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Estimating Solar Flux Density at Low Radio Frequencies Using a Sky Brightness Model  

Rohit Sharma   Submitted: 2017-05-31 09:59

Sky models have been used in the past to calibrate individual low radio frequency telescopes. In this article, we generalize this approach from a single antenna to a two element interferometer, and formulate the problem in a way that allows us to estimate the flux density of the Sun using the normalized cross-correlations (visibilities) measured on a low resolution interferometric baseline. For wide field-of-view instruments, typically the case at low radio frequencies, this approach can provide robust absolute solar flux calibration for well characterized antennas and receiver systems. It can provide a reliable and computationally lean method for extracting parameters of physical interest using a small fraction of the voluminous interferometric data, which can be computationally prohibitively expensive to calibrate and image using conventional approaches. We demonstrate this technique by applying it to data from the Murchison Widefield Array and assess its reliability.

Authors: Divya Oberoi, Rohit Sharma and Alan E.E. Rogers
Projects: None

Publication Status: Published in Solar Physics, 30th May 2017
Last Modified: 2017-05-31 13:49
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On the Bright Loop Top Emission in Post Eruption Arcades  

Rohit Sharma   Submitted: 2016-03-16 21:26

The observations of post eruption arcades (PEAs) in X-rays and EUV reveal strong localised brightenings at the loop top regions. The origin of these brightenings and their dynamics is not well understood to date. Here, we study the dynamics of PEAs using one-dimensional hydrodynamic modelling with the focus on the the understanding of the formation of localised brightening.Our findings suggest that these brightenings are the result of collisions between the counter-streaming chromospheric evaporation from both the foot points. We further perform forward modelling of the emission observed in simulated results in various spectral lines observed by the Extreme-Ultraviolet Imaging Telescope aboard Hinode. The forward modelled intensities in various spectral lines are in close agreement with a flare observed in December 17, 2006 by EIS.

Authors: Rohit Sharma, Durgesh Tripathi, Hiroaki Isobe, Avyarthana Ghosh
Projects: None

Publication Status: Accepted by ApJ
Last Modified: 2016-03-21 15:33
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Estimating Solar Flux Density at Low Radio Frequencies Using a Sky Brightness Model
On the Bright Loop Top Emission in Post Eruption Arcades

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