Simulating Coronal Loop Implosion and Compressible Wave Modes in a Flare Hit Active Region

• Published in: The Astrophysical journal 2017-12, Vol.851 (2), p.120
• Main Authors: Sarkar, Aveek, Vaidya, Bhargav, Hazra, Soumitra, Bhattacharyya, Jishnu
• Format: Article
• Language: English
• Subjects: Astrophysics; Compressibility; Computational fluid dynamics; Computer simulation; Coronal loops; Disturbance; Fluid flow; Magnetic fields; Magnetohydrodynamics; methods: numerical; Rigidity; Solar corona; Solar energy; Solar flares; Sun: corona; Sun: flares; Sun: oscillations; Sun: UV radiation; Three dimensional models; Velocity
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa9a45

There is considerable observational evidence of implosion of magnetic loop systems inside solar coronal active regions following high-energy events like solar flares. In this work, we propose that such collapse can be modeled in three dimensions quite accurately within the framework of ideal magnetohydrodynamics. We furthermore argue that the dynamics of loop implosion is only sensitive to the transmitted disturbance of one or more of the system variables, e.g., velocity generated at the event site. This indicates that to understand loop implosion, it is sensible to leave the event site out of the simulated active region. Toward our goal, a velocity pulse is introduced to model the transmitted disturbance generated at the event site. Magnetic field lines inside our simulated active region are traced in real time, and it is demonstrated that the subsequent dynamics of the simulated loops closely resemble observed imploding loops. Our work highlights the role of plasma β in regards to the rigidity of the loop systems and how that might affect the imploding loops' dynamics. Compressible magnetohydrodynamic modes such as kink and sausage are also shown to be generated during such processes, in accordance with observations.