Anomalous circular polarisation in the He I nm multiplet M. J. Martínez González A. Asensio Ramos, R. Manso Sainz, C. Beck, L. Belluzzi

observations VTT nm He I triplet – noise in pol I max – spatial res. ≈ 0.6”

regular V profile d observations VTT nm He I triplet – noise in pol I max – spatial res. ≈ 0.6”

regular V profile d anomalous V profile a observations VTT nm He I triplet – noise in pol I max – spatial res. ≈ 0.6”

I Q U V

patches of net circular polarisation are consistent during more than 135 min a d b 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 modelτ red B [G] θ B [deg] χ B [deg] v th [km s -1 ] v II [km s -1 ] d 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] modelτ red B [G] θ B [deg] χ B [deg] v th [km s -1 ] v II [km s -1 ] a a a a

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] modelτ red B [G] θ B [deg] χ B [deg] v th [km s -1 ] v II [km s -1 ] b b b b

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] modelτ red B [G] θ B [deg] χ B [deg] v th [km s -1 ] v II [km s -1 ] c c c c

how to generate atomic orientation in the He 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 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 embedded in 100 G inferred value

how to generate atomic orientation in the He 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 of magnitud 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 % The most likely scenario to generate this orientation are dynamical processes In the presence of magnetic fields.

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