Polarity relevance in flux rope deflections triggered by coronal holes

TL;DR

This study investigates how the magnetic polarity between flux ropes and coronal holes influences CME deflections, revealing that polarity alignment determines whether CMEs are attracted or repelled, with numerical simulations matching a peculiar observed event.

Contribution

It introduces a numerical simulation approach to understand flux rope deflections by coronal holes based on magnetic polarity configurations, explaining both attraction and repulsion phenomena.

Findings

Deflections depend on magnetic polarity alignment.

Numerical simulations reproduce observed double-deflection events.

Magnetic null points influence CME trajectories.

Abstract

Many observations show that coronal holes (CHs) deviate coronal mass ejections (CMEs) away from them. However, there are some peculiar events reported where the opposite occurs. To contribute to a space weather forecast efforts, in relation to the prediction of CME trajectories, we study the interaction between flux ropes (FRs) and CHs through numerical simulations. We perform 2.5D numerical simulations where FRs and CHs interact with different relative polarity configurations. We also reconstruct the trajectory and magnetic environment of a peculiar event occurred on 30 April 2012. The numerical simulations indicate that at low coronal levels, depending on the relative magnetic field polarity between the FR and the CH, the deflection will be attractive, i.e. the FR moves towards the CH (for anti-aligned polarities) or repulsive, i.e. the FR moves away to the CH (for aligned polarities). This is likely due to the formation of vanishing magnetic field regions or null points, located between the FR and the CH or, at the other side of the FR, respectively. The analysed observational event shows a double-deflection, first departing from the radial direction by approaching the CH and then moving away from it suggesting that the trajectory could result from a magnetic configuration with an anti-aligned polarity. We numerically reproduce the double deflection of the observed event, providing support to this conjecture.