18
Anomalous circular polarisation in the He I 1083.0 nm multiplet M. J. Martínez González A. Asensio Ramos, R. Manso Sainz, C. Beck, L. Bel
Anomalous circular polarisationin the He I 1083.0 nm multiplet
M. J. Martínez GonzálezA. Asensio Ramos, R. Manso Sainz, C. Beck, L. Belluzzi
observations
TIP @ VTT1083.0 nm He I triplet – noise in pol. 10-3 Imax – spatial res. ≈ 0.6”
regular V profile
d
observations
TIP @ VTT1083.0 nm He I triplet – noise in pol. 10-3 Imax – spatial res. ≈ 0.6”
regular V profile
d
anomalous V profile
a
observations
TIP @ VTT1083.0 nm He I triplet – noise in pol. 10-3 Imax – spatial res. ≈ 0.6”
I
Q
U
V
patches of net circular polarisation are consistent during more than 135 min
adb c
how to interpret net circular polarisation?
Zeeman effect+
radiative transfer effects(gradients of vel. and mag. Field)
atomic orientation(population imbalance of σ components symmetric contribution to Stokes V)
how to interpret net circular polarisation?
Zeeman effect+
radiative transfer effects(gradients of vel. and mag. Field)
VERY UNLIKELY
one-lobbed V profiles due to gradients have half width of the intensity profile
our observed V profiles are as broad as the intensity
atomic orientation(population imbalance of σ components symmetric contribution to Stokes V)
how to interpret net circular polarisation?
Zeeman effect+
radiative transfer effects(gradients of vel. and mag. Field)
VERY UNLIKELY
one-lobbed V profiles due to gradients have half width of the intensity profile
our observed V profiles are as broad as the intensity
INVERSION OF 4 STOKES PROFILES
1) one slab with constant properties
2) 1 + atomic orientation
3) two slab along the LOS with constant properties
4) 3 + atomic orientation
atomic orientation(population imbalance of σ components symmetric contribution to Stokes V)
one slab with constant properties
fits most of the prominence profiles, although some of them have non-zero net circular polarisation
transfer effects should be taken into account to properly fit those profiles
Δλ
model τredB
[G]θB
[deg]χB
[deg]vth
[km s-1]vII
[km s-1]
d 1.6 28 44 3 5.5 -1.8
subject to ambiguities
1: one slab
2: one slab + ad-hoc orientation of the rad. Field
3: two slab along LOS
4: two slab + ad-hoc orientation of the rad. Field
Δλ [nm]
model τredB
[G]θB
[deg]χB
[deg]vth
[km s-1]vII
[km s-1]
a1 0.83 28 18 58 11 -1.5
a2 0.83 11 87 57 11 -1.5 0.05
a3 0.78 79 38 4 9 -0.8
0.54 179 94 109 10.4 -2.7
a4 0.78 57 36 3 9 -0.5 0.013
0.54 93 93 119 10.4 -4.4 0.013
1: one slab
2: one slab + ad-hoc orientation of the rad. Field
3: two slab along LOS
4: two slab + ad-hoc orientation of the rad. Field
Δλ [nm]
model τredB
[G]θB
[deg]χB
[deg]vth
[km s-1]vII
[km s-1]
b1 1.5 7 92 46 11.5 -1.5b2 1.5 5 92 46 11.5 -1.5 0.01b3 1 38 41 7 8.4 0.3
0.7 60 88 131 10.3 -4.7b4 0.9 35 41 6 9.2 0.3 0.006
0.6 71 88 130 11 -4.8 0.006
1: one slab
2: one slab + ad-hoc orientation of the rad. Field
3: two slab along LOS
4: two slab + ad-hoc orientation of the rad. Field
Δλ [nm]
model τredB
[G]θB
[deg]χB
[deg]vth
[km s-1]vII
[km s-1]
c1 3 19 40 3 10.5 -0.6c2 3 21 40 3 10.9 -0.6 -0.004c3 1.7 29 93 85 10 -0.1
1.3 23 86 31 12.3 -0.1c4 1.4 75 14 25 10.1 -0.7 -0.006
1.2 22 65 30 13.3 -0.6 -0.006
how to generate atomic orientation in the He 1083.0 nm line?
alignment to orientation transfer mechanism by electric fields[López Ariste et al. 2005]
[atom non hydrogenic]
VERY UNLIKELY
differential excitation of σ components
how to generate atomic orientation in the He 1083.0 nm line?
alignment to orientation transfer mechanism by electric fields[López Ariste et al. 2005]
[atom non hydrogenic]
VERY UNLIKELY
differential excitation of σ components
a) illuminating the atoms with circular polarisation +relative vel. atom-rad.
b) splitting the transition and diferentially illuminating the σ comp.
underlying photosphere 1 kG
scatterers embeddedin 100 G
inferred value
how to generate atomic orientation in the He 1083.0 nm line?
alignment to orientation transfer mechanism by electric fields[López Ariste et al. 2005]
[atom non hydrogenic]
VERY UNLIKELY
differential excitation of σ components
a) illuminating the atoms with circular polarisation +relative vel. atom-rad.
prominences are found in neutral lines cancelations
b) splitting the transition and diferentially illuminating the σ comp.
orientation of the order ofmagnitud of the inferred one is achieved with 8-10 km s-1 (vel. easily found in spicules)
UNLIKELY MOST PROBABLE
Conclusions
Stokes V profiles in spicules have a large amount of NCP (mostly one-lobbed)
We reproduce them with 2 magnetized components and orientation of the incoming radiation field.
The orientation needed is of 0.06-0.1%
The most likely scenario to generate this orientation are dynamical processesIn the presence of magnetic fields.
thank you!
