The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration
Year: 2021
Type: conference-abstract
Abstract: The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 Rs, allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP's fourth solar encounter, likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with spectral index close to -5/3 rather than -3/2), a lower Alfvenicity, and a "1/f" break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ~4 degrees from the HCS, suggesting ~8 degrees as the full-width of the streamer belt wind at these distances. While the majority of the Alfvenic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind.
Authors: Christopher Chen, Benjamin Chandran, Lloyd Woodham, Shaela Jones, Jean Perez, Sofiane Bourouaine, Trevor Bowen, Kris Klein, Michel Moncuquet, Justin Kasper, Stuart Bale
Institutions: Queen Mary University of London, University of New Hampshire, Imperial College London, Goddard Space Flight Center, Florida Institute of Technology, Johns Hopkins University, Johns Hopkins University Applied Physics Laboratory, Space Sciences Laboratory, University of California, Berkeley, University of Arizona, Centre National de la Recherche Scientifique, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Laboratoire d’études spatiales et d’instrumentation en astrophysique, Smithsonian Astrophysical Observatory, University of Michigan
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
OpenAlex ID: W3174834513