Warren, HP; Ugarte-Urra, I; Doschek, GA; Brooks, DH; Williams, DR; (2008) Observations of active region loops with the EUV imaging spectrometer on Hinode. Astrophysical Journal Letters , 686 (2 PART 2) 10.1086/592960.
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Previous solar observations have shown that coronal loops near 1 MK are difficult to reconcile with simple heating models. These loops have lifetimes that are long relative to a radiative cooling time, suggesting quasisteady heating. The electron densities in these loops, however, are too high to be consistent with thermodynamic equilibrium. Models proposed to explain these properties generally rely on the existence of smaller scale filaments within the loop that are in various stages of heating and cooling. Such a framework implies that there should be a distribution of temperatures within a coronal loop. In this paper we analyze new observations from the EUV Imaging Spectrometer (EIS) on Hinode. EIS is capable of observing active regions over a wide range of temperatures (Fe viii-Fe xvii) at relatively high spatial resolution (1"). We find that most isolated coronal loops that are bright in Fe xii generally have very narrow temperature distributions (σ ≤ 3 × 10 K), but are not isothermal. We also derive volumetric filling factors in these loops of approximately 10%. Both results lend support to the filament models. © 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A.
|Title:||Observations of active region loops with the EUV imaging spectrometer on Hinode|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics|
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