Prasad Subramanian: Research Interests


My research interests range from solar physics to black hole accretion, within the overall framework of plasma astrophysics. They include black hole accretion disks, AGN and microquasar jets and radiation processes, solar radio emission, solar coronal mass ejections (CMEs) and space weather.

  • Please click here for my research publications.


  • Please click here for a general-purpose article on solar coronal mass ejections that I wrote in 2003, for Khagol, the quarterly bulletin of IUCAA.


    • My work on black hole accretion disks has concentrated on accretion disk viscosity the disk-jet connection. My work on jet launching from the accretion disk/corona remains one of the few which can explain the presence of hadrons in relativistic jets. The presence of hadrons in such jets is now being increasingly recognized as being essential for explaining very high energy radiation from nearby blazars. I have also worked on particle acceleration processes in different contexts. Recent results on rapid variability of multi TeV emission from nearby blazars raise interesting questions regarding the emission mechanisms, and consequently on the basic constituents of their jets. This is an area I expect to concentrate on in the near future.


    In solar coronal physics I have focussed on eruptive events and observations and theory related to meter wavelength emission. I have explored the diversity of CME source regions and investigated some unexpected consequences of the interaction between CMEs and their overlying streamer structures. I have examined the basic energetics of CME propagation and unambiguously showed that the CME magnetic fields have to be the primary source of their driving power.

    I initiated a program of solar observations at the Giant Metrewave Radio Telescope (GMRT) since 2001. Using data from the GMRT and the Nancay Radio Heliograph (NRH) in France, my collaborators and I have obtained what are arguably the best meter wavelength maps of the solar corona. We have combined visibilities from the NRH and GMRT to produce approximately 2 sec snapshot maps with dynamic ranges as high as 400--500. Such high dynamic ranges were hitherto possible only with synthesis observations lasting a few hours. Our observations have revealed the presence of very compact sources, which are helping us arrive at some unexpected conclusions regarding the amplitude of turbulence in the inner corona. Motivated by GMRT-NRH observations of noise storms, I have estimated the power input to the nonthermal electron population responsible for this emission. I have also participated in a serendipitous observation of a flare-CME event with the GMRT. Among other aspects, this observation provided us with an opportunity to observationally demonstrate for the first time the formation of a current sheet below the erupting arcade that constitutes the CME; a feature that is central to leading theories of the flare-CME phenomenon.

    I have recently begun working on Forbush decreases, which are a cosmic ray manifestation of the near-earth effects of CMEs, using data from the GRAPES-3 muon telescope array at Ooty, operated by the Tata Institute of Fundamental Research (TIFR). Together with colleagues at the TIFR, I have used this data to obtain interesting results regarding the turbulence levels near CME fronts. There are a number of interesting issues pertaining to space weather disturbances that can be addressed with this data, and I intend to work actively in this area.