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During transient events such as major solar eruptions, the plasma can be farfrom the equilibrium ionization state because of rapid heating or cooling.Non-equilibrium ionization~(NEI) is important in rapidly evolving systems wherethe thermodynamical timescale is shorter than the ionization or recombinationtime scales. We investigate the effects of NEI on EUV and X-ray observations bythe Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory andX-ray Telescope (XRT) on board Hinode. Our model assumes that the plasma isinitially in ionization equilibrium at low temperature, and it is heatedrapidly by a shock or magnetic reconnection. We tabulate the responses of theAIA and XRT passbands as functions of temperature and a characteristictimescale, $n_{e}t$. We find that most of the ions reach equilibrium at$n_{e}t\leq$10$^{12}$ cm$^{-3}$s. Comparing ratios of the responses betweendifferent passbands allows us to determine whether a combination of plasmas attemperatures in ionization equilibrium can account for a given AIA and XRTobservation. It also expresses how far the observed plasma is from equilibriumionization. We apply the ratios to a supra-arcade plasma sheet on 2012 January27. We find that the closer the plasma is to the arcade, the closer it is to asingle-temperature plasma in ionization equilibrium. We also utilize the set ofresponses to estimate the temperature and density for shocked plasma associatedwith a coronal mass ejection on 2010 June 13. The temperature and densityranges we obtain are in reasonable agreement with previous works.

Non-equilibrium ionization effects on solar EUV and X-ray imaging observations