Multi-Wavelength Diagnostics of Pre-Flare Evolution with Aditya-L1: From the Solar Chromosphere to the Corona

arXiv:2607.26171 · astro-ph.SR · Submitted 2026-07-28 · Read on arXiv

Adithya H. N., Sreejith Padinhatteeri, Soumya Roy, K. Sankarasubramanian, Durgesh Tripathi, Abhilash R Sarwade, Srikar Paavan Tadepalli, Harshavardhan G Hegde, Nived V. N, Janmejoy Sarkar, Rahul Gopalakrishnan, Rushikesh Deogaonkar, A. N. Ramaprakash, Sami K. Solanki, Dibyendu Nandy, Dipankar Banerjee

Manipal Centre for Natural Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India · Manipal Centre for Natural Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India · Physical Research Laboratory, Navrangpura, Ahmedabad, Gujarat, India · Centre for Excellence in Space Sciences India, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India · Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune, Maharashtra, India · U R Rao Satellite Centre, Old Airport Road, Vimanapura Post, Bengaluru, Karnataka, India · U R Rao Satellite Centre, Old Airport Road, Vimanapura Post, Bengaluru, Karnataka, India · Sri Dharmasthala Manjunatheshwara College · Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune, Maharashtra, India · Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany · Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune, Maharashtra, India · Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune, Maharashtra, India · Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune, Maharashtra, India · Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany · Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India · Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram, Kerala, India

astro-ph.SR

Submitted: 2026-07-28

Comments: 17 pages 14+5 Figures

DOI: 10.1093/mnras/stag1416

Code: https://github.com/sunpy/sunkit-spex

Project page: https://pradan1.issdc.gov.in/al1

License: http://creativecommons.org/licenses/by/4.0/

The gist: The pre-flare phase of solar flares provides important insight into the processes that drive active regions toward instability.

Terminology

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) 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 alpha 1 = 1.64+0.59-0.57 and alpha 2 = 3.12+0.64-0.61, with the higher-energy slope consistent with the Ly- alpha 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.

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