On the Variation of Volumetric Evolution of CMEs from Inner to Outer Corona

TL;DR

This study extends the GCS model to inner corona observations, revealing power law relationships in CME volume evolution and indicating different expansion mechanisms at various heights, enhancing understanding of CME dynamics.

Contribution

The paper introduces a modified GCS model for inner corona data, enabling 3D CME analysis and revealing differential volume expansion and power law dependencies in CME evolution.

Findings

Power law dependence of CME volume with distance from the Sun.

Different power laws for volume expansion of leading front and legs.

Distinct expansion mechanisms in inner and outer corona.

Abstract

Some of the major challenges faced in understanding the early evolution of Coronal Mass Ejections (CMEs) are due to limited observations in the inner corona ($<\,3$ R$_{\odot}$) and the plane of sky measurements. In this work, we have thus extended the application of the Graduated Cylindrical Shell (GCS) model to the inner coronal observations from the ground--based coronagraph K--Cor of the Mauna Loa Solar Observatory (MLSO) along with the pair of observations from COR--1 onboard the Solar Terrestrial Relations Observatory (STEREO). We study the rapid initial acceleration and width expansion phase of 5 CMEs in white-light in the lower heights. We also study the evolution of the modelled volume of these CMEs in inner corona and report for the first time, a power law dependence of the CME volume with distance from the Sun. We further find the volume of ellipsoidal leading front and the conical legs follow different power laws, thus indicating differential volume expansion through a CME. The study also reveals two distinct power laws for the total volume evolution of CMEs in the inner and outer corona, thus suggesting different expansion mechanisms at these different heights. These results besides aiding our current understanding on CME evolution, will also provide better constraints to CME initiation and propagation models. Also, since the loss of STEREO-B (and hence COR--1B data) from 2016, this modified GCS model presented here will still enable stereoscopy in the inner corona for the 3D study of CMEs in white-light.