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Context. Coronal heating is currently thought to proceed via the mechanism ofnanoflares, small-scale and possibly recurring heating events that releasemagnetic energy. Aims. We investigate the effects of a periodic high-energyelectron beam on the synthetic spectra of coronal Fe ions. Methods. Initially,the coronal plasma is assumed to be Maxwellian with a temperature of 1 MK. Thehigh-energy beam, described by a kappa-distribution, is then switched on everyperiod $P$ for the duration of P/2. The periods are on the order of severaltens of seconds, similar to exposure times or cadences of space-bornespectrometers. Ionization, recombination, and excitation rates for therespective distributions are used to calculate the resulting non-equilibriumionization state of Fe and the instantaneous and period-averaged syntheticspectra. Results. Under the presence of the periodic electron beam, the plasmais out of ionization equilibrium at all times. The resulting spectra averagedover one period are almost always multithermal if interpreted in terms ofionization equilibrium for either a Maxwellian or a kappa-distribution.Exceptions occur, however; the EM-loci curves appear to have a nearlyisothermal crossing-point for some values of kappa_s. The instantaneous spectrashow fast changes in intensities of some lines, especially those formed outsideof the peak of the respective EM(T) distributions if the ionization equilibriumis assumed.

Non-equilibrium ionization by a periodic electron beam. I. Synthetic coronal spectra and implications for interpretation of observations