4D Data Cubes from Radio-Interferometric Spectroscopic Snapshot Imaging

Abstract

The new generation of low radio-frequency interferometric arrays have enabled the imaging of the solar corona at high spectro-temporal resolutions and sensitivity. In this article we introduce and implement a formalism to generate flux density and brightness temperature ($T_{\mathrm B}$) maps from such images, using independently obtained disc-integrated solar flux density dynamic spectra. These images collectively generate a 4D data cube, with axes spanning angular coordinates ($\theta,\phi$), frequency ($\nu$) and time ($t$). This 4D data cube is the most informative data product which can be generated from interferometric radio data. It will allow us to track solar emission simultaneously in these four dimensions. We also introduce SPatially REsolved Dynamic Spectra (SPREDS), named in analogy to the usual dynamic spectra. For any arbitrary region, ($\theta_i,\phi_j$), in the maps, these 2D projections of the 4D data cube correspond to the dynamic spectrum of emission arising from there. We show examples of these data products using observations from the Murchison Widefield Array (MWA). These are also the first calibrated solar maps from the MWA

Synthetic Radio Imaging for Quiescent and CME-flare Scenarios

“…Please note that only our synthetic results are illustrated in Figure 3. Our results show a good first order agreement with the observations illustrated in Figure 6 of Mohan & Oberoi (2017). The synthetic image constructed based on our simulation results has captured the most intense feature at the center of the solar disk, as shown in their Figure 6.…”

“…Solar radio observations have been available for a number of years in different frequencies for quiet full sun (Takano et al 1997;Oberoi et al 2011;Mohan & Oberoi 2017) and flaring conditions (e.g. Kundu et al 2009;Kochanov et al 2013;Chen et al 2015).…”

“…In Figure 3, we show the radio synthetic intensity map as calculated by our simulation in the low frequency regime and in particular for a frequency of 125 MHz. Recently, Mohan & Oberoi (2017) used Murchison Widefield Array 3 (MWA) to obtain low frequency radio observations of the Sun. Refraction is playing a major role in the low frequency regime.…”

“…The Sun is of special importance, not only because it is a great laboratory for plasma physical mechanisms, but also due to its proximity, which makes it possible for radio observers to spatially resolve the structures above the photosphere (e.g. Oberoi et al 2011;Mohan & Oberoi 2017). The morphology of the radio emissions from the quiet solar atmosphere depends on the magnetohydrodynamic (MHD) plasma quantities (density, temperature and magnetic field) as well as the radio emission mechanisms.…”

Solar physics with the Square Kilometre Array

“…A testament to this argument is the important results that have come out of data obtained with SKA's "precusor" and "pathfinder" projects: the LOFAR (e.g Morosan et al, 2014Morosan et al, , 2015Morosan et al, , 2017Reid & Kontar, 2017;Kontar et al, 2017b;Chen et al, 2018), the MWA (e.g. Oberoi et al, 2011;Mohan & Oberoi, 2017;McCauley et al, 2017;Suresh et al, 2017;Cairns et al, 2018;Sharma et al, 2018), the VLA (Spangler & Whiting, 2009;Chen et al, 2013;Kooi et al, 2014;Chen et al, 2015), and the LWA (Tun Beltran et al, 2015). This paper is organized as follows.…”