J/ApJS/239/12 Small-scale magnetic flux ropes in the solar wind (Hu+, 2018)
Automated detection of small-scale magnetic flux ropes in the solar wind: first
results from the Wind spacecraft measurements.
Hu Q., Zheng J., Chen Yu, le Roux J., Zhao L.
<Astrophys. J. Suppl. Ser., 239, 12 (2018)>
=2018ApJS..239...12H 2018ApJS..239...12H
ADC_Keywords: Magnetic fields; Sun
Keywords: magnetohydrodynamics (MHD) ; methods: data analysis ; solar wind ;
Sun: heliosphere ; turbulence
Abstract:
We have developed a new automated small-scale magnetic flux ropes
(SSMFR) detection algorithm based on the Grad-Shafranov (GS)
reconstruction technique. We have applied this detection algorithm to
the Wind spacecraft in situ measurements during 1996-2016, covering
two solar cycles, and successfully detected a total number of 74241
small-scale magnetic flux rope events with duration from 9 to 361min.
This large number of small-scale magnetic flux ropes has not been
discovered by any other previous studies through this unique approach.
We perform statistical analysis of the small-scale magnetic flux rope
events based on our newly developed database, and summarize the main
findings as follows. (1) The occurrence of small-scale flux ropes has
strong solar-cycle dependency with a rate of a few hundred per month
on average. (2) The small-scale magnetic flux ropes in the ecliptic
plane tend to align along the Parker spiral. (3) In low-speed
(<400km/s) solar wind, the flux ropes tend to have lower proton
temperature and higher proton number density, while in high-speed
(≥400km/s) solar wind, they tend to have higher proton temperature
and lower proton number density. (4) Both the duration and scale size
distributions of the small-scale magnetic flux ropes obey a power law.
(5) The waiting time distribution of small-scale magnetic flux ropes
can be fitted by an exponential function (for shorter waiting times)
and a power-law function (for longer waiting times). (6) The
wall-to-wall time distribution obeys double power laws with the break
point at 60 minutes (corresponding to the correlation length). (7) The
small-scale magnetic flux ropes tend to accumulate near the
heliospheric current sheet (HCS).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 193 74241 Flux rope events
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See also:
J/ApJ/737/L35 : Pulsed Alfven waves in the solar wind (Gosling+, 2011)
http://fluxrope.info/ : Small-scale Magnetic Flux Rope Database
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [0/74240] Index identifier
7- 22 A16 "date" Obs.S Observation start; mm/dd/yyyy hh:mm
24- 39 A16 "date" Obs.E Observation end; mm/dd/yyyy hh:mm
41- 43 I3 min Time [9/361] Observation duration
45- 51 F7.5 --- ResDif [0/0.2] Residual (1)
53- 60 F8.4 nT Bavg [5/123.4] Average magnetic field strength
62- 74 F13.9 nT Bmax [5/138] Maximum magnetic field strength
76- 88 F13.9 --- beta [0.0003/120]? Average plasma β value
90-100 E11.5 --- betap [5.2e-06/129]? Average proton β value
102-112 F11.7 km/s Vsw [188/911] Solar wind velocity
114-121 F8.6 MK TpAvg [0.002/1.1]? Average proton temperature
123-125 I3 deg theta [0/180] Polar angle
127-129 I3 deg phi [0/360]? Azimuthal angle
131-142 F12.9 --- zAxis0 [-1/1] Z-axis orientation0 (2)
144-155 E12.5 --- zAxis1 [-1/1] Z-axis orientation1 (2)
157-168 F12.9 --- zAxis2 [-1/1] Z-axis orientation2 (2)
170-180 E11.5 AU Size [4.7e-05/0.11] Scale size
182-193 F12.9 cm-3 Np [0.03/99] Mean proton number density
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Note (1): Represents the point-wise difference between two branches, in which
both (Pt)i1st and (Pt)i2nd are calculated from
observational data.
Note (2): In Geocentric Solar Ecliptic (GSE) cartesian coordinates.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Dec-2018