The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration
- 1School of Physics and Astronomy, Queen Mary University of London, London E1 4NS, UK
- 2Department of Physics and Astronomy, University of New Hampshire, Durham, NH 03824, USA
- 3Department of Physics, Imperial College London, London SW7 2AZ, UK
- 4NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
- 5Department of Aerospace, Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901, USA
- 6Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
- 7Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA
- 8Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85719, USA
- 9LESIA, Observatoire de Paris, Universite PSL, CNRS, Sorbonne Universite, Universite de Paris, 92195 Meudon, France
- 10Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- 11Smithsonian Astrophysical Observatory, Cambridge, MA 02138 USA
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.
How to cite: Chen, C., Chandran, B., Woodham, L., Jones, S., Perez, J., Bourouaine, S., Bowen, T., Klein, K., Moncuquet, M., Kasper, J., and Bale, S.: The Near-Sun Streamer Belt Solar Wind: Turbulence and Solar Wind Acceleration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3426, https://doi.org/10.5194/egusphere-egu21-3426, 2021.
