8.11.2020

A coronal mass ejection (CME) is seen in this image captured by the Solar Terrestrial Relations Observatory spacecraft on 7 October 2012. The Sun and the base of this CME are shown in extreme ultraviolet light, and the outer part of the bulb is in visible light. Credit: NASA

The damaging effects of storms, from flooding caused by heavy rain or storm surges to strong winds knocking trees to the ground, are familiar to most people. Fewer, however, are aware of the hazards of solar storms, though these events can disrupt radio communications, knock out electrical power, and damage satellites. With our increasing reliance on technology, solar storm damage is now a greater threat than ever before.

In a new study, Jones et al. turned to crowdsourced science to help protect against this hazard by identifying potential patterns in coronal mass ejections (CMEs), vast eruptions of plasma and magnetic field flung from the Sun. The researchers showed participants side-by-side images of numerous CMEs taken by the Solar Terrestrial Relations Observatory (STEREO) spacecraft and asked them to select which one looked more “complicated.”

A standard CME is bulb shaped in appearance, with a bright outline, dark interior, and another bright prominence within, but CME structure varies greatly in these images. In choosing the purposefully vague term “complicated,” the scientists hoped the participants could draw out patterns that could form the basis of future study. The researchers used participant input to rank 1,111 images from most to least complicated, then analyzed the images.

Participants tended to look at a mix of factors to decide whether a CME was complicated. They labeled as more complicated images in which CMEs had a larger angular width, were brighter, and had more detailed interior structures. These patterns stood out to participants, but what do they tell us about CMEs? A large angular width might result from an inconvenient camera angle and does not necessarily correlate with CME size, the researchers note. Patterns of brightness and shadow in the STEREO images, meanwhile, relate to CME mass and movement.

Prior research has found that the angular width and mass of CMEs tend to follow the 11-year solar cycle. But what about the solar cycle causes these changes in complexity? The researchers suggested that perhaps a more active Sun emits more complex CMEs, that wilder solar winds or magnetic fields complicate CMEs after they erupt, and that if the Sun emits more CMEs at its maximum, it’s possible these storms collide and merge into complex structures. One thing is clear: Coronal mass ejections change markedly over the solar cycle, and more work is needed to understand how and why. (Space Weather, https://doi.org/10.1029/2020SW002556, 2020)

Quelle: EOS American Geophysical Union