Please use this identifier to cite or link to this item:
For citation please use:
Main Title: Modeling the Solar Wind Turbulent Cascade Including Cross Helicity: With and Without Expansion
Author(s): Grappin, Roland
Verdini, Andrea
Müller, W.-C.
Type: Article
Abstract: Simulations of the turbulent cascade forming in the solar wind, including cross helicity, commonly adopt a homogeneous setup, not taking into account wind expansion. Here we want to assess the predictions of decaying 3D compressible (low Mach number) MHD simulations, respectively homogeneous and with expansion, in order to examine which is the most fruitful approach to understanding the turbulent cascade in the solar wind. We follow turbulent evolution during 10 nonlinear turnover times, considering several initial values of the initial spectral slope and cross helicity. In the expanding case, the transverse sizes of the plasma volume are stretched by a factor of 5 during the simulation, corresponding to traveling from 0.2 up to 1 au. In homogeneous simulations, the relative cross helicity rises, and the Elsässer spectra E± show “pinning,” with a steep dominant spectrum and flat subdominant spectrum, the final spectral indices depending on cross helicity but not initial indices. With expansion, the relative cross helicity decreases, and dominant and subdominant spectra share the same index, with the index relaxing to an asymptotic value that generally depends on the initial index. The absence of pinning, as well as the decrease of relative cross helicity, probably both rely on the permanent injection by expansion of an excess of magnetic energy at the largest scales, equivalent to injecting subdominant energy. Also, spectra generally steepen when initially starting flatter than k−5/3 but stop evolving at a finite time/distance.
Subject(s): interplanetary turbulence
solar wind
space plasmas
alfven waves
interplanetary medium
Issue Date: 19-Jul-2022
Date Available: 1-Aug-2022
Language Code: en
DDC Class: 520 Astronomie und zugeordnete Wissenschaften
Journal Title: The Astrophysical Journal
Publisher: IOP
Volume: 933
Issue: 2
Article Number: 246
Publisher DOI: 10.3847/1538-4357/ac6ba4
EISSN: 1538-4357
ISSN: 0004-637X
TU Affiliation(s): Fak. 2 Mathematik und Naturwissenschaften » Zentrum für Astronomie und Astrophysik
Appears in Collections:Technische Universität Berlin » Publications

Files in This Item:
Format: Adobe PDF | Size: 2.51 MB
DownloadShow Preview

Item Export Bar

This item is licensed under a Creative Commons License Creative Commons