Automated Detection and Characterization of Solar Filaments and Sigmoids K. Wagstaff, D. M. Rust, B. J. LaBonte and P. N. Bernasconi Johns Hopkins University Applied Physics Laboratory Laurel, Maryland USA Solar Image Recognition Workshop Brussels October 23-24, 2003
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Automated Detection and Characterization of Solar Filaments and Sigmoids
Automated Detection and Characterization of Solar Filaments and Sigmoids. K. Wagstaff, D. M. Rust, B. J. LaBonte and P. N. Bernasconi Johns Hopkins University Applied Physics Laboratory Laurel, Maryland USA Solar Image Recognition Workshop Brussels October 23-24, 2003. - PowerPoint PPT Presentation
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Automated Detection and Characterization of Solar Filaments and Sigmoids
K. Wagstaff, D. M. Rust, B. J. LaBonte and P. N. Bernasconi
Johns Hopkins University Applied Physics LaboratoryLaurel, Maryland USA
Solar Image Recognition WorkshopBrussels
October 23-24, 2003
Objectives of Solar Filament Detection and Classification
• Report automatically on filament disappearances
• Provide warning of geomagnetic storms• Characterize magnetic flux rope chirality and
orientation of principal axis• Forecast pattern of Bz in magnetic clouds
Filaments observed in H on 1 January 2003 at 1708 UTC (BBSO image)
Filament Detection Method
• Identify filament pixels– Apply darkness threshold– Group dark pixels into contiguous regions– Prune out small dark regions and artifacts– Draw contours around filament boundary
• Find spines (filament centerlines)– Use simplified Kegl’s algorithm for finding the
principal curve defined by a set of points
Detected filaments with borders outlined.
Filaments with spines indicated.
Find Barbs (protrusions from filament)
• Identify points farthest from the spine• Follow boundary in each direction to find
bays, i.e. local minimum distances from spine
• Establish each barb centerline by connecting the farthest point to the midpoint of left and right bays
Barbs indicated by white lines.
Chirality (handedness) Classification
• Calculate angle between barb centerline and spine
• Classify barbs by obtuse and acute angles• Assign filament chirality based on majority
classification: right-handed for acute angles; left-handed for obtuse angles
Deducing filament chirality from barb counts.
The solar disk observed in H on 30 June 2002 at 1540 UTC (BBSO image). Ten filaments identified, five filaments classified.
Contoured filament with first approximation to spine.
Second approximation.
Fourth approximation.
Sixth approximation.
Eighth approximation.
Final approximation to spine and classification of filament.
Southern hemisphere filament rests in a right-handed flux rope.
Solar disk in H on 22 August 2002 at 1603 UTC (BBSO image)
Northern hemisphere filament rests in a left-handed flux rope.
Mirror image would be associated with right-handed flux rope.
Future Developments
• Make detection algorithm more robust• Test against man-made lists• Compare filament positions on successive
images after correcting for solar rotation• Set alarm bit if filament can’t be found• Estimate geoeffectiveness from filament
position on the disk and magnetic indices
Sigmoid Detection
• Sigmoid = elongate structure, S or inverse-S shape = signal of enhanced CME probability