Speaker
Description
First Name: Mario
Last Name: Roco-Moraleda
Affiliation: Max Planck Institute for Solar System Research
All Authors: Mario Roco-Moraleda, Luca Teriaca, Pradeep Chitta, Hardi Peter, Sami K. Solanki
Abstract: Coronal holes have been known since decades to be the main source regions of the fast solar wind by correlating in situ particle speed measurements to their presence on the solar disk. In addition, past spectroscopic measurements within coronal holes have revealed persistent blue shifts in coronal spectral lines of the order of about 10 km/s that have been interpreted as a signature of the emerging solar wind. Recent very high-resolution observations from the HRIEUV telescope of the EUI instrument on Solar Orbiter show evidence that the fast solar wind and the Alfvénic slow wind originate from largely unipolar, open field region characterized by low emission in coronal lines (T = 1 MK). Those observations reveal widespread picoflare jets with plane-of-sky (PoS) speeds of 100-150 km/s, possessing kinetic energy content in the range of 10^21-10^24 erg, emerging from coronal holes. These PoS measurements seems to be difficult to reconcile with the Doppler shift measurements of only 10 km/s at the base of the corona. However, excess emission in the blue wing of the line might be the signature of the high-speed apparent upflows seen when imaging small jets in EUV observations. Here, we revisit high quality SUMER observations of an on-disk equatorial coronal hole. We perform a very accurate wavelength calibration and analysis of the spectral profiles with the aim at detecting signature of high-speed flows in the spectral profile of the Ne VIII 77.0428 nm line (formed around 0.6 MK) observed in the second order of diffraction. Our analysis reveals the importance of a proper evaluation of blends from first order lines and our results challenge some of our understanding of Doppler shift at the base of the corona in coronal holes.