# PSP Bibliography

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Isotropization and Evolution of Energy-containing Eddies in Solar Wind Turbulence: Parker Solar Probe, Helios 1, ACE, WIND, and Voyager 1

 Author Cuesta, Manuel; Chhiber, Rohit; Roy, Sohom; Goodwill, Joshua; Pecora, Francesco; Jarosik, Jake; Matthaeus, William; Parashar, Tulasi; Bandyopadhyay, Riddhi; Keywords Parker Data Used; Two-point correlation function; Heliosphere; Solar wind; interplanetary turbulence; 1951; 711; 1534; 830; Astrophysics - Solar and Stellar Astrophysics; Physics - Plasma Physics; Physics - Space Physics Abstract We examine the radial evolution of correlation lengths perpendicular ( $\lambda _C^\perp$ ) and parallel ( $\lambda _C^\parallel$ ) to the magnetic-field direction, computed from solar wind magnetic-field data measured by Parker Solar Probe (PSP) during its first eight orbits, Helios 1, Advanced Composition Explorer (ACE), WIND, and Voyager 1 spacecraft. Correlation lengths are grouped by an interval s alignment angle; the angle between the magnetic-field and solar wind velocity vectors (\ensuremath\Theta$_BV$). Parallel and perpendicular angular channels correspond to angles 0\textdegree < \ensuremath\Theta$_BV$ < 40\textdegree and 50\textdegree < \ensuremath\Theta$_BV$ < 90\textdegree, respectively. We observe an anisotropy in the inner heliosphere within 0.40 au, with $\lambda _C^\parallel /\lambda _C^\perp \approx 0.75$ at 0.10 au. This anisotropy reduces with increasing heliocentric distance and the correlation lengths roughly isotropize within 1 au. Results from ACE and WIND support a reversal of the anisotropy, such that $\lambda _C^\parallel /\lambda _C^\perp \approx 1.29$ at 1 au. The ratio does not appear to change significantly beyond 1 au, although the small number of parallel intervals in the Voyager data set precludes unambiguous conclusions from being drawn. This study provides insights regarding the radial evolution of the large, most energetic interacting turbulent fluctuations in the heliosphere. We also emphasize the importance of tracking the changes in sampling direction in PSP measurements as the spacecraft approaches the Sun, when using these data to study the radial evolution of turbulence. This can prove to be vital in understanding the more complex dynamics of the solar wind in the inner heliosphere and can assist in improving related simulations. Year of Publication 2022 Journal \apjl Volume 932 Number of Pages L11 Section Date Published jun ISBN URL DOI 10.3847/2041-8213/ac73fd