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Back Reaction on the Photospheric Magnetic field in Solar Eruptions Dandan Ye

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Contents Paper review: 2005 J.J. Sudol and J.W. Harvey ‘Longitudinal magnetic field changes accompanying solar flares’ My work about flare-related magnetic field evolutions to the X1.8 flare on 2012.10.23

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Paper review Background: Re-examined the basic assumptions of flare theories: the photospheric magnetic field does not change significantly during flares Data:15 X-class solar flares Global Oscillation Network Group (GONG) magnetograms

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Paper review

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The time variation of the magnetic field that occurs during a flare can be characterized to first order with a step function. (Sudol&Harvey 2004) a, b, c, n, and t 0 are the free parameters

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Paper review 2003.11.2 X8.3 flare Time variation plots for (10*10) pixels

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Paper review Left: magnetic field image of a 10-min average Middle: dB map Right: B vs t (representative points for four hours)

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Paper review

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Comparison with flare emission GONG & TRACE

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Paper review Discussion: Abrupt, significant, and permanent changes of the photospheric longitudinal magnetic field are ubiquitous features of X-class flares. Reasons: unclear (like flows compress the field; parts of the field shift horizontally; flux submerges out of sight…..)

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Paper review Many of the field changes with penumbrae and the recent observations show that penumbrae weaken during flares Penumbral magnetic field more vertical So, the field lines are pulled or relax upward by the erupting flare.

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My work AR 11598 (close to the west limb) Line-of sight component of magnetic field change Vector of magnetic field change Intensity Data

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My work Data: Helioseismic and Magnetic Imager(HMI) data on board the SDO LOS: Magnetogram with a spatial resolution of ~1'' and a cadence of 45 seconds Vector: Vector magnetic field with a spatial resolution of ~1'' and a cadence of 12 min. Intensity: Continuum data with a cadence of 45 seconds

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My work Intensity

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My work Intensity Dif_image 10.23 3:24-3:12

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My work Transformation of field vectors Bh represents the components of B in the directions parallel to the photosphere Br is the radial field component

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My work

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Vector

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My work

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LOS Dif_image 10.23 3:30-3:00

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My work LOS

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My work LOS

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My work LOS

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My work LOS

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My work Summary: 1. Obviously the X1.8 flare produces abrupt and significant magnetic field structure change in intensity, vector field and LOS. 2. For this X1.8 flare, the diskward flux would decrease and the limbward flux would increase.

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My work

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3. Prove the speculation in Wang & Liu (2010): Field lines changing to more vertical state when the central region pressure is released after flares. 4. Prove the speculation in Sudol & Harvey (2005).

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Thanks!

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