CoronaPhotosphere Connection with Spectropolarimeter

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Corona-Photosphere Connection with
Spectropolarimeter

• Yukio Katsukawa
• (Univ. of Tokyo)

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Corona ? B at photosphere

• Global relation between AR corona and magnetic
  fields has been well studied

Fisher et al. (1998)
Energy flux
Magnetic fields
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But, Not so simple

• Non-uniformity in AR corona
• Strong magnetic fields do not always make large
  heat input (e.g. core of sunspot umbra)
• What kinds of magnetic properties make coronal
  activities and heating?
• ? precise measurements of magnetic fields
• ? identification of loops and their
  footpoints

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Observations with spectropolarimeter
Stokes profiles (I, Q, U, V)

• magnetic fields (Bx, By, Bz)
• filling factors
• Doppler velocities
• temperature

Advanced Stokes Polarimeter (ASP)
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B and Jz map
NOAA9912 observed with ASP
10arcsec 20mA/m2
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Observations of loop footpoints

• Identification of coronal loops and their
  footpoints is essential

Magnetic fields (Bx, By, Bz) Velocity fields (Vx,
Vy, Vz)

• Coronal loops extracted from X-ray or EUV
  observations
• Footpoint positions
• Connectivity

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TRACE loops

• 3 types of loops
• post-flare loops
• (C4.1)
• transient loops
• steady loops

TRACE 191A NOAA9912
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Footpoint locations of TRACE loops
Footpoints on Bz map
Footpoints on Jz map
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Relation of Bz between two footpoints

• Observed loops
• If potential fields

not potential ?
no correlation
weak correlation
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Relation of Jz between two footpoints
Not force-free
a
Jz
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Properties of coronal loop footpoints

• Magnetic fields
• Electric currents

EUV loop footpoints generally have strong
magnetic fields.
Post-flare loops and transient loops have
enhanced currents at their footpoints.
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Footpoints of post-flare loops
TRACE
ASP Jz
Footpoint-brightenings just after the flare are
coincident with photospheric current structure
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Summary

• Non potentiality
• Non force-freeness
• Enhanced magnetic fields at loop footpoints
• Post-flare loops and transient loops have
  enhanced electric currents at their footpoints

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Advantages of Solar-B SOT

• SOT ? seeing-less and accurate magnetic field
• vector maps with uniform
  cadence
• Time evolution of current carrying magnetic
  loops
• (appearance, motions, and disappearance )

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Evolution of photospheric current structure
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