Higher-order Analysis of Three-dimensional Anisotropy in Imbalanced Alfvénic TurbulenceShow others and affiliations
2025 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 993, no 1, article id 142Article in journal (Refereed) Published
Abstract [en]
We examine the applicability of homogeneous, negligible cross-helicity magnetohydrodynamic (MHD) turbulence models incorporating "critical balance" (CB) and "scale-dependent dynamic alignment" (SDDA) to Parker Solar Probe observations of a highly Alfv & eacute;nic, high cross-helicity solar wind stream. At energy-injection scales, both Alfv & eacute;nic modes satisfy chi lambda +/-equivalent to tau A +/-/tau nl +/-<< 1 , where tau A +/- and tau nl +/- denote the linear and nonlinear timescales. The outward cascade remains weak, chi lambda+approximate to 0.2 , across all scales, while the inward cascade reaches CB at the onset of the inertial range ( chi lambda-similar to 1 ), yet with spectral scalings that depart from the canonical weak-to-strong transition. Within the domain conventionally designated as the inertial range, we identify two statistically distinct subranges. At larger scales (R2; 200-6000, di), the average eddy displays a field-aligned, tube-like morphology. An inverse correlation is observed between alignment angle and gradient intensity, and the conditional structure-function exponents zeta n-measured perpendicular to both the local mean field and fluctuation direction-agree with the predictions of B. D. G. Chandran et al. and A. Mallet & A. A. Schekochihin, although the parallel and displacement components show more concave scaling than anticipated. At smaller scales (R1; 10-100, di), spectra steepen, eddies become ribbon-like, and intermittency weakens. Within a narrow interval near the ion characteristic scales, eddies approach isotropy before the trend of increasing anisotropy resumes at smaller scales. Analysis using five-point increments further demonstrates a stronger multifractal character at kinetic scales than is resolved with conventional two-point methods. Finally, we discuss the influence of solar wind expansion, finite cross helicity, "anomalous coherence," and the emergence of a "helicity barrier" in modifying CB/SDDA phenomenology and shaping the statistical properties of solar wind turbulence.
Place, publisher, year, edition, pages
American Astronomical Society , 2025. Vol. 993, no 1, article id 142
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-375046DOI: 10.3847/1538-4357/ae0934ISI: 001604926400001Scopus ID: 2-s2.0-105028424125OAI: oai:DiVA.org:kth-375046DiVA, id: diva2:2027774
Note
QC 20260113
2026-01-132026-01-132026-06-30Bibliographically approved