Departure of high temperature iron lines from the equilibrium state in flaring solar plasmas

The aim of this study is to clarify if the assumption of ionization equilibrium and a Maxwellian electron energy distribution is valid in flaring solar plasmas. We analyze the 2014 December 20 X1.8 flare, in which the \ion{Fe}{xxi} 187~\AA, \ion{Fe}{xxii} 253~\AA, \ion{Fe}{xxiii} 263~\AA\ and \ion{Fe}{xxiv} 255~\AA\ emission lines were simultaneously observed by the EUV Imaging Spectrometer onboard the Hinode satellite. Intensity ratios among these high temperature Fe lines are compared and departures from isothermal conditions and ionization equilibrium examined. Temperatures derived from intensity ratios involving these four lines show significant discrepancies at the flare footpoints in the impulsive phase, and at the looptop in the gradual phase. Among these, the temperature derived from the \ion{Fe}{xxii}/\ion{Fe}{xxiv} intensity ratio is the lowest, which cannot be explained if we assume a Maxwellian electron distribution and ionization equilibrium, even in the case of a multi-thermal structure. This result suggests that the assumption of ionization equilibrium and/or a Maxwellian electron energy distribution can be violated in evaporating solar plasma around 10MK.

Stories from the Inside:The Prisons Memory Archive

A close textual reading of the online-available recording of ex-prison officer, John Heatherington, who is filmed as he returns to the site of the Maze and Long Kesh Prison, which was the largest prison oeperating during the Troubles in Northern Ireland. Using the empty site as stimulant for his memory, John recalls the tension, violence and dark humour of the period, while also showing exceptional empathy for all those, including prisoners, who passed through the prison system.The interview is taken from the Prisons Memory Archive (www.prisonsmemoryarchive.com) and, as director of the PMA, I have a particular insight to the recording process and John's special contribution to it.