Exploring the Impact of Imaging Cadence on Inferring CME Kinematics

TL;DR

This study investigates how different imaging cadences affect the accuracy of CME kinematic measurements, finding that a 1-minute cadence balances precision and practicality for most CME speeds.

Contribution

It provides an analysis of the impact of imaging cadence on CME kinematic inference, guiding observational campaign planning with upcoming coronagraph missions.

Findings

Average CME velocity is minimally affected by cadence.

Average acceleration shows significant dependence on cadence.

A 1-minute cadence is generally suitable for CME studies.

Abstract

The kinematics of coronal mass ejections (CMEs) are essential for understanding their initiation mechanisms and predicting their planetary impact. Most acceleration and deceleration occur below 4 R$\odot$, which is crucial for initiation understanding. Furthermore, the kinematics of CMEs in the inner corona ($<$ 3 R$_\odot$) are closely related to their propagation in the outer corona and their eventual impact on Earth. Since the CME kinematics are mainly probed using coronagraph data, it is crucial to investigate how imaging cadence affects the precision of data analysis and conclusions drawn and also for determining the flexibility of designing observational campaigns with upcoming coronagraphs. We study ten CMEs observed by the K-Coronagraph of the MLSO. We manually track the CMEs using high cadence (15 s) white-light observations of K-Cor and vary the cadence as 30 s, 1 min, 2 min, and 5 min to study the impact of cadence on the kinematics. We also employed the bootstrapping method to estimate the fitting parameters. Our results indicate that the average velocity of the CMEs does not have a high dependence on the imaging cadence, while the average acceleration shows significant dependence on the same, with the confidence interval showing significant shifts for the average acceleration for different cadences. The decrease in cadence also influences the determination of acceleration onset time. We further find that it is difficult to find an optimum cadence to study all CMEs, as it is also influenced by the pixel resolution of the instrument and the speed of the CME. However, except for very slow CMEs (speeds less than 300 Kms$^{-1}$), our results indicate a cadence of 1 min to be reasonable for the study of their kinematics. The results of this work will be important in the planning of observational campaigns for the existing and upcoming missions that will observe the inner corona.