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Investigating the Kinematics of Coronal Mass Ejections with the Automated CORIMP Catalog  

Jason P. Byrne   Submitted: 2015-06-15 02:16

Studying coronal mass ejections (CMEs) in coronagraph data can be challenging due to their diffuse structure and transient nature, compounded by the variations in their dynamics, morphology, and frequency of occurrence. The large amounts of data available from missions like the Solar and Heliospheric Observatory (SOHO) make manual cataloging of CMEs tedious and prone to human error, and so a robust method of detection and analysis is required and often preferred. A new coronal image processing catalog called CORIMP has been developed in an effort to achieve this, through the implementation of a dynamic background separation technique and multiscale edge detection. These algorithms together isolate and characterise CME structure in the field-of-view of the Large Angle Spectrometric Coronagraph (LASCO) onboard SOHO. CORIMP also applies a Savitzky-Golay filter, along with quadratic and linear fits, to the height-time measurements for better revealing the true CME speed and acceleration profiles across the plane-of-sky. Here we present a sample of new results from the CORIMP CME catalog, and directly compare them with the other automated catalogs of Computer Aided CME Tracking (CACTus) and Solar Eruptive Events Detection System (SEEDS), as well as the manual CME catalog at the Coordinated Data Analysis Workshop (CDAW) Data Center and a previously published study of the sample events. We further investigate a form of unsupervised machine learning by using a k-means clustering algorithm to distinguish detections of multiple CMEs that occur close together in space and time. While challenges still exist, this investigation and comparison of results demonstrates the reliability and robustness of the CORIMP catalog, proving its effectiveness at detecting and tracking CMEs throughout the LASCO dataset.

Authors: Jason P. Byrne
Projects: SoHO-LASCO

Publication Status: Journal of Space Weather & Space Climate (in press)
Last Modified: 2015-06-15 10:45
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Bridging EUV and white-light observations to inspect the initiation phase of a "two-stage" solar eruptive event  

Jason P. Byrne   Submitted: 2014-06-19 18:41

The initiation phase of CMEs is a very important aspect of solar physics, as these phenomena ultimately drive space weather in the heliosphere. This phase is known to occur between the photosphere and low corona, where many models introduce an instability and/or magnetic reconnection that triggers a CME, often with associated flaring activity. To this end, it is important to obtain a variety of observations of the low corona in order to build as clear a picture as possible of the dynamics that occur therein. Here, we combine the EUV imagery of the SWAP instrument on board PROBA2 with the white-light imagery of the ground-based Mk4 coronameter at MLSO in order to bridge the observational gap that exists between the disk imagery of AIA on board SDO and the coronal imagery of LASCO on board SOHO. Methods of multiscale image analysis were applied to the observations to better reveal the coronal signal while suppressing noise and other features. This allowed an investigation into the initiation phase of a CME that was driven by a rising flux rope structure from a "two-stage" flaring active region underlying an extended helmet streamer. It was found that the initial outward motion of the erupting loop system in the EUV observations coincided with the first X-ray flare peak, and led to a plasma pile-up of the white-light CME core material. The characterized CME core then underwent a strong jerk in its motion, as the early acceleration increased abruptly, simultaneous with the second X-ray flare peak. The overall system expanded into the helmet streamer to become the larger CME structure observed in the LASCO coronagraph images, which later became concave-outward in shape. Theoretical models for the event are discussed in light of these unique observations, and it is concluded that the formation of either a kink-unstable or torus-unstable flux rope may be the likeliest scenario.

Authors: Byrne, J. P., Morgan, H., Seaton, D. B., Bain, H. M., Habbal, S. R.
Projects: GOES X-rays ,MLSO Mk4 K-Coronameter,PROBA2/SWAP,SDO-AIA,SoHO-LASCO,STEREO

Publication Status: Solar Physics (accepted)
Last Modified: 2014-06-20 06:32
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Improved methods for determining the kinematics of coronal mass ejections and coronal waves  

Jason P. Byrne   Submitted: 2013-07-31 18:20

Context: The study of solar eruptive events and associated phenomena is of great importance in the context of solar and heliophysics. Coronal mass ejections (CMEs) and coronal waves are energetic manifestations of the restructuring of the solar magnetic field and mass motion of the plasma. Characterising this motion is vital for deriving the dynamics of these events and thus understanding the physics driving their initiation and propagation. The development and use of appropriate methods for measuring event kinematics is therefore imperative. Aims: Traditional approaches to the study of CME and coronal wave kinematics do not return wholly accurate nor robust estimates of the true event kinematics and associated uncertainties. We highlight the drawbacks of these approaches, and demonstrate improved methods for accurate and reliable determination of the kinematics. Methods: The Savitzky-Golay filter is demonstrated as a more appropriate fitting technique for CME and coronal wave studies, and a residual resampling bootstrap technique is demonstrated as a statistically rigorous method for the determination of kinematic error estimates and goodness-of-fit tests. Results: It is shown that the scatter on distance-time measurements of small sample size can significantly limit the ability to derive accurate and reliable kinematics. This may be overcome by (i) increasing measurement precision and sampling cadence, and (ii) applying robust methods for deriving the kinematics and reliably determining their associated uncertainties. If a priori knowledge exists and a pre-determined model form for the kinematics is available (or indeed any justified fitting-form to be tested against the data), then its precision can be examined using a bootstrapping technique to determine the confidence interval associated with the model/fitting parameters. Conclusions: Improved methods for determining the kinematics of CMEs and coronal waves are demonstrated to great e ffect, overcoming many issues highlighted in traditional numerical di fferencing and error propagation techniques.

Authors: J. P. Byrne, D. M. Long, P. T. Gallagher, D. S. Bloomfield, S. A. Maloney, R. T. J. McAteer, H. Morgan, S. R. Habbal
Projects: SDO-AIA,SoHO-EIT,SoHO-LASCO,STEREO

Publication Status: Accepted
Last Modified: 2013-08-01 11:17
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Automatically Detecting and Tracking CMEs I: Separation of dynamic and quiescent components in coronagraph images  

Jason P. Byrne   Submitted: 2012-06-13 13:25

Automated techniques for detecting and tracking CMEs in coronagraph data are of ever-increasing importance for space weather monitoring and forecasting. They serve to remove the biases and tedium of human interpretation, and provide the robust analysis necessary for statistical studies across large numbers of observations. An important requirement in their operation is that they satisfactorily distinguish the CME structure from the background quiescent coronal structure (streamers, coronal holes). Many studies resort to some form of time-differencing to achieve this, despite the errors inherent in such an approach - notably spatiotemporal crosstalk. This article describes a new deconvolution technique that separates coronagraph images into quiescent and dynamic components. A set of synthetic observations made from a sophisticated model corona and CME demonstrates the validity and effectiveness of the technique in isolating the CME signal. Applied to observations by the LASCO C2 and C3 coronagraphs, the structure of a faint CME is revealed in detail despite the presence of background streamers that are several times brighter than the CME. The technique is also demonstrated to work on SECCHI/COR2 data, and new possibilities for estimating the 3D structure of CMEs using the multiple viewing angles are discussed. Although quiescent coronal structures and CMEs are intrinsically linked, and although their interaction is an unavoidable source of error in any separation process, we show in a companion paper that the deconvolution approach outlined here is a robust and accurate method for rigorous CME analysis. Such an approach is a prerequisite to the higher-level detection and classification of CME structure and kinematics.

Authors: Huw Morgan, Jason P. Byrne, Shadia R. Habbal
Projects: SoHO-LASCO,STEREO

Publication Status: Published
Last Modified: 2012-06-13 15:34
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Automatic Detection and Tracking of Coronal Mass Ejections II: Multiscale Filtering of Coronagraph Images  

Jason P. Byrne   Submitted: 2012-06-13 13:24

Studying coronal mass ejections (CMEs) in coronagraph data can be challenging due to their diffuse structure and transient nature, and user-specific biases may be introduced through visual inspection of the images. The large amount of data available from the Solar and Heliospheric Observatory (SOHO), Solar TErrestrial RElations Observatory (STEREO), and future coronagraph missions also makes manual cataloging of CMEs tedious, and so a robust method of detection and analysis is required. This has led to the development of automated CME detection and cataloging packages such as CACTus, SEEDS, and ARTEMIS. Here, we present the development of a new CORIMP (coronal image processing) CME detection and tracking technique that overcomes many of the drawbacks of current catalogs. It works by first employing the dynamic CME separation technique outlined in a companion paper, and then characterizing CME structure via a multiscale edge-detection algorithm. The detections are chained through time to determine the CME kinematics and morphological changes as it propagates across the plane of sky. The effectiveness of the method is demonstrated by its application to a selection of SOHO/LASCO and STEREO/SECCHI images, as well as to synthetic coronagraph images created from a model corona with a variety of CMEs. The algorithms described in this article are being applied to the whole LASCO and SECCHI data sets, and a catalog of results will soon be available to the public.

Authors: Jason P. Byrne, Huw Morgan, Shadia R. Habbal, Peter T. Gallagher
Projects: SoHO-LASCO,STEREO

Publication Status: Published
Last Modified: 2012-06-08 07:27
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The Kinematics of Coronal Mass Ejections using Multiscale Methods  

Jason P. Byrne   Submitted: 2008-12-17 09:10

Aims. The diffuse morphology and transient nature of coronal mass ejections (CMEs) make them difficult to identify and track using traditional image processing techniques. We apply multiscale methods to enhance the visibility of the faint CME front. This enables an ellipse characterisation to objectively study the changing morphology and kinematics of a sample of events imaged by the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO). The accuracy of these methods allows us to test the CMEs for non-constant acceleration and expansion. Methods. We exploit the multiscale nature of CMEs to extract structure with a multiscale decomposition, akin to a Canny edge detector. Spatio-temporal filtering highlights the CME front as it propagates in time. We apply an ellipse parameterisation of the front to extract the kinematics (height, velocity, acceleration) and changing morphology (width, orientation). Results. The kinematic evolution of the CMEs discussed in this paper have been shown to differ from existing catalogues. These catalogues are based upon running-difference techniques which can lead to over-estimating CME heights. Our resulting kinematic curves are not well fitted with the constant acceleration model. It is shown that some events have high acceleration below ∼5 solar radii. Furthermore, we find that the CME angular widths measured by these catalogues are over-estimated, and indeed for some events our analysis shows non-constant CME expansion across the plane-of-sky.

Authors: J. P. Byrne, P. T. Gallagher, R. T. J. McAteer, C. A. Young
Projects: SoHO-LASCO,STEREO

Publication Status: A&A (in press)
Last Modified: 2008-12-18 04:38
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Abstracts by Author
Investigating the Kinematics of Coronal Mass Ejections with the Automated CORIMP Catalog
Bridging EUV and white-light observations to inspect the initiation phase of a "two-stage" solar eruptive event
Improved methods for determining the kinematics of coronal mass ejections and coronal waves
Automatically Detecting and Tracking CMEs I: Separation of dynamic and quiescent components in coronagraph images
Automatic Detection and Tracking of Coronal Mass Ejections II: Multiscale Filtering of Coronagraph Images
The Kinematics of Coronal Mass Ejections using Multiscale Methods

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