Flux erosion of magnetic clouds by reconnection with the Sun's open flux

TL;DR

This study reveals that magnetic clouds lose significant magnetic flux through reconnection with the Sun's open flux during their journey, affecting their space weather impact and linking this erosion to the solar cycle.

Contribution

It demonstrates a linear relationship between magnetic cloud erosion and solar open flux, uncovering a new pathway for solar cycle influence on magnetic cloud properties.

Findings

Magnetic clouds lose flux via reconnection with open flux.

Erosion correlates linearly with solar open flux.

This process influences the geoeffectiveness of magnetic clouds.

Abstract

Magnetic clouds (MCs) are flux-rope magnetic structures forming a subset of solar coronal mass ejections which have significant space weather impacts. The geoeffectiveness of MCs depends on their properties which evolve during their interplanetary passage. Based on an analysis of observations spanning two solar cycles we establish that MCs interacting with the ambient solar wind magnetic field (i.e., heliospheric open flux) lose a substantial amount of their initial magnetic flux via magnetic reconnection, which in some cases, reduce their geoeffectiveness. We find a linear correlation between the eroded flux of MCs and solar open flux which is consistent with the scenario that MC erosion is mediated via the local heliospheric magnetic field draping around an MC during its interplanetary propagation. The solar open flux is governed by the sunspot cycle. This work therefore uncovers a hitherto unknown pathway for solar cycle modulation of the properties of MCs.