Sigmoid Structure of an Emerging Magnetic Flux Tube

We have simulated the emergence of a twisted flux tube into the corona using a three-dimensional, time-dependent code. After emergence, the outer, azimuthal field of the tube expands to naturally form potential-like arcade structure, while the inner, axial field that emerges after the tube axis produces a twisted sigmoidal structure. The low-lying, inner field lines originate from regions of the highest current concentration and therefore will be the most visible in coronal emission such as soft X-rays (Magara & Longcope 2001).


References

Magara, T. & Longcope, D. W. 2001 ApJ, 559, L55