Observations of Plasma Upflow in a Warm Loop with Hinode/EIS

TL;DR

This paper reports the first observations of plasma upflows in warm coronal loops at specific temperatures, revealing how upflow speeds decrease with height and temperature, supporting the chromospheric evaporation model.

Contribution

It provides new observational evidence of plasma upflows in warm coronal loops at multiple temperatures, enhancing understanding of loop heating mechanisms.

Findings

Upflows observed at loop footpoints with speeds around 20 km/s in Fe VIII.

Upflow speeds decrease with increasing temperature and height.

First evidence of plasma upflow in coronal loops at these temperature ranges.

Abstract

A complete understanding of Doppler shift in active region loops can help probe the basic physical mechanism involved into the heating of those loops. Here we present observations of upflows in coronal loops detected in a range of temperature temperatures (log T=5.8 - 6.2). The loop was not discernible above these temperatures. The speed of upflow was strongest at the footpoint and decreased with height. The upflow speed at the footpoint was about 20 km/s in Fe VIII which decreased with temperature being about 13 km/s in Fe X, about 8 km/s in Fe XII and about 4 km/s in FeXIII. To the best of our knowledge this is the first observation providing evidence of upflow of plasma in coronal loop structures at these temperatures. We interpret these observations as evidence of chromospheric evaporation in quasi-static coronal loops.