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작성일 : 17-11-24 09:07
11/28(화) 세미나 안내 - 권륜영박사님, "The Density Compression Ratio of Shock Fronts Associated with Coronal Mass Ejections"
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안녕하세요우주과학과, 우주탐사학과 여러분.
 
이번 세미나 11 28일 오후 4 30천문대 영상실에서 있습니다.
Department of Physics and Astronomy, George Mason University / Applied Physics Laboratory, The Johns Hopkins University권륜영 박사님께서 "THE DENSITY COMPRESSION RATIO OF SHOCK FRONTS ASSOCIATED WITH CORONAL MASS EJECTIONS"에 관한 강연을 해 주실 예정입니다.

강연은 한국어로 진행되며, 초록은 아래에 나타나있습니다. 세미나 참석을 원하시는 분은 세미나 시작 10분 전까지 입실해 주시기 바랍니다. 많은 참석 부탁드립니다. 감사합니다.
 
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Dear Colleagues,
 
There will be an Astronomy and Space Science seminar on 11/28, 4:30 PM, in the Auditorium, Kyung Hee University Astronomical Observatory.

Dr. Ryun Young Kwon of Department of Physics and Astronomy, George Mason University / Applied Physics Laboratory, The Johns Hopkins University will give a presentaion about "THE DENSITY COMPRESSION RATIO OF SHOCK FRONTS ASSOCIATED WITH CORONAL MASS EJECTIONS."
 
The language of the seminar will be Korean and abstract is shown below.
 
You are asked to join the seminar five to ten minutes before it starts. Your attendance will greatly be appreciated.
  
Thank you.


* Abstract: We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with Coronal Mass Ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (~2000 km/s) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the three-dimensional (3D) geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a chi-square approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvenic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a free-propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and last longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.