Injection of helicity flux and the eruptive nature of solar Active Regions [Note the unusual day!]
Nordita Astrophysics seminars
Friday 19 October 2018
to 14:20 at
P. Vemareddy (Indian Institute of Astrophysics, Bengalure)
The magnetic helicity and energy in the solar active regions (ARs) are two important parameters for a quantitative study of magnetic origins of solar eruptions. Understanding the nature and evolution of the photospheric helicity flux transfer is crucial to reveal the role of magnetic helicity in coronal dynamics of solar ARs. The estimations of magnetic energy and helicity flux from line-tied surface (photosphere) requires velocity and magnetic field distributions in the AR. Recent studies using HMI vector magnetic field observations of emerging ARs present three kinds of AR evolution with a net positive, negative, and successive injection of positive and negative helicity flux. Further, the ARs with a predominant sign launch CMEs at some point in time whereas the AR with successive injection of opposite helicity exhibits only C-class flaring activity characterized by delayed enhanced coronal emission with respect to the time of sign change of helicity flux. These results suggest that the ARs with a predominant sign of helicity flux indicate flux rope formation and its bodily ejection as CME however, the AR with successive injection of opposite helicity exhibits cancellation of coronal helicity leading to field reconfiguration and dissipation of energy heating the corona. I shall discuss the theoretical ideas and observational results concluding with a new idea of how the normalized helicity flux be used to distinguish the eruptive and non-eruptive ARs.