Rohit Sharma

Visiting Fellow
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA
Status: Left

Main Research Areas: Solar Physics, Array Optimization.


Rohit obtained a 5-year Integrated M.Sc. degree in Physics from the Centre for Excellence in Basic Sciences, Mumbai, in 2012. He then joined NCRA in 2012 for his doctoral studies, and is working with Divya Oberoi on imaging the Sun at metre wavelengths.

Research description:

Imaging the Sun at Metre Wavelengths:
Conventional solar physics deals with the chromosphere and the photosphere of the sun. However, observing the Sun at metre wavelengths is unique as metre waves alone are generated in the plasma of the solar corona, and thus provide a tool to probe conditions in the corona. Until recently, the limitations of radio telescope meant that little information was available at these wavelengths. The Murchison Widefield Array (MWA), being built in Western Australia, is an excellent instrument for observing the Sun at metre wavelengths. The combination of the sensitivity of the MWA, its low frequency of operation, wide field of view, large number of polarized sources with sufficient flux density, allows one to measure the coronal and heliospheric Faraday rotation simultaneously to several different lines of sight and out to much larger distances from the Sun ( 50 solar radii). I am studying the system characteristics of the MWA with high dynamic range maps. Using multi-wavelength physics, we study the energy transportation in the corona. We are also studying the role of magnetic field in corona in energy transportation and deposition.
Optimising Antenna Layout for e-GMRT:
The GMRT is the best low-frequency interferometer in the world, at frequencies below 1 GHz, in sensitivity, frequency coverage and image fidelity. To retain its premier status, it is critical to extend the GMRT's capabilities over the next decade. I am trying to optimise the antenna configurations of the extended GMRT (e-GMRT) for various science cases. The sciences cases are driven by Galactic plane imaging, requiring utlra short baselines(< 1km), pulsar observations and HI surveys at z <~ 1, requiring Intermediate baselines (5-10 km), and finally extra-galactic imaging studies, requiring long baselines (50km - 60km), to beat the current confusion limit. For optimisation, the technique of tomographic projection is used. The aim is to come up with a single antenna layout for all science cases.

Selected publications:

(1) On the energization of charged particles by fast magnetic reconnection (R. Sharma, D. Mitra, D. Oberoi, 2017, MNRAS, 470, 723)

(2) Quantifying weak non-thermal solar radio emission at low radio frequencies (R. Sharma, D. Oberoi, M. Arjunwadkar 2017, ApJ, submitted)

(3) Wavelet-based Characterization of Small-scale Solar Emission Features at Low Radio Frequencies (A. Suresh, R. Sharma, D. Oberoi et al., 2017, ApJ, 843, 19)

(4) Estimating Solar Flux Density at Low Radio Frequencies Using a Sky Brightness Model (D. Oberoi, R. Sharma, A. E. Rogers 2017, Solar Physics, 292, 75)