Formation Heights of Extreme Ultraviolet Lines in an Active Region Derived by Correlation of Doppler Velocity and Magnetic Field

Abstract

We study the correlation heights, which indicate the formation height of Extreme Ultraviolet (EUV) lines in an active region using observations from the EUV Imaging Spectrometer (EIS) and Solar Optical Telescope (SOT) on board \emph{Hinode}. The nonlinear force-free field (NLFFF) optimization method is adopted to extrapolate the 3D magnetic fields to higher layers. Three subregions with different characteristics are selected in the active region for this study. The results show that the formation heights in different subregions vary with their different magnetic fields or velocity patterns. After solving the line blending problem between the He {\sc \romannumeral 2} 256.32 Åand Si {\sc \romannumeral 10} 256.37 Ålines by the double Gaussian curve fitting, we find that the transition region lies higher in a strong magnetic area. In a pre-flare heating area there possibly exist multithermal loops as implied by comparing the Doppler velocity and the magnetic field on the solar disk.

17 pages, 5 figures, 1 table, accepted for publication in ApJ

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Cited by in corpus (6)

• A Numerical Study of Long-Range Magnetic Impacts during Coronal Mass Ejections
• Different Patterns of Chromospheric Evaporation in a Flaring Region Observed with Hinode/EIS
• Solar transition region above sunspots
• Study on two Methods for Nonlinear Force-free Extrapolation Based on Semi-Analytical Field
• New views on the emission and structure of the solar transition region
• Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode