Turbulent Velocities and Ion Temperatures in the Solar Corona Obtained from SUMER Line Widths

Abstract

Turbulent plasma velocities and ion temperatures were determined from the line widths recorded by the Solar Ultraviolet Measurements of Emitted Radiation instrument on the Solar and Heliospheric Observatory spacecraft. From the widths of the lines of five light elements (Ne, Na, Mg, Si, and S) and a heavy element (Fe), it was possible to determine the contributions of turbulent plasma motion and ion thermal motion to the line widths. The results indicated that the turbulent velocity was approximately 22 km s Ϫ1 at 30Љ above the limb and decreased to less than 10 km s Ϫ1 at 109Љ and 209Љ above the limb. At 30Љ above the limb, the ion temperatures of the hotter lines were comparable to the electron temperatures for ionization equilibrium. The ion temperatures of the cooler lines were higher than the ionization equilibrium temperatures; at 109Љ and 209Љ above the limb, the ion temperatures were at least a factor of 2.5 higher than the ionization equilibrium temperatures.