Coronal Hole Influence on the Observed Structure of Interplanetary CMEs

TL;DR

This study investigates how coronal holes influence the deflection and observed structure of interplanetary CMEs, supporting the idea that all CMEs are flux ropes but may appear differently due to CH-induced deflections.

Contribution

Introduces a CH influence parameter (CHIP) to quantify coronal hole effects on CME deflection, revealing conditions under which CMEs appear as flux ropes or not.

Findings

High CHIP values correlate with distinct deflection patterns of MCs and non-MCs.

Proximity to coronal holes affects CME deflection and observed structure.

Results support all CMEs being flux ropes, with apparent differences caused by deflections.

Abstract

We report on the coronal hole (CH) influence on the 54 magnetic cloud (MC) and non-MC associated coronal mass ejections (CMEs) selected for studies during the Coordinated Data Analysis Workshops (CDAWs) focusing on the question if all CMEs are flux ropes. All selected CMEs originated from source regions located between longitudes 15E-15W. Xie, Gopalswamy, and St, Cyr (2013, Solar Phys., doi:10.1007/s11207-012-0209-0) found that these MC and non-MC associated CMEs are on average deflected towards and away from the Sun-Earth line respectively. We used a CH influence parameter (CHIP) that depends on the CH area, average magnetic field strength, and distance from the CME source region to describe the influence of all on-disk CHs on the erupting CME. We found that for CHIP values larger than 2.6 G the MC and non-MC events separate into two distinct groups where MCs (non-MCs) are deflected towards (away) from the disk center. Division into two groups was also observed when the distance to the nearest CH was less than 3.2x10^5 km. At CHIP values less than 2.6 G or at distances of the nearest CH larger than 3.2x10^5 km the deflection distributions of the MC and non-MCs started to overlap, indicating diminishing CH influence. These results give support to the idea that all CMEs are flux ropes, but those observed to be non-MCs at 1 AU could be deflected away from the Sun-Earth line by nearby CHs, making their flux rope structure unobservable at 1 AU.