Background: We recently published a paper that examines a striking phenomena: solar eruptions. The paper elegantly models how these eruptions, known as coronal mass ejections, are produced from the ejection of twisted magnetic ropes.
Coronal mass ejections are large-scale eruptions in the solar atmosphere that consist of a giant cloud of solar plasma embedded in a magnetic field. They have the potential to produce solar storms here on Earth that can damage artificial satellites and disrupt ground-based power generation.
Design challenge: I was taken with the figures from the paper, specifically fig 4 (above) showing the evolution and eruption of the twisted flux rope. We asked Tahar Amari, one of the authors, to submit a few of his other visualisations to be considered for the cover. (We loved the rope itself, but on the cover we thought we should show something that was more obviously on the sun.)
Amari sent us several striking images, but in the end we decided on the cover above, as it clearly showed several key elements: the twisted rope is clearly seen in blue (on the left); plus, the whole model can be seen in action, complete with a map of the sun’s more active regions (using a triangular grid). All of these elements combined give a stunningly complete picture of a solar storm.
I asked Amari to send along specifics about his modelling technique. This from Amari:
“This image was produced using a new high performance unstructured mesh based numerical code MESHMHD, which solves the physical equations relevant to the Sun’s atmosphere. With its adaptive refinement scheme, the code solves both the large scale structure of the global Sun as well as the smaller active region scale at the very high resolution of the data provided by the NASA Solar Dynamics Observatory mission.
Rendering of the solution was performed using Ensight software, with several specific issues.
First, it was important to draw only a set of selected field lines of the magnetic field, and not all of them which would fill all the volume, but in particular those who exhibit magnetic ropes (in blue), with variable diameters of the ropes to enlighten the main structures from the background ones.
Also, to show the power of the adaptive mesh refinement computational model, the triangles on the surface of the Sun were not color-filled, but only their edges. For the high resolution cover, those edges had to be drawn with an optimal thickness.”
The final step was to create the warm glow of the sun with just the right orange-yellow colour. Using a very specific color palette, implying a balance of various hues (actually selected by Amari’s 14-year daughter, Myriam!) we were able to create the impression of fire-like light of the Sun, from each active region.
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