The Extreme Ultraviolet Imaging Spectrometer (EIS) on board Hinode provides us with an excellent opportunity to study the physical parameters in spatially resolved coronal structures. In this paper we have carried out a study of active region loops using observations from the EIS. The active region was observed on 2007 Ma 19 using the 1 arcsec slit of EIS. At coronal temperatures, we find that electron densities measured from Fe XII and Si X line ratios decrease along the loop length, being ≈10100 cm-3 at foot point and ≈108.5 cm-3 at a height of about 75 Mm. However, the electron densities measured from the Mg VII line ratios (at a transition region temperature) show significantly lower values at the foot point. The electron temperature along the loop increases with height from ≈0.8 MK (at foot point) to ≈1.5 MK (at a height of 75 Mm). The temperature diagnostics using EM-loci at different locations along the loop show that the loop is ``nearly isothermal'' or ``mildly multi-thermal'' along the LOS. These measurements provide important constraints on the theoretical modelling of coronal loops.
The Second Hinode Science Meeting: Beyond Discovery-Toward Understanding
- Pub Date:
- December 2009