Research highlights

The changes in the magnetic activity of a star leaves imprints in spectral lines such as Ca II H&K lines. The most commonly used magnetic activity proxy, the S-index, quantifies the emission in the Ca II H&K lines. Despite its broad usage, the dependence of S-index on stellar intrinsic parameters and inclination remains poorly understood. I develop models capable of calculating the S-index and its time variation. These models are validated against solar S-index data for over 40 years. I use these models to study the sensitivity of the S-index to stellar inclination and stellar fundamental parameters, and compare solar chromospheric activity to that of its peers.

Astrometry is one of the techniques used in the detection of exoplanets. It uses the stellar wobble i.e., the astrometric jitter, resulting from the gravitational interaction between planet/s and host star to infer the presence of exoplanet/s. One of the sources of noise in astrometric measurements is the stellar magnetic activity. The presence of surface magnetic features leads to a change in the position of the star's brightness centre leading to jitter. I work on the prediction of this stellar magnetic activity jitter. I develop models to estimate the dependence of jitter on stellar inclination, rotation rate, active region nesting, and fundamental parameters such as metallicity, effective temperature etc.

Chromoshperic downflows are plasma flows in the solar chromosphere which are directed away from the observer. At times, these flows attain speeds greater than the local sound speed and become supersonic. Such supersonic flows can be identified through the intensity spectrum. I study the characteristics of these flows using the ground-based data in He I 10830 A triplet and investigate their generation mechanisms.