Differential Emission Measure Analysis of a Polar Coronal Hole During the Recent Solar Minimum
Abstract
We have performed a differential emission measure (DEM) analysis for a polar coronal hole observed during the solar minimum in 2007. The analysis was performed for the above-limb portions of five observations from the EUV Imaging Spectrometer on Hinode. The slit pointings also included quiet Sun corona near the boundary with the coronal hole. Our DEM analysis showed that none of the positions were completely isothermal. Instead the emitting material appeared to have a significant high-temperature tail and was consistent with being composed of two plasmas at different temperatures, as measured in K, of log T = 5.95 and log T = 6.15. The lower temperature peak was dominant in the coronal hole and the higher temperature peak dominant in the quiet Sun corona. We used our DEM curves to model isothermal analyses and found that relatively small deviations from isothermality can distort the results inferred using an isothermal analysis method. Isothermal temperature analyses actually measure a DEM-weighted average and can infer artificial temperature gradients if the high and low temperature parts of the DEM curve do not change uniformly with position. The isothermal analyses also do not detect different structures along the line-of-sight, which can affect the interpretation of density diagnostic line ratios.
- Publication:
-
AAS/Solar Physics Division Abstracts #42
- Pub Date:
- May 2011
- Bibcode:
- 2011SPD....42.1827H