Penumbral-like structures in the solar photosphere: the role of flux emergence

1. Penumbral-like structures in the solar photosphere: the role of flux emergence Salvo L. Guglielmino1, Francesca Zuccarello1 & Paolo Romano2 1Dipartimento di Fisica e Astronomia – Università di Catania, Italy2INAF – Osservatorio Astrofisico di Catania, Italy 1st SOLARNET Workshop “Radiative Processes in the Sun and Stars”Wrocław, 1 – 2 April 2014

2. Magneticfluxemergence • A complete studyofmagneticfluxemergence, interaction, and diffusionshould take into account some “anomalies” • In the solarphotospherewe can observe • large-scalefluxconcentrations • sunspots (umbrae & penumbrae) • small-scalefluxconcentrations • pores, ephemeralregions, brightpoints …

3. Sunspot: typicalstructure Penumbra Bright dot Umbra Penumbral filaments butalso: orphanpenumbraeandnakedsunspots

4. Why “orphanpenumbrae”? Orphanpenumbraeare bundlesoffilamentarystructures, verysimilartosunspotpenumbralfilaments, butthat are notadjacenttoanysunspot umbra The orphanpenumbrashows the samemotionsobserved in the sunspotpenumbra Zirin & Wang (1991)

5. Models: penumbral-likestructures MHD simulations (Rempel, 2012): magnetoconvection in presenceofhorizontalfieldsisabletoformpenumbralstructureswhen a magneticcanopyoverlies the fluxregion

6. Orphanpenumbrae: properties Orphanpenumbraeactlikebridgesthatconnectdifferentsmallgroupsofpores They are identifiedasrisingmagneticfluxtubes, formingfilaments in the upper atmo-sphericlayers Kuckein, MartínezPillet & Centeno (2012) foundanorphanpenumbrabelow a chromosphericfilament

7. Orphanpenumbrae: formationmechanism photospheric manifestation of a flux rope trapped in the photosphere (Kuckein et al., 2012a,b) the result of an emerging Ω-loop trapped in the photosphere by overlying canopy fields (Lim et al., 2013) the effect of submerging horizontal field in flattened Ω-loops (Jurčak et al., 2014)

8. Answer: evolution and spectropolarimetry LARGE orphan penumbrae in NOAA 11089 Zuccarello et al., ApJ, in press SMALL orphan penumbra in NOAA 11391 Guglielmino et al., ApJL, in press

9. NOAA 11089 • Visible from 2010 July 20 to July 30 • SDO – DOT – HINODE observations: July 22-24, 2010 • Recurrent AR (5 passages on the solar disk)

10. SDO full-disk observations

11. SDO full-disk observations

12. SDO full-disk observations • The orphan penumbrae are visible for more than 48 hours and are larger than umbra regions • The structures appear to fragment during their evolution • These observations clearly that: • the eastern orphan penumbra is formed as the main sunspots lose part of their penumbrae • the western orphan penumbra is forming independently • In both the structures the SDO movie indicates several episodes of flux emergence • Peculiar motions are found in the orphan penumbrae: • upflows in their central regions

13. DOT datasets Hα • Spatial resolution 0".2 (despeckle algorithm) • Imaging in G-band / Red continuum • Spectroscopy in Hα (Gaussian fit: velocity) G-band Red continuum

14. DOT observations Note the sequenceofbrightgranules at the borderof the orphanpenumbra Note the chromosphericfilamentarystructureabove the orphanpenumbra In the chromospherewefindupflows in the central part of the structure

15. HINODE datasets Filtergrams • Broad-band • G-band (4305 Å) • Ca II H (3968.5 Å) • Narrow-band • Na I D1 (5896 Å) StokesI&V • from 22/07/2010 – 21:06 UT to 24/07/2010 – 08:45 UT • FOV: 188" x 111" Spectropolarimetry • Fe I pair • 6301.5 Å and 6302.5 Å • from 22/07/2010 – 22:16 UT to 24/07/2010 – 02:03 UT • FOV: 120" x 120" • Pixel scale: 0.32" • Fast mode • 18 rasterscans

16. Hinode/SP observations Maps of physical parameters from the standard M-E Hinode CSAC inversions (level 1.5 data) Azimuth ambiguity was solved using the Non-Potential Field Calculation (Georgoulis, 2005) Line-of-sight (LOS) velocities were calibrated assuming plasma at rest in umbrae Raster scans aligned through cross-correlation algorithms Asymmetryin Stokesprofiles

17. Asymmetry in Stokesprofiles • Stokes Q, U, and V profiles exhibit a very asymmetric shape in individual points of the orphan penumbra • Stokes I has often an asymmetric, broadened profile in these points • These asymmetries indicate the presence of a multi-component magnetic atmosphere in these pixels, that suggests the presence of differently oriented field lines along the line of sight “uncombed” structure!!!

18. HINODE/SP: evolution Dark blue/bluecontours (upflow): -3/-1.5 km s-1 Red/light redcontours (downflow): +3/+1.5 km s-1 Red contours: PolarityInversionLines (PILs)

19. HINODE: peculiarmotions • Peculiar plasma flows are cospatial with the western orphan penumbra: a central upwardmotion and downflows at the edges of the structure, with max values at about -4 km s-1 / +6 km s-1 • These motions last for ≈ 8 hours, and decrease in time • The upflowing region seems to fragment the penumbra • Downflows are found in the structure until the end of Hinode observations • These steady motions are interpretedasevidenceofEvershedflows in the orphanpenumbrafilaments

20. HINODE: magneticconfiguration • The penumbral filaments of the orphan penumbrae connect regions of opposite magnetic polarity • The western orphanpenumbrahasanaveragemagneticfieldof≈ 1000 G, with a maximumof≈ 1800 G, decreasingwithtime • Thisstructureliesabove a PIL, with a maximumhorizontalfieldof≈ 1500 G • The azimuth angle in the region is very homogeneous • Magneticfieldlines show a “directconfiguration”, beingalmostperpendicularto the PIL and following the positive-negative direction

21. HINODE/SP: parameters

22. Higheratmosphericcounterpart • Hαimages do NOT show anyfilamentsabove the orphanpenumbrae • Also AIA images at 304 Å, referringto the lower corona, do NOT show the presenceofanyfilamentsabove the orphanpenumbrae in the followinghours • After a solar rotation, the recurrent AR NOAA 11089 (= NOAA 11100) has a filamentabove a highlysheared PIL • no clearcorrelationwith the presenceof the orphanpenumbrae

23. NOAA 11391 • Visible from 2012 January 3 to January 13 • SDO – HINODE observations: January 10-12, 2012 • Decaying AR (2 passages on the solar disk)

24. High-resolutionosbervations • Lim et al. (2013) studied this AR using observations carried out at the New Solar Telescope, in the TiO band (705.7nm) and in the Hαblue wing • They found an “orphan penumbra” near the large trailing sunspot of the AR, with overlying fields

25. HINODE datasets Filtergrams • Broad-band • G-band (4305 Å) • Ca II H (3968.5 Å) • Narrow-band • Na I D1 (5896 Å) StokesI&V • from 10/01/2012 – 15:34 UT to 11/01/2012 – 02:07 UT • FOV: 188" x 111" Spectropolarimetry • Fe I pair • 6301.5 Å and 6302.5 Å • from 10/01/2012 – 15:34 UT to 10/01/2012 – 18:35 UT • FOV: 297" x 164" • Pixel scale: 0.32" • Fast mode • 2 rasterscans

26. Photosphericevolution: G band

27. HINODE/SP: parameters

28. HINODE/SP: parameters

29. HINODE: results • The penumbral filaments form after the emergence of an ephemeral region, that gives rise to two pores • The emergence zone has upflow of ≈ 1 km s-1 and an averagehorizontalfieldof≈ 650 G • The penumbralfilamentsformafterabout 2 hours and slightlymoveeastwardswithrespectto the leading spot of the AR • The regionhasanaveragefieldof≈ 1000 G and liesabove a S-shapedPIL, alongwhichline-of-sightmotionsofabout±2 km s-1 are observed (bothinversion and Doppler) • No evidenceof a fluxropeabove the structure

30. Chromosphericevolution: Ca II H • Lim et al. (2013) found a magnetic canopy over the filaments and an Hαbrightening at oneof the edgeof the structure • Indirect confirmation of the presence of the magnetic canopy • interaction between the positive patch of the emerging bipole and the plage negative field • presence of a strong Ca II H brightening, likely due to magnetic reconnection between these two flux systems

31. Summary • NOAA 11089 shows the presenceoflargeareas– 23" x 5" – coveredbyorphanpenumbraethathave a lifetime of days and fragment during their evolution • The magneticfieldlineshavedifferentinclinationsalong the lineofsight,indicatinganuncombedstructure • The orphanpenumbrae show upflows in the central part and downflows at the edges, lastingforhours and decreasing in time • The magneticfieldvectorhas a strong horizontalcomponent in the western orphanpenumbra, thatliesabove a PIL • NOAA 11391 show the presenceofpenumbral-likefilamentsnear the leadingsunspot, in a regionofpolarityinversion The combination of the horizontal fields of emerging Ω-loops and an overlying canopy can give rise to the observed structures

32. Orphanpenumbrae: formationmechanism photospheric manifestation of a flux rope trapped in the photosphere (Kuckein et al., 2012a,b) the result of an emerging Ω-loop trapped in the photosphere by overlying canopy fields (Lim et al., 2013) the effect of submerging horizontal field in flattened Ω-loops (Jurčak et al., 2014)