The detection of solar flare non-thermal ions using extreme ultraviolet spectroscopy
Natasha Jeffrey
University of Glasgow
Lyndsay Fletcher (University of Glasgow), Nicolas Labrosse (University of Glasgow)
During a solar flare, a large fraction of the released energy goes into accelerating electrons, detected via X-ray observations. In the majority of flares, the forms of the proton and heavier ion distributions are unknown due to a lack of MeV gamma-rays. Using non-Gaussian line fitting of solar flare extreme ultraviolet (EUV) spectral lines, we propose a method to detect and infer low energy accelerated ion populations during flare SOL2014-03-29T17:44. The EUV spectral lines are studied using the Hinode EUV Imaging Spectrometer (EIS). Suitable spectral lines of Fe XVI (262.976 A, ~3 MK) and Fe XXIII (263.766 A, ~13 MK) are fitted with a convolved kappa-Gaussian function, that can account for a Gaussian EIS instrumental profile and any physical line profiles produced by accelerated non-Maxwellian ion populations or plasma motions. Non-Gaussian Fe XVI and Fe XXIII line profiles with low kappa values are confidently observed during SOL2014-03-29T17:44. For Fe XXIII, the lowest kappa index values (~3) are observed close to the coronal X-ray sources at different times, with kappa increasing with time (3 to 8). Fe XVI kappa values are smaller (2 to 4) than those for Fe XXIII, and they are located closer to ribbon and hard X-ray footpoint regions. We also explore the possibility that the non-Gaussian profiles are produced by the EIS instrumental profile and hence we will discuss whether the method can be used to map the spatial and temporal distributions of suitable low energy non-thermal ion populations during a solar flare.