ORIGIN OF THE SLOW SOLAR WIND K. Fujiki , T. Ohmi, M. Kojima, M. Tokumaru Solar-Terrestrial...
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Transcript of ORIGIN OF THE SLOW SOLAR WIND K. Fujiki , T. Ohmi, M. Kojima, M. Tokumaru Solar-Terrestrial...
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ORIGIN OF THE SLOW SOLAR WIND
K. Fujiki , T. Ohmi, M. Kojima, M. Tokumaru
Solar-Terrestrial Environment Laboratory, Nagoya University and
K. HakamadaDepartment of Engineering Physics, Chubu University
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Slow solar wind from a small equatorial coronal hole
Slow solar wind from a polar coronal hole
19912000
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Intermediate and slow streams originated not in smaller coronal holes at low latitudes and from open field regions just outside coronal hole boundaries. [Neugebauer et al., 1998]
The speed of the solar wind scales with the coronal hole area.[Nolte et al., 1976]
Relation between speed and coronal hole area
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Wang & Sheely model
RADIAL DISTANCE
Magnetic field configuration
smaller expansion
larger expansion
high speed
low speed
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Slow SW from an equatorial small CH
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Solar Wind Structure at Solar Minimum
slower solar wind
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Carrington Rotations 1899-1901
The slower wind originates from the vicinity of active regions
August 6 – October 17, 1995
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Carrington Rotations 1895-1897
The slower wind also originates from the vicinity of active regions
April 19 – July 10, 1995
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CR1897
HPS slow wind slow wind from seCHfast wind
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106K
CR1897
HPS slow wind slow wind from seCHfast wind
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CR1897
HPS slow wind slow wind from seCHfast wind
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Parameter Slow (HPS) Slower (seCH) Fast (leCH)VP [km/s] 343±12 323±9 673±14
NP [cm-3] 11.7±3.3 10.2±0.6 3.2±0.5
TP [105 K] 0.39±0.14 0.55±0.11 2.20±0.39
TO [106 K] 1.85±0.24 1.99±0.19 1.42±0.13
Nα/ NP 0.009±0.003 0.031±0.008 0.039±0.004
Solar Wind in CR 1897 (June 12 – July 10, 1995)
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Solar Wind in CR 1897 (June 12 – July 10, 1995)
Parameter Slow (HPS) Slow (seCH) Fast (leCH)VP [km/s] 343±12 323±9 673±14
NP [cm-3] 11.7±3.3 10.2±0.6 3.2±0.5
TP [105 K] 0.39±0.14 0.55±0.11 2.20±0.39
TO [106 K] 1.85±0.24 1.99±0.19 1.42±0.13
Nα/ NP 0.009±0.003 0.031±0.008 0.039±0.004
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fast wind slow wind (HPS)
Source coronal hole helmet
N variance steady variable
Na/Np large small
slow wind (SCH)
coronal hole
steady
large
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Slow SW from a polar CH
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Polar Low-speed Solar Wind at Solar Activity Maximum of Cycle 22
Ohmi et al. [2001]
June 27, 1990
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Polar Low-speed Solar Wind at Solar Activity Maximum of Cycle 23
Ohmi et al. [2002]
October 23, 1999
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Small Polar Coronal Hole
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ConclusionsIn addition to the slow solar wind from helmet streamer, the slow solar wind originates from small coronal holes.
slowerslower
fast
Wang and Sheely model of inverse correlation between velocity and expansion factor seems to explain these slower solar winds.
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Magnetic Field in the Coronal Holes
high latitudeCH
12 G Fast wind
small polarCH
4 ~ 6 G Slow wind large flux expansion &
less magnetic energysmall
equatorialCH
18 G Slow wind large flux expansion &
large magnetic energy
Is it really possible to explain same acceleration mechanism?Photospheric Condition is significantly different.
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Required
• More in situ observations of the slow stream from small coronal holes.
・・・ is difficult to observe the polar wind.
• Physical properties of density, acceleration profile, and temperature in corona of the slow streams.
・・・ can be observed by SOLAR-B.(EIS/XRT)
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~fin~