Search For Signatures of A Coronal Hole in Transition Region Lines Near Disk Center

摘要

The analysis of data taken by SUMER near disk center, where a small coronal hole is observed in EIT images, is performed. From the measurements of Doppler non-thermal velocities and intensities, we search for the diagnostics and the signature of small scale structures in the coronal hole using transition region lines. Transition region lines in the range of 7 X 10~4 K to 2.5 * 10~5 K have a non-thermal velocity excess of 4.0 to 5.5 km s~(-1) relative to the contiguous quiet Sun. While the average intensity is lower in the coronal hole than in the quiet area, this result shows an increase of turbulence at the base of the high speed solar wind.