Freely propagating flanks of wide coronal-mass-ejection-driven shocks: Modelling and observational insights

Abstract

Widespread solar energetic particle (SEP) events remain poorly understood phenomena in space weather. These events are often linked to coronal mass ejections (CMEs) and their shocks, but the mechanisms governing their global particle distribution remain debated. The 13 March 2023 event is particularly notable as a widespread SEP event associated with an exceptionally fast interplanetary shock. With speeds of up to 3000 km/s, it is one of the most extreme shocks observed in recent years. We aim to investigate whether the flanks of a wide CME-driven shock can decouple from the CME and continue propagating as freely propagating shock waves. If shocks are the primary SEP source, such a mechanism could help explain some of the widest SEP events. Using EUHFORIA, a 3D magnetohydrodynamic heliospheric model, we simulated the evolution of wide CME-driven shocks. We modified the model to allow direct shock injection at the inner boundary, upstream of the CME ejecta. Applying this to the 13 March 2023 event, we modelled two simultaneous CMEs whose shocks form a single, wide shock envelope that spans 280° in longitude. We then compared our results to in situ observations. Our simulations show that the flanks of wide CME shocks can persist as freely propagating waves beyond 2 au. For the 13 March 2023 event, the modelled shock arrival times and amplitudes of associated plasma parameters (e.g. speed and density) show good agreement with observations from various spacecraft distributed across different radial distances and longitudes. Furthermore, the combined shock structure expands into a quasi-circumsolar wave as it propagates outwards. These findings indicate that the shock flanks of fast CMEs can persist for a long time, supporting the idea that such freely propagating shock flanks play a key role in the global distribution of SEPs in widespread events.

13 pages, 7 figures, accepted for publication in Astronomy \& Astrophysics

References in corpus (14)

• Advancements in the ADAPT Photospheric Flux Transport Model
• Solar-MACH: An open-source tool to analyze solar magnetic connection configurations
• Large-scale Coronal Propagating Fronts in Solar Eruptions as Observed by the Atmospheric Imaging Assembly on Board the Solar Dynamics Observatory\,--\,An Ensemble Study
• Observation-based modelling of magnetised Coronal Mass Ejections with EUHFORIA
• The Solar Energetic Particle Event on 2013 April 11: An Investigation of its Solar Origin and Longitudinal Spread
• Perpendicular Diffusion of Solar Energetic Particles: Model Results and Implications for Electrons
• The 17 April 2021 widespread solar energetic particle event
• Implementation and validation of the FRi3D flux rope model in EUHFORIA
• Three-dimensional Propagation of the Global EUV Wave associated with a solar eruption on 2021 October 28
• Observation-based modelling of the energetic storm particle event of 14 July 2012
• The effect of the ambient solar wind medium on a CME-driven shock and the associated gradual solar energetic particle event
• Evidence of a complex structure within the 2013 August 19 coronal mass ejection. Radial and longitudinal evolution in the inner heliosphere
• The unusual widespread solar energetic particle event on 2013 August 19. Solar origin and particle longitudinal distribution
• On the reason for the widespread energetic storm particle event of 13 March 2023