A study of line widths and kinetic parameters of ions in the solar corona

TL;DR

This study analyzes EUV emission lines from ions in the solar polar corona, revealing a strong linear correlation between line widths and ion mass, and estimating plasma temperature and non-thermal velocities.

Contribution

It demonstrates a linear relationship between line width parameters and ion mass, providing new insights into coronal ion kinetic properties.

Findings

Strong linear correlation between $(\sigma/\lambda)^2$ and $M^{-1}$

Estimated coronal temperature around 2.8 MK at specified heights

Non-thermal velocities of approximately 21.6 km/s and 25.2 km/s at different heights

Abstract

Solar extreme-ultraviolet (EUV) lines emitted by highly charged ions have been extensively studied to discuss the issue of coronal heating and solar wind acceleration. Based on observations of the polar corona by the SUMER/SOHO spectrometer, this paper investigates the relation between the line widths and kinetic parameters of ions. It is shown that there exists a strongly linear correlation between two variables $(\sigma/\lambda)^2$ and $M^{-1}$, where $\sigma$, $\lambda$ and $M$ are the half-width of the observed line profile at $1/\sqrt{e}$, the wavelength and the ion mass, respectively. The Pearson product-moment correlation coefficients exceed 0.9. This finding tends to suggest that the ions from a given height of polar corona have a common temperature and a common non-thermal velocity in terms of existing equation. The temperature and non-thermal velocity are obtained by linear least-square fit. The temperature is around $2.8$ MK at heights of 57$''$ and 102$''$. The non-thermal velocity is typical 21.6 km s$^{-1}$ at height of 57$''$ and 25.2 km s$^{-1}$ at height of 102$''$.