Abstract
A new, automated method of detecting coronal mass ejections (CMEs) in three dimensions for the LASCO C2 and STEREO COR2 coronagraphs is presented. By triangulating isolated CME signal from the three coronagraphs over a sliding window of five hours, the most likely region through which CMEs pass at 5 solar radii is identified. The centre and size of the region gives the most likely direction of propagation and approximate angular extent. The Automated CME Triangulation (ACT) method is tested extensively using a series of synthetic CME images created using a wireframe flux rope density model, and on a sample of real coronagraph data; including halo CMEs. The accuracy of the angular difference between the detection and true input of the synthetic CMEs is 7.14 degrees, and remains acceptable for a broad range of CME positions relative to the observer, the relative separation of the three observers and even through the loss of one coronagraph. For real data, the method gives results that compare well with the distribution of low coronal sources and results from another instrument and technique made further from the Sun. The true three dimension (3D)-corrected kinematics and mass/density are discussed. The results of the new method will be incorporated into the CORIMP database in the near future, enabling improved space weather diagnostics and forecasting.
Highlights
First observed by the Skylab mission in the early 1970s, coronal mass ejections (CMEs) are the largest and most dynamic phenomena that originate from the Sun, and can be observed in the extended corona by white light coronagraphs (Gosling et al 1974; Webb & Howard 2012; Chen 2011 and references within)
This date was chosen as the spacecrafts were separated from one another by close to 120◦ (LA:124◦, LB:116◦, AB:120◦, where L, A and B denote the positions of Large Angle Spectrometric Coronagraph (LASCO), Solar Terrestrial Relations Observatory (STEREO) Ahead and Behind respectively) giving an ideal configuration
The accuracy of the detection is tested by comparing the longitude/latitude results to those used as input parameters for the synthetic CME
Summary
First observed by the Skylab mission in the early 1970s, coronal mass ejections (CMEs) are the largest and most dynamic phenomena that originate from the Sun, and can be observed in the extended corona by white light coronagraphs (Gosling et al 1974; Webb & Howard 2012; Chen 2011 and references within). Huge eruptions of magnetised plasma, CMEs can propagate at speeds of up to thousands of kilometers per second and have a broad range of masses (Liu et al 2010; Yashiro et al 2004). Given that these eruptions and their associated bursts of energetic particles can have adverse effects such as geomagnetic storms at Earth, early warnings of their presence and their direction of propagation are needed for space-weather forecasting (Schwenn et al 2005). CME events and charateristics (such as spatial size, velocity, acceleration, type, morphology and distribution) have been detected and catalogued using both manual and automated methods. The most widely used catalogues are: the Coordinated Data Analysis Workshop (CDAW1) CME catalogue, the Computer Aided CME Tracking (CACTus2) catalogue, the Solar Eruptive Event Detection System (SEEDS3), Automatic Recognition of Transient Events and Marseille Inventory from Synoptic maps (ARTEMIS4), and, more recently,
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