Abstract Details

Name: Vasantharaju N
Affiliation: Indian Institute of Astrophysics
Conference ID: ASI2021_503
Title : REVISIT OF MAGNETIC IMPRINTS OF SOLAR FLARES: AN OBSERVATIONAL STUDY
Authors and Co-Authors : N. Vasantharaju (Indian Institute of Astrophysics), P. Vemareddy (Indian Institute of Astrophysics), B. Ravindra (Indian Institute of Astrophysics) and Vijayakumar H Doddamani (Department of Physics, Bangalore University)
Abstract Type : Oral
Abstract Category : Sun and the Solar System
Abstract : The abrupt, permanent changes of photospheric magnetic field in the active regions (ARs) due to the changes in coronal magnetic field structure during solar flares have been observed for more than two decades. The well known “coronal implosion” model is assumed to explain such flare associated changes of photospheric magnetic field but the complete physical understanding is still missing and debatable. In this study, we made a systematic analysis of flare related changes of photospheric magnetic field during 12 flares using the high cadence of 135 s vector-magnetogram data obtained from Helioseismic Magnetic Imager onboard Solar Dynamics Observatory. We observed the change of Lorentz force implied by the rapid step-wise enhancement of the horizontal component of magnetic field during all flares in the sample. The integrated change of fields and total change of Lorentz force over an area signifying the strength of magnetic imprints are well correlated with the flare strength and the CME momentum. It appears that the strength of magnetic imprints are not stronger for eruptive flares in comparison with non-eruptive flares. Further, the amount of decrease in free energy during the flares has a strong positive correlation (0.8) with downward impulse resulted from the total change of Lorentz force indicating that the part of energy released during flares would penetrate into the photosphere. These results strongly favor the idea of significant feedback from corona to photosphere during flares. On contrary to these results, we observed the simultaneous step-wise increase and decrease of horizontal magnetic field during flares led to the cancellation of impulsive Lorentz force, thought to provide the CME momentum. These contradictions indicate that present understanding of flare associated magnetic field changes is limited and hints the need for improvement of coronal implosion model.