The Temperature and Density Structure of the Solar Corona. I. Observations of the Quiet Sun with the EUV Imaging Spectrometer (EIS) on Hinode

Abstract

Measurements of the temperature and density structure of the solar corona provide critical constraints on theories of coronal heating. Unfortunately, the complexity of the solar atmosphere, observational uncertainties, and the limitations of current atomic calculations, particularly those for Fe, all conspire to make this task very difficult. A critical assessment of plasma diagnostics in the corona is essential to making progress on the coronal heating problem. In this paper we present an analysis of temperature and density measurements above the limb in the quiet corona using new observations from the EUV Imaging Spectrometer (EIS) on \textit{Hinode}. By comparing the Si and Fe emission observed with EIS we are able to identify emission lines that yield consistent emission measure distributions. With these data we find that the distribution of temperatures in the quiet corona above the limb is strongly peaked near 1 MK, consistent with previous studies. We also find, however, that there is a tail in the emission measure distribution that extends to higher temperatures. EIS density measurements from several density sensitive line ratios are found to be generally consistent with each other and with previous measurements in the quiet corona. Our analysis, however, also indicates that a significant fraction of the weaker emission lines observed in the EIS wavelength ranges cannot be understood with current atomic data.

Submitted to ApJ

References in corpus (3)

• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
• Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode
• Static and Impulsive Models of Solar Active Regions

Cited by in corpus (15)

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• Evolution of microflares associated with bright points in coronal holes and in quiet regions
• The Role of High-frequency Transverse Oscillations in Coronal Heating
• Modeling Coronal Response in Decaying Active Regions with Magnetic Flux Transport and Steady Heating
• Electron Densities in the Solar Corona Measured Simultaneously in the Extreme-Ultraviolet and Infra-Red
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• The Slowly Varying Corona. II. The Components of F ${}_{10.7}$ and Their Use in EUV Proxies
• Quiet Sun electron densities and their uncertainties derived from spectral emission line intensities
• The Quiet-Sun DEM Under Kappa: Diagnostic Degeneracy and the Failure of the Conductive Closure