Coronal Mass Ejections Deflected by Newly Emerging Flux: A Combined Analytic and Numerical Study

TL;DR

This study combines analytic theory and numerical simulations to show how newly emerging flux influences the stability, eruption dynamics, and deflection of solar filaments and CMEs, enhancing space-weather prediction accuracy.

Contribution

It introduces a novel integrated approach linking catastrophe theory with MHD simulations to analyze NEF's role in filament eruptions and CME deflections.

Findings

NEF can trigger or suppress eruptions by reshaping coronal stability.

NEF causes filament eruptions to deflect, with deflection magnitude depending on flux polarity.

The study provides predictive angles for eruption deflection directions.

Abstract

Newly emerging flux (NEF) has been widely studied as a trigger of solar filament eruptions, but its influence on the subsequent dynamics remains poorly explored. Because NEF typically emerges adjacent to filaments, it imposes magnetic asymmetry that can drive non-radial eruptions and complicate space-weather forecasting. We bridge analytic catastrophe theory with 2D resistive MHD simulations: analytic solutions provide magnetic configurations containing a flux rope at the loss-of-equilibrium point, which are then used as initial conditions for simulations to examine the following dynamics. We find that NEF governs the kinematics of filament eruptions in two ways. First, by reshaping coronal stability, NEF can create or eliminate a higher equilibrium in corona, thereby producing failed eruptions or CMEs. In the transitional situation where a metastable equilibrium appears, the rising filament decelerates and stalls before re-accelerating into a CME, consistent with observed two-step eruptions. Second, by breaking symmetry, NEF deflects eruptions away from the radial direction: depending on its polarity, it acts as a repulsor or an attractor on eruptive filaments, and the deflection magnitude increases with the degree of asymmetry. Our theory yields two characteristic angles that predict the deflection directions of CMEs and failed eruptions, and simulations closely aligns with these predictors. These results highlight the NEF not only as a trigger but also as a key factor that governs both the acceleration and deflection of eruptions during their propagation in the low corona.