IRIS observations of chromospheric evaporation in multiple flaring kernels

David Graham, Luca Zangrilli, Gianna Cauzzi INAF - Osservatorio Astrofisico di Arcetri

X1.6 flare of September 10th 2014 IRIS 1400Å Slitjaw Image (Si IV)!

•  Sit and stare - 9.4 second cadence

•  Full coverage of impulsive phase

•  Simultanoeus coronal + chromospheric temperature lines (FeXXI + Mg II)

•  High spatial resolution: 0.33’’ x 0.167’’ pixel size

Ribbon development

During ~17:25 – 17:35 UT, the flare ribbon develops at constant rate across IRIS’ slit:

every pixel shows a unique and complete flare evolution at high cadence (81 flares for the price of 1!)"

BIGGER, CLEARER

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NUV flare spectrum

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Mg II sub. 2791.5!

FUV flare spectrum

Fe XXI 1354.1!

Plasma dynamics at max of impulsive phase

81 pixels, 600 time steps

Mg II intensity overlaid with: Red contours = Mg II flows, 15, 30 km/s ; Yellow/blue contours = Fe XXI flows, >270, 200, 100 km/s

Co-spatial Mg II intensity and condensation flows!

Co-spatial Mg II down- and Fe XXI up-flows -> chromospheric evaporation !

Apparent delay in Fe XXI flows wrt chromospheric ones (~65s)!

17:26 17:28 17:30 17:32 17:34Start Time (10−Sep−14 17:25:11)

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17:26 17:28 17:30 17:32 17:34Start Time (10−Sep−14 17:25:11)

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Graham & Cauzzi 2015

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Superposed epoch analysis of all (81) pixels

Temporal evolution of condensation/evaporation

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Fe XXI Velocity

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Mg II Velocity (30% bisector)

Condensation: 30-60 seconds (consistent with older simulations of Fisher 1986/89)!

Graham & Cauzzi 2015

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Superposed epoch analysis of all (81) pixels

Temporal evolution of condensation/evaporation

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Fe XXI Velocity

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Mg II Velocity (30% bisector)

Condensation: 30-60 seconds (consistent with older simulations of Fisher 1986/89) Evaporation duration: ~ 500 s !

Graham & Cauzzi 2015

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Fe XXI Velocity

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Temporal evolution of condensation/evaporation

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Remarkably similar curves for all flaring pixels: "Evidence of elementary flaring kernels?!

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Fermi HXR light curves and spectra SPEX FERMI GBM Count Flux vs Time

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Detectors: NAI_024.6 to 15.2 keV (Data with Bk)15.2 to 24.3 keV (Data with Bk)24.3 to 50.9 keV (Data with Bk)50.9 to 98.8 keV (Data with Bk)98.8 to 296.4 keV (Data with Bk)296.4 to 601.2 keV (Data with Bk)601.2 to 2000.0 keV (Data with Bk)

28-Jul-2015 09:44

Fermi has no spatially resolved information

Fermi HXR light curves and spectra SPEX FERMI GBM Photon Flux vs Energy with Fit Function, Interval 0

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Detectors: NAI_0210-Sep-2014 17:31:00.157 to 17:31:05.277 (Data-Bk)

28-Jul-2015 09:57

thick2 139.,5.20,5.00e+03,6.00,14.5,5.00e+03 vth 0.585,1.90,1.00 full chian 1.26e-04vth+thick2

No fit done.

Power ~ 4 x 1029 erg s-1!

δ=5.2

Ec~15 keV

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UV flaring kernels (IRIS SJIs)

10−Sep−2014 17:31:03.890 UT

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UV flaring kernels (IRIS SJIs)

17:20 17:24 17:28 17:32 17:36Start Time (10−Sep−14 17:18:51)

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New Kernel IntensityFermi 50 − 100 keV

Electron flux > 1011 – 1012 erg cm-2 s-1!

Conclusions

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•  IRIS gives us the most complete view of evaporation/condensation to date

•  Evaporation and condensation flows co-spatial (possible delay)

•  Fe XXI line is always completely blue-shifted

•  Condensation time of < 60 seconds very similar to (old) simulations.

•  Ribbon size <1.5’’ Excitation time ~ 30 seconds

•  Sources show remarkably similar evolution - flare is a progression of single events

•  First attempts of 1-D HD modeling do not give satisfactory agreement with flow evolution; will attempt RHD models handling radiative transfer in chromosphere

“The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 606862 (F-CHROMA)”