Fig. 1: Observations of the flaring region from 23 March 2024 at ~23:30–23:50 UT.

The top left panel shows an EUI/HRI_EUV snapshot, indicating the location of the M2.5 flare and the microflare ribbons that SPICE observed. Intensities are in data numbers per second per pixel (DN s⁻¹ px⁻¹). The cyan lines indicate the approximate location of the SPICE 4″ slit. The top right panels show a sequence of EUI/HRI_EUV images that illustrate the development of the microflare that SPICE observed a portion of. The bottom panel shows the evolution of the EUV and X-ray emission. The background image is the Fe xx 72.156 nm spectral line intensity observed by the SPICE slit as a function of time (note the reversed colour scale). Bright loops from the M2.5 flare are present in the north. The microflare emission is seen in the south (starting at around t ≈ 800 s). The time evolution of the EUI/HRI_EUV 174 Å emission is overlaid, along with X-ray observations taken by the Geostationary Operational Environmental Satellite’s X-ray Sensor (GOES/XRS; blue line) and STIX (4–9 keV in green, and 25–50 keV in red). The microflare is much fainter than the GOES M2.5 flare seen earlier. The GOES and STIX signal are consequently dominated by emissions from the M2.5 flare. Nevertheless, STIX observes a small enhancement above E > 20 keV at the time of the microflare. The EUI/HRI_EUV 174 Å intensity for the M2.5 flare and the microflare are shown separately (violet and orange lines, respectively). Both profiles show the classic flare picture with rapid time variations (a few seconds) during the impulsive phase originating from the flare ribbons, followed with a delay of several minutes of the emissions from the cooled-down flare loops. Note that we have corrected the SPICE pointing information for an approximate x, y = [−18, −50]″ offset between EUI/HRI_EUV and SPICE.