Speaker
Description
On 18 January 2026, the active region 4341 produced a long-duration X1.9 flare, a fast halo coronal mass ejection (CME) with a projected speed above 2000 km/s, and one of the largest >10 MeV proton enhancements in the GOES record (S4). In SolO/STIX, the flare shows a clear train of quasi-periodic pulsations (QPPs) in the non-thermal hard X-rays, pointing to repeated episodes of electron acceleration during the impulsive phase. From the STIX non-thermal bands (25–84 keV), we measure the pulsation period and track the evolution of the X-ray spectrum from pulse to pulse, then test whether the same pattern appears in the EOVSA microwaves and the OVRO-LWA low-frequency radio data. SDO/AIA and HMI provide the EUV and magnetic context, SOHO/LASCO and STEREO-A/COR2 reconstruct the CME, and the type II burst traces the CME-driven shock. SolO/EPD provides in situ electron and ion spectra of escaping particles, while at 1 AU, GOES monitors protons and the arriving CME and its shock, which drove a G4-severe geomagnetic storm. By tying the QPP signal in STIX to the radio, EUV, white-light, and in-situ data, we investigate whether bursty energy release in the corona shapes how and when particles escape, and we weigh the flare and shock contributions to this severe SEP event.