The SWAP Filter: A Simple Azimuthally Varying Radial Filter for Wide-Field EUV Solar Images

Abstract

We present the SWAP Filter: an azimuthally varying, radial normalizing filter specifically developed for EUV images of the solar corona, named for the Sun Watcher with Active Pixels and Image Processing (SWAP) instrument on the Project for On-Board Autonomy 2 spacecraft. We discuss the origins of our technique, its implementation and key user-configurable parameters, and highlight its effects on data via a series of examples. We discuss the filter's strengths in a data environment in which wide field-of-view observations that specifically target the low signal-to-noise middle corona are newly available and expected to grow in the coming years.

arXiv commentContact D. B. Seaton for animations referenced in figure captions

References in corpus (21)

• Preparing Red-Green-Blue (RGB) Images from CCD Data
• Multi-scale Gaussian normalization for solar image processing
• JHelioviewer - Time-dependent 3D visualisation of solar and heliospheric data
• The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
• The Depiction of Coronal Structure in White Light Images
• Genesis and impulsive evolution of the 2017 September 10 coronal mass ejection
• Observations of an Eruptive Solar Flare in the Extended EUV Solar Corona
• The SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration
• The High-Resolution Coronal Imager, Flight 2.1
• Defining the Middle Corona
• Observations of the Formation, Development, and Structure of a Current Sheet in an Eruptive Solar Flare
• SWAP Observations of the Long-Term, Large-Scale Evolution of the EUV Solar Corona
• Study of EUV Emission and Properties of a Coronal Streamer from PROBA2/SWAP, Hinode/EIS and Mauna Loa Mk4 Observations
• The Sun's Dynamic Extended Corona Observed in Extreme Ultraviolet
• Image enhancement with wavelet-optimized whitening
• Direct observations of a complex coronal web driving highly structured slow solar wind
• Coronal Imaging with the Solar UltraViolet Imager
• Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Imager on board Solar Orbiter
• Influence of misalignments on performance of externally occulted solar coronagraphs. Application to PROBA-3/ASPIICS
• Modeling and removal of optical ghosts in the PROBA-3/ASPIICS externally occulted solar coronagraph
• Simultaneous High Dynamic Range Algorithm, Testing, and Instrument Simulation

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