Description:
<jats:title>Abstract</jats:title>
<jats:p>In a solar flare, a large fraction of the magnetic energy released is converted rapidly to the kinetic energy of non-thermal particles and bulk plasma motion. This will likely result in non-equilibrium particle distributions and turbulent plasma conditions. We investigate this by analyzing the profiles of high temperature extreme ultraviolet emission lines from a major flare (SOL2014-03-29T17:44) observed by the <jats:italic>EUV Imaging Spectrometer</jats:italic> (EIS) on <jats:italic>Hinode</jats:italic>. We find that in many locations the line profiles are non-Gaussian, consistent with a kappa distribution of emitting ions with properties that vary in space and time. At the flare footpoints, close to sites of hard X-ray emission from non-thermal electrons, the <jats:italic>κ </jats:italic>index for the Fe <jats:sc>xvi</jats:sc> 262.976 Å line at 3 MK takes values of 3–5. In the corona, close to a low-energy HXR source, the Fe <jats:sc>xxiii</jats:sc> 263.760 Å line at 15 MK shows <jats:italic>κ</jats:italic> values of typically 4–7. The observed trends in the <jats:italic>κ</jats:italic> parameter show that we are most likely detecting the properties of the ion population rather than any instrumental effects. We calculate that a non-thermal ion population could exist if locally accelerated on timescales ≤0.1 s. However, observations of net redshifts in the lines also imply the presence of plasma downflows, which could lead to bulk turbulence, with increased non-Gaussianity in cooler regions. Both interpretations have important implications for theories of solar flare particle acceleration.</jats:p>