Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

The calm before the storm: High spatial resolution mosaic of active region NOAA 14274 at the onset of an X1.2 flare

Carsten Denker, Robert Kamlah, Meetu Verma, Alexander G. M. Pietrow

TL;DR

The paper demonstrates how to capture a full, high-resolution view of an active solar region in a mosaic, enabling detailed study of flare initiation. Using HiFI+ on the 1.5 m GREGOR telescope and KISIP speckle restoration, it builds a 240arcsec x 150arcsec mosaic from 84 raster datasets across Ca II H, TiO, and H-alpha channels, obtained about 30 minutes before an X1.2 flare. The results reveal stressed magnetic structuring—curved trailing-spot penumbral filaments, parasitic polarities, braided filaments, and PIL shear—that power multiple big flares; flare signatures emerge in a sequence along the trailing sunspot and surrounding filament, with early post-flare loops observed. This mosaic approach demonstrates a powerful avenue for high-cadence, wide-field solar imaging to link magnetic topology with flare dynamics and energy release.

Abstract

Active region NOAA 14274 produced some of the strongest flares of Solar Cycle 25, including the X1.2 and X5.1 flares on 10 and 11 November 2025, respectively. We present the first large mosaic of speckle-restored images obtained with the improved High-resolution Fast Imager (HiFI+) at the 1.5-meter GREGOR solar telescope at the Observatorio del Teide in Izaña, Tenerife, Spain. The observations were obtained approximately 30 minutes before the onset of the X1.2 flare. The active region exhibited strongly curved penumbral filaments, sunspot rotation, and shear motions along the polarity inversion line (PIL), which led to a highly stressed magnetic field configuration that stored sufficient energy to release multiple M- and X-class flares. The first flare signatures appeared as small-scale brightenings, each with a width of a few tenths of an arcsecond, that trace penumbral filaments in the trailing sunspot.

The calm before the storm: High spatial resolution mosaic of active region NOAA 14274 at the onset of an X1.2 flare

TL;DR

The paper demonstrates how to capture a full, high-resolution view of an active solar region in a mosaic, enabling detailed study of flare initiation. Using HiFI+ on the 1.5 m GREGOR telescope and KISIP speckle restoration, it builds a 240arcsec x 150arcsec mosaic from 84 raster datasets across Ca II H, TiO, and H-alpha channels, obtained about 30 minutes before an X1.2 flare. The results reveal stressed magnetic structuring—curved trailing-spot penumbral filaments, parasitic polarities, braided filaments, and PIL shear—that power multiple big flares; flare signatures emerge in a sequence along the trailing sunspot and surrounding filament, with early post-flare loops observed. This mosaic approach demonstrates a powerful avenue for high-cadence, wide-field solar imaging to link magnetic topology with flare dynamics and energy release.

Abstract

Active region NOAA 14274 produced some of the strongest flares of Solar Cycle 25, including the X1.2 and X5.1 flares on 10 and 11 November 2025, respectively. We present the first large mosaic of speckle-restored images obtained with the improved High-resolution Fast Imager (HiFI+) at the 1.5-meter GREGOR solar telescope at the Observatorio del Teide in Izaña, Tenerife, Spain. The observations were obtained approximately 30 minutes before the onset of the X1.2 flare. The active region exhibited strongly curved penumbral filaments, sunspot rotation, and shear motions along the polarity inversion line (PIL), which led to a highly stressed magnetic field configuration that stored sufficient energy to release multiple M- and X-class flares. The first flare signatures appeared as small-scale brightenings, each with a width of a few tenths of an arcsecond, that trace penumbral filaments in the trailing sunspot.

Paper Structure

This paper contains 3 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Observations
  3. Results and Conclusions

Figures (1)

  • Figure 1: The mosaics of speckle-restored images have a combined FOV of $240\arcsec \times 150\arcsec$ and shows active region NOAA 14274 at around 08:33 UT on 10 November 2025, about 30 min before an X1.2 flare began. The mosaics were created using four HiFI+ channels: Ca ii H $\lambda$396.8 nm, TiO $\lambda$705.8 nm, and broad- and narrow-band H$\alpha$$\lambda$656.3 nm (clockwise from the top-left panel). The FOV of the Ca ii H channel ($48.2\arcsec \times 30.8\arcsec$) is too small to overlap vertically (as shown by the horizontal blue lines in the Ca ii H panel), while the FOV of the other channels ($76.5\arcsec \times 60.5\arcsec$) is much larger.