2026/07/25 by Adithya H. N., Adithya H. N, Sreejith Padinhatteeri +20
Earth and Planetary Sciences · Physics and Astronomy · #Earthquake Detection and Analysis #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics #astro-ph.SR
paper · pdf · doi:10.1093/mnras/stag1416
17 pages 14+5 Figures
openalex publication_date 2026/07/25 · arxiv created 2026/07/28 · openalex created_date 2026/07/28 · openalex updated_date 2026/07/28 · arxiv updated 2026/07/30
Abstract The pre-flare phase of solar flares provides important insight into the processes that drive active regions toward instability. We investigate chromospheric pre-flare activity using observations from the Solar Ultraviolet Imaging Telescope (SUIT) onboard Aditya-L1, complemented with X-ray measurements from High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) and Solar Low Energy X-ray Spectrometer (SoLEXS). We analyse seven M- and X-class flares, focusing on spatially resolved Mg ii h (2803 Å) observations from SUIT. We identify 102 pre-flare transients within regions of interest prior to flare onset. These transients are detected in the Mg ii h channel, with no counterparts in continuum filters, confirming their chromospheric origin. In most cases, the transients are co-spatial with polarity inversion lines (PILs) and the eventual flaring region. Approximately 28% of transients have X-ray counterparts in HEL1OS (10-30 keV); The Spectrometer Telescope for Imaging X-rays (STIX) spectral analysis reveals non-thermal emission in a subset, indicating that some transients are small-scale flare-like events. A hot X-ray onset is identified in four cases. For the remaining three cases, the signal-to-noise ratio above the background is insufficient to determine whether a hot-onset phase is present. The peak-flux distribution of the transients follows a broken power law with indices α 1 = 1.64+0.59-0.57 and α 2 = 3.12+0.64-0.61, with the higher-energy slope consistent with the Ly-α flare distribution. These results suggest that chromospheric pre-flare transients represent small-scale magnetic energy-release events that contribute to the progressive destabilisation of active regions prior to major flare onset.