Coronal response of bi-directional jets

EUV bi-directional jets are a prominent class of phenomena characterizing the solar transition region. Using simultaneously obtained SUMER observations in the chromospheric Si II 1251.16 Angstrom and C I 1251.17 Angstrom transition region N v 1238.8 Angstrom and coronal Mg X 625 Angstrom lines we show an example of a bi-directional jet observed in the chromospheric and the transition region lines but not showing any detectable signature in the coronal line. The phenomenon, however, was also clearly detected by the TRACE imager with the 171 Angstrom filter. This discrepancy is explained here with a non-Maxwellian electron distribution which makes a significant fraction of the plasma in the TRACE 171 Angstrom pass-band to be derived from temperatures around approximate to300 000 K, as opposed to approximate to800 000 K. This could have implications for other phenomena observed in the TRACE pass-bands, including the transition region 'moss' and the 3- and 5-min oscillations.