Tracking CMEs using data from the Solar Stormwatch project; observing deflections and other properties†

With increasing technological dependence, society is becoming ever more affected by changes in the near-Earth space environment caused by space weather. The primary driver of these hazards are coronal mass ejections (CMEs). Solar Stormwatch is a citizen science project in which volunteers participated in several activities which characterized CMEs in the remote sensing images from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument package on the twin STEREO spacecraft. Here we analyze the results of the Track-it-back activity, in which CMEs were tracked back through the COR1, COR2, and EUVI images. Analysis of the COR1, COR2, and EUVI data together allows CMEs to be studied consistently throughout the whole field of view spanned by these instruments (out to 15R(S)). A total of 4783 volunteers took part in this activity, creating a data set containing 23,801 estimates of CME timing, location, and size. We used these data to produce a catalogue of 41 CMEs, which is the first to consistently track CMEs through each of these instruments. We assess how the CME speeds, propagation directions, and widths vary as the CMEs propagate through the fields of view of the different imagers. In particular, we compare the observed CME deflections between the COR1 and COR2 fields of view to the separation between the CME source region and the heliospheric current sheet (HCS), demonstrating that in general, these CMEs appear to deflect toward the HCS, consistent with other modeling studies of CME propagation. Plain Language Summary Coronal mass ejections are the main driver of hazardous space weather. The Solar Stormwatch citizen science project asked members of the public to find and measure coronal mass ejections (CMEs) in images of the Sun's atmosphere taken by NASA's twin STEREO spacecraft. In particular, participants tracked CMEs through the fields of view of three imagers that monitor different regions of the Sun's atmosphere: an extreme ultraviolet camera, EUVI, and two Coronagraphs, COR1 and COR2. In this work we process the measurements of the citizen scientists to produce a catalogue of 41 CMEs, including details of the CME source location, size, and speed. The resulting catalogue is the first that self-consistently tracks CMEs through each of the EUVI, COR1, and COR2 imagers. We demonstrate that CMEs tend to accelerate, increase in width, and deflect toward the heliospheric current sheet as they propagate through the combined EUVI, COR1, and COR2 fields of view.