TRANSITION REGION LINESHIFTS IN THE REBOUND SHOCK SPICULE MODEL

Spectral emission lines created in the solar chromosphere - corona tra nsition region show Doppler shifts indicating widespread plasma down-f lows. It has been proposed that this may be the result of the return o f spicular material. We simulate a spicule numerically using the rebou nd shock model and find that the resulting hydrodynamic evolution lead s to a perceived up-flow in transition region spectral lines even thou gh the average velocity in the line forming region is directed downwar d. The explanation for this apparent paradox is found in the correlati on between density and velocity in the waves generated by the rebound shock 'spicule'.