Abstract Details
| Name: Surajit Mondal Affiliation: National Center for Radio Astrophysics Conference ID: ASI2018_1290 Title : Ionospheric Studies Using By-products of a Low-radio Frequency Solar Imaging Pipeline Authors and Co-Authors : Surajit Mondal (National Centre for Radio Astrophysics), Divya Oberoi (National Centre for Radio Astrophysics), Leonid Benkevitch (MIT Haystack Observatory),Meagan Crowley (University of Massachusetts), Philip Erickson (MIT Haystack Observatory), Colin J. Lonsdale (MIT Haystack Observatory), John Morgan (Curtin University) Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : Solar imaging at metre wavelengths has improved dramatically with the advent of new low-frequency radio interferometers like the Murchison Widefield Array (MWA), the Long Wavelength Array (LWA) and the Low-Frequency Array (LOFAR). Now it is possible to image the sun at high temporal and spectral resolution with dynamic ranges at least an order of magnitude higher than what was possible before. This is essential for studying the complex dynamic nature of the solar corona. The traditional approach to radio imaging is however very interactive in nature and is hence very human effort intensive. This is also true for solar radio imaging. To reduce the tedium of generating these images, we have developed an automated imaging pipeline to deliver calibrated science-ready solar radio images. Here, we briefly introduce this pipeline and then focus on the information about the ionosphere which can be extracted from its by-products, namely the antenna based complex gains. Apart from they being interesting in their own right, our interest in ionospheric studies stems from the fact that there is substantial evidence for imaging dynamic range of solar MWA images to be limited by the direction dependent ionospheric effects. Higher dynamic range images of the sun are needed if we want to observe the synchrotron emission from the Coronal Mass Ejection (CME) plasma; and to measure the Faraday rotation due to heliospheric plasma, especially CMEs. Other sensitive radio interferometric measurements, although generally taken during the night, will also benefit from this work. At very low noise levels, the impact of these tiny ionospheric effects might begin to become discernible in the data. It is therefore important to study and understand such ionospheric effects in greater detail. Radar and GPS based ionospheric studies have been conducted for a long time. Radio astronomers have also been developing increasingly sophisticated techniques to measure and remove the impact of ionospheric propagation from radio interferometric data. Our novel method offers a few advantages over all of these techniques. These advantages stem from a confluence of the very high SNR arising from observations of the Sun; the large angular size of the Sun, which translates to illuminating a correspondingly large ionospheric patch; and the compact and dense distribution of MWA elements. This enables us to study the ionosphere at very small temporal and spatial scales than has usually been possible before. Here, we present our initial results from this investigation. |