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Upcoming Seminar/Colloqium

Topic:

Solar Eruptive flares and coronal mass ejections: initiation and propagation characteristics.

Speaker : Dr. Syed Ibrahim
Affiliation : ARIES
Date & Time :
Venue : Online/Zoom
Abstract :

The aim of this work is twofold. First one is to analyze the initial and the evolution of the filament eruption, considered as a flux rope. Also find the link between the evolution of flux rope and radio emissions. Initial signatures of eruption from the solar source region are confirmed using the observations from Atmospheric Imaging Assembly in the Solar Dynamics Observatory. These observations confirm that the source of the CME was associated with a twisted filament which was visible before the flare initiation. The photospheric magnetic configuration displayed a complex network of βδ sunspots. After the eruption, the CME was observed by SOHO/LASCO coronagraph with linear speed and acceleration of 740 km s-1 and -2 m s-2 respectively. Dynamic radio spectrum observation from Learmonth Observatory in metric frequency range shows type III and type II radio emissions that reveal the field line opening and coronal shock formation closely associated with the CME. From metric type II radio observation and assuming Newkirk’s density model, we estimate the shock formation height range of 1.14 - 1.54 Rʘ with the corresponding shock speed (~650 km s-1). With the heliographic observations from Nancay heliograph at different frequencies we could disentangle type II bursts from type III bursts. Type III would correspond to the filament eruption while type II from the northern flank of the CME. Second is that we analyzed a multi-wavelength and multi-instrument investigation of a helical prominence from active region NOAA 11907 on 2013 December 04. The uniqueness of the study is that this is the first time we found KINK and Kelvin Helmholtz Instability (KHI) in a single case. Multi-wavelength observations of the source active region suggest that the initiation of the prominence eruption is KINK. From 171 Å images, we estimated the half pitch length of observed helical structure as 34 Mm. The length of the total arc of the prominence is measured as 182 Mm. From these estimated height information, we manipulated the twist number is 2.69. Using the helical twist/turns number, we confirmed that the entire prominence body is kinked. The clear helical kink instability visible in the flux rope and caused the slow rise of the prominence during the flare. In addition to this, the helical magnetic structure of the prominence eruption clearly visible in 171 Å and ARIES H-alpha images. At the time of rising phase, we can see the KHI in the prominence propagation.

About Speaker :

Dr. Syed Ibrahim is a Post Doctoral Fellow at ARIES.