Login

The magnetic field of coronal mass ejections
Coronal Mass Ejections (CMEs) are violent explosions in the solar corona, during which large quantities of plasma gets ejected from the Sun into interplanetary space. When these CMEs reach the Earth, they are known to cause significant damage to telecommunications, power transmission lines, etc in many occasions. The potential of a CME to produce these terrestrial effects is known as its geo-effectiveness. The geo-effectiveness of a CME depends significantly on its magnetic field. In fact, the eruption of the CME also depends on the details of its magnetic field. Due to this, measuring the CME magnetic field is very important for accurate predictions of a CME’s geo-effectiveness. Radio observations are known to be well suited for this purpose due to their high sensitivity to nonthermal emissions and magnetic field. The imaging and calibration techniques I have been involved in developing has allowed the detection of very faint emissions from CMEs, which in turn could be modelled to determine the CME magnetic field.

Coronal Heating and its indirect signatures.
It is a mystery, more than 50 years since its first discovery, how the solar corona, which is the outermost layer of the solar atmosphere, maintains its million K temperature, when the photosphere, which is the lowest layer of the atmosphere, is only at a temperature of ~6000 K. This phenomenon is known as the coronal heating problem. A plausible model hypothesises that the ubiquitous small-scale magnetic reconnections in the solar corona are responsible for maintaining its high temperature. However, these small-scale reconnections, also known as nanoflares, occur at scales not resolvable by current instruments. Hence, scientists have continuously been searching for indirect evidence of nanoflares and probing weaker flares with more sensitive instrumentation. Radio observations are very sensitive to the nonthermal particles which are expected to be produced during these reconnection processes. I have investigated these nonthermal emissions across wavelengths, and was the first to detect evidence for ubiquitous nonthermal emissions in the solar corona.

Solar Bursts and associated phenomena
Solar radio bursts are very bright coherent emissions. Historically these have been studied using the solar-disc integrated dynamic spectrum. Recent advances in spectroscopic snapshot imaging have opened to door to investigate these phenomena in much greater detail than that possible earlier. Recently, we have also been able to do spectroscopic snapshot polarimetric imaging of the solar corona. This implies that, for every time and frequency chunk of the data, we can create full Stokes images. This new capability, along with the successful usage of the high angular resolution data available from instruments like the uGMRT and VLA, has opened up a very new phase-space which is rich in discovery. One of our key discoveries is the detection of linear polarisation from the solar corona at metre wavelengths. My work has also questioned the belief that it is exceptional to observe radio sources at very small angular-scales. Both of these topics have the potential to throw a new light into the solar corona.