On the Relation between the In Situ Properties and the Coronal Sources of the Solar Wind

Abstract

Abstract We categorize the types of solar wind using a new classification scheme based on the location of the wind’s coronal source regions in the solar atmosphere and near-solar heliosphere. We first trace the solar wind measured by ACE/SWEPAM and SWICS from 1998 to 2011 at 1 au back to a 2.5 R s solar surface using ballistic mapping at constant proton speed; then we map them back to their magnetic footpoints on the 1 R s solar surface via the potential field source surface (PFSS) model. Coronal structures are identified using a classification scheme based on the pixel brightness in the SOHO or STEREO EUV Carrington images. The angular distances between each mapped solar wind footpoint to the different coronal structure pixels are calculated and used as a criterion to identify the type of solar wind source region. Depending on the proximity of the solar wind footpoints to a given coronal or heliospheric structure, we classify the solar wind into six types: active region (AR), AR-boundary, quiet Sun (QS), coronal hole (CH), CH-boundary, and helmet-streamer associated wind. The in situ properties of these six types of solar winds are then examined and compared, and their solar cycle dependences are also discussed.