Abstracts Details


First Name * : jayant
Last Name * : joshi
Affiliation * : RoCS, University of Oslo
Abstract Type * : Oral
Title * : Spectro-polarimetry of two B-class flares in the Ca II 8542 ร… line
Author(s) * : Jayant Joshi
Abstract Session * : Solar flares and coronal mass ejections
Abstract * : We study the temporal evolution of the thermodynamic parameters and the magnetic field in two B-class flares. Analyzed data consist of a 2-hour 40-minute long time-series of high temporal cadence observations acquired in the Ca II 8542 ร… and Fe I 5250 ร… lines with the CRISP spectropolarimeter at the Swedish 1-m Solar Telescope (SST). The atmospheric parameters including the magnetic field in flare ribbons are obtained by inversion of the Ca II and Fe I lines simultaneously using non-thermodynamical equilibrium (non-LTE) inversion code NICOLE. Our analysis leads to three main results: (1) In the chromosphere (log ๐œ = -5), the Doppler velocity show quasiperiodic oscillations in the flare ribbons. During both the flares, the dominating period of oscillation was around 5 minutes, which was around 3 minutes before and after the flares. (2) The micro-turbulence rises (from 6-8 km/sec to 12-15 km/sec) 31-62 seconds prior to the temperature rise in the ribbons at the chromospheric heights, suggesting the turbulence driven heating in the lower chromosphere. (3) In the chromosphere, the magnetic field increases by 200-400 G in the ribbons during the flares above a pore. We attribute the increase in the magnetic field to change in the formation height of the Ca II 8542 ร… line during the flares.