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Probing Coronal Magnetism with M ulti-wavelength Polarimetry

Silvano Fineschi INAF-Torino Astrophysical Observatory, Italy. Probing Coronal Magnetism with M ulti-wavelength Polarimetry. 25 May, 2013, Bern (CH). Coronal Magnetism. Line formation in magnetized (B) plasma Vis.-light /UV lines : ( lin . & circular pol .).

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Probing Coronal Magnetism with M ulti-wavelength Polarimetry

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  1. Silvano Fineschi INAF-Torino Astrophysical Observatory, Italy Probing Coronal Magnetismwith Multi-wavelengthPolarimetry 25May, 2013, Bern (CH)

  2. CoronalMagnetism

  3. Line formation in magnetized (B) plasma Vis.-light/UVlines: (lin. & circularpol.) B & resonancescattering from anisotropic source UV (permitted) lines: Blos;los VIR (forbidden) lines: pos Scattering and SuperradialDoppler-dimmingeffect UV lines: EffectofB on ions v (i.e., kinetic T& T//)

  4. 10 Ro Beta HI Lyman series, OVI 103.2 nm & Fe IR lines 2 Ro 1.05 Ro CIV 150 nm MgII h & k 280 nm Temp. minimum HI Ly- 122 nm Photospheric VIR lines G.A.Gary. 2001 (photospheric field range: 100-2500 G)

  5. HanleEffect(tutorial) If Larmour >> A (VIR forbiddenlines) incident light  Pis // or  B Larmour A

  6. What is the Hanle effect sensitivity of coronal UV lines to magnetic fields? • How many photons are needed to detect the Hanle effect in UV coronal lines?

  7. Hanle effect Sensitivity A [107 s-1] ~ 0.88  gJ  B [G] A FeXIII= 14 Hz  BHanle 0.2-2 G A FeXIII<<Bcorona(“saturated” Hanleeffect)

  8. HI Lyman , 97.2 nm Fineschi, van Ballegooijen & Kohl, 1999

  9. LOS contributionto the Stokesparameters Fineschi, 1993

  10. P P  (Min. Detectable Rot. Angle)  ~ P/P P (Min. detectable Polariz.) ~ 1/signal-to-noise ratio P ~ P0/(1+Coll/Rad)  [rad] ~ 0.88  gJ  B/A

  11. Coronal UV LinesSensitivitiesto B OVI 103.2 nm HI Ly- 121.6 nm HI Ly- 103.2 nm HI Ly- 97.2 nm

  12. Resonance-scatteringPolarization

  13. CoronalLinesDoppler-dimming OVI 103.7 nmDoppler-dimming; CII pumping(S. Giordano courtesy)

  14. Super-radialDoppler-dimmingEffect on ResonancePolarization Sahal-Brechot, 1992, 1998

  15. On-disk profiles: T = 1–3 million K Off-limb profiles: T > 200 million K ! UVCS results: solar minimum (1996-1997) • The fastest solar wind flow is expected to come from dim “coronal holes.” • In June 1996, the first measurements of heavy ion (e.g., O+5) line emission in the extended corona revealed surprisingly wide line profiles . . .

  16. The impact of UVCS Discoveries UVCS has led to new views of the collisionless nature of solar wind acceleration. Key results include: • The fast solar wind becomes supersonic much closer to the Sun (~2 Rs) than previously believed. • In coronal holes, heavy ions (e.g., O+5) both flow faster and are heated hundreds of times (250 MK) more strongly than protons(3 MK) and electrons (1 MK), and have anisotropic temperatures. (e.g., Kohl et al. 1997,1998)

  17. Anisotropic temperatures from Ion-cyclotronresonancebetweenAlfvenwaves and Larmorgyrationsofions+

  18. Super-radialAnisotropic ResonancePolarization Fineschi (2001) Raouafi & Solanki (2002)

  19. Anisotropic Super-radialDoppler-dimmingeffect Fineschi (2001) Raouafi & Solanki (2002)

  20. Source of the Solar Wind Habbal, Fineschi, et al. ApJ (1997)

  21. AnisotropicSuper-radialDoppler-dimmingeffect (OVI 103.2 nmline) Kahn (2012)

  22. Solarwindeffects on UV Polarization B & windspeed 0 B & windspeed = 0 Khan, Fineschi et al., 2011

  23. HI Ly- Khan (2012)

  24. AnisotropicSuper-radDoppler-dimmingeffectIntegrationalong LOS 2 different electron density models (CranmerApJ 2008)

  25. Effects on Polarization of B, AnisotropicDistributions, Active Regions, HI Ly- HI Ly- HI Ly- Khan, Degl’Innocenti, Fineschi et al. (2011)

  26. Whatdoesit take to measureit? (Min. Detectable Rot. Angle)  ~ P/P SNR ~ (P  ) -1  ~ 5 ~ 10-1 rad P ~ 10-1  SNR ~ 102

  27. UV Spectro-polarimetry Polarimetry UV coronallines Spectroscopy UV coronallines Doppler-dimming -shift, -width Hanleeffect Super-radial Doppler -dimming effect Coronal B (Blos;los) Coronal plasma parms (Nion, w, T//, T) + Coronal B effects on plasma (coronalheatingmechanisms, solarwindacceleration)

  28. SUMER MeasurementofHanle and ASD effects? P=(92)%; = 96 Helioctr. Dist. = 1.3 R Wind speed w  40 km/s (Raouafi,1999) Hanleeffect: B > 10 G; B < 10; w > 50 km/s SR Doppler-dim.: B < 3 G; B > 30; w > 50 km/s Anisotr. SR Doppler-dim.: B <<1 G; B  20; w  40 km/s (Fineschi, 2001;Raouafi, 2002; Khan, 2012)

  29. SolmeX – COMPASS (ESA M-mission) Peter, et al. Exp. Astron. 2011

  30. Coronal UV Spectro-Polarimeter (CUPS)

  31. Non-Formation Flying CUPS Telescopeexternallyocculted withmulti-stackedapertures Moses, et al. SPIE 2011

  32. INAF-CorMag – 2010 Eclipse The CorMag was operated during the total solar eclipse of July, 11th 2010 on Tatakoto Atoll (French Polynesia)

  33. UV Spectro-polarimetry Polarimetry UV coronallines Spectroscopy UV coronallines Doppler-dimming -shift, -width Hanleeffect Super-radial Doppler -dimming effect Coronal B (Blos;los) Coronal plasma parms (Nion, w, T//, T) + Coronal B effects on plasma (coronalheatingmechanisms, solarwindacceleration)

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