Chromospheric evaporation as the driver of helium enrichment in active region solar wind: A case study

Context. The physical mechanisms of helium abundance ( A He ) depletion in the corona and solar wind are closely linked to coronal heating, solar wind origin, and acceleration processes. The relationships between the A He in the solar wind and the properties and activity of the source regions are crucial for understanding the depletion of A He . Aims. We aim to investigate the impact of active region (AR) activity and properties on the A He in the solar wind. Methods. First, we established the link between carefully selected ARs and the solar wind. Then, the AR chromospheric activity was quantitatively investigated using observations from the Atmospheric Imaging Assembly and Helioseismic Magnetic Imager on board the Solar Dynamics Observatory. The AR temperatures were derived with the differential emission measure method. We also statistically analyzed the A He in the solar wind with higher and lower charge states during solar cycles 23 and 24. The parameters of solar wind were measured by the instruments on board ACE and Wind. Results. We find that an AR with greater chromospheric activity has higher A He in its associated solar wind. The statistical analysis shows that the median A He in solar wind with higher charge states is higher than A He in solar wind with lower charge states. Conclusions. We conclude that chromospheric activity, primarily chromospheric evaporation processes, is possibly the main heating and transportation mechanism leading to a higher A He in the corona and solar wind. This could also reasonably explain the variation in A He in AR solar wind during different solar activity phases and the higher A He in AR solar wind compared to quiet Sun solar wind.