chromospheric and transition region signatures of emerging...
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Chromospheric and Transition Region
Signatures of Emerging Magnetic Flux Bubbles
Viggo H. Hansteen & Ada OrtizLuis Bellot, Jaime de la Cruz
Mats Carlsson, Bart De Pontieu Luc Rouppe van der Voort
Schmieder & Pariat 2007 Scholarpedia 2(12):4335
…complex evolution as field and plasma rise into outer atmosphere.
What do we observe when field penetrates photosphere and rises into outer atmosphere?
Swedish 1-meter Solar Telescope (SST) observations
Ortiz et al. 2014, ApJ 781, 126see also Title 1994, AAS 26, 1464, Strous et al. 1996, A&A 306, 947, and Strous & Zwaan ApJ 527, 435
1. Field breaks through photosphere in the form of bubbles
2. Pushing aside and/or reconnecting with ambient field
3. Large perturbations to upper atmosphere properties
Small scale flux emergence
Archontis & Hansteen 2014 ApJL 788 L2Ortiz et al. 2014 ApJ 781 126
Simulations •BIFROST: MHD+RT •24x24 Mm box •Vertical range: -2.5 Mm to +14 Mm above •3360 G flux sheet injected at lower boundary for 105 min
Ortiz et al. 2014, ApJ 781, 126
25 September 2013: case 1
Schematic representation of flux emergence event #1
Configuration of the magnetic field lines at 09:11:34 UT
Positive (white) polarities
Negative (black) polarities
Newly emerged bipole
Pre-existing loop(s)
SJI 1400: …both dark bubble and bright footpoints, some indication of loops joining
Ca 854.2 -60 nm: Dark bubble and (later) bright footpoints
Wavelength
Time
Time-sliced spectra at highlighted pixel:
history of event #2
LP pierces photosphereBlue shift in Ca 8542
Blue shift in Mg II k 2796
Blue shift in Si IV 1403
Ortiz et al. 2015, in prep
Transient blueshifts within the dark bubble region
Ca II 8542 blueshift and strong emission at
08:54:16 UT
Si IV blueshifts at 09:02:11 UT
… and 8 minutes later, higher up …
4 ideas: 1. everything happens within the dark bubble
perimeter2. plasma moving upwards3. delay4. transient events
Discussion/Summary
• Can follow small scale flux emergence (in active regions) from photosphere through chromosphere to transition region and perhaps beyond
• Observations, inversions, and simulations tell a quantitatively consistent story
• Pre-existing ambient field plays an important role
• High lying, cool material with high opacity can obscure coronal response
• How much of AR heating is due to reconnection of ambient field with fresh new field from below?
Flux emergence: a trilogy. Paper IIIOrtiz et al. (2015, to be submitted)
Up, up and above!: connecting SST - IRIS - SDO observations
• This paper takes the study initiated in Ortiz et al. (2014) and de la Cruz Rodriguez (2015) further up in the atmosphere.
• Goal: to follow a single event of magnetic flux emergence from the photosphere to the corona with unprecedented spatial, spectral and temporal resolution, presenting thus an integral multi-wavelength study of the solar atmosphere in a case of FE.
• IRIS: 25 September 2013; AR11850: four-step dense raster
• Slit -jaw images: 1330 (TR), 1400 (TR), 2796 (upper chrom.) and 2832 Å (photosphere)
• FOV=50” x 51”
•Rasters in 3 spectral windows:
•FUV 1: 1331.6 - 1358.4 Å (C II)
•FUV 2: 1380.6 - 1406.6 Å (Si IV)
•NUV: 2782.6 - 2833.9 Å (Mg II k)
IRIS
• AIA/SDO images at 171 (Fe IX, upper TR), 193 (Fe XII, corona) and 304 (He II,. chromosphere & TR) ÅAIA
• CRISP @ 1-m SST: 25 September 2013; AR11850: flux emergence
• Scans of Fe I 6302.5 Å (full Stokes), 6563 Å and Ca II 8542 Å:
•1 + 15 + 25 points sequence in 11 s.
• sampling = 200 mÅ for Halpha and 100 mÅ for Ca IR
• FOV=60” x 60”
SST
Time: 7 minutes 1 min. / time step
Wavelength Photosphere Chromosphere
core - 400 mÅ - 600 mÅ - 300 mÅ - 200 mÅ - 100 mÅ
Dark bubbles
Velocities
upflow: -2.4 km/s
upflow: -2 km/s
downflows: 2-3.5 km/s
Time
chromospheric upflows: -5 km/s
Height Photosphere
Chromosphere
Numerical simulations: shape of Ca II 8542 profiles
Using the 3D MHD simulations to understand the profiles:
• The emission is present on both wings without a velocity gradient. The displacement of the absorption profile blocks the peak in the blue wing and reduces the opacity in the red wing (Scharmer 1984).
• The source function increases exactly when the temperature drops steeply at the base of the bubble. non-LTE behaviour already from z~450 km.