Alfvénicity of Quiet-Sun-associated Wind during Solar Maximum

Abstract

The quiet Sun (QS) and helmet streamer (STR) are generally considered to account for sources of slow solar wind with low Alfvénicity and low proton temperature. The solar wind with high Alfvénicity is often associated with coronal holes (CHs). Recently, the solar wind measured by the Advanced Composition Explorer spacecraft at 1 au was mapped back to its magnetic footpoints. Depending on the proximity of the solar wind footpoints to a given coronal or heliospheric structure, we classify solar winds into different types based on their sources: QS, STR, active region (AR), and CH. Here, we compare the properties of the solar winds originated from QS, STR, AR, and CH using 2 hr data. We find that at solar maximum 34% of the quiet-Sun-associated slow wind ( V SW < 450 km s −1 ) has high Alfvénicity ( ). This significantly higher proportion of Alfvénic fluctuations indicates that the quiet-Sun-associated wind at 1 au has similar properties as fast wind, which originates from the CH. Accordingly, we speculate that this type of solar wind at 1 au could come from open fields within the quiet-Sun region. This observational study will help us understand more about the coronal source regions of the solar wind in interplanetary space.