sola
r e
clip
se,
11.8
.19
99
, W
en
dy
Ca
rlos
an
d J
oh
n K
ern
Structure of solar coronal loops:
from miniature to large-scale Hardi Peter
Max Planck Institute
for Solar System Research
Germany
S. Bingert,
J. A. Klimchuk, C. de Forest,
J. W. Cirtain, L. Golub,
A. R. Winebarger,
K. Kobayashi, K. E. Korreck
– miniature loops
– sub-structure of loops
A&A in press / arXiv 1306.4685
Corona and chromosphere in Hi-C FOV
→ very complex active region: group with may spots
→ no “normal” nice large active region loops…
Small coronal structures
► Hi-C sees structures down to resolution limit
► are these “miniature coronal loops” ? 100x shorter than “normal” loops
→ length: 1.5”– 2” → width: 0.3”– 0.4”
0.2” x 0.2” →Hi-C resolution:
SDO context
Nature of the small coronal structures
– footpoints of hot loops ?probably not: where is the hot loop?!
– really small loops ?HMI shows “monopolar” region…but opposite polarities might be hidden…
15” x 15”
Magnetic field on small scales: the photosphere
–1000
vert
ical m
ag
neti
c fi
eld
[G
]
+1000
0
–400
+400
0
l.o.s
mag
neti
c fi
eld
[G
]HMI / SDO (0.5”/pxl) IMaX/SUNRISE (0.05”/pxl)40” x 40”
Wiegelmann et al (2010) ApJ 723, L185
comparison of HMI and IMaX, not showing the same structures…
≈0.6”
SUNRISE data:opposite polaritieswith footpoint distance ≈ 1”within “unipolar” regions
4.5” x 4.5”
15” x 15”
15” x 15”
miniature loop
Miniature coronal loops ?!
^
^
corona
chromosphere& photosphere
interior
~ 2 Mm
~ 2 Mm
≈ 2”
► there is observational evidence small magnetic loops that reach “into corona”
e.g. Ishikawa et al (2010) ApJ 713, 1310
► can such loops exist ?!
Corona and chromosphere in Hi-C FOV
→ very complex active region: group with may spots
→ no “normal” nice large active region loops…
Comparison of Hi-C and AIA→ clear difference in plage region (upper left)
→ similar appearance in loop region
Hi-C193 Å
Comparison of Hi-C and AIA→ clear difference in plage region (upper left)
→ similar appearance in loop region
AIA193 Å
No sub-structure of loops
► Hi-C has more noise (higher resolution / less photons)
► no substructure visible in loops ! (within noise level)
0.2” x 0.2” →Hi-C resolution:
Getting a lower limit for the strand diameter
diameter ofindividual strands
number of strandsin whole loop:
Either strands have to be smaller than 15 km or the loop is monolithic !
Visualization of strands and cross-loop profile
Hi-C
AIA
integrate along Y – apply PSF – bin to AIA/Hi-C pixel size
Morphological comparison to modelobservations show:
(a) constant cross-section loops in expanding envelope
(b) thin individual loops
(c) thick non-expanding structures
3D MHD modelsshow similar features
→ more work is needed for quantitative comparison…
See also talk by Feng Chenon Wed morning:
“A coupled model for the formation of active region corona”
Conclusions
Structure of solar coronal loops:
from miniature to large-scale
► tiny coronal loop-like structures exist (loop length below 2 Mm)
→ are these miniature coronal loops?
→ how are they connected to the photosphere ?
→ how are they sustained ?
► long coronal loops appear to have no substructure in Hi-C observations (0.2” spatial resolution)
→ either smooth structures
→ or very thin strands (much smaller that 100 km)
High-resolution Coronal Imager (Hi-C)
– single rocket flight on 11 Jul 2012 (NASA/MSFC/CfA/LMSAL)
– imaging in 193 Å band identical to AIA/SDO
– 6x higher resolution compared to AIA
– 5 minutes of data from one active region– first results and description: Cirtain et al (2013) Nat. 493, 501
Hi-C AIA/SDO
pixel size 0.1” 0.6”
FOV ~400” full disk
channel 193 Å 193 Å and many more [ Fe XII ~1.5 MK ]
time cadence 5.5 s 12 sobs. time: 5 min … years
SDO context
Nature of the smallest coronal structures– footpoints of hot loops ?
probably not: where is the hot loop?!
– really small loops ?HMI shows “monopolar” region…but opposite polarities might be hidden…
15” x 15”
45” x 45”
^
Observation of small “photospheric loops
4” x 2.3”
circularpolarization
linearpolarization
integratedlight
time → Dt = 0 s 130 s 260 sHinode/SOTIshikawa et al (2010) ApJ 713, 1310
emergingfluxin / arounda granule
1- signal in lin. pol.
2- circ. pol. at sides
3- lin.pol. vanishes
^
corona
photosphere
interior
consistentwithflux tubebreakingthroughphotosphere
^
Observation of small “photospheric loops
4” x 2.3”
circularpolarization
linearpolarization
integratedlight
time → Dt = 0 s 130 s 260 sHinode/SOTIshikawa et al (2010) ApJ 713, 1310
emergingfluxin / arounda granule
1- signal in lin. pol.
2- circ. pol. at sides
3- lin.pol. vanishes
^
Ish
ika
wa
et a
l (20
10)
reconstruction of B at Dt = 130 s: is this a “photospheric loop” ?