The multi-wavelength analysis revealed a sigmoidal brightening appearing at the onset of the flare. As the event approached its peak, the flare brightenings and ribbons evolved into a complex morphology, reflecting the tangled magnetic geometry of the active region as reconnection proceeded.

One of the most notable findings came from the hard X-ray light curve: quasi-periodic pulsations with a dominant period of approximately four minutes were detected during the impulsive phase.

To understand how the flare was triggered, the team constructed the coronal magnetic field at a pre-flare stage using a non-force-free-field (NFFF) extrapolation model.

The extrapolated field revealed several significant magnetic features within the flaring region: a magnetic flux rope, a three-dimensional magnetic null point, a sheared arcade, and quasi-separatrix layers (QSLs).

The authors propose that recurrent reconnection occurring at these features played a role in initiating the flare and in producing the associated quasi-periodic pulsations. In this interpretation, repeated episodes of reconnection at the null, flux rope and QSLs could naturally generate the quasi-regular modulation observed in the hard X-ray emission.

The event, catalogued as SOL2024-10-09T0125, offers a well-observed case study of how complex magnetic topology translates into observable flare behaviour.

Because the analysis is based on a single flare, the findings describe one event rather than a statistical trend, and the proposed link between the extrapolated magnetic structures and the QPPs remains a model-based interpretation.

Subject of Research: Multi-wavelength analysis of an X1.8 solar flare and its quasi-periodic pulsations using SDO and Aditya-L1 data with non-force-free-field magnetic extrapolation.

Article Title: Exploring an X1.8 Flare and Associated Quasi-Periodic Pulsations Using SDO and Aditya-L1 Observations, Alongside NFFF Extrapolation

Article References: Kumar, P., Kumar, S., Sadashiv, Kanaujiya, S. R., & Maurya, Y. K. (2026). Exploring an X1.8 Flare and Associated Quasi-Periodic Pulsations Using SDO and Aditya-L1 Observations, Alongside NFFF Extrapolation. Solar Physics, 301(10), Article 164. https://doi.org/10.1007/s11207-026-02760-9

Image Credits: AI Generated

DOI: 10.1007/s11207-026-02760-9

Keywords: solar flare, quasi-periodic pulsations, SDO, Aditya-L1, magnetic reconnection, flux rope, magnetic null, quasi-separatrix layers, NFFF extrapolation, hard X-rays, active region 13848, Solar Physics