Abstract Details
| Name: K Sasikumar Raja Affiliation: Post Doctoral Research Fellow Conference ID: ASI2016_458 Title : Radio Polarization Studies of the Solar Corona at Low-frequencies Authors and Co-Authors : Supervisor: Dr. R. Ramesh, Indian Institute of Astrophysics, Bangalore, India Abstract Type : Oral Abstract Category : Thesis Abstract : The dedicated radio telescopes to continuously monitor the Sun and solar corona are limited. But such telescopes provide crucial information on coronal magnetic field strength, weak energy events, radio wave propagation in the corona, space weather and Earth's climate and different plasma parameters etc, which are further useful in understanding the unresolved mysteries of the solar corona. The electron density and hence the plasma frequency decreases in the solar corona with the radially outward increasing height. Also, different frequencies of observations correspond to different heights in the solar corona. Therefore, we designed and constructed a polarimeter, called Gauribidanur Radio Interference Polarimeter (GRIP) at Gauribidanur Radio Observatory, India, to monitor the corona in the Stokes I (total intensity) and Stokes V (circularly polarized intensity) modes which primarily operates in the bandwidth of 30-150 MHz. This operating bandwidth corresponds to the height approximately 1-2 R_sun above the photosphere. Note that the observations of the corona is difficult in this regime even with the `existing' space based coronagraphs because of the practical limitations. The GRIP consists of 40 log-periodic dipole antennas arranged in East-West direction in horizontal and vertical directions. After successful construction of the array, the observation of the Sun is being carrying out every day. In this talk, I will present the design and instrumental details of the GRIP and the observational results obtained with it. Some of them are observations of the weakest energy events in the corona (called picoflares) and their role in coronal heating, indirect methods of estimation of the magnetic field strength using the observations of quasi-periodic type III bursts in polarimetric mode, magnetic field strength associated with the coronal mass ejections (CMEs) and scattering studies using the Crab nebula occultation technique. I will conclude the talk by explaining the improved, newly designed/fabricated cross-polarized log-periodic dipole antenna system and the future scope. |