Kinematical properties of coronal mass ejections

TL;DR

This paper reviews observational methods and studies on the kinematic properties of coronal mass ejections, highlighting challenges in understanding their evolution and improving space weather forecasting.

Contribution

It summarizes recent techniques for deriving CME kinematics and discusses physical processes affecting CME propagation from Sun to Earth.

Findings

Recent methods improve CME velocity profile estimation

Projection effects significantly impact CME parameter measurements

Understanding CME-environment interactions aids in better forecasting

Abstract

Coronal mass ejections (CMEs) are the most dynamic phenomena in our solar system. They abruptly disrupt the continuous outflow of solar wind by expelling huge clouds of magnetized plasma into interplanetary space with velocities enabling to cross the Sun-Earth distance within a few days. Earth-directed CMEs may cause severe geomagnetic storms when their embedded magnetic fields and the shocks ahead compress and reconnect with the Earth's magnetic field. The transit times and impacts in detail depend on the initial CME velocity, size, and mass, as well as on the conditions and coupling processes with the ambient solar wind flow in interplanetary space. The observed CME parameters may be severly affected by projection effects and the constant changing environmental conditions are hard to derive. This makes it difficult to fully understand the physics behind CME evolution, preventing to do a reliable forecast of Earth-directed events. This short review focusing on observational data, shows recent methods which were developed to derive the CME kinematical profile for the entire Sun-Earth distance range as well as studies which were performed to shed light on the physical processes that CMEs encounter when propagating from Sun to Earth.