The August 24, 2002 Coronal Mass Ejection: When a Western Limb Event Connects to Earth

TL;DR

This study uses 3D magneto-hydrodynamic simulations to analyze the August 24, 2002 CME, revealing how magnetic reconnection influences its deflection and connectivity, with implications for space weather prediction.

Contribution

It introduces a realistic initiation mechanism in simulations to study CME deflection and connectivity changes, enhancing understanding of CME propagation from the Sun to Earth.

Findings

Simulated shock does not reach Earth but spans about 120° angularly.

CME shows no significant deflection in the heliosphere.

Reconnection modifies solar magnetic connectivity during eruption.

Abstract

We discuss how some coronal mass ejections (CMEs) originating from the western limb of the Sun are associated with space weather effects such as solar energetic particles (SEPs), shock or geo-effective ejecta at Earth. We focus on the August 24, 2002 coronal mass ejection, a fast (~ 2000 km/s) eruption originating from W81. Using a three-dimensional magneto-hydrodynamic simulation of this ejection with the Space Weather Modeling Framework (SWMF), we show how a realistic initiation mechanism enables us to study the deflection of the CME in the corona and the heliosphere. Reconnection of the erupting magnetic field with that of neighboring streamers and active regions modify the solar connectivity of the field lines connecting to Earth and can also partly explain the deflection of the eruption during the first tens of minutes. Comparing the results at 1 AU of our simulation with observations by the ACE spacecraft, we find that the simulated shock does not reach Earth, but has a maximum angular span of about 120$^\circ$, and reaches 35$^\circ$ West of Earth in 58 hours. We find no significant deflection of the CME and its associated shock wave in the heliosphere, and we discuss the consequences for the shock angular span.