coronal dynamics - can we detect mhd shocks and waves by solar b ?
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2003 Feb. 3-5 Solar B Meeting @ ISAS. Coronal Dynamics - Can we detect MHD shocks and waves by Solar B ?. K. Shibata Kwasan Observatory Kyoto University. Introduction. - PowerPoint PPT PresentationTRANSCRIPT
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