Multiple shocks generated by the 2024 May 14 coronal mass ejection

¹ Astronomy & Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, DIAS Dunsink Observatory, Dublin D15 XR2R, Ireland
² Centre for Astrophysics & Relativity, School of Physical Sciences, Dublin City University, Glasnevin Campus, Dublin D09 V209, Ireland
³ School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland
⁴ LIRA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université, Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France
⁵ ASTRON – Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 4 July 2025
Accepted: 13 February 2026

Abstract

Context. A series of powerful solar flares and coronal mass ejections (CMEs) occurred between 10 and 14 May 2024. As these eruptions propagated through the corona, they generated multiple solar type II radio bursts, indicating the presence of shock waves.

Aims. This study characterises a series of type II radio bursts associated with a CME that occurred on 14 May, focusing on the coronal conditions during the event and identifying the likely location of the shocks where the radio bursts are generated.

Methods. The CME was tracked using a combination of white light and extreme ultraviolet observations of the solar corona taken by three instruments: the Geostationary Operational Environmental Satellite (GOES) Solar Ultraviolet Imager (SUVI) and two coronagraphs of the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO), together with ground-based radio observations between 10−240 MHz from the Irish Low–Frequency Array (I−LOFAR). The radial distances of the radio sources were examined using a series of density models, with both potential field source surface and magnetohydrodynamic models used to examine the coronal plasma conditions.

Results. Four type II bursts were identified in the I−LOFAR radio dynamic spectrum over ∼15 minutes, exhibiting features such as band splitting, herringbones, and fragmentation. The shocks were found to have speeds ranging between ∼443−2075 km s⁻¹, with drift rates of ∼−361 to −78 kHz s⁻¹. The shocks were found to have a M_A ≈ 3.21 − 3.57. indicating that they were super–Alfvénic. The first type II burst was triggered ∼18 minutes after the CME launch, with each burst appearing to have been generated at a different height in the corona. Analysis of the derived kinematics and modelling results suggests that the type II bursts were likely produced at the shoulders of the CME near the flanks, where open magnetic field lines and relatively low Alfvén speeds facilitated shock formation.

Conclusions. This multi-instrument study shows that multiple type II bursts from a single CME originated at different coronal heights, with modelling indicating their generation near the CME flanks where low Alfvén speeds and open magnetic field lines facilitated shock formation. The findings highlight the role of coronal conditions, particularly the magnetic field configuration and the Alfvén speed distribution, in determining the heights and locations where these bursts originate. Our results reinforce the importance of continuous, multi-wavelength observations for understanding shock dynamics and improving constraints on coronal models.