Jets or High-Velocity Flows Revealed in High-Cadence Spectrometer and Imager Co-observations?

Abstract

We report on active region EUV dynamic events observed simultaneously at high cadence with SOHO SUMER and TRACE. Although the features appear in the TRACE Fe IX/X 171 Å images as jets seen in projection on the solar disk, the SUMER spectral line profiles suggest that the plasma has been driven along a curved large-scale magnetic structure, a preexisting loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 10⁴ to 10⁶ K. The spectral analysis revealed that a sudden heating from an energy deposition is followed by a high-velocity plasma flow. The Doppler velocities were found to be in the range from 90 to 160 km s^-1. The heating process has a duration which is below the SUMER exposure time of 25 s while the lifetime of the events is from 5 to 15 minutes. The additional check on soft X-ray Yohkoh images shows that the features most probably reach 3 MK (X-ray) temperatures. The spectroscopic analysis showed no existence of cold material during the events.