New insight into transition region dynamics via SUMER observations and numerical modelling

We explore the idea that the occurrence of nanoflares in a magnetic loop ar ound the O VI formation temperature could explain the observed red-shift of mid-low transition region lines as well as the blue-shift observed in low coronal lines (T > 6 x 10(5) K). Observations are compared to numerical sim ulations of the response of the solar atmosphere to an energy perturbation of 4 x 10(24) ergs representing an energy release during magnetic reconnect ion in a I-D semi-circular flux tube. The temporal evolution of the thermod ynamic state of the loop is converted into C IV 1548, O VI 1032 and Ne VIII 770 line profiles in non-equilibrium ionization. Performing an integration over the entire period of simulations, a redshift of similar to 6 km s(-1) is found in C Iv, while a blue-shift of similar to 2 km s(-1) and similar to 10 km s(-1) were derived for O VI and Ne vIII, respectively, in reasonab le agreement with observations.