Astronomy & Astrophysics

All Figures

$\begin{figure} {\epsfig{file=H4311f1.eps,width=8.8cm,angle=0,clip=0} } \end{figure}$ Figure 1: Sequence of TRACE 173 Å negative images of the active region. Many loops are visible. The images are plotted with the same intensity scale, and show that the loops were stationary during the whole period of the CDS observation.
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In the text

$\begin{figure} {\epsfig{file=fig2.eps,width=8.8cm,angle=0,clip=0} } \end{figure}$ Figure 2: Monochromatic images (negative) of the NIS observation. The loops are only seen in upper transition region lines (Mg VII, Ca X) emitted in the range Log T = 5.8-6.0, a clear indication of their isothermality.
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In the text

$\begin{figure} { \epsfig{file=4311f3a.eps,width=4.65cm,angle=0,clip=0 }\epsfig{f... ...0,clip=0 }\epsfig{file=fig3f.eps,width=4.65cm,angle=0,clip=0 } } \end{figure}$ Figure 3: From top to bottom: TRACE 173 and 195 Å negative images of the active region; the same images rebinned by a factor of 10 (each pixel $\rm size=5\hbox {$^{\prime \prime }$ }$ ); the CDS images in Mg IX and Fe XII; Note: 1) the strong similarities between the TRACE 173 Å and CDS Mg IX, which confirm: a) the lines that contribute to the 173 Å band are emitted over similar temperatures as Mg IX; b) the CDS spatial resolution is approximately 5 $^{\prime \prime }$ . 2) The almost complete absence of loop emission in the TRACE 195 Å image. 3) The presence of structures in the TRACE 195 Å image that cannot be attributed to Fe XII emission.
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In the text

$\begin{figure} {\epsfig{file=H4311f4.eps,width=8.8cm,angle=0,clip=0 } } \end{figure}$ Figure 4: The areas selected to obtain average spectra in the loop (marked in white) and in the background (marked in black), projected on the TRACE image. Also shown is the area selected to show profiles of count rates across the loop.
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In the text

$\begin{figure} {\epsfig{file=H4311f5.eps,angle=90,width=8.8cm,clip=0 } } \end{figure}$ Figure 5: The profile of the TRACE count rates across the loop, close to area C (see Fig. 4). Over-plotted with a dashed line is the 173 Å intensity profile that would be expected from a circular cross-section with constant density and a width of 8 $^{\prime \prime }$ . Note the small difference in the loop and background signal, in particular for the 195 Å band.
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In the text

$\begin{figure} { \epsfig{file=H4311f6_1.ps,width=2.9cm,height=3.7cm,clip=0 }\eps... ... }\epsfig{file=H4311f6_12.ps,width=2.8cm,height=3.7cm,clip=0 } } \end{figure}$ Figure 6: Sample averaged spectra (photon-events vs. wavelengths in Å) for the loop area (above) and background (below) of region B (see Fig. 4). Note that the intensity of the spectral lines formed above 1 MK are almost the same in the loop and background regions, indicating that most of the emission is in the background. Also note in the loop area the large increase in the emission of lines formed in the 0.7-0.9 MK range (e.g.: Mg VII, Si VIII, Mg IX). The lines shown have been used for density, emission measure and elemental abundance estimates.
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In the text

$\begin{figure} { \epsfig{file=H4311f7_1.ps,angle=90,width=4.2cm,clip=0 }\epsfig{... ...ip=0 }\epsfig{file=H4311f7_10.ps,angle=90,width=4.2cm,clip=0 } } \end{figure}$ Figure 7: The emission measure curves obtained from the background-subtracted line intensities of the loop (left) and those of the background (right), for the regions A-E. The ionization equilibrium calculations of Arnaud & Rothenflug (1985) have been used, with the coronal abundances of Feldman (1992). The lines plotted here are listed in Table 1. The curves in loop regions A, B with lowest T are due to O V. They should be regarded as upper limits, since this line in off-limb spectra is blended (see Del Zanna et al. 2001a).
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In the text

$\begin{figure} {\epsfig{file=H4311f8.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$ Figure 8: Top: simulated spectra for the region C (background-subtracted) in the TRACE 173 Å band (the TRACE effective area, rescaled, is shown with a dashed line). Bottom: simulated spectra folded with the TRACE effective area.
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In the text

$\begin{figure} {\epsfig{file=H4311f9.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$ Figure 9: Same as Fig. 8 for the 195 Å band.
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In the text

$\begin{figure} {\epsfig{file=H4311f10_1.ps,angle=90, width=8.8cm,clip=0 } } {\epsfig{file=H4311f10_2.ps,angle=90, width=8.8cm,clip=0 } } \end{figure}$ Figure 10: A comparison of various ionization equilibrium calculations for Fe VIII and Fe IX.
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In the text

$\begin{figure} {\epsfig{file=H4311f11.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$ Figure 11: The TRACE responses, calculated at constant emission measure by folding the CHIANTI V.4 emissivities with the TRACE effective areas, using a set of standard parameters. For comparison, the standard TRACE responses, available via Solarsoft (SSW) and calculated with CHIANTI V.2 are displayed.
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In the text

$\begin{figure} {\epsfig{file=H4311f12.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$ Figure 12: The TRACE 195/173 Å ratio calculated using different ionization balance calculations (MAZZ_98: Mazzotta et al. 1998; ARO_85: Arnaud & Rothenflug 1985). The standard ratio values available within Solarsoft (SSW) are also displayed for comparison. Note the large differences between the current SSW values and the new ones, the uncertainty associated with the use of different ionization balances and the multi-value character of the ratio.
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In the text

$\begin{figure} {\epsfig{file=H4311f13.ps, width=8.8cm,angle=0,clip=0} } \end{figure}$ Figure 13: The areas selected to obtain average TRACE count rates of the loop and background.
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In the text

$\begin{figure} {\epsfig{file=H4311f14_1.ps,width=8.8cm,angle=0,clip=0 } } {\epsfig{file=H4311f14_2.ps,angle=90,width=8.8cm,clip=0 } } \end{figure}$ Figure 14: Top two plots: the TRACE 173, 195 Å averaged count rates of the loop (crosses, with error bars) and background (circles) areas displayed in Fig. 13. Bottom plot: the TRACE 195/173 Å ratios obtained with the above count rates. Note the large effect that background subtraction has. The ratios values in the 110-140 $^{\prime \prime }$ region are contaminated by the presence of a weak interconnecting loop.
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In the text

$\begin{figure} {\epsfig{file=H4311f15.ps, width=8.8cm,angle=0,clip=0} } \end{figure}$ Figure 15: From top to bottom: the assumed model densities and temperatures (solid lines), with the measured values (see Table 2) over-plotted; the peak TRACE 173 Å count rates with the predicted values; the observed and calculated intensities of some CDS lines along the leg of the loop. For both TRACE and CDS the loop values (filled circles) and the corresponding background-subtracted values (open squares) are plotted. The solid lines are the values calculated with the Arnaud & Rothenflug (1985), while the dashed ones are calculated with the Mazzotta et al. (1998) ion balance.
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In the text

$\begin{figure} {\epsfig{file=H4311f1.eps,width=8.8cm,angle=0,clip=0} } \end{figure}$	Figure 1: Sequence of TRACE 173 Å negative images of the active region. Many loops are visible. The images are plotted with the same intensity scale, and show that the loops were stationary during the whole period of the CDS observation.
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$\begin{figure} {\epsfig{file=fig2.eps,width=8.8cm,angle=0,clip=0} } \end{figure}$	Figure 2: Monochromatic images (negative) of the NIS observation. The loops are only seen in upper transition region lines (Mg VII, Ca X) emitted in the range Log T = 5.8-6.0, a clear indication of their isothermality.
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$\begin{figure} {\epsfig{file=H4311f4.eps,width=8.8cm,angle=0,clip=0 } } \end{figure}$	Figure 4: The areas selected to obtain average spectra in the loop (marked in white) and in the background (marked in black), projected on the TRACE image. Also shown is the area selected to show profiles of count rates across the loop.
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$\begin{figure} {\epsfig{file=H4311f5.eps,angle=90,width=8.8cm,clip=0 } } \end{figure}$	Figure 5: The profile of the TRACE count rates across the loop, close to area C (see Fig. 4). Over-plotted with a dashed line is the 173 Å intensity profile that would be expected from a circular cross-section with constant density and a width of 8 $^{\prime \prime }$ . Note the small difference in the loop and background signal, in particular for the 195 Å band.
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$\begin{figure} {\epsfig{file=H4311f8.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$	Figure 8: Top: simulated spectra for the region C (background-subtracted) in the TRACE 173 Å band (the TRACE effective area, rescaled, is shown with a dashed line). Bottom: simulated spectra folded with the TRACE effective area.
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$\begin{figure} {\epsfig{file=H4311f9.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$	Figure 9: Same as Fig. 8 for the 195 Å band.
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$\begin{figure} {\epsfig{file=H4311f10_1.ps,angle=90, width=8.8cm,clip=0 } } {\epsfig{file=H4311f10_2.ps,angle=90, width=8.8cm,clip=0 } } \end{figure}$	Figure 10: A comparison of various ionization equilibrium calculations for Fe VIII and Fe IX.
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$\begin{figure} {\epsfig{file=H4311f11.ps, width=8.8cm,angle=0,clip=0 } } \end{figure}$	Figure 11: The TRACE responses, calculated at constant emission measure by folding the CHIANTI V.4 emissivities with the TRACE effective areas, using a set of standard parameters. For comparison, the standard TRACE responses, available via Solarsoft (SSW) and calculated with CHIANTI V.2 are displayed.
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$\begin{figure} {\epsfig{file=H4311f13.ps, width=8.8cm,angle=0,clip=0} } \end{figure}$	Figure 13: The areas selected to obtain average TRACE count rates of the loop and background.
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