Shannon Jones

Coronal Mass Ejections (CMEs), or solar storms, are huge eruptions of particles and magnetic field from the Sun. If a huge CME were to hit Earth, there could be serious consequences such as long-term power cuts. Many of these impacts could be reduced if we had adequate warning that a storm was going to hit. Therefore, we created a citizen science project to investigate CMEs, to help improve our space weather forecasts.

4,028 citizen scientists participated in our Zooniverse project ‘Protect our planet from solar storms”. We showed pairs of images from the wide-angle white-light cameras on board the twin STEREO spacecraft and asked the participants to decide which CME in each pair looked most complicated, or complex. The images shown were running differenced, i.e. the previous image was subtracted from each image, to highlight the movement of the storm.

We fitted a Bradley-Terry model to this data (a statistical model widely used by psychologists to rank items by human preference) and ranked 1,110 CMEs by their relative visual complexity, i.e. we gave each CME a complexity value which describes how complex that CME appeared compared to the other 1,109 CMEs in the dataset.

The Sun has an approximately 11-year cycle, over which the number of sunspots (darker spots on the surface of the Sun) rise and fall. We call the period when the Sun has a higher number of sunspots ‘solar maximum’, and the period when the Sun has fewer sunspots ‘solar minimum’. Many studies have found that the number of CMEs rises and falls with the number of sunspots, and that CMEs appear wider and travel faster at solar maximum.

From our ranking of the relative visual complexity of 1,110 CMEs, we found that the average complexity of CMEs also changes with the solar cycle. At solar maximum, CMEs appear more complex, and towards solar minimum, CMEs appear less complex. Complex CMEs appear wider and brighter, whilst simpler CMEs appear narrower and less bright. The figure on this slide shows the relative complexity of all 1,110 CMEs, with CMEs observed by the STEREO-A spacecraft shown by pink dots, and CMEs observed by the STEREO-B spacecraft shown by blue dots. This shows that the average complexity of CMEs observed by STEREO-B is consistently lower that the complexity of CMEs observed by STEREO-A.

When we asked the citizen scientists how they chose the most complex CME, they described complex CMEs as “big”, “messy” and “bright” with complicated “waves”, “patterns” and “shading”. We plan to quantitatively determine which of these characteristics are associated with visual complexity. We will also investigate what is causing the CMEs to appear differently. Possible causes include: the complexity of the magnetic field at the CME source region on the Sun; the structure of the solar wind the CME passes through; or multiple CMEs merging, causing a CME to look more complex. Our results suggest that there is some predictability in the structure of CMEs, which may help to improve future space weather forecasts.

Thank you for looking at my poster! If you have any questions, please feel free to drop an email to s.jones2@pgr.reading.ac.uk, or if you are a citizen scientist, you can message us on the Protect our Planet from Solar Storms talk page.