Changyi Tan et al.Changyi Tan et al.

NJIT, April 2008NJIT, April 2008

Evolution of Evershed and Evolution of Evershed and Shear Flows Associated Shear Flows Associated

with the X3.4 Flare of 2006 with the X3.4 Flare of 2006 December 13December 13

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MotivationMotivation NJIT solar group has reported the rapid NJIT solar group has reported the rapid

penumbra decays are associated with the X-penumbra decays are associated with the X-class flares (Spirock et al. 2002; Wang et al. class flares (Spirock et al. 2002; Wang et al. 2002a,b,2004; Liu et al. 2005; Deng et al. 2002a,b,2004; Liu et al. 2005; Deng et al. 2005).2005).

We rise two questions:We rise two questions: Is Evershed flow change accompanying with Is Evershed flow change accompanying with

flare and the penumbra decay?flare and the penumbra decay? Magnetic shear angle could be a proxy of Magnetic shear angle could be a proxy of

magnetic nonpotentiality (Zhang 2001; magnetic nonpotentiality (Zhang 2001; Falconer 2001; Wang et al. 2006). Can we Falconer 2001; Wang et al. 2006). Can we expect a decrease in shear flow after the expect a decrease in shear flow after the flare?flare?

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Data SetData SetHinode SOT Hinode SOT

G-band images are from Broadband Filter G-band images are from Broadband Filter Imager (BFI) , 0.109”, 2 minutes cadence.Imager (BFI) , 0.109”, 2 minutes cadence.

Stokes V images are from Narrowband Stokes V images are from Narrowband Filter Imager (NFI), 0.16”, 2 minutes Filter Imager (NFI), 0.16”, 2 minutes cadence. cadence.

From 01:00:32 to 04:36:37 UT Dec. 13, From 01:00:32 to 04:36:37 UT Dec. 13, 20062006

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MethodMethod

Local correlation tracking (LCT).Local correlation tracking (LCT). Running calculation technique, time Running calculation technique, time

window is 62 minutes.window is 62 minutes. Correction of the pixel size Correction of the pixel size

foreshortening.foreshortening. Shear flow is estimated by the relative Shear flow is estimated by the relative

motions between two magnetic motions between two magnetic polarities near the magnetic neutral polarities near the magnetic neutral line.line. pos negshearV V V

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Penumbra DecayPenumbra Decay

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Penumbra DecayPenumbra Decay

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LCT applied LCT applied

on G-Band on G-Band data to get data to get the Evershed the Evershed flows in the flows in the penumbra penumbra

decay areas.decay areas.

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LCT applied LCT applied

on Stokes V on Stokes V data to get data to get the shear the shear

flows.flows.

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ResultsResults

1

2

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ResultsResults

3

4

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ResultsResults As a comparison, area 5 is a relatively penumbra As a comparison, area 5 is a relatively penumbra

constant area.constant area.

5

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ResultsResults

6

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ConclusionsConclusions The penumbra decay appeared obviously in this The penumbra decay appeared obviously in this

active region associated with the X3.4 flare. active region associated with the X3.4 flare. The mean magnitude of the horizontal Evershed The mean magnitude of the horizontal Evershed

flows inside the penumbra decay areas varied flows inside the penumbra decay areas varied from 0.4 to 1 km/s temporally and spatially. from 0.4 to 1 km/s temporally and spatially.

The attenuation of Evershed flows in all the four The attenuation of Evershed flows in all the four penumbra decay areas happened during the flare. penumbra decay areas happened during the flare.

The Evershed flows decreased before the flare The Evershed flows decreased before the flare eruption in two of the four strong penumbra eruption in two of the four strong penumbra decay areas. decay areas.

The mean shear flows along the magnetic neutral The mean shear flows along the magnetic neutral of this delta sunspot started to decrease before of this delta sunspot started to decrease before the flare and continued to decrease for another the flare and continued to decrease for another hour after the flare. The magnitude of this flow hour after the flare. The magnitude of this flow apparently dropped from 0.2 to 0.05 km/s.apparently dropped from 0.2 to 0.05 km/s.

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DiscussionsDiscussions

Open questions:Open questions: Why do the Evershed flows cease Why do the Evershed flows cease

before the flare?before the flare? When do the flow decays exactly When do the flow decays exactly

start? Can we propose the flow start? Can we propose the flow decay as one of flare precursors?decay as one of flare precursors?

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Thank YouThank You