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tokens: the far off-limb region but give a hint of slight increase in the velocity up to 1.3 R ⊙ . Fig. 12. Effective velocity (combined thermal and non-thermal velocity) obtained along the coronal loop from various spectral lines as labelled. In Fig. 13 , we plot the non-thermal velocities ( ξ ) obtained from Fe X 184.54, Fe XI 188.23, Fe XII 193.51, and Si X 258.37 Å spectral lines. For this purpose, we incorporated electron temperature T e obtained in Sect. 3.3 to calculate the thermal velocity. Again Fe XII 193.51 Å, the strongest line, shows almost constant non-thermal velocity with height. Other lines show some increasing trend in the non-thermal velocity with height, however, the data points are highly scattered. The average non-thermal velocity, as obtained from Fe XII 193.51 Å is ≈23 km s −1 . Si X 258.37 Å shows an average value of ≈30 km s −1 with some increase with height. However, non-thermal velocities from Fe X 184.54, and Fe XI 188.23 Å show relatively lower values. Interestingly, Del Zanna et al. (2018b) have noted that the instrumental width for Fe XII 193.5 Å line appears to be constantly larger than that of the other lines. They also noticed the overestimation in line widths from Fe XII 193.51 Å line, which is partly due to instrumental issues and partly due to opacity effects in the stronger lines of Fe XII based on line ratio of Fe XII λ 193.51/ λ 195.12. However, in our coronal loop, deviation of line ratio is within 10% (see Fig. 6 ). Thus, non-thermal velocity estimation from Fe XII 193.51 Å is mildly affected. Fig. 13. Non-thermal velocity obtained along the coronal loop from various spectral lines as labelled. 3.6. Alfvén wave energy flux The Alfvén wave energy flux density is given by where ρ is mass density ( ρ = m p N e , m p is proton mass, and N e is electron number density), ξ is Alfvén wave velocity amplitude, 2 for two degrees of freedom, and V A is Alfvén wave propagation velocity given as . Therefore, the total Alfvén wave energy crossing a surface area A per unit time is given by Henceforth, the total Alfvén wave energy propagating along the loop depends on the electron number density, wave amplitude, magnetic field, and area of cross section. However, the product of magnetic field B and cross-section area A is always a constant along the loop owing to magnetic flux conservation. Therefore, the total Alfvén wave energy propagating along the loop is always proportional to . The product of is expected to be constant with height if the total Alfvén wave energy is conserved as wave propagates along the loop. Thus, we obtain the proportional Alfvén wave energy () along the loop using the N e (see Sect. 3.2 ) and ξ (see Sect. 3.5 ) obtained from Fe XII spectral lines. In Fig. 14 , we plot variations of with height. The plot shows that decreases with height. Thus this provides evidence of damping of Alfvén wave energy with height along the coronal loop, although associated error bars are very large on individual data