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Abstract: The relationships among coronal loop structures at different temperatures isnot settled. Previous studies have suggested that coronal loops in the core ofan active region are not seen cooling through lower temperatures and thereforeare steadily heated. If loops were cooling, the transition region would be anideal temperature regime to look for a signature of their evolution. TheExtreme-ultraviolet Imaging Spectrometer EIS on Hinode provides monochromaticimages of the solar transition region and corona at an unprecedented cadenceand spatial resolution, making it an ideal instrument to shed light on thisissue. Analysis of observations of active region 10978 taken in 2007 December 8- 19 indicates that there are two dominant loop populations in the activeregion: core multi-temperature loops that undergo a continuous process ofheating and cooling in the full observed temperature range 0.4-2.5 MK and evenhigher as shown by the X-Ray Telescope XRT; and peripheral loops which evolvemostly in the temperature range 0.4-1.3 MK. Loops at transition regiontemperatures can reach heights of 150 Mm in the corona above the limb anddevelop downflows with velocities in the range of 39-105 km-s.



Author: Ignacio Ugarte-Urra, Harry P. Warren, David H. Brooks

Source: https://arxiv.org/







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