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On the Origin of Hard X-Ray Emissions from the Behind-the-limb Flare on 2014 September 1
2021, Wu, Yihong, Rouillard, Alexis P., Kouloumvakos, Athanasios, Vainio, Rami, Afanasiev, Alexandr N., Plotnikov, Illya, Murphy, Ronald J., Mann, Gottfried J., Warmuth, Alexander
The origin of hard X-rays and γ-rays emitted from the solar atmosphere during occulted solar flares is still debated. The hard X-ray emissions could come from flaring loop tops rising above the limb or coronal mass ejection shock waves, two by-products of energetic solar storms. For the shock scenario to work, accelerated particles must be released on magnetic field lines rooted on the visible disk and precipitate. We present a new Monte Carlo code that computes particle acceleration at shocks propagating along large coronal magnetic loops. A first implementation of the model is carried out for the 2014 September 1 event, and the modeled electron spectra are compared with those inferred from Fermi Gamma-ray Burst Monitor (GBM) measurements. When particle diffusion processes are invoked, our model can reproduce the hard electron spectra measured by GBM nearly 10 minutes after the estimated on-disk hard X-rays appear to have ceased from the flare site.