Spectroscopic Detection of Reconnection Evidence with SolarB II. Signature of Flows in MHD simulatio

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Spectroscopic Detection of Reconnection Evidence
with Solar-B II. Signature of Flows in MHD
simulation

• Hiroaki ISOBE
• P.F. Chen, D. H. Brooks, D. Shiota, and K.
  Shibata
• Kwasan and Hida Observatories, Kyoto University
• Department of Astronomy, Nanjing University

The Fourth Solar-B Science Meeting February 3-5,
2003
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Observational evidence of reconnection in the
solar corona from Yohkoh and SOHO

• Cusp-shaped post flare loop (Tsuneta et al. 1992)
• Loop top hard X-ray source (Masuda et al. 1994)
• Plasmoid ejection (Shibata et al. 1995)
• Bi-directional jets in explosive events (Innes et
  al. 1997)
• Downflow (McKenzie and Hudson 1999)
• Inflow (Yokoyama et al. 2001)

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Objective of spectroscopic detection of
reconnection associated flows

• More direct evidence for reconnection in the
  corona
• Determine the real (not apparent) velocity
• Impact on the study of reconnection physics
• Reconnection rate
• Diffusion region/current sheet structure
• Petschek, Sweet-Parker, or other?

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MHD modeling

• Based on Chen Shibata (2000) CME-flare model
  triggered by emerging flux.
• 2.5D resistive MHD with heat conduction.
• Anomalous resistivity
• Gravitational stratification

Chen and Shibata (2000) Shiota et al. (2003)
FeXII 195 movie SXT movie
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CME (dimming region)
flux rope (prominence)
current sheet and reconnection jet
Inflow
Velocity differential emission measure (VDEM) and
line profiles are calculated from the result of
MHD simulation.
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Reconnection inflow
observation
simulation
Yokoyama et al. 2001

• Based on the same calculation, Chen et al. (2003)
  show that the inward motion in the EIT images are
  apparent motion real plasma velocity is several
  times larger than the apparent velocity.

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Example of VDEM and line profile
Fe XII 195 line profile (resolution 23mA)
Fe XII 195 line profile
VDEM (V0 150 km/s
Line of sight
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Pseudo 3 dimensional view

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Pseudo 3D view of blue and red shift components
outflow (CME)
inflow
Inflows are seen as red and blue shifted
converging flows just above the postflare
loops/arcades
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Summary of inflow

• Giant arcades in quiet regions
• Size 100-500 (arcsec), Velocity 5-100 (km/s)
• Temperature 1-2 (MK), Emission Measure 1025-27
  (cm-5)
• Essential spatial resolution 10-50 (arcsec)
• Essential temporal resolution 100-1000 (sec)
• Flares in active region (11 M in 1995 148 C in
  1995)
• Size 10-200 (arcsec), Velocity 5-100 (km/s)
• Temperature 3-5MK, Emission Measure 1027-29
  (cm-5)
• Essential spatial resolution 1-20 (arcsec)
• Essential temporal resolution 10-100 (sec)
• It is difficult to distinguish inflows components
  from outflow (CME) components.
• Inflows can be recognized as blue and red shifted
  converging flows just above postflare
  loops/arcades.

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Reconnection jet/outflow and current sheet

• Reconnection jet
• bi-directional jet from X-point (diffusion
  region)
• velocity nearly Alfven velocity (1000-3000 km/s)
• slow and fast shocks

X-point is dark in any line gtinconsistent with
observations of explosive events (Innes et al.
1997)
Fe XII 195.115
Ca XVII 192.82
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• The physical process of magnetic reconnection is
  not well understood.
• Classical resistivity is too small to drive
  flares via Sweet-Paerker type reconnection.
• Petschek type fast reconnection occurs when
  resistivity is localized. But the origin of
  anomalous resistivity is not clarified yet.
  Microscopic scale (lt100 cm) is much smaller than
  the scale of pehnometa (109 cm)
• Recent scenario
• Sweet-Parker reconnection gt tearing instability
  gtplasmoid ejection gt fast reconnection (Tanuma
  et al. 2001)
• Turbulent or fractal current sheet (Shibata and
  Tanuma 2001)
• Effectively large resistivity gtS-P like
  reconnection

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Line profiles of jet in Petschek and Sweet-Parker
reconnection
Petschek
Sweet-Parker
Line of sight
Doppler shift changes suddenly across the
diffusion region
Doppler shift changes continuously in the current
sheet
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Turbulent current sheet

• The current sheet can be highly turbulent due to
  tearing instability and plasmoid (magnetic
  island) formation/ejection. If so, non-thermal
  broadening will be observed.
• Another possibility is that the ion temperature
  than the electron temperature.

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Summary of jet/current sheet

• Giant arcades in quiet region
• Length ?-200 (arcsec) Width ?
• Velocity 500-2000 km/s
• Temperature 3-5 (MK) Emission Measure ? cm-5
  
• Essential spatial resolution ?-20 (arcsec)
• Essential tempoal resolution ?-1000 (sec)
• Flares in active region
• Length ?-100 arcsec Width ?
• Velocity 1000-3000 (km/s)
• Temperature 30-50 (MK) Emission Measure ? (cm-5
  )
• Essential spatial resolution ?-10 (arcsec)
• Essential temporal resolution ?-100 (sec)

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Conclusions

• For inflows, spatial relation ship with postflare
  loops (arcades) and ejecta is important to
  distinguish from outflow materials.
• gtcoordinated observation with XRT
• Detection of reconnection jets and current sheets
  is more challenging task, but has a large impact
  on space and laboratory plasma physics.
• Giant arcade formation is an interesting target
  for EIS and XRT observations from the viewpoint
  of reconnection physics
• time scale is long
• large gt spatial resolution
• less affected by ambient plasma

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