s.l. guglielmino eheroes final meeting leuven – 8 th february 2015 analysis of a c4.1 flare...
TRANSCRIPT
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015
Analysis of a C4.1 flareoccurred in a δ spot
S.L. Guglielmino1, F. Zuccarello1, P. Romano2,A. Cristaldi3,4, M. Falco1, I. Ermolli4, S. Criscuoli5
1Dipartimento di Fisica e Astronomia – Università di Catania, Italy2INAF – Osservatorio Astrofisico di Catania, Italy
3Dipartimento di Fisica – Università Roma Tor Vergata, Italy4INAF – Osservatorio Astronomico di Roma, Italy 5NSO – National Solar Observatory, Sunspot, USA
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 2
Delta spot characteristics
Delta spot: a sunspot with umbrae of opposite polarities inside the same penumbra
Photospheric properties:Strong shear flows are often observed along the PIL of flaring δ
spots (Denker & Wang, 1998). Curved penumbral filaments, cospatial to these shear flows and
almost tangential to the sunspot umbra, can be observed in δ spots. Such tangential penumbral filaments provide a first indication of
highly twisted (sheared) magnetic field lines.
Many of the strongest and most geo-effective flares occur in δ spots!!!
Cristaldi et al. (2014), ApJ 789, A162
Many of the strongest and most geo-effective flares occur in δ spots!!!
Cristaldi et al. (2014), ApJ 789, A162
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 3
Observational data sets – NOAA 11267
Instruments Wavelength Spectral points
Pixel size (arcsec)
Time resolution
(sec)Observation days
SST
Fe I 5576 Å 20 0.0592 28 6 - 19 Aug 2011
Fe I pair 6302 Å 15+15 0.0589 28 6 - 19 Aug 2011
Ca II H core and WB - 0.0338 9 6 - 19 Aug 2011
SDO
hmi.M magnetograms - 0.5 720 5 - 7 Aug 2011
hmi.IC continuum - 0.5 720 5 -7 Aug 2011
hmi.V_Doppler velocities - 0.5 720 6 Aug 2011
aia.intensity - 0.6 12 6 Aug 2011
Observed on the 6th of August, 2011
37 minutes of SST observations, starting at 09:00:05 UT
Ancillary data sets: XRT, Rhessi, Goes
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eHeroes Final MeetingLeuven – 8th February 2015 4
- At the time of the observations AR NOAA 11267 was 2-days old- Classified as βγδ- 5 C-class flares during its passage across the solar disk
HMI/SDO: Magnetograms and continuum images
SST FoV SDO subFoV SDO Doppler velocities subFoV
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eHeroes Final MeetingLeuven – 8th February 2015 5
HMI/SDO: Magnetic flux trend in NOAA 11267
The green band indicates the CRISP observing period
The vertical lines indicate the flares and their magnitude
During the time of CRISP observations the negative magnetic flux (blue symbols) is in a decreasing phase
The positive flux is almost constant (red symbols) The analyzed time interval corresponds to HMI
magnetograms acquired from 00:00:00 UT on 5 August to 23:59:00 UT on 7 August.
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eHeroes Final MeetingLeuven – 8th February 2015 6
- red contours: umbra- yellow contours: penumbra- red arrow: δ spot
During the 21 hours reported in this sequence the δ spot changes its shape: the positive umbra decreases, while the the negative fragment persists and rotates in the clockwise direction
HMI/SDO: Evolution of AR NOAA 11267
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eHeroes Final MeetingLeuven – 8th February 2015 7
Characterization of the plasma properties of the δ spotobserved during the post-flare phase
High Resolution Observations+ SDO
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eHeroes Final MeetingLeuven – 8th February 2015 8
Velocity fields in δ spots
Earlier LOS velocity measurements of the region of separation between opposite polarities in δ spots (δ spot PIL) gave indication of upward motions.
More recently:
Martinez Pillet et al., 1994
Lites et al., 2002;
Denker et al., 2007; Prasad Choudhary & Deng, 2012
Takizawa et al., 2012
Supersonic downflows (14 km/s) and lower upflows of 1.5 km/s were detected along the δ spot PIL for about 3 hours
Downflows and upflows (3 km/s) along the PIL: origin in the Evershed flow due to fluted penumbral filaments with opposing flows in interleaved magnetic field lines:abrupt bending of the penumbral filaments in proximity of the PIL
Motions due to the submergence of an Ω-loop
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 9
HMI/SDO Dopplergrams
Black arrow: location of the PIL separating the two opposite polarities of the delta spot.
The LOS motions in the proximity of the δ spot PIL lasted for almost 15 hours !!
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eHeroes Final MeetingLeuven – 8th February 2015 10
Indication of the location of upward (- 3 km/s) and downward (+ 3 km/s) motions along the δ spot PIL in the chromospheric image (inverted colors)
Part of SST FoV selected for SIR inversionFoV of the figures displayed in the right panelFoV of the zoomed region
CRISP/SST Data analysis
Chromospheric brightenings: ribbons during the post-flare phase…
Here is the δ spot !!!
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 11
CRISP/SST: velocity fields along the δ spot PIL
BC
A
Velocity map obtained from the Gaussian fit of the Fe I 557.6 nm line
Strong evidence of upflows and downflows along the PIL separating the two magnetic polarities of the δ spot
The temporal behavior of the velocity in squares (9 x 9 pixels) A and B are reported in the plot
The trend reported indicates persistent upflows and downflows in the regions analyzed
The velocity measured in squares A and B can reach up to +/- 3 km/s
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eHeroes Final MeetingLeuven – 8th February 2015 12
Map of the horizontal velocity field • deduced using the
LCT on Ca II H wide band images
• convergence in the region between opposite polarities
Local Correlation Tracking (LCT)
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 13
Maps from SIR inversion of CRISP data - zoom
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eHeroes Final MeetingLeuven – 8th February 2015 14
The region between the two magnetic polarities of the δ shows its filamentary structure: a collection of highly sheared penumbral filaments
In the low chromosphere, we observe the evolution of the ribbons …
SST: Ca II H WB and line core at 396.8 nm
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eHeroes Final MeetingLeuven – 8th February 2015 15
Analysis of the C4.1 flare observed in the δ spot
SDO + XRT + Rhessi + High Resolution Observations
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eHeroes Final MeetingLeuven – 8th February 2015 16
Delta spot & flares
The complex configuration of δ spots magnetic fields often gives rise to a number of flares and eruptive phenomena, due to rearrangement of the magnetic field lines by reconnection
We identify such events in AR NOAA 11267
The yellow band indicates the CRISP observing period
The vertical lines indicate the flares and the eruptive phenomena
orange lines: flares green line: CME blue lines: ERU and
LEA events
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 17
HMI/SDO: Magnetic flux trend in NOAA 11267
Again, vertical lines indicate the flares and the eruptive phenomena
The C4.1 flare occurs during a flux decay
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eHeroes Final MeetingLeuven – 8th February 2015 18
HMI/SDO: Helicity flux trend in NOAA 11267
Most of the flares occur during the increasing phase of the helicity flux (LOS measurements)
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eHeroes Final MeetingLeuven – 8th February 2015 19
The C4.1 flare in AR NOAA 11267
The strongest flare observed during the lifetime of
the AR
Timing
• begin 08:37 UT
• peak 08:47 UT
• end 08:51 UT
XRT activated the Target-of-Opportunity mode
SST began observations at 09:00 UT
Rhessi was in night at the peak, began observations
at 08:59 UT
The flare occurred during the first decrease phase of
negative flux of the δ spot and during helicity
accumulation
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eHeroes Final MeetingLeuven – 8th February 2015 20
SST: Ca II H line core post-flare ribbons
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eHeroes Final MeetingLeuven – 8th February 2015 21
AIA/SDO: the C4.1 flare in NOAA 11267
Isophotes suggest that the C4.1 flare takes place in the δ spot PIL
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eHeroes Final MeetingLeuven – 8th February 2015 22
AIA/SDO: the C4.1 flare in NOAA 11267
• red contours: Rhessi 3-6 keV • green contours: Rhessi 6-12 keV
blue contours: AIA 335 isophotes
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eHeroes Final MeetingLeuven – 8th February 2015 23
AIA/SDO: light curves
Starting time 08:00 UT
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eHeroes Final MeetingLeuven – 8th February 2015 24
XRT/Hinode: evolution
FoV encompassing NOAA 11267FoV encompassing control boxes (quiet regions)
Starting time 08:00 UT
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eHeroes Final MeetingLeuven – 8th February 2015 25
XRT/Hinode: light curves
T_decay XRT Be thick = 8.73 secT_decay Goes 0.5 – 4 Å = 8.06 sec / Goes 1 – 8 Å = 4.47 sec
Starting time 08:40 UT
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Conclusions (i)
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 region shows a filamentary structure resembling a bunch of penumbral filaments wrapped around the negative polarity
The most probable process is related to penumbral filaments bending and diving in the subphotospheric layers, not to Ω-loop submergence
. The observed motions may betherefore related to the Evershed flow in the bending field lines
++
- -
S.L. Guglielmino
eHeroes Final MeetingLeuven – 8th February 2015 27
Conclusions (ii)
AIA observations of the flares occurring in δ spot indicate that:
the flare occurs near the PIL there are three ribbons and a Y-shaped structure the light curves reach saturation…
Rhessi measurements suggest that the bulk of the X-ray emission is located near the crossing point of the Y-shaped structure
The emission in the XRT hardest filter has a trend comparable with that of Goes in the 0.5 – 4 Å channel.
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eHeroes Final MeetingLeuven – 8th February 2015 28
Future work
Determine with full SDO spectropolarimetric measure-ments the helicity flux in this region
Compare more in detail the photospheric characteristics of the flare (HMI) with the chromospheric/coronal structures (AIA)
Study in detail the Ca II H SST dataset during the post-flare phase
Determine if the C4.1 flare occurred in NOAA 11267 is related with a CME observed after about 1.5 hour