A Major Geomagnetic Storm in 2024 October Linked to Sympathetic CME--Prominence Eruptions

TL;DR

This study analyzes a 2024 October geomagnetic storm caused by interacting CMEs linked to sympathetic solar eruptions, providing insights into solar source properties and their space weather impacts.

Contribution

It presents a detailed analysis of CME interactions and their geomagnetic effects, highlighting the importance of multi-viewpoint observations and shock modeling for space weather prediction.

Findings

The storm resulted from two distinct CMEs caused by sympathetic eruptions.

Interacting CMEs completed impulsive acceleration before coronagraph observation.

Enhanced southward magnetic fields from CME interactions drove the geomagnetic storm.

Abstract

Improving predictions of the geomagnetic impact of coronal mass ejections (CMEs) requires understanding how solar source properties relate to in-situ measurements at Earth. However, major geomagnetic storms frequently arise from interacting CMEs, complicating the link back to their solar origins. We analyze a CME interaction event that caused a major geomagnetic storm in 2024 October 10-11 (D$_{st}$ $\sim$-333 nT). Multiviewpoint observations reveal that the storm was related to a sympathetic eruption involving a quiescent filament and an active-region CME. The coronagraph on board the Advanced Space-based Solar Observatory clearly shows that this sympathetic eruption resulted in two distinct CMEs. Due to the overlap of the CMEs in the coronagraph field of view (FOV), a spheroid shock model was used to fit the observed shock. Kinematic analysis indicates that the interacting CMEs had completed their impulsive acceleration phase before entering the coronagraph FOV, with a slow deceleration continuing beyond 100 R$_\odot$. In-situ measurements indicate that the enhanced southward magnetic fields, arising from compression during CME interactions, were the primary driver of the storm. Compared to photospheric fields, the in-situ magnetic fields suggest that the trailing CME maintained flux-rope-like signatures consistent with the source region. In contrast, the compressed leading CME displayed varying magnetic configurations between Wind and STEREO-A, featuring distorted flux-rope signatures and inconsistent inferred axis orientations. Our study bridges solar source dynamics to in-situ multipoint measurements, providing key insights for space weather prediction. Nevertheless, the direct linkage between source-region magnetic field configurations and these measurements remains tentative and requires further investigation.