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
• 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
Unified
model
LDE flares
~ 10^10 cm
impulsive flares
~ 10^9 cm
CMEs
(Giant arcades)
~ 10^11 cm
CDS spinning jet (Pike&Mason)
Solar Jets
•
•
•
•
H alpha jets (surges)
EUV macrospicules
EIT jets
H alpha spinning jet (Kurokawa/Canfield)
LASCO jets
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
Fast shock
(Shibata 1999)
Slow shock
Fast shock
(a,b)： LDE/impulsive
flares and
CME/plasmoid
(c,d) ：microflares
and jets
Should be tested by Solar B
Alfven wave
Can we detect MHD shocks/waves by Solar B ?
-- today’s talk : related new studies
• Modeling of Peculiar Mass Ejections
Associated 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 Ejections
Associated 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
(Jan. 22-25, 1992)
(April 14, 1994)
Giant Cusp Arcade and
Peculiar Mass Ejection
Jan 24, 1992
(Hiei, Hundhausen, & Sime 1993)
Ejection (Y-shaped structure)
velocity
30～40 km/s
Simulations
(Shiota et al. 2003;
extention of Chen-Shibata model, including
heat conduction)
Normalization units
L0  2  10 km T0  10 K t 0  A  7.8 s
4
6
Predicted soft X-ray intensity
（SXT/Al.1）
Y-shaped ejection
1010 cm
What is Y-shaped structure ?
Y-shaped structure = Slow Shock ＆ Fast Shock
Observations : height-time diagram
10
10 cm
the center of
Y-shape
the top of cusp
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
0<DN/s<200
0<DN/s<50
Assume uniform arcade with length of 10^5 km
Angle=0°
Angle=10°
Angle=20°
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°
DN/s/pix
pix
exposure time
Count=100 →10～15 sec
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
=> coronal heating ?
we performed the 1.5D-MHD numerical experiment
including heat conduction and radiative cooling
100000km
Initial condition
T = 104 K = uniform
  (height )4
photosphere
Twist flux tube randomly
 V 2   1 km/s
based on 2D-MHD simulation
of emerging flux
（Shibata et al.1989)
Simulation Results (propagation of
nonlinear Alfvén waves)
Simulation results
(temperature distribution)
Temperature distribution
Heating mechanism
Alfvén wave
Nonlinear effect
Compressional wave
(slow mode & fast mode)
shock formation
Shock heating
Average coronal temperature vs
photospheric velocity amplitude
“Observations” of
simulation results
Yohkoh/SXT
=> flare-like brightening
SXT intensity is too low
TRACE (171Å)
TRACE(EUV) intensity is comparable
to observed intensity for 10^5 km
coronal loop
1998/6/4
TRACE (171Å)
Statistics of “flare”
(shock heating) peak
Index:-1.6 ~ -2
frequency distribution show
power law
↓
intermittent heating due to
MHD shocks generated by
Alfvén waves might be
observed as microflares or
nanoflares !
Conclusion
1.
2.
3.
Unified (reconnection) model of flares and jets predict
generation of slow and fast mode MHD shocks as
well as Alfven waves.
Slow and fast mode MHD shocks can be identified in
Y-shaped mass ejection above giant cusp arcade
(Shiota et al. 2003)
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
Nonthermal
Coronal
Line width