Prospects for numerical solar activity...
Transcript of Prospects for numerical solar activity...
H.N. Wang,X. Huang, H. He
National Astronomical Observatories,
Chinese Academy of Sciences
Prospects for numerical
solar activity forecasting
Outline
1. Background
2. Conventional short-term solar
activity forecasting techniques
3. Pre-eruption indicators
4. Solar eruption models
5. Summary
Please tell us when solar eruptions will come !
1. Background
Please tell us when solar eruptions will come !
Please tell us when solar eruptions will come !
CMCC on line forcasting model :
WSA-ENLIL + Cone-CME
CME
propagation
When and how will CMEs
take place in the solar corona?
2. Conventional short-term solar activity
forecasting techniques
(1) Measures from sunspot
number and area
morphological classification
magnetic classification
Advantages:
easily identified by persons with
a long period of forecasting experience
Disadvantages:
limited physical implications
projection effect
(2) Measures from magnetograms
longitudinal magnetic field:
horizontal gradient
length of neutral line
transversal magnetic field:
singular points
shear angle
current helicity
Advantages:
quantitatively identified by computers
many physical implications
Disadvantages:
projection effect
HSOS magnetogram ( a part of AR 9077)
Singular points in transverse field
Solar flare productivity and magnetic measures
(Cui, Y. M. et al , 2006; Wang, H. N. et al, 2009)
Maximun of horizontal gradient
Number of singular pointsLength of neotral lines
Testing samples
Physical parameters
Magnetic complexity
Training samples
Physical parameters
Magnetic complexity
Artificial intelligence Training model
Test
Results
Modeling with artificial intelligence (NAOC)Li, R. et al, 2007; Wang, H. N., 2008, Yu, D. R., et al, 2009
Model testing results
for M flares in 2001
>=M
correction
rate
<M correction
rate
missing rate
false rate
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
>=M correction rate
<M correction rate
missing rate
false rate
3. Pre-eruption indicators
(1)Photosphere:
Morphology of magnetic field
(magnetic types, neotral lines, singgular
points)
Non-potentiality of magnetic field (shear,
strong gradient, magnetic & current helicity)
Evolution of magnetic field
(flux emerging & cancellation, shear and twist
motion )
Horizontal gradient
Length of neotal line Number of singgular point
1unit =1 pixel
AR 9574(8/11/2001)
Magnetic complexity of photospheric field
HSOS magnetogram
Cui et al, 2007
Implications for:
• those flux-emergence-triggered or
other boundary-variation-
associated CMEs.
• why complicated regions easier to
erupt.
(Zhang & Flyer 2008, ApJ, 683, 1160 )
Bipolar: ~ 0.2 Φp2
Multipolar: ~ 0.035 Φp2
• The upper bound of total
magnetic helicity depends on
boundary condition.
• The upper bound of total
magnetic helicity of multipolar
fields can be 10 times smaller.
Time delay and flare productivity
Cui et al, 2006
(2)Chromoshere and corona
Filament oscillation, repetitive surges,
cavities, sigmoids
Chen, P. f., et al. 2008
Courtesy of H. M. Wang
Sympathetic flares
SXT/Yohkoh XRT/Hinode
http://solar.physics.montana.edu/canfield/sigmoids.shtml
http://solar.physics.montana.edu/press/XRT_Sigmoid.html
Photosphere Chromoshere
and corona
free
energy
building
magnetic types,
neotral lines,
singgular points
magnetic shear,
strong gradient,
magnetic & current
helicity,
filaments
cavities,
sigmoids,
…
eruption
triggering
(driving)
flux emerging &
cancellation, shear
and twist motion
Filament
oscillation,
repetitive
surges, …
Pre-Eruption Indicators
Free energy building indcators
Eruption triggering indicators ?
√
This picture is extracted from G. Holman , 2005
Three-dimensional magnetic reconnection in a solar eruption
Sun, et al., Nature- Com., 2014 Li, et al., Nature-Phy., 2016
Magnetic reconnection between a solar
filamentand nearby coronal loops
Observational samples
Slow and rapid steps of magnetic
reconnection in the chromosphere and
the corona.
(Yang et al. , ApJ, 2015)
Observational samples
Kusano et al., 2008
4. Solar eruption models
Lin & Forbes 2000
MHD equations :
Observations : 8/20/1999
BBSO BBSO SOHO/EIT
SOHO/EIT YOHKOH SOHO/MDI
HSOS
KPNO
Magnetic fields on the photospheric surface
can be taken as a boundary condition
Data-driven numerical simulation
Roussev, I. I. , et al., 2005; Wu, S. T., et al., 2006
Kusano, K ., et al., 2008;Amari, T., et al., 2014
Jiang C. W., et al., 2016, ……
Different
models
Different
resultsWhich one is
reliable?
Case studiesLarge sample
surveys
A twisted flux rope moves out of equilibriumor becomes
unstable, and the subsequent reconnection then powers a
solar eruption (Amari, T., et al., Nature, 2014)
Evolution of the observed magentic field in
AR10930 by SOT/Hinode during the first
half of December 2006
Evolution and eruption
of the twisted flux rope driven driven
by photospheric changes
Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption (Jiang, et al., Nature Com., 2016)
Evolution of the observed magentic field in
AR 11283 by HMI/SDO during September
6-8, 2006
Evolution and eruption
of Topology of corona magnetic field
driven driven by photospheric changes
5. Summary
Data-driven numerical simulation is a promising
technology for numerical solar activity forecasting.
The following points should be emphasized:
High spatial and temporal resolution solar magnetic
field measurement
High spatial and temporal resolution solar
chomospheric and corona imaging
Improved models for coronal magnetic field
reconstruction
Reliable tools for magnetic topological analysis
Improved solutions of MHD equtions
High performance computing
We have a long way to make friend with the Sun
夸父逐日
A Chinses fairy story : KuaFu chasing after the Sun
Thanks !