EUV filaments in 3D from magnetic extrapolations toward stereoscopic observations

1
EUV filaments in 3D from magnetic
extrapolations toward stereoscopic observations

• G. Aulanier B. Schmieder
• Observatoire de Paris, LESIA

2
Disc observations of EUV filaments
SoHO/CDS

• Observed only for l lt 912 A
• (Chiuderi Drago et al. 2001)
• a EUV lines absorbed in the Lyman
• continuum of Hydrogen
• t912 60-100 tHa
• (Heinzel et al. 2001, Schmieder et al.,
  2002)
• a fewer material can absorb the
• background EUV radiation
• a EUV shows more mass than Ha

THEMIS/MSDP
(Heinzel et al. 2001)

• distribution of cool material ?
• magnetic topology ? 3D is
  missing
• extra mass loading of CMEs ?

3
3D magnetic field extrapolation for one
observed filament
Joint THEMIS/SoHO campaign, 05/05/2000
(conducted at MEDOC)
0752 UT
0812 UT
located at E17 S21
4
linear magneto-hydrostatic method

• x B a B z e-z/H sBz x uz
  (Low 1992)
• j (force free) j
  (spg)

Departure from the force free approximation

• Lower boundary -D/2 lt xy lt D/2
  periodic
• - Bz (z 0) B// (MDIdeproj) /cos q
• - D observed
  quasi-periodicity in x
• - y axis filament axis
• Upper boundary 0 lt z lt Dz arbitrary
• lim B (z a ) 0

h

Filament axis
-

D
-
h
05/05/00, 0800 UT, SoHO/MDI magnetogram
8
(a H) cannot be fixed a grid of 35 LMHS
models
5
Selection of the best LMHS model
h For each 3D model, compute plot magnetic dips

- Locus of dips
(B . s) B gt 0
Bz 0
z
- Portion visible in Ha
dipped field line
da Hg 300 km
(Aulanier et al. 1999)
h Compare dips with Ha observations only
- dips to be matched with
filament curved body elbow
a / ares 0.94 a 3.08 x 10-8 m-1
- Physical parameters
H 25 Mm
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LMHS model of the Ha filament
Calculation of dips on a 64 3 mesh a
2100 dips for z 4 96 a 3500
dips for z 0 4
h
Ha filament body feet
Sheet of dips in high altitude flux
tube Side dips on
the edge of photospheric parasitic
polarities
(Aulanier Démoulin 1998)
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LMHS model of the EUV filament
Plot onto the EUV image the SAME dips from the
SAME model built so as to match the Ha filament
a 2100 dips for z 4 96
a 3500 dips for z 0 4
h
h
Magnetic dips computed up to a dLyman
1700 km (calculated with
approximated RT)
For hydrostatic-isothermal dips a M
(each dip) 1.5 x M (Ha)
h
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Magnetic topology of filament channels
Magnetic loops filament flux tube overlaying
arcades
Magnetic dips z gt 4 Mm z lt 4 Mm
Filament body magnetic dips in weakly
twisted (0.6 turns) and discontinuous flux
tube Ha EUV extensions low-lying dips
due to parasitic polarities located near
the footpoints of some long overlaying
sheared loops
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Estimate for the mass loading of CMEs
Overlaying arcades
CME front cavity
Filament flux tube
M (CME core) x 1.5
M (each dip) 1.5 x M (observable in Ha)
unchanged
Not ejected
fall down to chromosphere
Ha feet
MOST of the mass observed in EUV
filament channels will NOT be loaded
into CMEs
Wide EUV feet
10
Toward STEREO observations
EUV filament channels optically thick enough
stereo reconstruction SECCHI / EUVI
3D structure evolution of EUV channels
same shape as observed in the 4 EIT wavelengths
SoHO/CDS FOV
SoHO/CDS FOV
05/05/00, 0812 UT, SoHO/CDS, OV
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Compare LMHS model with observed transit
on the disc
Magnetic loops filament flux tube overlaying
arcades
Magnetic dips z gt 4 Mm z lt 4 Mm
Several projections of one model LMHS
extrapolation of the 05/05/00, 800 UT, SoHO/MDI
magnetogram