Solar Image Processing at SIDC - Royal Observatory of Belgium J.-F. Hochedez, V. Delouille, S. Gissot, E. Robbrecht, B. Nicula, O. Podladchikova, J. de Patoul, D. Berghmans

Necessity & timeliness In modern coronal physics, solar image processing (SIP) appears more and more as a needed and timely tool. SIP is necessary because of: –the large sizes of the current and future missions/observatories archives, –the wish to process solar data automatically in order to evidence hidden trends (e.g. solar cycle or instrumental effects), –the need for systematic detection of rare or faint events such as EIT waves.

Benefits This quest is even more acute in the context of Space Weather forecasting where quasi-real time is required. As additional benefits, the algorithmic techniques provide reproducibility and some level of objectivity. They also alleviate the effort of expert forecasters. They are sometimes able to reveal information that would remain otherwise buried in the noise or in the dynamics. Finally, they improve data representation and visualization. The necessity comes furthermore at a propitious time when the available CPU power and the underlying mathematics have developed considerably.

Link to Science The scope of SIP goes beyond the role of a tool. It is an integral part of our science, like visual inspection, statistical science or physics modeling. Confidence in the outcomes of any technique participates to the data analysis. In the near future and especially with AIA onboard SDO, we expect MHD modeling, SIP, statistics and data assimilation schemes to merge in one indissociable research for which certitudes involve expertise in all fields.

CACTus Computer Aided CME Tracking 11 November 2003 θ t θ V (km/s) Start time, Principal angle, Width and velocity profile 15h18 15h5417h06 sidc.be/cactus Method: Hough transform and clustering Robbrecht and Berghmans A&A ’04 and SoPh ‘05 Result: Real-time extraction of LASCO CMEs + Catalog AIA relevance: AIA-coronagraph coordinated studies

B2X flare detector Just before the flare begins At flare peak log(scale) ½ log(μ(scale)) Method: Wavelet spectrum (scale measure) analysis Hochedez et al ’02 Solspa2 Proc., Delouille et al SoPh ’05 Result: Small flares automatic detection Relevance: Sympathetic flaring studies

EIT waves detector Method: Histogram skewness and kurtosis + Ring analysis. Podladchikova et Berghmans SoPh ’05 Result: Wavefront and dimming studies, 90% detection AIA relevance: EIT waves automation, coronal seismology

Method: Multiscale Local Optical Flow Gissot et Hochedez A&A ’06 (in prep.) Result: Motion and ‘brightness variation’ both estimated and qualified at each pixel from local similarity & texture AIA relevance: Flares, dimmings (CMEs, EIT waves), loop motions, Dif. Rot., coronal seismology… Velociraptor

EUV Disc segmentation Method: Fuzzy clustering Barra, Delouille, Hochedez, Chainais ’05 Proc. SPM11 Result: 5 regions: AR core + AR + AR aureole + QS + CH AIA relevance: e.g. Source regions of irradiance, etc.

Image enhancement Scale map of a 195 EIT image NCT of a 195 EIT image Method: Normalized Contrast Transform (NCT) or Scale maps. Unpublished Expected result & AIA relevance: Preprocessing and enhance the irreplaceable visual inspection

Loop extraction Method: Multiscale ridge detection. Unpublished Expected result & AIA relevance: loop identified and labelled, DEM reconstruction, loop modeling, coronal seismology…

Beauty spotter Method: Extraction in scale space by Lipschitz coefficient Hochedez et al 2002, Soho11 WS Proc., Hochedez et al 2003 Soho13 WS Result: BPs, brightenings and Cosmic Ray Hits extracted Relevance: Oscillations in point-like structures

Network scale analysis EIT 304 typical quiet sun Method: Wavelet spectrum analysis Delouille et al SoPh ’05, Hochedez et al ’02 Solspa2 Proc. Result: TR network characteristic scale, cycle study AIA relevance: Continued cycle studies

Synthetic Quiet Sun Method: Infinitely divisible cascades constrained by EIT histogram and fractal spectrum. in Prep Result: Artificial QS for testing algorithm (e.g. optical flow). Coronal heating relevance TBD AIA relevance: Better spatial resolution

Image and movie compression Recoded pixel distortion after decompression Method: recoding and MPEG4 AVC/H.264 Nicula private com + Nicula, Berghmans, Hochedez SoPh ‘05. Result: x180 compression! AIA relevance: Save Internet bandwidth!

SWB Solar Weather Browser This is a Simple tool for easy visualisation of important Space Weather data. sidc.be/SWB Near-real-time images Combine with overlays Save images with overlays as PNG Cycle through images Dynamical interface Simple and portable !! Method: Client-Server architecture. Nicula, Berghmans, Katsiyannis, Lawrence, Baumann Result & AIA relevance: Visualisation made easy!