On The Influence Of The Solar Wind On The Propagation Of Earth-impacting Coronal Mass Ejections

TL;DR

This study examines how the solar wind influences the propagation, deflection, and rotation of Earth-impacting CMEs, using observations from the STEREO spacecraft and flux rope modeling to understand their complex heliospheric behavior.

Contribution

It provides new insights into CME deflections and rotations in the heliosphere, highlighting the roles of solar wind interaction and magnetic fields, based on a small but detailed observational sample.

Findings

About half of CMEs expanded self-similarly up to 40 R_sun

Most CMEs did not undergo significant rotation in the heliosphere

Deflections are influenced by ambient solar wind and magnetic fields

Abstract

Coronal Mass Ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties as they interact with the variable solar wind. We investigated the heliospheric propagation of 15 Earth-impacting CMEs observed during April 2010 to August 2018 in the field of view (FOV) of the Heliospheric Imager (HI) onboard the STEREO. About half of the 15 events followed self-similar expansion up to 40 $R_\odot$. The remaining events showed deflection either in latitude, longitude, or a tilt change. Only two events showed significant rotation in the HI1 FOV. We also use toroidal and cylindrical flux rope fitting on the in situ observations of interplanetary magnetic field (IMF) and solar wind parameters to estimate the tilt at L1 for these two events. Although the sample size is small, this study suggests that CME rotation is not very common in the heliosphere. We attributed the observed deflections and rotations of CMEs to a combination of factors, including their interaction with the ambient solar wind and the influence of the ambient magnetic field. These findings contribute to our understanding of the complex dynamics involved in CME propagation and highlight the need for comprehensive modeling and observational studies to improve space weather prediction. In particular, HI observations help us to connect observations near the Sun and near Earth, improving our understanding of how CMEs move through the heliosphere.