1. Anomalous circular polarisation in the He I 1083.0 nm multiplet M. J. Martínez González A. Asensio Ramos, R. Manso Sainz, C. Beck, L. Belluzzi

2. observations TIP @ VTT 1083.0 nm He I triplet – noise in pol. 10 -3 I max – spatial res. ≈ 0.6”

3. regular V profile d observations TIP @ VTT 1083.0 nm He I triplet – noise in pol. 10 -3 I max – spatial res. ≈ 0.6”

4. regular V profile d anomalous V profile a observations TIP @ VTT 1083.0 nm He I triplet – noise in pol. 10 -3 I max – spatial res. ≈ 0.6”

5. I Q U V

6. patches of net circular polarisation are consistent during more than 135 min a d b c

7. 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)

8. 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)

9. 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)

10. 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 ] d1.6284435.5-1.8 subject to ambiguities

11. 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 ] a10.8328185811-1.5 a20.8311875711-1.50.05 a30.78793849-0.8 0.541799410910.4-2.7 a40.78573639-0.50.013 0.5493 11910.4-4.40.013

12. 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 ] b1 1.57924611.5-1.5 b2 1.55924611.5-1.50.01 b3 1384178.40.3 0.7608813110.3-4.7 b4 0.9354169.20.30.006 0.6718813011-4.80.006

13. 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 ] c1 31940310.5-0.6 c2 32140310.9-0.6-0.004 c3 1.729938510-0.1 1.323863112.3-0.1 c4 1.475142510.1-0.7-0.006 1.222653013.3-0.6-0.006

14. 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

15. 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 embedded in 100 G inferred value

16. 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 of magnitud of the inferred one is achieved with 8-10 km s -1 (vel. easily found in spicules) UNLIKELY MOST PROBABLE

17. 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 processes In the presence of magnetic fields.

18. thank you!