Coronal Dynamics- Can we detect MHD shocks and waves

by Solar B ?

K. Shibata

Kwasan Observatory

Kyoto University

2003 Feb. 3-5 Solar B Meeting @ ISAS

Introduction

• Recent space observations such as Yohkoh, SOHO, TRACE have revealed various evidence of magnetic reconnection and common properties in flares/CMEs, leading to unified view of flares/CMEs.

Impulsive flares LDE flares Giant arcades (CMEs)

Plasmoid (flux rope) ejections

impulsive flares ~ 10^9 cm

LDE flares~ 10^10 cm

CMEs (Giant arcades) ~ 10^11 cm

Unified model

Solar Jets

• H alpha jets (surges)• EUV macrospicules• EIT jets• LASCO jets

CDS spinning jet (Pike&Mason)

H alpha spinning jet (Kurokawa/Canfield)

EIT-LASCO jet (Wang, Y. M.)

Unified model of flares and jets

(Shibata 1999)

(a,b) ： LDE/impulsive flares and CME/plasmoid

(c,d) ： microflares

　　　　　 and jets

Unified model of flares and jets

(Shibata 1999)

(a,b) ： LDE/impulsive flares and CME/plasmoid

(c,d) ： microflares

　　　　　 and jets

Fast shock

Slow shock

Fast shock

Alfven wave

Should be tested by Solar B

Can we detect MHD shocks/waves by Solar B ?-- today’s talk : related new studies

• Modeling of Peculiar Mass EjectionsAssociated with Giant Cusp Arcade- Fast and Slow Mode MHD Shocks are Identified !? Shiota et al. (2003)

• Coronal Heating by Alfven Waves- nanoflare is not reconnection, but propagating MHD shocks !? Moriyasu et al. (2003)

• Moreton wave => Narukage et al. (next talk)

Modeling of Peculiar Mass EjectionsAssociated with Giant Cusp Arcade- Fast and Slow Mode MHD Shocks

are Identified !?

Shiota et al. (2003)

Slow and Fast mode MHD shocks have not yet been identified

• no clear evidence of slow and fast mode MHD shocks in SXT images

Impulsive flares LDE flares

Giant Arcades are found at the base of Coronal Mass Ejections

(April 14, 1994)

(Jan. 22-25, 1992)

Giant Cusp Arcade and Peculiar Mass Ejection

(Hiei, Hundhausen, & Sime 1993)Jan 24, 1992

Ejection (Y-shaped structure)

velocity 　　 30 ～ 40 　 km/s

Simulations (Shiota et al. 2003; extention of Chen-Shibata model, including

heat conduction)

K1060 Tkm102 4

0 L s 7.8t A0 Normalization units

Predicted soft X-ray intensity （ SXT/Al.1 ）

Y-shaped ejection

cm 1010

What is Y-shaped structure ?

　 Y-shaped structure = 　 Slow Shock ＆ Fast Shock

Observations : height-time diagram

the top of cusp

the center of Y-shape

cm1010

Simulations : height-time diagram

Triangle = Y-shaped structure = slow and fast shocks

Effect of Angle between arcade axis and line-of-sight

SXT/Al.1 09:20 Angle=20°Angle=0°

0<DN/s<200

0<DN/s<50

Assume uniform arcade with length of 10^5 km

Angle=10°

XRT/Thin Al mesh

SXT/Al.1 XRT/Al mesh

Line-of-sight distance is 10^4 km

XRT/Thin Al poly

SXT/Al.1 XRT/Al poly

Line-of-sight distance is 10^4 km

XRT/Thin Ti poly

SXT/Al.1 XRT/Ti poly

Line-of-sight distance is 10^4 km

Intensity distribution XRT/Thin Al mesh

Depth=10^5 km 、 angle=20°

exposure timeCount=100 →10 ～ 15

sec

DN/s/pix

pix

Coronal Heating by Alfven Waves- nanoflare is not reconnection, but propagating MHD shocks !?

Moriyasu et al. (2003)

Motivation

• Kudoh & Shibata (1999), Saitoh et al. (2001) successfully developed Alfven wave model of spicules and nonthermal line width in corona

• Yokoyama (1998), Takeuchi & Shibata (2001)found that reconnection generate Aflven waves efficiently

• SOHO revealed magnetic carpet, suggesting ubiquitous reconnection in the photosphere

Photospheric reconnection (or turbulent convection) => Alfven waves => coron

al heating ?

we performed the 1.5D-MHD numerical experiment including heat conduction and radiative cooling

photosphere

100000kmInitial condition

T = 104 K = uniform4)height(

based on 2D-MHD simulation of emerging flux

（ Shibata et al.1989)Twist flux tube randomly

2V 1 km/s

Simulation Results (propagation of nonlinear Alfvén waves)

Simulation results (temperature distribution)

Temperature distribution

Alfvén wave

Nonlinear effectCompressional wave(slow mode & fast mode)

Shock heating

shock formation

Heating mechanism

Average coronal temperature vs photospheric velocity amplitude

“Observations” of simulation results

Yohkoh/SXT

TRACE (171Å)

=> flare-like brightening

SXT intensity is too low 　TRACE(EUV) intensity is comparableto observed intensity for 10^5 km coronal loop

1998/6/4TRACE (171Å)

Statistics of “flare” (shock heating) peak

frequency distribution show　　　　 power law

　　　　　　　↓　　 intermittent heating due to MHD shocks generated by Alfvén waves might be observed as microflares or nanoflares !

Index:-1.6 ~ -2

Conclusion 1. Unified (reconnection) model of flares and jets predict

generation of slow and fast mode MHD shocks 　 as well as Alfven waves.

2. Slow and fast mode MHD shocks can be identified in Y-shaped mass ejection above giant cusp arcade (Shiota et al. 2003)

3. Spicules, nonthermal line width, and coronal heating are all explained by Alfven waves if its velocity amplitude > 1 km/s in the photosphere. (Kudoh-Shibata 1999, Saitoh et al. 2001)

4. Alfven waves can be dissipated through nonlinear mode coupling with fast and slow mode MHD waves/shocks. MHD shock heating is flare-like and might be observed as microflares or nanoflares (Moriyasu et al. 2003).

=> Should be tested by Solar B

fast shock & slow shock

β<1 fast wave ： Va slow wave ： Cs

in the present case, these are weak shocks 　　 fast shock ~ fast wave ~ Va slow shock ~ slow wave ~ Cs

Va ~ 250 km/s Cs ~ 120 km/s

Alfven wave model of spicules:1.5D-MHD simulation (Kudoh-Shibata 1999)

3. Are sufficient energy flux carried by Alfven waves into corona ?

(Saitoh, Kudoh, Shibata 2001)

Energy flux transported to the corona

by Alfven waves

NonthermalCoronal Line width