-vantage-point observations. It reveals that CMEs exhibit early acceleration, non-radial motion, angular width expansion, and aerodynamic drag—key insights for improving space weather forecasting.

ABSTRACT

Solar coronal mass ejections (CMEs) are large-scale eruptions of plasma and magnetic field from the Sun into the corona and interplanetary space. They are the most significant drivers of adverse space weather at Earth and other locations in the heliosphere, so it is important to understand the physics governing their eruption and propagation. However the diffuse morphology and transient nature of CMEs makes them difficult to identify and track using traditional image processing techniques. In this thesis the implementation of multiscale image processing techniques to identify and track the CME front through coronagraph images is detailed. An ellipse characterisation of the CME front is used to determine the CME kinematics and morphology with increased precision as compared to techniques used in current CME catalogues, and efforts are underway to automate this procedure for applying to a large number of CME observations for future analysis. It was found that CMEs do not simply undergo constant acceleration, but rather tend to show a higher acceleration early in their propagation. The angular width of CMEs was also found to change as they propagate, normally increasing with height from the Sun. However these results were derived from plane-of-sky measurements with no correction for how the true CME geometry and direction affect the kinematics and morphology observed. With the advent of the unique dual perspectives of the STEREO spacecraft, the multiscale methods were extended to an elliptical tie-pointing technique in order reconstruct the front of a CME in three-dimensions. Applying this technique to the Earth-directed CME of 12 December 2008 allowed an accurate determination of its true kinematics and morphology, and the CME was found to undergo early acceleration, non-radial motion, angular width expansion, and aerodynamic drag in the solar wind as it propagated towards Earth.

Motivation & Objective

• To overcome limitations in traditional CME detection and tracking due to diffuse morphology and 2D coronagraph projections.
• To improve kinematic and morphological accuracy of CMEs by applying multiscale filtering and ellipse-based front characterization.
• To enable 3D reconstruction of CME structure using elliptical tie-pointing from STEREO’s dual perspectives.
• To quantify the true 3D kinematics and morphology of Earth-directed CMEs, particularly the 12 December 2008 event.
• To assess the reliability of standard 3-point Lagrangian interpolation for deriving CME velocity and acceleration under noisy data

Proposed method

• Implementation of multiscale filtering (e.g., Normalised Radial Graded Filter) to enhance faint CME features in coronagraph images.
• Use of ellipse fitting to characterize the CME front, enabling precise measurement of height, angular width, and position over time.
• Application of elliptical tie-pointing to triangulate CME front positions from STEREO-A and STEREO-B observations for 3D reconstruction.
• Adoption of 3-point Lagrangian interpolation to derive CME velocity and acceleration from height-time profiles.
• Evaluation of alternative methods such as inversion techniques (e.g., Kontar & MacKinnon, 2005) and bootstrapping to improve kinematic uncertainty estimation.
• Use of simulated noisy data to test the robustness of kinematic derivation methods under realistic observational errors.

Experimental results

Research questions

• RQ1 How do multiscale image processing techniques improve the detection and tracking of faint and diffuse CMEs in coronagraph images?
• RQ2 To what extent do CMEs exhibit non-constant acceleration, and how does this vary with propagation distance?
• RQ3 How does the angular width of CMEs change during propagation, and what does this imply about their 3D geometry?
• RQ4 What role does aerodynamic drag play in shaping the kinematics of Earth-directed CMEs in the inner heliosphere?
• RQ5 How do uncertainties in height measurements affect the reliability of derived CME kinematics using standard interpolation techniques?

Key findings

• CMEs exhibit significant early acceleration, contradicting the assumption of constant acceleration in many current models.
• The angular width of CMEs increases with height, indicating lateral expansion during propagation through the solar wind.
• The 12 December 2008 CME showed non-radial motion and 'pancaking'—a flattening effect due to magnetic pressure and drag forces.
• Aerodynamic drag in the inner heliosphere was confirmed as a key factor slowing down the CME, with a measurable deceleration profile.
• Standard 3-point Lagrangian interpolation can produce misleading kinematic trends under realistic noise levels, with opposing acceleration profiles arising from similar data scatter.
• Inversion techniques (e.g., Kontar & MacKinnon, 2005) offer a more robust alternative for deriving kinematic profiles with statistically sound uncertainties.