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Ion Temperature Diagnostics at the Off-limb Coronal Hole Boundary and Post-flare Loops and post-flare loops

Presentation #210.02 in the session Solar X-ray and VUV Spectra: Observation, Modeling and Planetary Atmospheric Impacts II.

Published onOct 20, 2022
Ion Temperature Diagnostics at the Off-limb Coronal Hole Boundary and Post-flare Loops and post-flare loops

Physical quantities, such as ion temperature and non-thermal velocity, provide critical information about the heating mechanism of the million-degree solar corona. We provide new constraints to ion temperatures using EUV line widths, only assuming that the plasma non-thermal velocity is the same for all ions. We perform our diagnostics on two very different coronal structures: a polar coronal hole boundary observed by Hinode/EIS and SOHO/SUMER, and post-flare loops observed by SUMER. The ion temperature is much higher than the local electron temperature at the coronal hole boundary. The measured ion temperature decreases with the charge-to-mass ratio to 0.25 and then slightly increases with the charge-to-mass ratio. We run the Alfvén Wave Solar Model-realtime (AWSoM-R) and the SPECTRUM module to validate the ion temperature diagnostic technique. We suggest that the differences in hot line widths (e.g., Fe XII, Fe XIII) are caused by the contamination from the background plasma. In the post-flare loops, we find significant flare-related Ly beta and Ly gamma emission enhancement in SUMER observations, allowing us to determine the proton/neutral hydrogen temperature log T = 6.6 in the lower solar corona. We also estimate ion temperature for other species in the post-flare loops and find that most ion temperatures are consistent with the electron temperature. Our study provides new constraints to the coronal heating and cooling models.

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