y. katsukawa and s. tsuneta national astronomical observatory of japan
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Observational Analysis of the Relation between Coronal Loop Heating and Photospheric Magnetic Fields. Y. Katsukawa and S. Tsuneta National Astronomical Observatory of Japan. Magnetic Flux. Soft X-ray Corona. Corona B at photosphere. - PowerPoint PPT PresentationTRANSCRIPT
Nov. 8-11, 200516th Solar-B science meeting
Observational Analysis of the Relation between Coronal Loop Heating and Photospheric Magnetic Fields
Y. Katsukawa and S. TsunetaNational Astronomical Observatory of Japan
Nov. 8-11, 2005 6th Solar-B science meeting 2
Corona B at photosphere
Global relation between AR corona and magnetic fields has been well studied
Fisher et al. (1998)
Magnetic Flux Soft X-ray Corona
BF Energy flux Magnetic flux
Yashiro et al. (2001)
Nov. 8-11, 2005 6th Solar-B science meeting 3
Multi-temperature corona (in active regions)
2MK1MK 10MK5MK
Coronal Temperature
Transiently heatedHotCoolSteady loops
What is the heating mechanism?
flares, microflares(magnetic reconnection)
Yoshida & Tsuneta (1996)
(Nagata et al. 2003)
Nov. 8-11, 2005 6th Solar-B science meeting 4
Falconer et al. (1997, 2000)Relation between Magnetic shear and bright SXT loops
Schmieder et al. (2004)In EFR, spatial and temporal distribution of SXT and TRACE loops were studied
Nov. 8-11, 2005 6th Solar-B science meeting 6
Magnetic fields at the footpoints of coronal loops
Magnetic energy is generated in the photosphere by the interaction between convection and magnetic fields. The energy is transported to the corona along magnetic field lines.
To understand coronal heating, it is important to resolve structure in the corona (i.e. coronal loops), and study magnetic properties at the footpoints of the coronal loops.
Today’s talik(1) Difference of magnetic properties between hot and cool loops(2) Magnetic structure at the footpoints of the cool loops
Identification of coronal loops
(TRACE, SXT)Precise measurement of magnetic fields (ASP)
Nov. 8-11, 2005 6th Solar-B science meeting 7
Observations with Spectro-Polarimeter
Polarized light induced by the Zeeman effect
Magnetic parameters of the photosphere– Intrinsic field strength – Inclination– Magnetic filling factoretc.
I Q VU
mag
mag
mag
magnmag
obs
obs
obs
obs
0
0
01
V
U
Q
I
f
I
f
V
U
Q
I
Nov. 8-11, 2005 6th Solar-B science meeting 8
Hot and cool loops (NOAA 9231)
TRACE 171A1MK corona
Yohkoh/SXT>2MK corona
MDImag. flux in the photosphere
ASP FOV
Katsukawa and Tsuneta 2005, ApJ
Nov. 8-11, 2005 6th Solar-B science meeting 9
Moss = Footpoints of hot loops
Patchy low-lying EUV structure at the footpoints of hot loops
The base of the corona is heated by heat conduction from the overlying hot corona.
Soft X-ray
EUV
>2MK
1MK 1MK
Hot loop
conduction
moss
We can determine footpoint positions of hot loops using moss structure
Nov. 8-11, 2005 6th Solar-B science meeting 10
Difference of magnetic parameters between Hot and Cool loops
Moss (hot Loops)
Cool Loops
Field strength (kG) Inclination (deg) filling factor continuum intensity
Similar Very different
EFR
Sunspot
Non-spot
Non-spot
Nov. 8-11, 2005 6th Solar-B science meeting 11
Formation of pores at the footpoints of the cool loops
In f >0.4 regions, continuum intensities become dark.
Signature of pores
filling factor filling factor
cont
inuu
m in
tens
ity
field
str
engt
h (k
G)
Nov. 8-11, 2005 6th Solar-B science meeting 12
Temperature in the corona vs. Magnetic filling factor in the photosphere
There are HOT corona above about 30 % of f <0.4 regions in the photosphere.
The cool loops can be seen only above f>0.3 regions in the photosphere.
In high f regions, there are little COOL plasma (<10%) as well as HOT plasma
Percentage of the area covered by the moss and the loop footpoints as a funciton of the magnetic filling factor
Nov. 8-11, 2005 6th Solar-B science meeting 13
Hot loops
magnetic elements
Magnetic elements and filling factor
Photospheric magnetic properties of the hot and cool loops– Magnetic filling factors are very different
Photospheric magnetic fields consist of fine magnetic elements. Their diameter is around 100km
filling factor number density
Cool loops
Hot loops Cool loops
Larg
e en
ergy
inpu
t
Sm
all e
nerg
y in
put
Nov. 8-11, 2005 6th Solar-B science meeting 14
Heating rate as a function of the fill. factor
In the quiet sun, the heating should be small. The much lower filling factor (0.01) might make the energy input small.
There is a peak of the heating rate around the filling factor 0.1-0.4
Cor
onal
Hea
ting
Rat
e
filling factor
SunspotPlageQuiet
10.10.01
tnt BBfvF4
1
Hot loops Cool loops
Nov. 8-11, 2005 6th Solar-B science meeting 15
Fan-like cool loops above a sunspot (NOAA 10306)
Steady coronal loops radially extending from the sunspot The temperature of the loops is 1MK Life time is a few hours Many loops have their feet near the boundary of the umbra.
TRACE 171A/continuum TRACE 171A/magnetogram
Katsukawa et al. 2005, in preparation
Nov. 8-11, 2005 6th Solar-B science meeting 16
How to determine the positions of the footpoints
2nd derivatives of intensity profiles are calculated along each loop.
The position where 2nd derivative = 0 is regarded as the footpoint position.
Nov. 8-11, 2005 6th Solar-B science meeting 17
Identification of footpoint positions
Loops and their footpoints are identified in TRACE 171A image.
All loops Bright loops
(I>4DN/pix/s)
Mar. 11
11 8
Mar. 12
16 8
Mar. 13
20 8
Total 47 24
Nov. 8-11, 2005 6th Solar-B science meeting 18
Umbra-Penumbra boundary region
Histogram of continuum intensity shows 3 peaks corresponding to umbra, penumbra, and the quiet sun.
The Umbra-Penumbra (U-P) boundary region is defined as where Ic is 0.2 - 0.7 of the quiet Sun.
umbra
penumbra
quiet
Continuum intensity
U-P boundary
Nov. 8-11, 2005 6th Solar-B science meeting 19
Footpoint positions in terms of cont. intensity
About a half of the loops have footpoints in the U-P boundary region. Umbral side is preferred rather than penumbra.
Umbra 11/47 25%
U-P boundary 22/47 47%
Penumra 13/47 28%
For all the loops
Umbra 8/24 33%
U-P boundary 12/24 50%
Penumra 4/24 17%
Only for the bright loops
umbra penumbra
U-P boundary
Nov. 8-11, 2005 6th Solar-B science meeting 20
Correlation between continuum intensity and magnetic fields
In the U-P boundary region, the field strength and the inclination have negative and positive correlation with the continuum intensity.
Umbra Strong and vertical fields Penumbra Weak and inclined fields
Umbra Penumbra PenumbraUmbra
Nov. 8-11, 2005 6th Solar-B science meeting 21
Magnetic structure in the U-P boundary
Along the U-P boundary, there is spatial fluctuation of the continuum intensity. Field strength and inclination also fluctuate simultaneously.
Interlaced magnetic structure with the spatial scale of 3000 – 4000km .
Nov. 8-11, 2005 6th Solar-B science meeting 22
Footpoint positions and magnetic structure
The footpoints of coronal loops are located where the spatial variability of continuum intensity is large.
Positions of the footpoints
Spa
tial v
aria
bilit
y of
co
ntin
uum
inte
nsity
Interlaced magnetic structure in the photosphere is important in the heating of the coronal loops
Nov. 8-11, 2005 6th Solar-B science meeting 23
Footpoint heating of the TRACE loops
Two kinds of magnetic fields form interlaced configuration
⇒ discontinuity of magnetic fields
⇒ magnetic reconnection heat the base of the corona
⇒ TRACE loops
umbra penumbra
Magnetic fields in the penumbra
Magnetic fields in the umbra TRACE loops
photosphere
corona
Interlaced magnetic structure is more pronounced in penumbrae, but the mag field lines might not reach the corona since the magnetic fields are nearly horizontal there.
Nov. 8-11, 2005 6th Solar-B science meeting 24
Temperature distribution along TRACE loops
TRACE gives nearly flat temperature profiles along loops. Heating is concentrated at their footpoints
The heating mechanism suggested here is consistent with such observations
Aschwanden et al. (2000)
Nov. 8-11, 2005 6th Solar-B science meeting 25
Signature of footpoint heating ?
Vis. cont. UV cont. Hα He I (104.5K)
171A (FeIX/X)O IV (105.2K) Ne VI (105.7K) Mg IX (106.0K)
Bright structures at the footpoints(Sunspot plume)
Katsukawa et al. (2005)
Images obtained with the CDS multi-wavelength observations of the spot
Nov. 8-11, 2005 6th Solar-B science meeting 26
DEM at the loop footpoints
(1)(2)
(3)
(1) (2) (3)Peak at 105.5K 1MK single temp.
(1)(2)
(3)
O V (105.4K) Mg X (106.1K)
LoopsFoopoints
Nov. 8-11, 2005 6th Solar-B science meeting 27
Summary of the TRACE cool loops
Coronal loops seen in the TRACE 171A images have footpoints mostly in the U-P boundary region.
Interlaced magnetic structure in the photosphere is important in the heating of the coronal loops.
Strong EUV emissions from the transition region were observed at the footpoints in the sunspot.
Nov. 8-11, 2005 6th Solar-B science meeting 28
International campaign observation in July, 2005
SOHO
TRACE
SST
DOT
VTT
Ca II HG-bandG-contFe I 6302 mag.(H-alpha) G-band
Ca II HBlue/red cont.H alpha Spectro-polarimetry
He 10830A/FeI 1.5mFeI 6302A Fe IX/X 171A
EIT, CDS, MDI
Shimizu et al. talkKano et al. (P28)
Nov. 8-11, 2005 6th Solar-B science meeting 29
TRACE loops emerging from decaying sunspots
Two small decaying sunspots were observed for several days.
TRACE TRACE WL 3-Jul-2005 06:12:41.000 UT
-140 -120 -100 -80 -60X (arcsecs)
140
160
180
200
Y (a
rcse
cs)
TRACE TRACE 171 3-Jul-2005 06:13:20.000 UT
-140 -120 -100 -80 -60X (arcsecs)
140
160
180
200
Y (a
rcse
cs)
TRACE TRACE 171 11-Jul-2005 18:03:11.000 UT
20 40 60 80 100X (arcsecs)
160
180
200
220
240
Y (a
rcse
cs)
TRACE TRACE WL 11-Jul-2005 18:02:19.000 UT
20 40 60 80 100X (arcsecs)
160
180
200
220
240
Y (a
rcse
cs)
U- Pboundary
nakedumbra
lightbridge
satellitepore
penumbra
umbr
a
The sunspots showed new kinds of the footpoint positions (1) Naked umbra (2) Light bridge
Nov. 8-11, 2005 6th Solar-B science meeting 30
TRACE loops from the naked umbra
Penumbrae had asymmetric distribution around the umbra. There was no penumbra on the northeastern side of the umbra.
The strong magnetic fields in the umbra were directly interacting with surrounding granule.
TRACE TRACE WL 3-Jul-2005 06:12:41.000 UT
-140 -120 -100 -80 -60X (arcsecs)
140
160
180
200
Y (a
rcse
cs)
TRACE TRACE 171 3-Jul-2005 06:13:20.000 UT
-140 -120 -100 -80 -60X (arcsecs)
140
160
180
200
Y (a
rcse
cs)
Nov. 8-11, 2005 6th Solar-B science meeting 31
Light bridge and TRACE loops
The TRACE loops were clearly associated with the formation of the light bridge.
After the formation of the light bridge, it became relatively darker above the light bridge in the TRACE images.
Nov. 8-11, 2005 6th Solar-B science meeting 32
Magnetic structure in a light bridge
In the light bridges, there are relatively weak and inclined magnetic fields close to the vertical umbral fields.
The situation is similar to the U-P boundary region.
Leka (1997)
See also the poster by Jurcak et al. (P15)
Nov. 8-11, 2005 6th Solar-B science meeting 33
Summary and target of Solar-B
We have found some key magnetic features in the heating of the coronal loops.
But, those observations suggest that sub-arcsec structure in the photosphere is important in the heating. (Spatial resolution is not enough to resolve such fine structure with ASP used in our work)
Clarify the relationship between fine magnetic structures and the heating with Solar-B !!