Probing Upflowing Plasma in Solar Coronal Holes to Categorise the most frequent Events

Abstract:

Coronal holes have many dynamic events in them, such as jets, plumes, and small filament eruptions. In addition, a class of jets has been observed [Young P., 2015] that are only visible in line-of-sight Doppler velocity measurements and tend to appear in the vicinity of coronal holes. In this work solar polar blue-shifted regions are explored and their sources classified. Doppler velocity maps are derived from the Fe XII 195.2Å emission line in Hinode/EIS measurements and analysed in combination with imaging data from SDO/AIA and SDO/XRT to characterise the regions of upflowing plasma. Of the analysed blue-shift events, some could be explained by weak standard jets, while other events are connected to small flaring bright points. Some blue-shift events do not leave any significant trace in the imaging instruments. Their contribution to the solar wind is unknown yet, however recent findings from Parker Solar Probe data show that there are frequent small-scale dynamics in the wind, even during quiet times [Bale S.D., Badman S.T., Bonnell J.W. et al., 2019]. These findings emphasise the importance of understanding all upflowing plasma events in coronal holes. Finally future Solar Orbiter observations of polar coronal holes, particularly during the out of ecliptic phase, are discussed.