Speaker
Description
The solar storms of May 2024 were a series of powerful solar flares and coronal mass ejections (CMEs) that occurred between 10 and 13 May 2024, followed by a few strong solar flares over the next few days during solar cycle 25. As these eruptions propagated through the corona, they generated multiple solar type II radio bursts, indicating the presence of shock waves.
This study aims to analyse the characteristics of a series of type II radio bursts associated with a CME that occurred on May 14th, with a focus on the coronal conditions during the event and findings on the likely location where the radio bursts are generated.
We utilised data from multiple sources, including satellite observations from the Solar Ultraviolet Imager (SUVI) onboard the Geostationary Operational Environmental Satellite (GOES) and the Large Angle and Spectrometric Coronagraph (LASCO) instrument onboard the Solar and Heliospheric Observatory (SOHO), along with ground-based radio observations between 10−240 MHz from the Irish Low-Frequency Array (I-LOFAR) in Birr. We also employed several electron-density models to estimate the radial distances of the radio sources and incorporated the Potential Field Source Surface (PFSS) and magnetohydrodynamic (MHD) models to examine the coronal plasma conditions.
We identified four type II bursts in the I-LOFAR radio dynamic spectrum over ∼15 minutes, exhibiting features such as band splitting, herringbones, and fragmentation. The characteristics of the type II bands and the shock speed were estimated. The shocks' speeds range between ~ 443−2075 km/s, with drift rates ranging from ~-361 to -78 kHz/s. The shocks’ strength range between MA ≈ 1.56−3.47, implying that the shocks were super-Alfvénic. The first type II burst was triggered ∼18 minutes after the CME launch. The bursts appear to have been generated at different heights in the corona, with the first two occurring within the SUVI field of view and the third and fourth within the gap between the SUVI and LASCO C2 instruments. From kinematics analysis and modelling results, we inferred that the type II bursts were likely produced at the CME’s bottom flank, where open magnetic field lines and relatively low Alfvén speeds facilitated shock formation.
This multi-instrument study provides new insights into the generation of type II radio bursts and their relationship with CME-driven shocks. 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.
| Do you plan to attend in-person or online? | In-person |
|---|
