Variation of temperature and non-thermal velocity with height in fan loops

Abstract

ABSTRACT We study the variation of temperature and non-thermal velocity with height in fan loops. For this purpose, we have used the observations recorded by the Extreme Ultraviolet Imaging Spectrometer onboard Hinode. We have employed the emission measure (EM)-loci method to estimate the temperatures of different coronal fan loops and then compute the non-thermal velocities using the obtained temperatures in Si vii 275.35 Å and Fe viii 185.21 Å lines. The EM-loci analysis provides nearly iso-thermal temperature along the fan loops. We obtain the peak temperatures in the range $\log \, T(K)$  = 5.85–5.95 for fan loops, and the subtraction of thermal broadening gives the non-thermal velocities in the range ≈5–15 and 11–29 km s−1 for Si vii 275.35 Å and Fe viii 185.21 Å, respectively. Our method provides quantitative accuracy in the measurement of non-thermal velocity, which is an important parameter in understanding the dynamics of heating of the solar atmosphere.