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 !