Abstract:
Some of the major challenges faced in understanding the early evolution of coronal mass ejections (CMEs) are due
to the limited observations in the inner corona (<3 Re) and the plane-of-sky measurements. In this work, we have
thus extended the application of the Graduated Cylindrical Shell (GCS) model to inner coronal observations from
the ground-based coronagraph K-Cor of the Mauna Loa Solar Observatory, along with the pairs of observations
from COR-1 on board the Solar Terrestrial Relations Observatory. We study the rapid initial acceleration and width
expansion phases of five CMEs in white light at the lower heights. We also study the evolution of the modeled
volumes of these CMEs in the inner corona and report, for the first time, a power-law dependence of CME volume
with distance from the Sun. We further find that the volumes of the ellipsoidal leading front and the conical legs
follow different power laws, thus indicating differential volume expansion throughout 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. Besides aiding our current understanding of
CME evolution, these results will also provide better constraints to CME initiation and propagation models. Also,
given the loss of the STEREO-B (and hence COR-1B data) from 2016, the modified GCS model presented here
will still enable stereoscopy in the inner corona for the 3D study of CMEs in white light.
