Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 3D Anisotropy of Solar Wind Turbulence, Tubes, or Ribbons?   We study the anisotropy with respect to the local magnetic field of turbulent
magnetic fluctuations at magnetofluid scales in the solar wind. Previous
measurements in the fast solar wind obtained axisymmetric anisotropy, despite
that the analysis method allows nonaxisymmetric structures. These results are
probably contaminated by the wind expansion that introduces another symmetry
axis, namely, the radial direction, as indicated by recent numerical
simulations. These simulations also show that while the expansion is strong,
the principal fluctuations are in the plane perpendicular to the radial
direction. Using this property, we separate 11 yr of Wind spacecraft data into
two subsets characterized by strong and weak expansion and determine the
corresponding turbulence anisotropy. Under strong expansion, the small-scale
anisotropy is consistent with the Goldreich & Sridhar critical balance. As in
previous works, when the radial symmetry axis is not eliminated, the turbulent
structures are field-aligned tubes. Under weak expansion, we find 3D anisotropy
predicted by the Boldyrev model, that is, turbulent structures are ribbons and
not tubes. However, the very basis of the Boldyrev phenomenology, namely, a
cross-helicity increasing at small scales, is not observed in the solar wind:
the origin of the ribbon formation is unknown.

29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs