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The Evolution of the 1/f Range within a Single Fast-solar-wind Stream between 17.4 and 45.7 Solar Radii
| Author | Davis, Nooshin; Chandran, B.~D.~G.; Bowen, T.~A.; Badman, S.~T.; de Wit, Dudok; Chen, C.~H.~K.; Bale, S.~D.; Huang, Zesen; Sioulas, Nikos; Velli, Marco; |
| Keywords | Parker Data Used; Magnetohydrodynamics; Solar wind; interplanetary turbulence; 1964; 1534; 830; Astrophysics - Solar and Stellar Astrophysics; Physics - Space Physics |
| 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. |
| Year of Publication | 2023 |
| Journal | \apj |
| Volume | 950 |
| Number of Pages | 154 |
| Section | |
| Date Published | jun |
| ISBN | |
| URL | |
| DOI | 10.3847/1538-4357/acd177 |
