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

AIA HMI Team meeting, Monterey, CA, USA, February 13-17 2006

Just before the flare begins

At flare peak

log(scale)

½ log(μ

(sca

le))

123

1 2 3

11 N

ovem

ber

2003

θ

t

θ

V (

km/s

)

500 -

1500 -

Start time, Principal angle, Width and

velocity profile

15h18 15h54 17h06

sidc.be/cactus

EIT 304 typical quiet sun

http://http://sidcsidc.be.be

Recoded pixel

distortion after

decompression

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 !!

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.

However, the scope of SIP goes actually 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.

Scale mapof a 195

EIT image

NCT of a 195

EIT image

VelociraptorMethod: Multiscale Local Optical FlowGissot 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…

Image and movie compression

Method: recoding and MPEG4 AVC/H.264Nicula private com + Nicula, Berghmans, Hochedez SoPh ‘05.

Result: x180 compression!

AIA relevance: Save Internet bandwidth!

CACTus Computer Aided CME Tracking

Method: Hough transform and

clustering Robbrecht and Berghmans A&A ’04 and SoPh ‘05

Result: Real-time extraction of LASCO CMEs + Catalog 1997-2004.

AIA relevance: AIA-coronagraph coordinated studies

EIT waves detectorMethod: 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

SWB Solar Weather BrowserMethod: Client-Server architecture.Nicula, Berghmans, Katsiyannis, Lawrence, Baumann

Result & AIA relevance: Visualisation made easy!

EUV Disc segmentationMethod: Fuzzy clusteringBarra, 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.

Automatic B-C-M-X Flares detection

Method: Wavelet spectrum (scale measure) analysis Hochedez et al ’02 Solspa2 Proc., Delouille et al SoPh ’05

Result: Small flares automatic detection, SpW nowcast

AIA relevance: Idem, continued

Network scale analysisMethod: 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 SunMethod: Infinitely divisible cascades constrainedby 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

Small features extractionMethod: Extraction in scale space by Lipschitz coefficientHochedez et al, ‘02, Soho11 WS, ‘03 Soho13 WS Proc.

Result: BPs, brightenings and Cosmic Ray Hits extracted

AIA relevance: BP studiesCRH removalDC coronal heating…

Loops extractionMethod: Multiscale ridge detectionUnpublished

Expected result & AIA relevance: loop identified and labelled, DEM reconstruction, loop modeling, coronal seismology…

Image enhancementMethod: Normalized Contrast Transform (NCT) or Scale maps. Unpublished

Expected result & AIA relevance:Preprocessing and enhance the irreplaceable visual inspection

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.