All Figures

Figure 1: Total line intensity maps ( first, third rows) and the corresponding Dopplergrams ( second and fourth rows) in O  V 630 Å (maximum ion concentration at 250 000 K), showing the evolution of the active region. The segments A and B in panels 2 and 3 show the selected loop. The loop evolution in panels 2 and 3 of the first row and the corresponding Dopplergrams indicate that the loop is replenished from its northern footpoint by a unidirectional flow. The first row images indicate proper motions of the order of  km s-1. The pattern of the loop remains roughly unchanged from 09:02 to 09:55 UT. The loop is fainter in the 09:56-10:06 UT raster and disappears in the 10:06-10:17 UT one. The Dopplergrams show a constant flow pattern along the loop for all its life time. We used a logarithmic scale for the intensities to enhance the loop contrast.

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In the text

Figure 2: A thorough study of the loop in O  V  630 Å. In panel 1, crosses are the sampling points along the loop and diamonds are the corresponding background ones. Panel 2 shows one spectral profile taken on the loop and the corresponding background one (dispersion axis is in km s-1). Panel 3 is the loop profile of panel 2 after the subtraction of the background profile. The smooth line is computed by the fitting procedure and estimates the total intensity and Doppler shift. Panel 4 shows the Doppler shift along the loop (starting from the northern footpoint). Panel 5 shows the flux emitted from the loop plasma along the loop in physical units. The two arrows in panels 4 and 5 indicate the Doppler shift and intensity values derived from the individual spectral profile of panel 3.

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In the text

Figure 3: Images from all spectral lines, observed during 6 rasters, ordered by increasing temperature of maximum ion concentration. The Mg  IX and Fe  XVI images co-alignment was corrected to account for the spatial offset between NIS-1 (308-379 Å) and NIS-2 (513-633 Å) parts of the CDS detector. The loop seems co-aligned in the O  V 630 Å, Ne  VI 563 Å and Mg  IX 368 Å spectral lines. However, the loop evolution is similar in the O  V and Ne  VI lines, while this is not the case for the Mg  IX line. As in Fig. 1 the unidirectional flow is evident by comparing the individual images in O  V and Ne  VI.

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In the text

	Figure 4: Intensity images of the O  V 630 Å, Ne  VI 563 Å and Mg  IX 368 Å lines, (09:13-09:23 UT) with the contours of O  V 630 Å line superimposed. Whereas the O  V contours match well the Ne  VI image, they match only part of the Mg  IX loop. Furthermore, the Mg  IX loop apex seems shifted to the right relative to the O  V contours.
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In the text

Figure 5: In panel 1, the emission measures for O  V  630 Å, Ne  VI 562 Å and Mg  IX 368 Å for a given part of the loop are plotted as functions of temperature. The loop plasma temperature is estimated at the crossing point between the O  V and Ne  VI curves. The dashed lines show the effect of the uncertainties discussed in Sect. 3.1. They produce two extreme crossing points for the emission measure curves and are translated to error bars on the temperature. Panel 2 shows the derived temperature along the loop. The arrow points to the temperature measurement presented in panel 1.

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In the text

Figure 6: A summary of the measurements we carried out along the loop, fitted with the MHD model. The data are represented as diamonds with their error bars and the MHD computations are the full lines. Here, the modelled flow is projected along the LOS so that we can compare with the data. In panel 2, the temperatures were constrained using the Emission Measure curves (see Fig. 5). Panel 3 shows the computed electron density along the loop. The computed temperatures and electron densities are used to compute the intensity in the O  V spectral line, which is compared with the observed one in panel 4. In panel 5, where we do not have any data measurements, we present the terms of the energy balance along the loop. The heating is the resulting energy from the balance of the other terms. Note that the conductive losses are very small in the scale of panel 5.

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In the text