Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode

Abstract

Observations of transition region emission in solar active regions represent a powerful tool for determining the properties of hot coronal loops. We present the analysis of new observations of active region moss taken with the Extreme Ultraviolet Imaging Spectrometer (EIS) on the Hinode satellite. EIS observations of a density sensitive Fe XII line ratio suggest moss densities of approximately 10¹⁰ cm^-3 and pressures of 3 × 10¹⁶ cm^-3 K. We find that the moss intensities predicted by steady, uniformly heated loop models are too intense relative to the observations, consistent with previous work. To bring the steady heating model into agreement with the observations a filling factor is required. Our analysis indicates that the filling factor in the moss is nonuniform and varies inversely with the loop pressure. The intensities predicted by steady uniform heating are generally consistent with the EIS moss observations. There are, however, significant discrepancies for the coolest emission line available in the data we analyze.