Coronal Magnetograph for Space and Ground-based Solar Observatories Silvano Fineschi Alessandro Bemporad, Gerardo Capobianco, Jessica Girella INAF –Astrophysical Observatory of Torino, Italy Jan Rybak AISAS-Lomnicky Observatory, Slovakia Sarah Gibson NCAR-High Altitude Observatory Punta Leona (Costa Rica)– 2 December 2014 Polarimetry: From the Sun to Stars and Stellar Environments

Summary Spectro-polarimetry of coronal line-emission in the IR & visible-light wavelength spectrum («forbidden lines», e.g., FeXIV) have demonstrated to be a promising, valuable diagnostics tool of the coronal magnetic field. New space optics for solar physics (e.g., LC-based spectropolarimetry optics) New modeling &computing capabilities (e.g., FORWARD numerical code) New ground- and space-based observatories with spectro-polarimeters (e.g., COSMO, Lomnicky-stit, Baloon-borne WAMIS, ASPIICS/Proba-3)

Hanle Effect (tutorial)  Larmour  A

Hanle Effect (tutorial)  Larmour  A If  Larmour >> A (VIR forbidden lines)  P is // or  B

Polarization vector Van Vleck angle 5  >  v  <  v Line Polarization Vector “Saturated” Hanle effect  Larmour >> A

Green Line Selection for Coronal B Diagnostics Judge, 1998 J’=1  J=0, Atomic alignment W 2 (1, 0) = 1 J’=3/2  J=1/2, Atomic alignment W 2 (3/2, 1/2) = 0.5 Coronal Green line polarimetry Theory: well undersood (Charvin, House, Sahal-Brechot, Casini) Observations: Edlen, Querfeld & Smartt, Arnaud & Newkirk, Mierla, …) FeXIV polarimetry for a coronal B diagnostics?! Past limitations in Instrumentation  simultaneous narrow bandpass imaging & polarimetry coronal atmosphere modeling  computationally demanding numerical codes Location, location, location!  ground coronagraphic sites, space

7 FeXIV line nm (configuration 3s 2 3p) is a magnetic dipole transition: 2 P 3/2 → 2 P 1/2 Fe XIV nm (“Green Line”) Judge, 1998

8 Turin - Liquid-crystal Tunable Lyot Filter for Solar Coronagraphy

LC Tunable-filter & Polarimeter Procurement

Turin - Liquid-crystal Tunable Lyot Filter Perfomances 10

2010 Eclipse Results of CorMag

Coronal Temperature contour levels: Blue: 1.  10 6 K green: 1.5  10 6 K Red: 2.  10 6 K 12 CorMag Spectroscoy

Polarization vector’s angle in a Coronal Cavity 13 Left: M. Druckmuller imaging (spatial resolution 1’’). Right: CorMag polarization vector direction (res. 12.4’’). CorMag Polarimetry

«Saturated» Hanle effect in the Coronal FeXIV Line 14  >  v  <  v Girella, 2014)

15 Model of global solar magnetic field based on extrapolation from phototospheric magnetograms (averaged over a Carrington rotation do) not include transient structures Forward modeling vs CorMag observations I I I CorMag (res. 12.4’’) Druckmuller (res. 1”)

16 CorMAg K- pB PredSci K-pB Left: Predictive Scence B model extrapolation. Center: Synthetic pB emission from Predictive Science. Right: pB measured by CorMag. Forward Modeling vs CorMag observations

17 E-corona Polarization Degree (pB/B) pB FORWARD model pB

18 Measured Stokes Paramenters of FeXIV Line (Q/I) (FORWARD code S. Gibson, P. Judge, R. Casini) Q FORWARD Model Q

19 Measured Stokes Paramenters of FeXIV Line (U/I) (FORWARD code S. Gibson, P. Judge, R. Casini) U FORWARD Model U

20 CorMag at Lomnicky Stit Observatory (Slovakia)

WAMIS Baloon-borne Lyot Spectro-Polarimeter (FeXIII nm) US Naval Reserach Lab. – HAO - Italy – France proposal submitted to NASA (2014)

Proba-3 – ASPIICS Coronagraph

ESA PROBA-3 Formation-Flying Coronagraph A coronagraph with the external occulter on one spacecraft and the optical instrument on the other spacecraft at ~150 meters from the first one. ASPIICS: 2009 selection; 2010 Phase-A (Startiger); 2011 Phase-B, 2015 Phase C/D; Proba-3 – ESA: launch Habbal 2011

Proba-3 Coronagraph – ASPIICS Observables LASCO-C1

LCVR for Proba-3 Coronagraph - ASPIICS Polarimeter: Liquid Crystal Variable Retarder Quarter-wave retarder (fixed) nm interf. filter (FWHM=0.15 nm) Linear polarizer (analyzer)

Fineschi, 2013

R1 R2 R3 R4 R5 R1 R2 R3 R4 R5

Summary Spectro-polarimetry of coronal line-emission in the IR & visible-light wavelength spectrum («forbidden lines», e.g., FeXIV) have demonstrated to be a promising, valuable diagnostics tool of the coronal magnetic field. New space optics for solar physics (LC-based spectropolarimetry optics) New computing capabilities (FORWARD numerical code) New ground- and space-based observatories with spectro-polarimeters (Lomnicky-stit, Baloon-borne WAMIS, ASPIICS/Proba-3)

OUTLINE Hanle effect of line linear polarization by resonance scattering as diagnostics tool to probe the coronal magnetic fields 2010 Eclipse observations of the coronal FeXIV nm linear polarization. Hanle effect interpretation and comparision with forward modeling Future spectro-polarimeters for ground- and space-based coronal magnetographs (ASPIICS/Proba-3)