Etude de la couronne solaire en 3D et de son évolution avec SOHO ...

tel-00089354, version 1 - 17 Aug 2006
286 F. PORTIER-FOZZANI ET AL.
Figure 16. SOHO/EIT Fe IX/X rebuilt by wavelet imaging taken on 6 April 1998 at (a) 02:06 UT, (b)
15:02 UT, and on 7 April 1998 at (c) 07:13 UT and (d) 13:16 UT (reverse LUT).
(5) Image labeling is done taking into account a multi-peak decomposition.
(6) Interscale relations are determined.
(7) Trees are deduced from the maximum in each wavelet frequency space
plane.
Thus sub-objects and objects are rebuilt.
The method is very efficient when the area studied has a low dynamic range.
Constraints for the method with SOHO/EIT images were derived with success.
Efficient applications of the method are obtained when the images are small with
low contrast.
Our first example took place on 5 – 6 November 1997. On EUV processed
images, highly sheared or twisted loops progressively form a Y-shape. The Yshape
usually characterizes fast magnetic reconnection with plasmoid ejections.
At the same time on a coronagraphic movie, a helicoidal structure observed in the
streamer, escapes. Then injection of material in a coronal streamer in relation with
coronal loop evolution is established.
Our second example happened on 6 –7 April 1998. Original images show global
coronal modifications with time. With MVM processed images, it becomes possible
to identify which structures show a change of morphology. In a complex active
region, openings of arcade loops are observed. Such phenomena are possible due
to helicity transfer. Consequences for filament stability and relations with shear,
twist and chirality will be discussed in a later paper.
Additional material can be found on the CD-ROM.