List of Figures

View Image Figure 1:
Images of the same active region, taken in the EUV band with TRACE (top) and in the X-ray band with Hinode/XRT (bottom), on 14 November 2006. The X-ray image shows more clearly that the active region is densely populated with coronal loops.
View Image Figure 2:
The X-ray corona contains loops with different spatial scales, e.g., bright points (BP), active region loops (AR), large scale structures (LSS). Credit: Yohkoh mission, ISAS, Japan.
View Image Figure 3:
Coronal loops have approximately a semicircular shape. Image: SDO/AIA, 171 A filter, 9 July 2010. Credit: NASA/SDO.
View Image Figure 4:
Magnetic field lines extrapolated from optical magnetogram superposed on a TRACE image. Credit: NASA/ESA/LMSAL.
View Image Figure 5:
TRACE image including a system of coronal loops (9 November 2000, 2 UT). Bundles of strands are clearly visible.
View Image Figure 6:
Temperature map of an active region obtained from the ratio of two images in different broadband filters with Hinode/XRT (12 November 2006, 12 UT).
View Image Figure 7:
EM-loci plots for two different loop systems, one showing a multi-thermal structure (top, from Schmelz et al., 2005, reproduced by permission of the AAS), the other an almost isothermal one (bottom, from Di Giorgio et al., 2003). The EM is per unit area in the top panel.
View Image Figure 8:
Loop system observed in several EUV spectral lines with Hinode/EIS (19 May 2007, 11:41 – 16:35 UT). The loops become less and less contrasted, i.e., fuzzier and fuzzier, at higher and higher temperature (courtesy of D. Tripathi).
View Image Figure 9:
X-ray light curve observed with the SXI telescope on board GOES. The loop lifetime is much longer than the characteristic cooling times (courtesy of J.A. Klimchuk and M.C. Lòpez Fuentes).
View Image Figure 10:
Monochromatic (negative) images and dopplergrams (km s–1) of an active region (NOAA 10926) observed with Hinode/EIS in Fe viii, Fe xii, Fe xv lines (courtesy of G. Del Zanna).
View Image Figure 11:
The plasma confined in a loop can be described with one-dimensional hydrodynamic modeling, with a single coordinate (s) along the loop (image: TRACE, 6 November 1999, 2 UT).
View Image Figure 12:
Emission in two TRACE filterbands predicted by a model of loop made by several thin strands (from Reale and Peres, 2000).
View Image Figure 13:
Distributions of temperature, density, and pressure along a hydrostatic loop computed from the model of Serio et al. (1981) for a high pressure loop (AR) and a low pressure one (Empty) with heating uniformly distributed along the loop.
View Image Figure 14:
Scheme of the evolution of temperature (T, thick solid line), X-ray emission, i.e., the light curve (LC, thinner solid line) and density (n, dashed line) in a loop strand ignited by a heat pulse. The strand evolution is divided into four phases (I, II, III, IV, see text for further details) (from Reale, 2007).
View Image Figure 15:
Scheme of the evolution of pulse-heated loop plasma of Figure 14 in a density-temperature diagram (solid line). The four phases are labeled. The locus of the equilibrium loops is shown (dashed-dotted line, marked with QSS), as well as the evolution path with an extremely long heat pulse (dashed line) and the corresponding decay path (marked with EQ) (adapted from Reale, 2007).
View Image Figure 16:
Pressure evolution obtained from a hydrodynamic simulation of a loop strand ignited by heat pulses of different duration (0.5, 1, 3 times the loop decay time, see text) and with a continuous heating. Most of the rise phase can be reasonably described with a linear trend (dashed lines) (from Reale, 2007).
View Image Figure 17:
Example of solutions of a siphon flow loop model including a shock (from Orlando and Peres, 1999).