The Evolution of the 1/f Range within a Single Fast-solar-wind Stream between 17.4 and 45.7 Solar Radii

Academic Article


  • Abstract The power spectrum of magnetic field fluctuations in the fast solar wind (V SW > 500 km s−1) at magnetohydrodynamic scales is characterized by two different power laws on either side of a break frequency f b. The low-frequency range at frequencies f smaller than f b is often viewed as the energy reservoir that feeds the turbulent cascade at f > f b. At heliocentric distances r exceeding 60 solar radii (R s), the power spectrum often has a 1/f scaling at f < f b, i.e., the spectral index is close to −1. In this study, measurements from the Parker Solar Probe's Encounter 10 with the Sun are used to investigate the evolution of the magnetic field power spectrum at f < f b at r < 60 R s during a fast radial scan of a single fast-solar-wind stream. We find that the spectral index in the low-frequency part of the spectrum decreases from approximately −0.61 to −0.94 as r increases from 17.4 to 45.7 R s. Our results suggest that the 1/f spectrum that is often seen at large r in the fast solar wind is not produced at the Sun, but instead develops dynamically as the wind expands outward from the corona into the interplanetary medium.
  • Authors

  • Davis, Nooshin
  • Chandran, Benjamin
  • Bowen, TA
  • Badman, ST
  • de Wit, T Dudok
  • Chen, CHK
  • Bale, SD
  • Huang, Zesen
  • Sioulas, Nikos
  • Velli, Marco
  • Status

    Publication Date

  • June 1, 2023
  • Has Subject Area

    Digital Object Identifier (doi)

    Start Page

  • 154
  • End Page

  • 154
  • Volume

  • 950
  • Issue

  • 2