Constraining the Kinematics of Coronal Mass Ejections in the Inner Heliosphere with In-Situ Signatures

TL;DR

This paper introduces a method combining remote sensing and in situ data to accurately determine the kinematics and propagation directions of coronal mass ejections in the inner heliosphere, improving understanding of their space weather impact.

Contribution

The study develops a new approach that integrates two geometric methods to constrain ICME kinematics using combined observational data, enhancing accuracy in propagation modeling.

Findings

Velocity profiles from Sun to 1 AU are similar across methods.

Harmonic Mean predicts propagation direction farther from spacecraft.

Geometrical assumptions influence estimated ICME directions.

Abstract

We present a new approach to combine remote observations and in situ data by STEREO/HI and Wind, respectively, to derive the kinematics and propagation directions of interplanetary coronal mass ejections (ICMEs). We used two methods, Fixed-Phi and Harmonic Mean, to convert ICME elongations into distance, and constrained the ICME direction such that the ICME distance-time and velocity-time profiles are most consistent with in situ measurements of the arrival time and velocity. The derived velocity-time functions from the Sun to 1 AU for the three events under study (1-6 June 2008, 13-18 February 2009, 3-5 April 2010) do not show strong differences for the two extreme geometrical assumptions of a wide ICME with a circular front (Harmonic Mean) or an ICME of small spatial extent in the ecliptic (Fixed-Phi). Due to the geometrical assumptions, Harmonic Mean delivers the propagation direction further away from the observing spacecraft with a mean difference of ~25 degree.