J/ApJ/871/93 Solar wind speed from 5yr data with ACE spacecraft (Wang+, 2019)
2D isotropic feature of solar wind turbulence as shown by self-correlation level
contours at hour timescales.
Wang X., Tu C., He J.
<Astrophys. J., 871, 93 (2019)>
=2019ApJ...871...93W 2019ApJ...871...93W
ADC_Keywords: Sun
Keywords: magnetic fields ; plasmas ; solar wind ; turbulence
Abstract:
The slow wind anisotropy is observed by Dasso+ 2005ApJ...635L.181D 2005ApJ...635L.181D as
elongation along the magnetic field direction in the magnetic
self-correlation contours calculated from data sets of two-day-long
data and averaged for five years in 1998-2002, which is consistent
with prediction by the "critical balance cascade theory". More
pronounced elongation at smaller scales than at larger scales has also
been predicted by this theory. However, this prediction has not yet
been checked by observations. Here, we present a check of the
variation trend of the anisotropy with scales by presenting level
contours of magnetic field and velocity self-correlations using
intervals with durations varying from two days to one hour as observed
by the Advanced Composition Explorer during 1998-2002 in the slow
wind. We find that the level contours elongate along the magnetic
field direction at durations of two days and one day. But they become
isotropic for shorter intervals from about 10 hours to 1 hour. We also
find that in the fast wind, the variation of the anisotropy with the
scale has the same trend as in the slow wind. The 2D isotropic feature
of the solar wind fluctuations shown by these statistical results is
not consistent with the existing theory and will open a new avenue for
studying solar wind turbulence.
Description:
We use roughly five-year data observed by the ACE spacecraft from 1998
February 10 to 2002 December 5 to calculate the level contours of the
magnetic field and velocity self-correlations following Milano+
(2004PhRvL..93o5005M 2004PhRvL..93o5005M) and Dasso+ (2005ApJ...635L.181D 2005ApJ...635L.181D). The magnetic
field data measured by the Magnetic Field Instrument are analyzed with
a cadence of Δ=16s, and the plasma data measured by the Solar
Wind Electron, Proton, and Alpha Monitor are analyzed with a cadence
of Δ=1min.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 38 36349 Start and end times of intervals selected
for analysis
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See also:
J/ApJ/759/69 : Solar electron events 1995-2005 with WIND/3DP (Wang+, 2012)
J/ApJS/230/21 : Solar wind 3D magnetohydrodynamic simulation (Chhiber+, 2017)
J/ApJS/239/12 : Small-scale magnetic flux ropes in the solar wind (Hu+, 2018)
J/ApJ/868/124 : ICMEs events from 1998 to 2011 with ACE and WIND (Feng+, 2018)
J/A+A/635/A79 : Pitch-angle distributions of solar wind (Carcaboso+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 d Duration [0.0416/2.0] Interval duration
8- 19 F12.4 d Start [2450855.33/2452614.4] Julian Day of
interval start which begins at noon
21- 32 F12.4 d End [2450855.37/2452614.5] Julian Day of
interval end which begins at noon
34- 38 F5.1 km/s Vsw [258.5/926.9] Solar wind speed
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 30-Jul-2020