Feb. 3-5, 2003 4th Solar-B science meeting 1

Corona-Photosphere Connection with Spectropolarimeter

Yukio Katsukawa

(Univ. of Tokyo)

Feb. 3-5, 2003 4th Solar-B science meeting 2

Corona B at photosphere• Global relation between AR

corona and magnetic fields has been well studied

Magnetic Flux Soft X-ray Corona

Fisher et al. (1998)BP Energy flux Magnetic fields

Feb. 3-5, 2003 4th Solar-B science meeting 3

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

Feb. 3-5, 2003 4th Solar-B science meeting 4

Observations with spectropolarimeter

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

Stokes profiles (I, Q, U, V)

Advanced Stokes Polarimeter (ASP)

Feb. 3-5, 2003 4th Solar-B science meeting 5

B and Jz map

0/ zBJz ),,( BzByBxB

NOAA9912 observed with ASP

～ 10arcsec～ 20mA/m2

Feb. 3-5, 2003 4th Solar-B science meeting 6

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

Feb. 3-5, 2003 4th Solar-B science meeting 7

TRACE loops • 3 types of loops post-flare loops

(C4.1)

transient loops

steady loops

TRACE 191ANOAA9912

Feb. 3-5, 2003 4th Solar-B science meeting 8

Footpoint locations of TRACE loopsFootpoints on Bz map

Footpoints on Jz map

Feb. 3-5, 2003 4th Solar-B science meeting 9

Relation of Bz between two footpoints• Observed loops…

• If potential fields…

no correlation

weak correlation

not potential →

Feb. 3-5, 2003 4th Solar-B science meeting 10

Relation of Jz between two footpoints

Jz α zz BB /

Not force-free

72%　 263 / 367All loops

63% 153 / 243steady loops

88%　 79 / 90transient loops

91%　 31 / 34post-flare loops

Probability that two footpoints of each loop have opposite sign of Jz

Feb. 3-5, 2003 4th Solar-B science meeting 11

Properties of coronal loop footpoints• Magnetic fields

• Electric currents

Post-flare loops and transient loops have enhanced currents at their footpoints.

EUV loop footpoints generally have strong magnetic fields.

Feb. 3-5, 2003 4th Solar-B science meeting 12

Footpoints of post-flare loops

Footpoint-brightenings just after the flare are coincident withphotospheric current structure

TRACE ASP Jz

Feb. 3-5, 2003 4th Solar-B science meeting 13

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

Feb. 3-5, 2003 4th Solar-B science meeting 14

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 …)

Feb. 3-5, 2003 4th Solar-B science meeting 15

Evolution of photospheric current structure

15:04:13

16:39:02

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