Dynamic Formation and Associated Heating of Magnetic Loop on the Sun
To seek an atmospheric heating mechanism operating on the Sun, we investigated heating source generated by downflow, both of which may arise in a magnetic loop dynamically formed on the Sun via flux emergence. Since an observation showed that illumination of evolving magnetic loops under the dynamic formation occurred sporadically and intermittently, we performed a magnetohydrodynamic simulation of the flux emergence to obtain a high-cadence simulated data where temperature enhancement was identified at a footpoint of a selected evolving loop. Unlike a rigid loop where only a field-aligned flow without transverse compression exists, the evolving loop in a low-plasma β atmosphere may be subjected to local transverse compression by the magnetic field surrounding the loop, which could drive a strong supersonic downflow generating the effective footpoint heating source (eFHS) in it. This suggests that an energy conversion system may be introduced to the magnetized atmosphere of the Sun; that is, free magnetic energy in the atmosphere is converted to flow energy via the local transverse compression of a loop by means of Lorentz force, and the flow energy is eventually reduced to thermal energy via formation of a standing shock wave behind which longitudinal compression further proceeds to stop the flow (complete thermalization) in the loop.
We investigated the local transverse compression of a magnetic loop by means of Lorentz force (magnetic compression) in the succeeding paper.
Reference
Magara, T., Jang, Y., & Son, D.
Journal of the Korean Astronomical Society, 55, 215
