In Situ Measurements of the Variable Slow Solar Wind near Sector Boundaries

• Published in: The Astrophysical journal Vol. 882; no. 1; pp. 51 - 62
• Main Authors: Sanchez-Diaz, E., Rouillard, A. P., Lavraud, B., Kilpua, E., Davies, J. A.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.09.2019; IOP Publishing; American Astronomical Society
• Subjects: Astrophysics; Density; Earth and Planetary Astrophysics; Electrons; Fluctuations; Helmets; In situ measurement; Magnetic fields; Magnetic flux; Magnetic reconnection; Mass flux; Protective equipment; Proton density (concentration); Remote sensing; Sciences of the Universe; Slow solar wind; Smoothness; Solar and Stellar Astrophysics; Solar corona; Solar magnetic reconnection; Solar maximum; Solar wind; Statistical analysis; Streamer formation; Sun
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab341c

The release of density structures at the tip of the coronal helmet streamers, likely as a consequence of magnetic reconnection, contributes to the mass flux of the slow solar wind (SSW). In situ measurements in the vicinity of the heliospheric plasma sheet of the magnetic field, protons, and suprathermal electrons reveal details of the processes at play during the formation of density structures near the Sun. In a previous article, we exploited remote-sensing observations to derive a 3D picture of the dynamic evolution of a streamer. We found evidence of the recurrent and continual release of dense blobs from the tip of the streamers. In the present paper, we interpret in situ measurements of the SSW during solar maximum. Through both case and statistical analysis, we show that in situ signatures (magnetic field magnitude, smoothness and rotation, proton density, and suprathermal electrons, in the first place) are consistent with the helmet streamers producing, in alternation, high-density regions (mostly disconnected) separated by magnetic flux ropes (mostly connected to the Sun). This sequence of emission of dense blobs and flux ropes also seems repeated at smaller scales inside each of the high-density regions. These properties are further confirmed with in situ measurements much closer to the Sun using Helios observations. We conclude on a model for the formation of dense blobs and flux ropes that explains both the in situ measurements and the remote-sensing observations presented in our previous studies.