Temporal evolution of the relaxing loop. (a) Peak temperature (solid line) and average temperature (dashed) for x, y ∈ [ − 1.9, 1.9] Mm, z ∈ [ − 23, 23] Mm, together with the emission in Fe XII integrated over the same volume, i.e. essentially from the whole loop. (b) Blue: magnetic energy in excess of the energy of the potential (uniform, vertical) field during the simulation. Black solid line: spectral line width with line of sight parallel to the y-axis and viewing window with limits x ∈ [ − 1.9, 1.9] Mm, z ∈ [ − 23, 23] Mm. Black dashed line: line width with LOS parallel to the loop axis for z ∈ [10, 20] Mm and viewing window x ∈ [ − 2.3, 2.3], y ∈ [ − 2.6, 2.6] Mm. Dotted: thermal width of 21 km s⁻¹ at T = 1.5 × 10⁶ K.