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The Astrophysical Journal, 601:L195–L198, 2004 February 1 2004.

RAPID PENUMBRAL DECAY FOLLOWING THREE X-CLASS SOLAR FLARES

H. Wang,1,2 C. Liu,1 J. Qiu,1 N. Deng,1 P. R. Goode,1,2 and C. Denker1,2

Received 2003 November 10; accepted 2003 December 19; published 2004 January 28

1 Center for Solar Research, New Jersey Institute of Technology2 Big Bear Solar Observatory, New Jersey Institute of Technology

太陽雑誌会2004.02.09

T.T.Ishii

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ABSTRACT

Penumbral segments decayed rapidly and permanently right after three X-class solar flares. (X17 on 2003-Oct-28, X10 on 2003-Oct-29 in NOAA 10486 X2.3 on 2000-Jun-6 in NOAA 9026)

Difference images highlighting the rapid changes between pre- and post- flare states of the flaring active region show distinct decaying penumbral segments and neighboring umbralcores becoming darker. Magnetic fields change from a highly inclined to a more vertical configuration within approximately 1 hr after the flares; i.e., part of the penumbral magnetic field is converted into umbral fields.

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NOAA 10486

SOHO / MDI intensitygram & magnetogram 500 Gauss contour ( face-on )

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NOAA 10486

SOHO / MDI magnetogram face-on (500 Gauss contour)

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NOAA 10486

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SOHO MDI / mag. H-alpha BBSO 　　 H-alpha & mag (500G)　　　　　　　　　　 and Kwasan Sartoirus red: positive blue: negative

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SOHO MDI / mag. H-alpha BBSO 　　 H-alpha & mag (500G)　　　　　　　　　　 and Kwasan Sartoirus red: positive blue: negative

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Difference image (pre-flare minus post-flare state),which was smoothed by a window of 10”×10”. Any dark feature in the difference image indicates a brightening in the post-flare image, e.g., an area of decaying penumbra, whereas any bright feature corresponds to a darkening in the post-flare image, e.g., the darkening of an umbral core.

TRECE white light Difference image

X10 flare on Oct. 29 peak 20:49 UT

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RHESSI hard X-ray contours: X10 flare on 2003-Oct-29 peak 20:49 UT 15–20 keV channel (red) 50–100 keV channel (blue)

TRACE1600 Å

TRACE195 Å

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TRECE white light Difference image

X10 flare on Oct. 28 peak 11:10 UT

Difference image (pre-flare minus post-flare state),which was smoothed by a window of 10”×10”. Any dark feature in the difference image indicates a brightening in the post-flare image, e.g., an area of decaying penumbra, whereas any bright feature corresponds to a darkening in the post-flare image, e.g., the darkening of an umbral core.

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RHESSI hard X-ray contours: X17 flare on 2003-Oct-28 peak 11:10 UT 15–20 keV channel (red) 50–100 keV channel (blue)

TRACE1600 Å

TRACE195 Å

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NOAA 9026 2000 June

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X2 flare on 2000 June 6peak 15:25 UT

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Summary

1. Penumbral decay was found for each event on a timescale of about 1 hr or less.

2. The locations of the penumbral decay are associated withflare emissions, but with distinct differences for each event.

X10 on Oct-29 : coincides with one of the two 50–100 keV hard X-ray sources

X17 on Oct-28 : not associated with any hard X-ray source. However, the decaying segment is related to a section of one of the two TRACE 1600 flare ribbons.

X2 on June-6: adjacent to but did not coincide with two TRACE white-light kernels

3. For each of the decaying areas, there is a darkening ofadjacent umbrae marked as E1, E2, and E3, respectively.

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A&A 411, L497–L500 (2003)

The flares associated with the abnormal rotation rates of the bipolar sunspots: Reconnection probably below the surface

K. M. Hiremath1 and G. S. Suryanarayana2

1 Indian Institute of Astrophysics, Bangalore-560034, India2 Indian Institute of Astrophysics, Kodaikanal-624103, India

Received 26 September 2003 / Accepted 14 October 2003

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Observational data

They use Kodaikanal observatory white light pictures to study the association between the rotation rates of the bipolar sunspots and triggering of the flares.

For the years 1969-1974, they compute daily rotation rates of theleading and the following spots of the bipolar sunspot groups during their life span.

Definition of abnormal rotation rate

Rotation rate l : helographic longitude

t : time of observation Abnormal rotation rate : average rotation rate

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iii tt

ll

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1

1~ i ~

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Left: The occurrence dates of abnormal rotation rates and the flares.

The continuous line is the linear least square fit. Here R represents occurrence date of abnormal rotation

rates and F is the occurrence date of the flares. Right: The occurrence day of the abnormal rotation rates and

the flares during the evolution of the bipolar spots.

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Left: The scatter diagram illustrating the association betweenthe occurrence days of the abnormal rotation rates and the flares during the evolution of the spot group.

Right: The magnitude of abnormal rotation rates for different classes of the flares: the □ represents f (faint), the is ◇ n (normal) and the represents △ b (bright). Here 0 along the x axis represents the S subclass flare. The numbers 1, 2, 3, 4 are higher subclass flares.