hinode observations of magnetic reconnection -...
TRANSCRIPT
2009/10/05 MR2009 1
Hinode observations of magnetic reconnection:
For understanding dynamics and heating in the solar atmosphere
Toshifumi SHIMIZU(ISAS/JAXA)
US-Japan Magnetic Reconnection 2009at Madison, Wisconsin
2009/10/05 MR2009 2
23 September 2006
23 September 2006
HinodeHinode
3 years of Hinode3 years of Hinode Sunspot - fine structures of magnetic and flow fields on solar surface
Corona – high temperature plasma
2009/10/05 MR2009 3
EUV ImagingSpectrometer（EIS）EUV spectroscopy to obtain LOS
velocity and turbulence maps.
Solar Optical Telescope（SOT）with 50cm diameter aperture0.2 arcsec vector-magnetic and photometric images to investigate magnetic and velocityfields at the solar surface
X-ray Telescope（XRT）High resolution imaging of
Soft X-ray corona
Main Aims: Systems approach to understand generation, energy transfer and release of solar magnetic energy with 3 well-coordinated advanced telescopes onboard Hinode
2009/10/05 MR2009 4
Outline of the talk
Magnetic topology of solar flares, mainly discussed in 1990’s with X-ray observations
Dynamic chromosphere, revealed by Hinode– Giant chromospheric jets– Recurrent jets along sunspot light bridge– Penumbral micro-jetsMagnetic topology of these phenomena
Coronal heating Summary
2009/10/05 MR2009 5
1. Magnetic reconnection as a key physical process in solar flares
Morphology and some signatures observed during major flares strongly suggests reconnection.
X-ray/EUV observations from Yohkohetc.
limbCusp structure(Soft X-rays)
Hard X-ray loop top source
(from Shibata’s cateen)
2009/10/05 MR2009 6
1. Magnetic reconnection as a key physical process in solar flares
X-ray jets and compact flaring in some small flares and micro-flares Emerging flux is involved in reconnecting processemerging flux model
Emerging bipole
SXR
H
(e.g., Shibata et al. 1992, Yokoyama 1996)
(e.g., Shimojo et al. 1998)
X-ray jet
Soft X-Ray(Yohkoh)
Magnetogram(La Palma)
10arcsec
5arcsecEmerging flux (8-16x1017Mx) exists!
2~2.8km/s
10min
Yohkoh SXT
(Shimizu et al. 2002)
2009/10/05 MR2009 7
2. Hinode’s new viewsDynamic chromosphere!
Hinode’s Ca II H imaging observations show that the chromosphere is in full of dynamic events.– Ubiquitous chromospheric jets
(Shibata et al. 2007)– A giant chromospheric jet
(Nishizuka et al. 2008) – Long-lasting recurrent jets along
sunspot light bridges (Shimizu et al. 2009)
– Sunspot penumbral micro-jets(Katsukawa et al. 2007)
2009/10/05 MR2009 8
Dynamic behaviors and Magnetic topology Many scientists believe that dynamic behaviors
observed are due to reconnection. Key observational information for the
understanding are magnetic fields and flows with high spatial resolution.
Inclination ofmagnetic fields(deg)
Azimuth angle of magnetic fields
(deg)
Continuum Intensity
zhoriz jB 0Vertical electrical current density(mA/m2)Stokes
Polarimeter of Solar Optical Telescope (SOT)
2009/10/05 MR2009 9
Surges (chromospheric jets) – Velocity higher than 100km/s– Twisting motion of ejectors– Strong brightening at the footpoint– Magnetic reconnection at low height,
e.g., chromosphere -low corona.
3. Giant chromospheric jets or surgesSimilar to the magnetic field configuration considered in the emerging flux model
(Nishizuka et al. 2008 & Poster)
2009/10/05 MR2009 10
Magnetic reconnections in the solar different atmospheric layers
Difficult to probe the reconnection (diffusion) region.– Strong emissions observed are mainly from plasma heated by
magnetic reconnection, and not from the reconnection site.– Hinode provide measurements of magnetic fields in the
photosphere. Possible to compare magnetic reconnections occurring
at different plasma parameters.
（from Shibata et al. 2007)
Radiation from plasma heated
B and V measurement in the photosphere
Reconnection region
X-ray、EUV VUV, Visible
2009/10/05 MR2009 11
4. Long-lasting recurrent chromospheric jets
SOT/BFI - Ca II H filtergramNOAA10953： 30 April 2007
0 20 40 60 80
020
40
60
80
(単位:秒角)
“Light bridge” in a sunspot umbra
(Shimizu et al. 2009, ApJ, 696, L66)
Jet speed: 26-180km/s(c.f. Vs~9km/s, VA~400km/s)
Almost 2 days
2009/10/05 MR2009 12
Note: Sunspot light bridge and activities Light bridge (LB) – One of fundamental structures in sunspots
– Penumbral (filamentary) structure or cell structures by convection– Lower field strength, more horizontal than in the neighboring umbrae– Field-free convection penetrates a strong magnetic field and forms a
cusp-like magnetic field.
NOAA10953
30 Apr 2007
(Jurcak et al. 2006)
Chromospheric activities– Long-lasting plasma ejections or surges
(e.g., Asai et al. 2001, Bharti et al. 2007)
– Brightness enhancement with TRACE1600A (Berger & Berdyugina 2003)
2009/10/05 MR2009 13
Magnetic fields and Vertical currents
Indicate lying “twisted”magnetic flux （current carrying) loops
In the period of frequent occurrence(29 April 20UT~ 1 May)
Before the frequent period
2009/10/05 MR2009 14
Activities in the LB：Interpretationejections Lying “twisted” magnetic flux
（current carrying) loop– Twisted flux loop is trapped below the cusp-like magnetic field
– Ejections were observed only at the left side of the twisted flux loopFormation of anti-parallel magnetic
field lines Magnetic reconnection Chromospheric plasma ejections
Observed twisted flux tubes– Observed current density jz = 200 mA/m2– Linear force-free field parameter α～ 0.5 – 2.0 [1/Mm]– Loop length L ＝ 8” ~ 6 Mm– Number of pitch along the loop Npitch = 0.2-0.9
2009/10/05 MR2009 15
Evolution of the light bridge over 4 days
Chromosphere: Ca II H time slice
0
5
10
15
20
arcs
ec
06 12 18 00 06 12 18 00 06 12 18 00 06 1229-Apr 30-Apr 1-May 2-May
0
5
10
15
20ar
csec
06 12 18 00 06 12 18 00 06 12 18 00 06 12
0 022
Photosphere: G-band time slice
（UT)
2009/10/05 MR2009 16
Evolution of the light bridge over 4 days
Chromosphere: Ca II H time slice
0
5
10
15
20
arcs
ec
06 12 18 00 06 12 18 00 06 12 18 00 06 1229-Apr 30-Apr 1-May 2-May
0
5
10
15
20ar
csec
06 12 18 00 06 12 18 00 06 12 18 00 06 12
0 022
Photosphere: G-band time slice
（UT)
Less number of jetsRecurrent jets
2009/10/05 MR2009 17
Inferred magnetic field configuration around reconnection site
ejections
The period when jets are recurrently ejected
130-45=8545:twist
85°Trapped flux loop
Umbralfield
The period when less number of jets are observed
90-100°Trapped flux loop
Umbralfield
Trapped flux loop shows less twisted
Note: measured result:field inclination/strength of trapped loop and umbral field
Horizontal to the solar surface
Vertical to the solar surface
Field direction at reconnection site
2009/10/05 MR2009 18
5. Sunspot chromosphere observed with HINODE SOT
CaII H Intensity High pass filtered
Many small-scale jet-like brightenings (penumbral micro-jets, Katsukawa et al. 2007) are newly found
2009/10/05 MR2009 19
Magnetic configuration for producing penumbral micro-jets
4000
km
1600km
CaII H f>3mHz The micro-jets are
launched from in between two penumbral filaments.
Magnetic reconnection can happen in the solar atmosphere even when magnetic fields are not anti-parallel.
Penumbral filament
Mic
ro-je
t
nearly horizontal flux tube(penumbral filament) (Solanki 2003)
more vertical fields
2009/10/05 MR2009 20
6. Coronal heating: Magnetic fields at the footpoints of coronal loops
(Brooks et al. 2008)
Footpoint of coronal loops is rooted in unipolar field regions.
Magnetic reconnection is a key mechanism for understanding the heating of the hot corona.
“Nanoflares heating” Lots of reconnection happen at the
magnetic field lines contacting with small angle?
Magnetic patches with single polarity
2009/10/05 MR2009 21
High-speed Upflows at Loop Footpoints
Excess nonthermal line broadening at temperatures of order 2 MK at footpoints of coronal loops.
Caused by weak component that is highly blueshifted (~100 km/s!)
Disappears at the limb (viewing angle)
DiskCenter (C)
Limb (L)
(Hara et al. 2008)White lines:Magnetic field lines
2009/10/05 MR2009 22
Spicules– Building blocks of the “magnetic” chromosphere– Classical spicules (3-5min, 20km/s), driven by shock waves formed when
global oscillations and convective flows leak upward.– Found much more dynamic spicules; Rapidly formed (~10s), short
lived (10-150sec) and send material upward at speed of 50-150km/s, which are possibly driven by magnetic reconnection.
The structures which connect magnetic flux at the photosphere to corona loops?
2009/10/05 MR2009 23
Important roles of hidden magnetic fields
waveIsobe et al. (2008)
Horizontal fields (yellow) overlapped on granule image
20,000 km
Tip of icebergs
Convective gas flows Horizontally oriented
magnetic flux tube
Ishikawa et al. (2008)
Vertical field not shown here
Hinode found that small-scale horizontal fields exist ubiquitously and behave dynamically (Lites et. al. 2007, Ishikawa et al. 2008)
Nature of hidden weak fields formed by convective gas flows and its roles in heating and dynamics of the atmosphere. (Future works)
2009/10/05 MR2009 24
Summary Hinode observations show that the solar
chromosphere is extremely dynamic. Dynamics is often accompanied by plasma
ejections (jets). Precise measurements of mangetic field vectors at
the photospheric layer provide the inference of the magnetic field configuration at reconnecting sites.
For many chromospheric dynamical phenomena, magnetic fields are not anti-parallel. Rather, magnetic field lines are contacted with small angle.
Magnetic reconnections are a key area for understanding the heating of corona.