Jets or high velocity flows revealed in high-cadence spectrometer and imager co-observations?

TL;DR

This study combines high-cadence spectrometer and imager data to analyze active region EUV events, revealing high-velocity plasma flows along magnetic loops associated with rapid heating and temperature increases up to 3 MK.

Contribution

It provides detailed spectroscopic evidence of high-speed plasma flows and rapid heating in active region EUV events, linking imaging and spectral data for the first time.

Findings

Doppler velocities ranged from 90 to 160 km/s.

Heating duration was less than 25 seconds.

Events reached temperatures up to 3 million Kelvin.

Abstract

We report on active region EUV dynamic events observed simultaneously at high-cadence with SUMER/SoHO and TRACE. Although the features appear in the TRACE Fe ix/x 171A 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 pre-existing loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 10^4 K to 10^6 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. 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 min. 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.