Numerical simulations and observations of coronal sigmoids.

The results of our numerical experiments on the formation and evolution of coronal sigmoids appear in the Astrophysical Journal, Volume 691, Issue 2, pp. 1276-1291 (2009). This model is able to explain how complex sigmoids are formed and evolve and how are connected to eruptive events of the solar corona. Click here if you want to download a copy of the paper (pdf file).

Figure 1. The left panel shows one snapshot from the numerical experiments and the right panel shows the 'corresponding' snapshot from the observations (as recorded by Hinode mission). The two figures show the 'internal complex structure' of the solar sigmoid, which has been observed with very high resolution and it is reproduced succesfully by our numerical experiments. As you can see, 'sigmoids' consist of a netwrok of thin 'ribbons' where the electric current is strong (the isosurfaces in the left panel show electric current) and thus, the plasma is heated to 1-2 million Kelvin degrees temperature. As you can see, there is a very good agreement between the observations and the numerical experiments.

Figure 2. This figure shows the time evolution and final eruption of the sigmoid. It consists of three columns (time is running from top to bottom). Columns 1 and 2 show results from numerical experiments. The yellow isosurfaces are surfaces of electric current (left panels). Column 2 (middle panels) shows temperature. Column 3 shows 'temperature' (intensity) as it is recorded by the observations (Hinode mission). Notice that the agreement on the shape of the sigmoid, internal structure and thermal distribution along the sigmoid, between numerical experiments and observations is very good and fairly balanced. Notice, that even the 'flaring' episode (flashing) at the middle of the sigmoid at the down-right snapshot from observations is reproduced exceptionally well by our numerical experiments (down-middle).