Using ForeCAT Deflections and Rotations to Constrain the Early Evolution of CMEs

TL;DR

This paper uses the ForeCAT model to analyze and constrain the early evolution, deflections, and rotations of CMEs, improving predictions of their impact and orientation at Earth.

Contribution

It demonstrates how ForeCAT can reconstruct CME trajectories and constrain their low-corona behavior using observational data and parameter exploration.

Findings

Successfully reproduced CME deflections and rotations

Constrained low-corona expansion and propagation behaviors

Differentiated CME behaviors based on initial conditions

Abstract

To accurately predict the space weather effects of coronal mass ejection (CME) impacts at Earth one must know if and when a CME will impact Earth, and the CME parameters upon impact. Kay et al. (2015b) presents Forecasting a CME's Altered Trajectory (ForeCAT), a model for CME deflections based on the magnetic forces from the background solar magnetic field. Knowing the deflection and rotation of a CME enables prediction of Earth impacts, and the CME orientation upon impact. We first reconstruct the positions of the 2008 April 10 and the 2012 July 12 CMEs from the observations. The first of these CMEs exhibits significant deflection and rotation (34 degrees deflection and 58 degrees rotation), while the second shows almost no deflection or rotation (<3 degrees each). Using ForeCAT, we explore a range of initial parameters, such as the CME location and size, and find parameters that can successfully reproduce the behavior for each CME. Additionally, since the deflection depends strongly on the behavior of a CME in the low corona (Kay et al. (2015a, 2015b)), we are able to constrain the expansion and propagation of these CMEs in the low corona.