First Solar Orbiter observation of an Alfvenic slow wind stream

Alfvénic turbulence, dominated by large-amplitude Alfvénic fluctuations mainly propagating away from the Sun, is a feature characterizing not only the high-speed streams but also some slow wind intervals. Within this framework, the present study focuses on an Alfvénic slow solar wind stream observed by Solar Orbiter in July 2020 at a heliocentric distance of 0.64 AU. Using data collected from the Solar Wind Analyzer (SWA) and the Magnetometer (MAG), we provide a fully description of this stream from many respects identifying different regions within the stream characterized by distinct features using different indicators and including also a spectral analysis to highlight spectral features and waves signature. In addition, we pinpoint several structures at different scales recalling the spaghetti-like flux-tube texture of the interplanetary magnetic field and we reconstruct the Solar Orbiter magnetic connectivity to the solar sources both via a ballistic and a potential field source surface (PFSS) model. The characterization of the Alfvénic slow wind stream observed by Solar Orbiter and the identification of its solar source are extremely important for improving the understanding of future observations of the same solar wind regime and the general problem of solar wind acceleration. This is particularly relevant for upcoming Solar Orbiter observations as solar activity is increasing toward a maximum, where a higher incidence of this solar wind regime has been observed over previous solar cycles.