Non-thermal electron acceleration is one of the earliest observable signatures of magnetic reconnection in solar flares and eruptions, and is key to understanding how it triggers and drives such events. I=In recent decades, modelling, as well as spatially integrated hard X-ray (HXR) observations, suggest that this process occurs on timescales less than or equal to 1s. However, further probing the acceleration process requires characterising the spatial and spectral evolution of the electrons with HXR imaging spectroscopy. Yet, this has not previously been available on such fast timescales.
In this talk, we discuss the first 1-s HXR spectroscopic imaging of non-thermal flare-accelerated electrons. Thanks to Solar Orbiter/STIX observations of one of the most intense solar flares ever observed (SOL2024-05-20T05:14L171C109, estimated at X16.5 class), we find physical changes in the non-thermal HXR source morphologies on timescales of at least 1 second. This is despite slower evolution of the spatially integrated HXR spectrum.
This may suggest a coherent driver linking different acceleration events within the flare whose spectrum varies on timescales longer than 1 second. Alternatively, it may be an illusion of the spatial averaging in the spectral analysis. Either way, these results show that sub-second electron acceleration in solar flares can be associated with morphological dynamics on similar timescales. This highlights the importance of high-spatial-resolution, sub-second HXR imaging spectroscopy for elucidating non-thermal electron acceleration and how it drives and sustains solar flares and eruptions.
