High resolution spectro-polarimetric observations of a delta spot hosting eruptive events

1. High resolutionspectro-polarimetricobservationsof a delta spot hosting eruptiveevents A. Cristaldi1,2, S.L. Guglielmino3, F. Zuccarello3, P. Romano4, M. Falco3, L. Rouppevander Voort5, J. de la Cruz Rodríguez6, I. Ermolli1, S. Criscuoli7 1Dipartimento di Fisica– Università Roma Tor Vergata, Italy2INAF – Osservatorio Astronomico di Roma, Italy3Dipartimento di Fisica e Astronomia – Università di Catania, Italy4INAF – Osservatorio Astrofisico di Catania, Italy5ITA, Universityof Oslo, Norway6Department ofPhysics and Astronomy, UppsalaUniversity, Sweden7NSO – National SolarObservatory, Sunspot, USA

2. Delta spot characteristics • Delta spot: a sunspotwithumbraeofoppositepolarities inside the samepenumbra • Strong shear flowsare often observed along the PIL of flaring δ spots (Denker & Wang, 1998). • Curvedpenumbralfilaments, cospatialtotheseshearflows and almosttangentialto the sunspot umbra, can beobserved, • Thesetangentialpenumbralfilamentsprovide a first indicationofhighlytwisted (sheared) magneticfieldlines.

3. Velocityfields in delta spots Earlier LOS velocitymeasurementsof the regionofseparationbetweenoppositepolarities in δspots(δ spot PIL) gaveindicationofupwardmotions. More recently: Supersonicdownflows (14 km/s) and lowerupflowsof 1.5 km/s weredetectedalong the δ spot PIL forabout 3 hours MartinezPilletet al, 1994 Liteset al., 2002; Denkeret al.,  2007; PrasadChoudhary & Deng, 2012 Takizawaet al., 2012  Downflows and upflows (3 km/s) along the PIL:origin in the Evershed flow due toflutedpenumbralfilamentswithopposingflows in interleavedmagneticfieldlines: abruptbendingof the penumbralfilaments in proximityof the PIL Motions due to the submergenceofanΩ-loop

4. Observational data sets – NOAA 11267 Observed on the 6th of August, 2011 37 minutesofobservations , from 09:00:05 UT

5. HMI/SDO: magnetograms and continuum images SST FoV SDO subFoV SDO Doppler velocitiessubFoV • At the timeof the observation the AR 11267 was 2-days old • Classified as βγδ • 6 C-classflaresduringitspassageacross the solar disk

6. HMI/SDO: magnetograms and continuum images Evolutionof AR NOAA 11267 • redcontours: umbra • yellowcontours: penumbra • redarrow: δ spot During the 21 hoursreported in thissequence the δ spot changesitsshape: the positive umbra decreases, but the presenceof the negative fragmentpersists

7. HMI/SDO: Magneticflux trend in NOAA 11267 • The greenband indicates the CRISP observingperiod • The verticallines indicate the flares and theirmagnitudes • During the timeof CRISP observations the negative magneticflux(bluesymbols) is in a decreasingphase • The positive flux (redsymbols) isalmostconstant The analyzedtimeintervalcorrespondsto HMI magnetogramsacquiredfrom 00:00:00 UT on 5 August to 23:59:00 UT on 7 August.

8. HMI/SDO Dopplergrams Blackarrow: location of the PIL separating the twooppositepolaritiesof the delta spot. The LOS motions in the proximity of the δ spot PIL lasted for almost 15 hours !!

9. CRISP/SSTdata analysis Indicationof the location ofupward (- 3 km/s) and downward (3 km/s) motions along the δ spot PIL in the chromospheric image (inverted colors) Part of SST FoVselectedfor SIR inversion FoVof the figuresdisplayed in the right panel FoVof the zoomedregion

10. CRISP/SST velocity fieldsalong the δ spot PIL • Velocitymapobtainedfrom the Gaussianfitof the 557.6 nmline • Strong evidence of upflows and downflows along the PIL separating the two magnetic polarities of the δ spot • The temporalbehaviorof the velocity in squares (9 x 9 pixels) A and B are reported in the plot • The trend reportedindicatespersistentupflows and downflowsin the regionsanalyzed • The velocitymeasured in squares A and B can reach up to +/- 3 km/s A B C

11. LocalCorrelationTracking (LCT) • Mapof the horizontalvelocityfield • deducedusing the LCT on wide band Ca II images.

12. Mapsfrom SIR inversionof CRISP data - zoom

13. SST: Ca II H WB and linecore at 396.8 nm • Light bridgesare present in the AR • The region between the two magnetic polarities of the δ spot is not separated by a “segmented light bridge”, • Weobserve a filamentary structure, having the aspect of a collection of highly sheared penumbralfilaments

14. Delta spot & flares • The complexconfigurationofδspotsmagneticfieldsoftengives rise to a numberofflares and eruptivephenomena, due torearrangementof the magneticfieldlines, due toreconnection • Westudysuchevents in AR NOAA 11267 • The yellow band indicates the CRISP observingperiod • The verticallines indicate the flares and the eruptivephenomena • orangelines: flares • green line: CME • bluelines: ERU and LEA events

15. HMI/SDO: Magneticflux trend in NOAA 11267 • We observe that some flaring events corresponds to abrupt decreases in the magnetic flux

16. HMI/SDO: Helicityflux trend in NOAA 11267 • Most of the flares occur during the increasing phase of the helicity flux

17. AIA/SDO: the C4.1 flare in NOAA 11267 • Isophotes suggest that the C4.1 flare takes place in the δ spot

18. Conclusions • Observations of persistent downflows and upflows (3 km/s) observed with CRISP (40 minutes) and HMI (15 hours) in proximity of the δ spot PIL • The magnetic field is highly sheared along the δ spot PIL • The regionshows a filamentarystructureresembling a bunchofpenumbralfilamentswrappedaround the negative polarity • The mostprobableprocessisrelatedtopenumbralfilamentsbending and diving in the subphotosphericlayers, nottoΩ-loopsubmergence • . The observedmotionsmaybe • thereforerelatedto the Evershed • flow in the bendingfieldlines +++ - - -

19. Future work • Analyze the AIA observationsof the flaresoccurring in δ spot • The C4.1 flareoccurred in NOAA 11267 seemstoberelatedwith a CME observedafterabout 1.5 hours • Determinewith full SDO spectropolarimetricmeasurements the helicityflux in thisregion • Study more in detail the evolutionof the CME • Analyzehigh-resolutionobservationsto deduce the presenceofflareprecursors