Solar Magnetism

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Solar Magnetism Activity(?????????)

• Jingxiu Wang
• National Astronomical Observatories
• Chinese Academy of Science

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0. Long list of the discoveries

• 1843 Samuel Heinrich Schwabe 11-y sunspot
  cycle
• 1852 Edward Sabine geo-storms vary with sunspot
  cycle
• 1859 Richard C. Carrington Richard Hodgson
  observe independently a solar flare in WL
• 1908 Ellery Hale intense magnetic fields in
  sunspots
• 1919 Ellery Hale discover 22-y magnetic cycle
• 1949 Alfred H. Joy Milton L. Humason stellar
  flares
• 1950-9 John Paul Wild et al Type II Type III
  radio bursts Andre Boischot Moving Type IV
  burst
• 1951-63 Herbert Friedman et al. intense X-ray
  emission
• 1960-1 Gail E. Moreton Moreton waves in
  chromosphere
• 1962-4 Charles P. Sonett interplanetary Shocks
• 1971-3 Richard Tousey 1974 John Thomas Gosling
  CMEs

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Long list of the discoveries

• 1972-3 Edward L. Chupp et al. Gamma ray lines
  in flare
• 1981 Robert P. Lin et al. flare hard X-ray
  source
• 1980-9 George Doschek Ester Antonucci
  chromospheric evaporation in flare
• 1982 Russell A. Howard et al. Earth-directed
  halo-CMEs
• 1980-82 Edward L. Chupp et al. -- energetic
  solar neutrons
• 1990-5 Donald V. Reames two-class solar
  energetic particles
• 1992 Saku Tsuneta cusp geometry of soft X-ray
  flares
• 1994 Satoshi Masuda et al. loop top hard X-ray
  source
• 1997-8 Alphonse C. Sterling, B.J. Thompson N.
  Gopalswamy et al. -- Coronal dimming and waves

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Key development of the theories

• 1946 Ronald G. Giovanelli idea of magnetic
  reconnection
• 1946 Thomas Gold Fred Hoyle flare theory in
  the view of magnetic loop interaction
• 1958 P.A. Sweet 1963 E.N. Parker slow
  reconnection
• 1964 Harry E. Petschek fast magnetic
  reconnection
• 1966-8 Peter Sturrock early standard flare
  model
• 1973-4 Yutaka Uchida theory of Moreton waves
• 1976 Tadashi Hirayama and 1978 Roger A. Kopp
  Gerald W. Pneuman standard flare models for
  two-ribbon flares
• 1981-2001 Ronald L. Moore et al. --
  tether-cutting model
• 1993 P.A. Isenberg et al. flux rope catastrophe
  model
• 1998-9 K.S. Antiochos magnetic break-out CME
  model

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Outline

• Overview of Solar Magnetism
• Measurements of Solar Vector Magnetic Field
• Studies Based on Vector Magnetic Field
  Measurements
• Flare-associated magnetic changes
• CME source regions and initiation

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Solar Atmosphere
Tachocline
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Solar activity

• Solar flares active region scale activity
• Coronal mass ejections large or global scale
  activity (?)
• Ubiquitous activity on the quiet Sun
  small-scale activity
• -network bright points (filigrees)
• -micro-flares
• -min-filament eruptions
• -X-ray bright points and X-ray jets
• -UV/EUV explosive events
• They are magnetic in nature, and powered by the
  free magnetic energy, and controlled by the
  structure and evolution of solar magnetic field
  

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1. Overview of Solar Magnetism

• 1.1 Scientific Opportunities
• Solar magnetism and activity are one of the most
  exciting and challenging disciplines in solar
  physics and astrophysics
• The magnetic Sun is a laboratory to the dynamic
  behavior of cosmic magnetic fields.
• A key for understanding and predicting the
  impacts of the Sun on the Earths global changes
  and space weather
• A basis for understanding the only known system
  in the Universe for the intelligent life been
  created and flourishing

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Solar Effects on Life and Society
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1.2 Morphology Classification of Solar Magnetic
Field

• 1.2.1 Active region field
• Sunspots strong field diagnosed by Hale (1908),
  which marked the beginning of astrophysics
• Plage enhanced magnetic network, bright areas
  surrounding sunspots and in decayed active
  regions
• EFRs emerging flux region, the basic brick to
  build solar active regions
• MMFs moving magnetic feature, intriguing
  properties of sunspot, and a puzzling phenomenon

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At 0.2 arcsec Spatial resolution
Granule
Penumbra
?Umbra
?
Lightbridge
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• H?Filtergram

?filament
?plage
?fibrils
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Plage how they come from decayed active region
and appear as enhanced network
Plage
Quiet
Enhanced
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• 1.2.2 Ubiquitous small-scale magnetic field on
  the quiet Sun
• Network magnetic field quiet magnetic network,
  first defined from chromospheric observations
  CaII k H? brightness pattern at the borders of
  supergranulation.
• Intranetwork magnetic field
• The weakest component of solar magnetism,
  contributed 1024Mxd-1 flux to the Sun
• Ephemeral (active) regions
• Small scale bipoles in both quiet and
  active Sun . Hageneer (2001) estimated
  5?1023Mxd-1 in the form of ephemeral regions

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• Hinode movie of an enhanced network area

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1.3 Intrinsic Properties

• 1.3.1 Concept of strong elementary flux tubes
• Since the early of 1970s, an idea has been
  widely accepted that more than 90 of Suns
  magnetic flux is in the form of strong flux tubes
  with field strength gt1kG, and diameter lt150 km.
  Convective collapse is the known interpretation.
  There has been debates on this the nature of
  magnetic elements on the Sun strong or weak?
  New facts and idea emerged in the middle of
  1990s.
• 1.3.2 Weak magnetic field on the Sun
• Several key works to re-activate this field
  are Keller et al.(1994), Wang et al.(1995),
  Lin(1995), indicating, indirectly or directly,
  the weakness of IN fields.

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• Indeed, hints of a weak magnetic field
  component that covers the entire Sun have
  been discovered in several recent observations.
  This global phenomenon may be of crucial
  importance for the magnetic cycle and
  variability.
• --- Report from American
  National Research Council (2001, p246)

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Importance of the Weak Field

• Significant amount of Sun flux is in the form
  of intrinsically weak magnetic element. Totally
  1024 Mx flux appeared to the Sun each day in the
  form of intranetwork elements (Wang et al. 1995)
  -- one order of magnitude larger than network,
  two order of magnitude larger than ARs.
• The interaction of IN and network fields may
  provide enough energy to heat the corona and
  accelerate the solar wind (Zhang et al.1998).
• Theoretically, another type of solar dynamo may
  operate in the solar surface layer.

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1.4 Large-scale pattern

• 1.4.1 Active Complex (activity Nests)
• It consists of one or more large and complex
  active regions, persists for several rotations,
  (even years) by additional region forming as
  earlier ones decay. The foci of super active
  regions and major solar events. Stellar spots in
  stellar astrophysics?
• 1.4.2 Coronal hole
• An extended region of the corona with low
  density and assciated with dominantly unipolar
  phtospheric regions having open field topology.
  They are the source of high-speed solar wind.
  Coronal hole are darker in X-ray, but brighter in
  HeI 10830å images.

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? Coronal Hole
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Discovery of Polar kG field by Hinode
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1.5 Two observed modes of magnetic field evolution

• 1.5.1 Flux emergence
• Emerging flux regions (EFRs) and Ephemeral
  regions (ER) in the form of ? loops.
• Moving magnetic features (MMFs) from the border
  of sunspot -- in small bipole pairs? What they
  are?
• Intranetwork elements in cluster of mixed
  polarities.
• U-loop emergence? How about the subsurface
  connection?

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Flux emergence in the form of ?-loops

• It should be understood why
• the appearance of new flux
• to solar surface is mostly
• in the form of ?-loops even
• for smallest ephemeral
• regions. Buoyancy instability?
• If we can simulate an active
• region from very beginning to
• the end of its life. How about
• magnetic fields in other stars?

?
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• The newly emerging magnetic flux region (EFR)
  plays a decisive role in almost all the forms of
  solar activity. EFR seems the driver of solar
  activity in most cases. To identify an EFR, to
  reveal its manifestations, to find the physical
  link of EFR to the energy storage and explosive
  release appear to be a key task in both
  observational and theoretical studies. Since the
  first detection (Bruzek, 1967 Martres et al.,
  1968 Zirin, 1972) EFR has been always a focus in
  solar activity studies.

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• Is there U-loop emergence?
• Spruit et al. (1987) use this model to
  interpret the magnetic flux cancellation and the
  intra- network fields

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1.5.2 Magnetic flux cancellation

• In 1985, magnetic flux cancellation was first
  described by using high resolution Big Bear
  magnetograms (Livi, Wang, Martin, 1995 Martin,
  Livi, Wang, 1995 Wang, Zirin, Shi, 1995). By
  definition, flux cancellation is the mutual flux
  disappearance of closely spaced magnetic fields
  of opposite polarities. It has been identified to
  be the most important mode of flux disappearance
  on the Sun. It is more likely the magnetic
  reconnection in the lower solar atmosphere.

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Flux cancellation (magnetic reconnection in the
lower atmosphere) seen in AR9077
Spatially coincided but time- scales are clearly
different
Two-step recon. scenario
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2. Measurements of Solar Magnetic Field

• 2.1 Zeeman Effect
• 2.2 Radiation Transfer of Stokes Parameters
• 2.3 Spectroscopic and Filter-based Measurements

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2.1 Zeeman effect
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• 2. 2 Radiation Transfer of Stokes parameters
• For a single wave, we can decompose the harmonic
• vibration of the electric vector, E , propagating
  along
• the
  z axis into its x and y
• 
  components. For a full
• 
  polarized wave, the four
• 
  Stokes parameters are
• 
  defined and used to
• 
  describe the magnitude,
• 
  orientation, and
• 
  polarization degree.
• 
  Stokes I is then defined
• as
  I (I,Q,U,V)

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Summary of key relations
?
?
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2.3 Spectroscopic and Filter-based Measurements

• 2.3.1 Spectroscopic measurements, or Stokes
  polarimetry
• -- Use full spectral information of four
  Stokes parameters to determine, at the same time,
  the magnetic vector, and the thermal and dynamic
  parameters of the magnetized plasma point by
  point.
• -- Basically an inversion or a non-linear
  fit of Stokes parameter line profiles.
• -- In principle, Hanle effect,
  magneto-optical effect can be treated in a
  consistent way.

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Transfer equations for polarized radiation

• The transfer equations for polarized radiation
  (Lites et al. 1988). I(I,Q,U,V) , z is the
  position along the line of sight toward the
  observer, is
• the absorption matrix, and j is

the emission vector

• A simple solution is based on the assumption of
  Milne-Eddington model atmosphere the source
  function is described by a linear variation with
  the optical depth, and the other physical
  parameters, such as the field strength, field
  inclination, field azimuth, Doppler shift,
  Doppler width, ratio between line absorption and
  continuum absorption, damping parameter,
  macro-turbulent velocity, stray-light fraction,
  and stray-light shift, are not changing with the
  optical depth.

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Inversion

• Based on the solution of transfer equations for
  polarized radiation, one obtains the best fit of
  observed Stokes profiles by using the
  least-squares algorithm, and considers the
  physical parameters corresponding to the best
  fitted profiles as the atmospheric parameters
  forming the observed Stokes profile.
• The merit function can be written
• .
• where the index i(1,2,,M) stands for
  the wavelength samples, the indices obs and
  syn refer to observed and fitted data,
  respectively. The inversion technique is robust
  when applied to stronger polarization signals
  from active region.

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Average Unsigned BVapp 11.2 Mx cm-2 Noise
(1s) 3 Mx cm-2
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Polarization integrated in wavelength

• The wavelength-integrated circular and Linear
  polarizations are defined as
• One determines the calibration constant relating
  Vtot to longitudinal field and relating Ltot to
  transverse field by these pixels with the
  stronger polarization signal in the quiet region.

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• 2.3.2 Filter-based measurements, or vector
  magnetograph
• -- Use narrow band birefringent filter to get
  images of I, V, Q, U at line wing (or line
  center for QU), then construct the Bx, By, and
  Bz images immediately.
• -- Only use partial information contained in
  the four Stokes profiles.
• -- The thermal and dynamic information of
  magnetized plasma should be determined from
  Dopplergrams or other diagnosis.
• -- Hard to get idea on how strong the
  magneto-optical effects would be.

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?o
Il-Ir??I/?????
?
?
2???2
An idea is that the transverse field is
related to the second order of derivatives of
intensity, therefore should be determined at the
line center since where there is the strongest
signals of the second order of derivatives. But
Jefferies et al.(1989) identified that this idea
was not deduced from accurate treatment.
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• Calibration of vector magnetograms is based on
  the following formulas
• where are calibration
  coefficients for line-of-sight and transverse
  components, respectively, and

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Some vector magnetographs
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2.3.3 Comparison of two types of vector field
measurements

• The Stokes polarimetry provides the most accurate
  measurements of the structural details of the
  magnetic vector and plasma dynamics. But often
  the temporal resolution and sensitivity are
  lower, the field of view is often smaller too.
• The filter-based measurements provide the
  information on the vector field structure and
  evolution, but may suffer from magneto-optical
  effect, crosstalks of Q/U and V. The sensitivity
  and temporal resolution are higher, and often the
  field of view is larger. We can easily integrate
  many thousands of vedio frames to enhance the
  sensitivity.

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3. Studies based on the observed vector
magnetograms

• 3.1 Magnetic connectivity
• 3.2 Magnetic shear (magnetic non-potentiality)
• 3.3 Electric currents
• 3.4 Magnetic helicity (magnetic complexity)
• 3.5 Topology peculiarity
• 3.6 Theoretical extrapolatio

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3.1 Magnetic connectivity

• For the observed bipole which
  configuration is correct ?

In an observed line-of-sight magnetogram
?
Interface
?
?
?-loop
?
?
Knotted Loop
?
-
-


U-loop
O-loop
-
-


?
?
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Two canceling fields are not connected by
magnetic lines in transverse magnetogram
?
?
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3.2 Magnetic shear

• 3.2.1 Definition
• Magnetic shear is a measure of the deviation of
  observed transverse field from the potential
  configuration
• . Hagyard et al.(1984) first
  suggested to use shear angle defined as
  to quantitatively desribe the
  shear degrees. ? is field azimuth.
• Magnetic free energy is defined as
• In more complicated cases, the minimum
  energy status is not that of potential
  configuration.

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Example in the original work of Hagyard et al.
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• Hagyards shear angle (1984)
• LÜ et al.(1993) suggested a vector shear angle
• 
  Where,
• It was suggested to be the only physically
  correct definition of shear angle. For a
  force-free field,

Bo
Bp
??
??
Bot
Bpt
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Two modes of shear development

• Theoreticians think that the magnetic
• shear is caused by shear motion of
• two footpoints of a single loop, but
• obsevers say NO ! For a force free
• field
• 
  from Wang(1994)

?
?
Emergence mode ?
? Generation mode
? Shear emergence
Rotation of the B??
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Evolution of the sheared core in X-rays (Su et
al. 2007)
Hinode observation of shear development
XRT observations of sheared field formation From
0019 UT on Dec 10 To 1243 UT on Dec 12
SOT observations Emerging flux West-to-east
Motion in the Lower sunspot (Kubo et al., 2007)
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3.3 Electric Currents

• Only the vertical currents can be deduced from
  the transverse components of B vector
• In the Fourier domain

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• In AR 6233 for a few flares (Wang et al. 1996)

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Quiet Sun magnetic fields are non-potential
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3.4 Magnetic Helicity

• 3.4.1 Helicity and topology constraint on energy
  status
• Helicity is a measure of magnetic complexity,
  helicity density is defined as
• When , the minimum energy
  status is Bpotential
• When , the minimum energy
  status is Bcons-fff
• that is
• When the connectivity is conserved, the minimum
  energy status is non-linear force-free field
• When all the magnetic lines of force is rooted
  in the photosphere, the maximum energy status is
  the open field, this is called as Aly
  Sturrock constraint

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• 3.4.2 Helicity in active regions
• For an solar active region which has an open
  boundary, the photosphere, the helicity is not
  conserved. Its evolution is determined by three
  physical processes (Wang, 1996)
• The cross helicity plays the decisive
  role surface dissipation contributes 10-3, while
  the dissipation from current helicity is
  ignorable, 10-7.

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• It is more interesting to see the different trend
  of current helicity and line-of-sight flux.

?
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3.5 Topology peculiarity 2D Magnetic
singular point

• If we can derive the peculiarity from
  observations?
• Poincare number by
• Wang Wang (1995)

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Zhao et al. (2005,2007)
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3D null pointsin AR 10720
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3D magnetic skeleton Associated with spiral
magnetic null ?
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4. Flare-associated magnetic changes

• Gradual pre-flare evolution
• Rapid magnetic changes in the course of flares
• Flare-induced signals in polarization

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Magnetic changes observed by Hinode at the
spatial resoultion of 200km
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Three inter-connected issues

• 4.1 Pre-flare magnetic configuration and
  evolution
• 4.2 Rapid magnetic changes in the course of
  flares
• 4.3 Flare-induced signals in polarization
  measurements
• The importance of these studies is to examine our
  physical understanding on the flare phenomenon
  which takes place in a wide range of
  astrophys-ical subjects.

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4.1 Pre-flare state (What we know by 2000 ?)

• Strongly curved magnetic neutral lines, e.g., in
  S shaped or reverse S shaped (Somov 1985)
• Steep gradient of line-of-sight fields, say
  several hundred G per kilometer (Wang Li 1998)
• Filament activation -- darkening, bifurcating
  twisting (Ramsey Smith 1963 Rust et al. 1994)
• Emerging flux regions (EFR) (Bruzeck 1967 Zirin
  1972 ), particularly within great d-sunspots
  (Zirin 1988 ), or in an activity center of active
  regions (Bumba 1986)
• Highly sheared transverse fields (Hagyard et al.
  1984 Lü et al. 1993)
• Magnetic flux cancellation (Livi, Wang, Martin
  1985 Martin, Livi, Wang 1985)
• Current concentration (Moreton and Severny 1968
  Lin Gaizauskas, 1987 Ding et al. 1987)

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Pre-flare State (Whats later attention?)

• Helicity injection introduced into flare and
  active region studies (Wang 1996 Pevtsov et al.
  1996 Bao et al. 1999 Moon et al. 2002a,b
  LaBonte et al. 2007) Relevant theoretical flare
  model proposed (Kusano et al. 2003).
• New attentions on sunspot dynamics in driving (or
  triggering) flares based on more detailed
  observations (Hiremath et al. 2005 Tian
  Alexander 2006 Zhang et al. 2007, 2008).
• Flare productivity based on systematic data-base
  and large sample(Cui et al. 2006, 2007)

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Pre-flare State (More recent efforts)

• Discriminant Analysis of flaring flare-quiet
  ARs (Leka Bernas,2003a,b, 2006, 007), Falconer
  et al (2001, 2003, 2006)
  
• Search for synthesized or effective parameter
  (Schrijver 2007 Georgoulis Rust 2007 Regnier
  Priest 2007)
• Effective-connected fields Beff ??(Fi,j /
  L2i,j)
• gt1600, 2100 G for M, X class flares at 95
  probability
• Unsign flux within 15 Mm to neutral line gt
  2X1021Mx for major flares

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4.2 Rapid magnetic changes in the course of
flares (distinction?)

• First reported by Patterson and Zirin (1981) in
  term of flare-transient. It is soon recognized
  that the flare transient is not real magnetic
  change but produced by transient emission of the
  line for getting magnetograms (Patterson 1984).
• Distinction between magnetic transient and
  magnetic changes in the course of flares can be
  drawn by the facts (1) recover or not in
  magnetograms after the flare impulsive phase? (2)
  associate with the sites of particle
  precipitation ?

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Rapid magnetic changes in the course of flares
(reports in 1999-2008)

• 29 X-class 5 M-class flares
• 24 events with line-of-sight magnetograms
  presented magnetic flux changes
• 9 with vector magnetograms showed horizontal
  field and shear increase during flares
• 13 flares with white-light images presented
  sunspot umbra and penumbra changes
• Most with halo-CMEs

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Rapid magnetic changes in the course of flares
(key facts?)

• All are referring to major flares. (see Sudol
  Harvey 2005 ).
• The magnetic changes are abrupt, persistent, and
  significant in both longitudinal and horizontal
  fields
• Magnetic flux is in order of 1 - 6 times of 1020
  Mx (Wang et al. 2002, Meunier kosovichev 2003)
• Flux density is from 30 to over 200 G (Kosovichev
  Zharkova 1999, 2001 Sudol Harvay 2007).
• Horizontal changes diagnosed from limb events
  (Cameron Sammis 1999 61 Spirock, Yurchyshyn,
  and Wang 2002) and disk observations (Liu et al.
  2005 Wang et al. 2002, 2004 Chen et al.2007).

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Rapid magnetic changes in the course of flares
(key facts?)

• Rapid penumbra decay in the outer d-spot
  structures and the enhancement of inner penumbra
  and central umbra are a remarkable fact uncovered
  by Big Bear group (Wang et al. 2004, 2005 Liu et
  al. 2005 Deng et al. 2005 Chen et al. 2007).
• Penumbral decay seems more related to horizontal
  magnetic changes.

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Example from Sudol Harvey (2005) Why those
parts but not other sites changed?
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Before Flare After Flare
Example from Haimin Wang et al. (2002a) what
caused the rapid enhancement of B? shear ?
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Why study magnetic changes during flare in the
photosphere?

• An aspect has not been confronted by all flare
  models and most theoreticians
• Key facts in understanding flare physics, in
  particular, the triggering of major flares
• Only a few events were studied based on observed
  vector magnetograms, and largely improved
  observations of vector fields available now

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A basic assumption of flare models (Priest
Forbes 2002)

• For a given component (Bn) of the magnetic field
  at the
• solar surface, the magnetic energy in the
• overlying corona is a minimum when j 0.
• But Bn is observed not to change significantly
  
• during a large flare, and so the free energy
  for the
• flare comes from distortions of the magnetic
  field away
• from a current-free (or potential) state. In
  other words,
• the magnetic field before a flare can be
  written as
• B Bph Bcor, where Bph arises from
  photospheric
• or sub-photospheric currents and is invariant
  during a
• flare, whereas Bcor arises from large-scale
  coronal
• currents and is the sourceof the flare energy.
• (Ann. Rev. A
  Ap. 10, 313-377, 2002)

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Overall view of flare models
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An examination with majore flare on January 20
2005?

• A flare of X7.1 class, which took place from
  0626-0726 UT
• Hardest energetic proton event with the highest
  100 MeV proton flux since 1989
• Followed by Earth-directed CME at speed about 882
  km s-1 with clear acceleration
• Coverage of vector magnetograms with adequate
  cadence and sensitivity at HSOS

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Vector magnetograms of AR10720
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AR 10720 at N12W58
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• Difference magnetograms of
• 0731 0616 UT

? B?
? B??
WL
155nm
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• Time-sequence of TRACE 155 nm images

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• SOHO/EIT images Expansion speed of outer loops
  1, 6, 70 km/s, respectively

6.3 km/s
1.3 km/s
73.0 km/s
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Vector magnetograms in heliographic coordination
system
? B?
? B??
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• Free magnetic energy density distribution

0616
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Summary of the observations

• A rapid, significant enhancement of horizontal
  magnetic fields in an extended area centralized
  on the magnetic neutral line and reduction in the
  sunspot outskirts
• The rapid enhancement is likely caused by an
  impulsively fast growth of a sheared EFR
• The enhanced horizontal fields are co-spatial
  with a lower-lying flux rope
• The lower-lying rope remains in position, while
  the outer EUV loops erupted impulsively

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Implication to flare magnetism

• No any flare model has predicted such rapid
  changes in horizontal magnetic fields in the
  photosphere during flares. Each model, say
  standard model (since 1960s 80s), two-step
  reconnection (Wang Shi 1993), tether cutting
  (Moore et al. 1980s-2001), EFR-triggering (Chen
  Shibata 2000), magnetic breakout (Antiochos 1998)
  , seems to only be correct in one or some aspect
  of the physics of flare energy built-up and
  explosive release
• A set of lower-lying ropes and their associated
  horizontal fields seem to play a decisive role in
  triggering the flare in some catastrophic manner

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A suggested scenario

• Rapidly growing core flux rope results in a MHD
  catastrophe of magnetic reconnection, formation
  eruption of higher flux rope for flare/CME

92
4.3 Flare-induced signals in polarization
measurements

• The flare-induced signal in the form of polarity
  reversal in circular polarization, mostly in
  sunspot penumbrae, and recovers soon after the
  flare impulsive phase.
• Impact linear polarization of the Ha (Henoux et
  al. 1990), EUV (Henoux et al. 1983), and X-ray
  (Haug 1981) emissions in flare ribbons resulted
  from the collisional excitation by beams of
  charged particles electrons or ions

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Flare in AR 10720on Jan.15
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5. CME source regions initiation

• 5.1 Outstanding questions about CMEs
• 5.2 Trans-equatorial solar activity
• 5.3 Large-scale nature of the source regions
• -- classification
• -- global magnetic activity
• -- coupling of flare and trans-equatorial
  activity
• -- simultaneous flux emergence
• 5.4 Processes leading to CME initiation
• -- flux cancellation
• -- helicity annihilation
• -- sunspot dynamics

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5.1 Outstanding Questions on CMEs

• Physics of CME initiation signatures?
• What determine when, where how fast of CMEs?
• CME large-scale magnetic structure?
• CMEs long-term magnetic field evolution?
• Role of magnetic reconnection in CMEs?
• Role of magnetic helicity?
• CME flare, filament eruption?
• CME magnetic clouds (or ICME)?
• Why and what determine geo-effectiveness?
• Role Cyclic behaviour of CMEs?
• Mass ejection in stars galaxies?

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5.2 Trans-equatorial solar activity
Trans-equatorial Loops Filaments in Sun-Earth
connection events on November 2004
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• In the Sun-Earth Connection events of November
  2004, we found that solar flares in AR 10696 are
  often associated with large-scale
  trans-equatorial activity (TA) in the forms of
• the formation and eruption of trans-equatorial
  loops (TELs)
• the formation and eruption of trans-equatorial
  filaments (TEFs)
• the trans-equatorial brightening (TEB) beneath a
  trans-equatorial halo CME
• Only those flares that associated with TA are
  CME-associated.

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• Magnetic configuration for the TELs and TEFs
• TELs connecting opposite polarity flux of AR695
  695 ( a coroanal hole) on both hemispheres
• TEFs laying above the large-scale
  trans-equatorial magnetic neutral lines

99

• Brief notes
• Prominence (filament) flare were first detected
  in the 19-th century
• Trans-equatorial magnetic loop (TLs) was
  predicted by Babcock in 1961
• TLs were first detected by Skylab X-ray
  observations in 1973 Their correlation to CMEs
  was established by Khan Hudson (2000), Glover
  et al.(2003), Zhou et al. (2006)
• Trans-equatorial filament (TFs) was first
  described by Wang (2002), and its role in CMEs
  were discussed by Wang et al.(2005, 2006), Zhou
  et al.(2006)

100

• Trans-equatorial filament and its eruption

101

• Formation eruption of TFs

CME
102
6-7 November 2004 event
Related to filament eruptionand
trans-equatorialarcade
dominant electron flux
103
An example from Bastille Day flare/CME Event
104
5.3 Large-scale nature of the source regions
5.3.1CME????????
C1, ???????(EBR)
C2, ?????
C3, ?????
C4, EBR???????
(Zhou, Wang, and Zhang, 2006)
105
Extended Bipolar Regions seem to play a decisive
role in CME process
106
CME productivity
107
Nanchy Redioheliograph observations By (Yayuan
Wen et al. 2006)
108
5.3.2 Global magnetic connectivity in CMEs
Magnetic connectivity with the CME on Oct.
28 2003 (Zhang et al. 2007)
109

• Key topologic connectivity Patterns in some
  global flare/CMEs

Oct. 28, 2003
110
5.3.3 Coupling of trans-equatorial activity with
flares in AR

• It was noticed that one or several major flares
  in the AR are followed by an increase of
  brightness and non-potentiality of a TEL.
• These coupled events, have a lifetime of more
  than 12 hours.
• Their associated halo CMEs always have positive
  acceleration, indicating prolonged magnetic
  reconnections in the outer corona at high
  altitudes.

111
Halo CMEs
112

• Coupling of flare in AR and trans-equatorial loos
  

• ?????????????

TELlight curve
CMEs
113
Further Physics
What causes the formation of TLs and what makes
the TLs sheared, flared and Finally erupted
Why a CME associated with growth of TEL
accelerated that associated with TEL eruption,
decelerated ?
114

• ??????? TEL??????????

Brightness
Temperature
115
A scenario for TEL CME
116
A statistics of CMEs associated with
trans-equatorial activity
117
5.3.4 Quasi-simultaneous Flux Emergence (Zhou,
Wang, and Zhang, 2007 )
118
(No Transcript)
119
5.4 Processes leading to CME initiation

• 5.4.1 Flux cancellation magnetic reconnection
  in the lower solar atmosphere

Example for Bastille Day event on July 14 2000
120
Flux emergence and cancellation in homologous
CMEs initiated form AR 9236
121
5.4.2 Helicity annihilation

• CMEs are suggested to originate from the over
  accumulation of magnetic helicity (Rust Kumar
  1994 Low, 1996). But where helicity comes from?
• Recent studies (Chae et al. 2001 Demoulin et al.
  2002a, 2002b Green et al. 2002 Kusano et al.
  2002 Moon et al. 2002 Nindos Zhang 2002
  Nindos et al. 2003 Pevtsov et al. 2003) have
  revealed the inability of AR fields to create
  enough helicity

122

• This inability of ARs arouses a question whether
  or not the above approaches are fully reasonable?
  What is the source of magnetic helicity in CMEs?
• We tried, on the other hand, to examine whether
  particular helicity patterns are retained by
  CME-associated ARs. We focus on the helicity
  distribution and examine whether the helicity
  patterns support the known CME models.

123

• Contrary to the helicity-charging picture (Rust
  and Kumer 1994), we find evidence that the newly
  emerging flux often brings up helicity with a
  sign opposite to the dominant helicity of the AR.
  
• Moreover, the flare/CME initiation site is
  characterized by close contact with magnetic flux
  of the opposite helicity coinciding with observed
  flux cancellation.

124
Current
Helicity
125

• ( Wang et al. 2004)

126

• If flare/CME initiation results from magnetic
  flux cancellation (Zhang et al. 2001a, 2001b),
  then the opposite polarity flux in the
  cancellation also generally has opposite
  helicity.
• This suggests that the flare/CME initiation
  originates from the interaction of topologi-cally
  independent flux systems. Each flux system in the
  interaction has its own distinct chirality.
  Thusly, some type of topological collapse or
  degeneration must be involved in the flare/CME
  triggering processes.

127
5.4.3 Sunspot dynamics rapid rotation
128

• Rotation of sunspot penumbra (Zhang, Li,
  Song, 2007, ApJL)

129

• 5.4.4 Topology Collapse

130
0. General remarks

• The complexities of the Sun its internal
  structure, rotation and convection, and the
  resulting cyclic and random generation of its
  magnetic fields and the magnto-active, hot,
  explosive, extended solar atmosphere and solar
  wind are fascinating and challenging. Solar
  magnetism and activity are a field that deserves
  your energy and enthusiasm.

131
0. General remarks

• Pay more attention to observations
• Be critical to the well-known models
• Trying hard to not widen but narrow the gaps
  between theories and observations. Without the
  knowledge of Suns vector magnetic fields, we
  have no way to understand the physics of solar
  activity
• Trying hard to see new physics. When the
  mathematics becomes too much complicated it seems
  time to stop to find new physics when the
  observation goes into too many details it seems
  time to stop to think whats the physics we are
  working for

132

• Thank you for your patience
• Wish you a great progress in your studies