Hariharan K.

Visiting Fellow
Email: hara [at] ncra.tifr.res.in
Phone: +91- 20 - 25719213
Extn: 9213
Office: F229
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA

Main Research Areas: Antennas, Analog and Digital receivers for radio astronomy; Solar Radio Bursts, Seismology and Turbulence of the Solar Corona; Electron density distribution modelling in the solar atmosphere; Jupiter Radio Emission at Decameter wavelengths


K. Hariharan completed his Bachelor's degree studies in Instrumentation Engineering at St. Joseph’s College of Engineering in Chennai and obtained a B.E. from Anna University in 2010. He then joined the Indian Institute of Astrophysics (IIA) in Bangalore under the Integrated M.Tech.- Ph.D.(Tech) programme in Astronomical Instrumentation, a collaborative course with the Calcutta University (CU). Under the programme, he worked with the solar radio astronomy group at the Gauribidanur Radio Observatory (GRO), obtaining his M.Tech. degree in 2012, and continuing for his Ph.D. studies at the GRO. He submitted his Ph.D. thesis in April 2017 and then joined NCRA-TIFR as a Post-Doctoral Visiting Fellow.

Research description:

My main research interests are grouped as follows :
Digital Receivers for Radio Astronomy
A large part of astronomical data processing and analysis is now performed by receivers based on digital hardware and they prove to be more reliable in terms of system stability and affordability. The advent of digital technology in addition to fast processing algorithms have taken radio astronomy research to a new technological level. As part of my doctoral thesis work I developed a software-based cross-correlation spectrograph for solar radio observations on FPGA-based digital hardware. I’m now part of the expanded GMRT project (eGMRT) and working on the development of a multi-element GPU-based FX-correlator for a Focal Plane Array (FPA) system. This will be used to estimate the complex weights for the individual antenna elements of the FPA to perform multi-beam forming mode of observation.
Solar Radio Bursts
The Sun is the most powerful radio source in the sky, primarily due to its proximity to the Earth. The electromagnetic radiation from the different regions of the solar atmosphere is observed at different wavebands. The radio emission, particularly those at low frequencies (< 300 MHz), comes from the outer solar atmosphere which is the Corona. This region is presently inaccessible for observations at other wavebands due to various reasons and most of the dynamics associated with eruptive phenomena like flares, Coronal Mass Ejections (CMEs), etc. are thought to occur in this region. My research focus is on the study of impulsive radio signatures (called radio bursts) associated with such phenomena. The aim is to understand the local plasma environment, especially in the context of the Earth-Sun system, often referred to as “Space Weather”. I have particularly worked on Type II radio bursts, associated with coronal shocks from CMEs, as well as on moving Type IV bursts, associated with parts of the CME.
Radio Emission from Jupiter
All the Jovian planets tend to emit radio emission due to the interaction of their respective magnetic fields with the ambient plasma. In particular, Jupiter has been found to emit impulsive radio emission in the frequency range 10 – 40 MHz. The Jupiter ``bursts'' are mostly associated with the passage of its volcanic moon Io across the planet’s magnetosphere and are often referred to as “Io-bursts”. The enhanced emission is due to the acceleration of charged particles through the cyclotron maser instability process and categorized as Types A-, B-, C- and D- based on the central meridian longitude of Jupiter and the location of Io. There are other bursts of Jupiter which are not related to Io and are called “non-Io bursts”. I’m presently working on a project to study the connection between the non-Io bursts of Jupiter and the eruptive phenomena occurring on the Sun. For this study, I’m using data from my observations with the Long Wavelength Array station1 (LWA1) and archival data from the Nancay Decameter Array (NDA).

Selected publications:

1. Solar Type IIIb Radio Bursts as Tracers for Electron Density Fluctuations in the Corona (Mugundhan V. , Hariharan K., and Ramesh, R.: 2017, Solar Physics, 292, 155)

2. Constraining the Solar Coronal Magnetic Field Strength Using Split-Band Type II Radio Burst      Observations (Kishore P., Ramesh R., Hariharan K., Kathiravan C., and Gopalswamy N.:2016, ApJ, 832, 59.)

3. Simultaneous Near-Sun Observations of a Moving Type IV Radio Burst and the Associated White-Light Coronal Mass Ejection (Hariharan K., Ramesh R., Kathiravan C., and Wang T. J.: 2016. Solar Physics,  291, 1405)

4. High Dynamic Range Observations of Solar Coronal Transients at Low Radio Frequencies With a Spectro-Correlator (Hariharan K., Ramesh R., Kathiravan C., Abhilash H. N. and Rajalingam M.: 2016. ApJS, 222, 21.)