A Granular Light Bridge Observed by Hinode:

Evidence for Naked Granules

Andreas Lagg, Sami K. Solanki, Michiel van Noort

Max Planck Institute for Solar System ResearchKatlenburg-Lindau∗, Germany(*) February 2014: Gottingen

Hinode 7, 12-Nov-2013

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Introduction Light Bridges

Light Bridges

Shimizu (2011)

separate umbrae in two magnetically

similar polarity regions

source: convective motions

weak field plasma penetrates from

below photosphere

cusp/canopy configuration at surface

types: FLBs, SLBs, GLBs

→ different origins?

Light Bridge References

Sobotka & Puschmann (2009); Sobotka et al. (1993); Lites et al. (1991); Sobotkaet al. (1993); Rimmele (2008); Rezaei et al. (2012); Vazquez (1973); Lites et al.(1991); Sobotka et al. (1994); Leka (1997); Rouppe van der Voort et al. (2010);Louis et al. (2009); Bharti et al. (2013); Shimizu et al. (2009); Ruedi et al. (1995);Joshi (2013)

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GREGOR BBI AR11768 (trailing) 08:15 UT, frame #000

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y [a

rcse

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GREGOR BBI 486 nm, 14-Jun-20133 / 20

Observations Hinode SP: 2006-Nov-30

AR10926, G-band, temporal evolution

500

1000

1500

20002006−11−30T07:40:30.525

−160 −140 −120 −100 −80x [arcsec]

−140

−120

−100

y [a

rcse

c]

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Observations Hinode SP: 2006-Nov-30

AR10926,SOT/SP scan

−210 −200 −190 −180 −170

x [arcsec]

−200

−190

−180

−170

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y[arcsec]

DC

0.15

0.30

0.45

0.60

0.75

0.90

1.05

1.20

I/I C

AR10926

several granular light bridges:

Nov 26 – Dec 4 2006

µ = cosΘ = 0.96

SP scan (normal mode) on

Nov-30 2006, 2300 UT

Inversions van Noort (2012)

POSTER: S1 - P - 27

spatial coupling using PSF

−→ acts as deconvolution

3 nodes in T, B, γ, φ, vLOS, vmicro

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Method 2D-coupled Inversion

AR10926, intensity

−210 −200 −190 −180 −170

x [arcsec]

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y[arcsec]

DC

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0.90

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1.20

I/I C

−210 −200 −190 −180 −170

x [arcsec]

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−180

−170

−160

−150

y[arcsec]

DC

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I/I C

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Method 2D-coupled Inversion

AR10926, selected regions

−210 −200 −190 −180 −170

x [arcsec]

−200

−190

−180

−170

−160

−150

y[arcsec]

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

DC

−196 −195 −194

−167

−166

−165

−217 −216 −215

−187

−186

−185

0.15

0.30

0.45

0.60

0.75

0.90

1.05

1.20

I/I C

Broad light bridge

temporal evolution indicates

convective motions

brightness similar to QS

−→ granule

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Method 2D-coupled Inversion

AR10926, selected regions

−210 −200 −190 −180 −170

x [arcsec]

−200

−190

−180

−170

−160

−150

y[arcsec]

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

DC

−196 −195 −194

−167

−166

−165

−217 −216 −215

−187

−186

−185

0.15

0.30

0.45

0.60

0.75

0.90

1.05

1.20

I/I C

Broad light bridge

temporal evolution indicates

convective motions

brightness similar to QS

−→ granule

QS Granule

. . . not really “quiet” (too close to spot).

BUT: properties very similar to QS

granule

−→ selected for comparison

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Results Comparison: Granule in LB vs. QS

Comparison: LB Granule vs. QS Granule

−210 −200 −190 −180 −170

x [arcsec]

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y[arcsec]

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

DC

−196 −195 −194

−167

−166

−165

−217 −216 −215

−187

−186

−185

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0.45

0.60

0.75

0.90

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I/I C

LB granule

33

34

35

logτ=-2.0

5000 6000

T [K]−3 0 4 8

vLOS [km s−1]

0 1000 2000

B [G]30 90 150

γ [◦] (B>70G)

33

34

35

logτ=-0.8

4 5 6

33

34

35

logτ=0.0

4 5 6 4 5 6 4 5 6

x+200 [arcsec]

y+200[arcsec]

QS granule

13

14

15

logτ=-2.0

5000 6000

T [K]−3 0 4 8

vLOS [km s−1]

0 1000 2000

B [G]30 90 150

γ [◦] (B>70G)

13

14

15

logτ=-0.8

−17 −16 −15

13

14

15

logτ=0.0

−17 −16 −15 −17 −16 −15 −17 −16 −15

x+200 [arcsec]

y+200[arcsec]

Atmospheric parameters

Temp., LOS-velocity, magn. field

strength & direction

at three height nodes

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Results Comparison: Granule in LB vs. QS

Comparison LB / QS granule log τ = 0.0

Temp. vLOS B-field B-direction

4 5 6

33

34

35

logτ=0.0

5000 6000

4 5 6

−3 0 4 8

4 5 6

0 1000 2000

4 5 6

30 90 150

◦

x+200 [arcsec]

y+200[arcsec]

−17 −16 −15

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logτ=0.0

5000 6000

−17 −16 −15

−3 0 4 8

−17 −16 −15

0 1000 2000

−17 −16 −15

30 90 150

◦

x+200 [arcsec]

y+200[arcsec]

LB

GQ

SG

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Results Comparison: Granule in LB vs. QS

Comparison LB / QS granule log τ = − 0.8

Temp. vLOS B-field B-direction

4 5 6

33

34

35

logτ=-0.8

5000 6000

4 5 6

−3 0 4 8

4 5 6

0 1000 2000

4 5 6

30 90 150

◦

x+200 [arcsec]

y+200[arcsec]

−17 −16 −15

13

14

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logτ=-0.8

5000 6000

−17 −16 −15

−3 0 4 8

−17 −16 −15

0 1000 2000

−17 −16 −15

30 90 150

◦

x+200 [arcsec]

y+200[arcsec]

LB

GQ

SG

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Results Comparison: Granule in LB vs. QS

Comparison LB / QS granule log τ = − 2.0

Temp. vLOS B-field B-direction

4 5 6

33

34

35

logτ=-2.0

5000 6000

4 5 6

−3 0 4 8

4 5 6

0 1000 2000

4 5 6

30 90 150

◦

x+200 [arcsec]

y+200[arcsec]

−17 −16 −15

13

14

15

logτ=-2.0

5000 6000

−17 −16 −15

−3 0 4 8

−17 −16 −15

0 1000 2000

−17 −16 −15

30 90 150

◦

x+200 [arcsec]

y+200[arcsec]

LB

GQ

SG

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Results Comparison: Granule in LB vs. QS

AR10926, selected cuts

−210 −200 −190 −180 −170

x [arcsec]

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−180

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−150

y[arcsec]

ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd

DC

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I/I C

Cut through LB

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−1

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500G

500G

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6000

T[K

]

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500G -300

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300

T-T

QS[K

]

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500G

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vLO

S[km

s−1]

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−1

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500G

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B[G

]

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

500G

500G

30

90

150

γ[◦]

(B>

70G

)

Cut through QSG

−2

−1

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5000

6000

T[K

]

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−1

0-300

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T-T

QS[K

]

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3

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vLO

S[km

s−1]

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−1

0 0

1000

2000

B[G

]

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

30

90

150

γ[◦]

(B>

70G

)

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Results Vertical Cuts

Cut through LB / QS granule LOS-velocity

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

logτ

500G

500G

-3

0

3

6

9

vLO

S[km

s−1]

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

logτ

-3

0

3

6

9

vLO

S[km

s−1]

LB

GQ

SG

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Results Vertical Cuts

Cut through LB / QS granule magnetic field

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

logτ

500G

500G

0

1000

2000

B[G

]

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

logτ

0

1000

2000

B[G

]

LB

GQ

SG

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Results Vertical Cuts

Cut through LB / QS granule mag. field inclination

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

logτ

500G

500G

30

90

150

γ[◦]

(B>

70G

)

−1.0 −0.5 0.0 0.5 1.0

cut position [arcsec]

−2

−1

0

logτ

30

90

150

γ[◦]

(B>

70G

)

LB

GQ

SG

14 / 20

Results Vertical Cuts

Comparison: LB Granule vs. QS Granule

Similarities

central upflows (≈2 km s−1) of hot

material

surrounded by cooler downflows

−→ typical pattern for convection

decreasing velocities with height

field free / weak fields in deep layers

field concentrations at boundaries

15 / 20

Results Vertical Cuts

Comparison: LB Granule vs. QS Granule

Similarities

central upflows (≈2 km s−1) of hot

material

surrounded by cooler downflows

−→ typical pattern for convection

decreasing velocities with height

field free / weak fields in deep layers

field concentrations at boundaries

Differences

LB: faster downflows (10 vs. 4 km s−1)

LB: narrowing upflows with height

LB: enhanced temp. at downflows in

middle layers, lower in deepest layer

→ small radial gradient at τ = 1

LB: opposite polarity field at location of

downflows

LB: cusp-like field in highest layer

QS: canopy field in highest layer

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Summary & Outlook

Downflows: reconnection sites?

High speed downflows (10 km s−1)

Result of Reconnection? (Louis et al. 2009)

+ hints of polarity reversal

+ above downflows: T enhanced

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Summary & Outlook

Downflows: reconnection sites?

Configuration

U m b r a U m b r a

High speed downflows (10 km s−1)

Result of Reconnection? (Louis et al. 2009)

+ hints of polarity reversal

+ above downflows: T enhanced

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Summary & Outlook

Downflows: reconnection sites?

Configuration

U m b r a U m b r a

High speed downflows (10 km s−1)

Result of Reconnection? (Louis et al. 2009)

+ hints of polarity reversal

+ above downflows: T enhanced

– height: 200–300 km

– strong downflows by gravity &

reduced density

→ drag field lines and create opposite

polarity field

→ reconnection / current sheets (with

heating) result of downflows

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Summary & Outlook Exposed (“naked”) granules

“Naked” granules Summary & Outlook

Configuration

U m b r a U m b r a

Exposed granules (Wilson depression)

LBG and QSG similar in deep layer

−→ points to common origin

−→ anchored in deep layers

different from FLBs or umbral dots

(“surface” convection)

probe sub-surface spot structure

Outlook

→ investigate granular light bridges

under different viewing angles

possible to access granular interior

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Summary & Outlook Takayama - Furukawa

Furukawa Festival (town next to Takayama,every April)

many similarities

interior: turbulent

motions

boundary:

downflow

streamlines

cusp shape

“granule” exposed

to cold environment

“naked”: not quite

(only linecloths)

19 / 20

Summary & Outlook Takayama - Furukawa

Furukawa Festival (town next to Takayama,every April)

many similarities

interior: turbulent

motions

boundary:

downflow

streamlines

cusp shape

“granule” exposed

to cold environment

“naked”: not quite

(only linecloths)

19 / 20

Summary & Outlook Takayama - Furukawa

Furukawa Festival (town next to Takayama,every April)

many similarities

interior: turbulent

motions

boundary:

downflow

streamlines

cusp shape

“granule” exposed

to cold environment

“naked”: not quite

(only linecloths)

19 / 20

Summary & Outlook Takayama - Furukawa

Furukawa Festival (town next to Takayama,every April)

many similarities

interior: turbulent

motions

boundary:

downflow

streamlines

cusp shape

“granule” exposed

to cold environment

“naked”: not quite

(only linecloths)

19 / 20

Summary & Outlook Takayama - Furukawa

Furukawa Festival (town next to Takayama,every April)

many similarities

interior: turbulent

motions

boundary:

downflow

streamlines

cusp shape

“granule” exposed

to cold environment

“naked”: not quite

(only linecloths)

19 / 20

Summary & Outlook Takayama - Furukawa

Furukawa Festival (town next to Takayama,every April)

many similarities

interior: turbulent

motions

boundary:

downflow

streamlines

cusp shape

“granule” exposed

to cold environment

“naked”: not quite

(only linecloths)

19 / 20

Summary & Outlook Takayama - Furukawa

Bilbiography

Bharti, L., Hirzberger, J., & Solanki, S. K. 2013, A&A, 552, L1

Joshi, J. 2013, PhD thesis, Technische Universitat Carolo-Wilhelmina zuBraunschweig

Leka, K. D. 1997, ApJ, 484, 900

Lites, B. W., Bida, T. A., Johannesson, A., & Scharmer, G. B. 1991, ApJ,373, 683

Lites, B. W., Scharmer, G. B., Berger, T. E., & Title, A. M. 2004, Sol.Phys., 221, 65

Louis, R. E., Bellot Rubio, L. R., Mathew, S. K., & Venkatakrishnan, P.2009, ApJL, 704, L29

Rezaei, R., Bello Gonzalez, N., & Schlichenmaier, R. 2012, A&A, 537,A19

Rimmele, T. 2008, ApJ, 672, 684

Rouppe van der Voort, L., Bellot Rubio, L. R., & Ortiz, A. 2010, ApJL,718, L78

Ruedi, I., Solanki, S. K., & Livingston, W. C. 1995, A&A, 293, 252

Shimizu, T. 2011, ApJ, 738, 83

Shimizu, T., Katsukawa, Y., Kubo, M., et al. 2009, ApJL, 696, L66

Sobotka, M., Bonet, J. A., & Vazquez, M. 1993, ApJ, 415, 832

Sobotka, M., Bonet, J. A., & Vazquez, M. 1994, ApJ, 426, 404

Sobotka, M. & Puschmann, K. G. 2009, A&A, 504, 575

van Noort, M. 2012, A&A, 548, A5

Vazquez, M. 1973, Sol. Phys., 31, 377

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