Spectroscopic Detection of Reconnection Evidence with Solar-B

II. Signature of Flows in MHD simulation

Hiroaki ISOBEP.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

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)

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?

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

Inflow

CME (dimming region)

flux rope(prominence)

current sheetand reconnectionjet

Velocity differential emission measure (VDEM) and line profiles are calculated from the result of MHD simulation.

Reconnection inflow

• 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.

Yokoyama et al. 2001

observation

simulation

Example of VDEM and line profile

Line of sightVDEM(V=0 ～±150 km/s

Fe XII 195line profile

Fe XII 195 line profile(resolution=23mA)

Pseudo 3 dimensional view

Pseudo 3D view of blue and red shift components

total Fe XII

-30km/s blue shift 30km/s red shiftinflow

outflow (CME)

Inflows are seen as red and blue shifted converging flows just above the postflare loops/arcades

Summary of inflowGiant 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) component

s. • Inflows can be recognized as blue and red shifted converging flows just above p

ostflare loops/arcades.

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=>inconsistent with observations of explosive events (Innes et al. 1997)

Ca XVII 192.82Fe XII 195.115

• The physical process of magnetic reconnection is not well understood. – Classical resistivity is too small to drive flares via Sweet-Paerker type r

econnection. – Petschek type fast reconnection occurs when resistivity is localized. Bu

t the origin of anomalous resistivity is not clarified yet. Microscopic scale (<100 cm) is much smaller than the scale of pehnometa ( ～ 109 cm)

• Recent scenario– Sweet-Parker reconnection => tearing instability =>plasmoid ejection =

> fast reconnection (Tanuma et al. 2001)– Turbulent or fractal current sheet (Shibata and Tanuma 2001)– Effectively large resistivity =>S-P like reconnection

Line profiles of jet in Petschek and Sweet-Parker reconnection

Line of sightPetschek Sweet-Parker

Doppler shift changes suddenly across the diffusion region

Doppler shift changes continuously in the current sheet

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.

Summary of jet/current sheetGiant arcades in quiet region

Length: ?-200 (arcsec) Width: ?Velocity: 500-2000 km/sTemperature: 3-5 (MK) Emission Measure: ? cm-5 Essential spatial resolution: ?-20 (arcsec)Essential tempoal resolution: ?-1000 (sec)

Flares in active regionLength: ?-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)

Conclusions

• For inflows, spatial relation ship with postflare loops (arcades) and ejecta is important to distinguish from outflow materials.

=>coordinated observation with XRT• Detection of reconnection jets and current sheets is more challeng

ing 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 => spatial resolution – less affected by ambient plasma

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