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3D CME fitting technique and uncertainty analysis using multiple viewpoints.

Presentation #115.01 in the session Sun-to-Earth Campaign-style Study of Large Space Weather Events — Poster Session.

Published onOct 20, 2022
3D CME fitting technique and uncertainty analysis using multiple viewpoints.

This study introduces a fitting technique to obtain the 3-D geometric parameters of a CME and their uncertainties. CMEs are large-scale eruptions that carry plasma and magnetic field from the Sun to the interplanetary space. CMEs usually have a two-front structure that consists of the ejecta and the shock. The graduated cylindrical shell model (GCS model) has been used for years to replicate the shape of the ejecta and depends on six free parameters. These parameters are responsible for is propagation direction, orientation and shape and are the longitude, latitude, tilt angle, aspect ratio, half angle and leading height. Although studies that focus on the radial and toroidal dimension of CMEs can be found in the literature, there is not much information on their poloidal dimension, which leads to errors and not accurate interpretation of the size of the ejecta. The fitting technique we suggest uses the MPFIT minimization IDL routine and combines multi-viewpoint white light observations from the STEREO, SOHO and PSP spacecraft with the GCS point cloud in order to obtain the best values of the geometric parameters along with their uncertainties. Using this technique we examine CMEs that were observed by one, two and three viewpoints. This method relies only on two input parameters, which are a set of observations and a set of initial guesses in order to minimize the chi-square between the observations and the model which accelerates the fitting process. A robust, fast and easy to use technique to estimate the CME geometric parameters along with their uncertainties will be of great help to space weather predictions.


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