1yang liu/magnetic fieldhmi science – 1 may 2003 magnetic field goals – magnetic field &...

1Yang Liu/Magnetic FieldHMI Science – 1 May 2003

Magnetic Field Goals – magnetic field & eruptive events

Yang Liu

Stanford University


• Sources and drivers of solar activity and disturbances.

• Links between the internal processes and dynamics of the corona and heliosphere.

• Applications for space-weather forecasts.


• Sources and drivers of solar activity and disturbances (mechanisms of flares, CMEs, and filament eruption).

– Change of magnetic field during eruption of filaments.

– Change of magnetic field during flares.

– Change of magnetic field during CMEs.

– Emergence of magnetic flux and solar transient events.


• Change of magnetic field during eruption of filaments.


• Change of magnetic field during flares.

q1u1


• Change of magnetic field during CMEs.

Li et al. (2002) used Potential-Field Source-Surface model to detect occurrence of CMEs.

Before CMEs

After CMEs


• Emerging magnetic flux and solar eruptive events.– Emerging flux associated with flares, eruption of filament, CMEs.


• Sources and drivers of solar activity and disturbances (summary).

– Magnetic field changes during transient events; emerging of magnetic flux associates with ( causes?) solar eruptive events.

– Need a method to quantitatively describe this change.

› Magnetic shear angle; Electric current; Source field; Others …

– Need a method to describe variation of this change versus time.

– Need to incorporate this information with further research, application for investigation of mechanisms of solar eruption and for space weather forecast.

– Data requirements.

Obs. Accuracy Spatial Res. Temp. res. cadence interval

B_v priority 2 arcsec -- 10min 6hour

B_los priority 2arcsec -- 5min 6hour

EUV -- priority priority 2min 1hour

Coronal img -- priority priority 10min 1hour

Brightness -- 2arcsec -- 5min 6hour?


• Links between the internal processes and dynamics of the corona and heliosphere.

– Complexity and energetics of the solar corona (instability & energy buildup).

– Relationship of small-scale and large-scale field.

– Large-scale coronal field estimates.


a. 86 active regions with more than 3 major flares (Tian & Liu, 2003);

b. 99 active regions from Mees ( Canfield & Pevstov, 1998);

c. 203 bipolar active regions from Huairou (Tian, et al. 2001);

d. 22 bipolar active regions with long lifetime (at least one rotation) (Lepoz Fuentes, et al., 2003)


• Relationship between small-scale and large-scale magnetic field.– To understand flares and CMEs;– To understand the role of active regions to large-scale field structure.

Wang, et al. (2002)


• Relationship between small-scale and large-scale magnetic field (cont’)

Potential Field Model

Force-free Field Model


• Large-scale coronal field estimates (based on a Horizontal Current Current-Sheet Source-Surface model (HCCSSS)).


• Links between the internal processes and dynamics of the corona and heliosphere (summary).

– Processes for energy & instability buildup still remain unknown. Two mechanisms, the subphotospheric process or the photospheric shear motion, may in fact both work.

– Observations show links between small-scale and large-scale fields, and also relates with solar eruptive events.

– Coronal modeling discovers two types of large-scale closed field, one of them, helmet streamer, strongly associates with halo-CMEs.

– Need a way to link those stuffs.

› Helicity; magnetic topology; …

– Data requirements:

› Same as previous one.


• Applications for space-weather forecasts.

– Coronal magnetic structure and solar wind.

› Based on coronal field extrapolation ( generally from a Potential Field Source Surface model) and Wang & Sheeley’s empirical model.

– Space weather based on an integrated model coupling efforts of modeling from the Sun to the Earth.

› Provide boundary, initial condition for the integrated model (observation of synoptic sun; solar coronal modeling from various models; etc.);

› Provide data representative to solar transient turbulence (such as change of magnetic field described previously), solar eruptive mechanism, and etc… based on SDO’s observation and basic research worldwide.

1yang liu/magnetic fieldhmi science – 1 may 2003 magnetic field goals – magnetic field &...

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