ar092.lara01 Posted: 26-Apr-96 Updated: Events specified: See Text
PhD Thesis Project of
Alejandro Lara
To be sobmited to the National University of Mexico Advisors:
N. Gopalswamy and R. Perez-Enriquez
ar090.yashiro01 A Study of Evolution of Active Regions using Yohkoh SXT Images
(Note that this is also thesis project.)
MOTIVATION. A large number of phenomena, both of fast and slow time scales take place in Solar Active Regions. It is important to study the slow evolution of the active region structures: the change in vertical and horizontal structure of the active region reflects the change in the distribution of magnetic field as well as plasma parameters. A proper understanding of these changes may help us understand the conditions which lead to transient phenomena such as flares.
ABSTRACT. We shall use simultaneus microwave (1.5 and 17 GHz) and Soft X-ray images obtained with the Very Large Array (VLA), the Nobeyama Radio Heliograph (NRH) and the Soft X-ray Telescope (SXT) on board the Yohkoh spacecraft, as well as photospheric magnetograms from KPNO to study the development of Solar Active Regions. We shall follow the development of various observed parameters such as brightness temperature and polarization in the radio images of the active regions. The X-ray data will be used to track the development of density and temperature of active regions. Using the fact that the quiet active region radiation is due to thermal emmision and identifying the proper emission mechanism for each frequency domain, we construct a consistent model for the three dimensional structure of the active regions. Particular atention will be paid to the mode coupling at 17 GHz as the active regions cross the solar disk. Data used: VLA, NRH and SXT data for April 17-28 1993.