Small-scale flows in SUMER and TRACE high-cadence co-observations

TL;DR

This study investigates small-scale transient flows in the solar atmosphere using high-cadence co-observations from SUMER spectrometer and TRACE imager, revealing diverse flow properties and emphasizing the importance of combined imaging and spectroscopic data.

Contribution

It provides new insights into the nature of transient solar phenomena by analyzing simultaneous high-resolution spectroscopic and imaging data, highlighting the complexity of flow velocities and temperatures.

Findings

Numerous transient flows observed in small-scale loops up to 30 Mm.

Flows have temperatures from 10,000 K to 250,000 K.

Some flows reach supersonic velocities and are associated with Doppler shifts.

Abstract

We report on the physical properties of small-scale transient flows observed simultaneously at high cadence with the SUMER spectrometer and the TRACE imager in the plage area of an active region. Our major objective is to provide a better understanding of the nature of transient phenomena in the solar atmosphere by using high-cadence imager and spectrometer co-observations at similar spatial and temporal resolution. A sequence of TRACE Fe IX/X 171 A and high-resolution MDI images were analysed together with simultaneously obtained SUMER observations in spectral lines covering a temperature range from 10 000 K to 1 MK. We reveal the existence of numerous transient flows in small-scale loops (up to 30 Mm) observed in the plage area of an active region. These flows have temperatures from 10 000 K (the low temperature limit of our observations) to 250 000 K. The coronal response of these features is uncertain due to a blending of the observed coronal line Mg X 624.85 A. The duration of the events ranges from 60 s to 19 min depending on the loop size. Some of the flows reach supersonic velocities. The Doppler shifts often associated with explosive events or bi-directional jets can actually be identified with flows (some of them reaching supersonic velocities) in small-scale loops. Additionally, we demonstrate how a line-of-sight effect can give misleading information on the nature of the observed phenomena if only either an imager or a spectrometer is used.