Modelling explosive events in the solar atmosphere

High–resolution ultraviolet (UV) spectra of the outer solar atmosphere show transient brightenings often referred to as explosive events. These are localized regions of small spatial extent that show sudden enhancements in the intensities of lines formed between 20,000 and 200,000 K, accompanied by strong non-gaussian profiles. The present work is an attempt to extract observational consequences from computational simulations of the dynamic response of a coronal loop to energy perturbations. Explosive events are simulated in semi-circular magnetic flux tubes. Thermal energy perturbations drive flows along the flux tube giving rise to thermodynamic phenomena. The temporal evolution of the thermodynamic state of the loop is converted into C iv λ 1548.2 Å line profiles in (non)-equilibrium ionization. Time dependent carbon ion populations are obtained in the nonequilibrium conditions derived from the thermodynamic variables by means of an adaptive grid code. Most important, departures from ionization equilibrium are assessed for the first time under conditions such as those encountered in explosive events.