Solar Dynamo:

The periodic variation of the Sun's large scale magnetic field is a well observed phenomenon. The complex interplay between the plasma flows and magnetic fields in the solar interior results in this periodic modulation of the global magnetic field activity of the Sun. The magnetohydrodynamic dynamo theory is able to provide better insight into the basic physical processes causing this variational nature of solar activity.

Dibyendu Nandi from IISER Kolkata along with his PhD students has been involved in developing numerical models to study the effects of plasma flows on the magnetic field deep within the solar convection zone. The adjacent figure (obtained from the developed dynamo model) depicts the plasma flow profile inside the solar convection zone.

Gravitational Waves:

Gravitational waves are one of the several predictions of Einstein’s General Theory of Relativity. Just as Maxwell’s theory of electromagnetism leads to the conclusion that light is a wave, Einstein’s theory tells us that spacetime itself can show the same behavior. These ‘ripples’ in spacetime can give us new insights in understanding phenomena in the universe where gravity is extremely strong, like the collapse of massive stars, rapidly spinning black holes, and mergers of binary black holes and pulsars. With the detection of gravitational waves by LIGO, we have in our hands a new way of exploring the mysteries of the universe.

At CESSI, Rajesh Kumble Nayak works mainly on gravitational wave data analysis, where he uses statistical techniques to extract and analyze the signals detected by instruments like LIGO.

Helioseismology:

Helioseismology is a tool to probe the solar interior using solar oscillations. These oscillations are due to seismic waves, generated by the turbulent convection of the solar interior. Information about the solar interior helps us to refine the existing theories of stellar structure and evolution developed using the global properties like radius, luminosity, mass, composition and age. It helps in studying the flows in the solar interior and hence gives better insight on solar magnetism.

In CESSI, our focus is on helioseismology of magnetic fields and large­scale flows in the solar interior. We mainly work on local helioseismology, which uses local propagation of waves to measure the properties of a relatively small area of the solar interior. We use techniques like time- distance seismology and ring diagram analysis for our work.

Instrumentation:

CESSI, being committed towards the development of a scientific workforce in all areas of Space Sciences, puts significant effort into developing state-of-the-art instruments for both space and ground borne observatories. One of our current projects in instrumentation involves the development of a payload, the SUIT ( Solar UltraViolet Imaging Telescope ) on­board the Aditya-­L1 mission. Aditya­L1 is India's first venture towords studying the Sun with a satellite. Besides being an engineering marvel, it also boasts of being the first mission aimed at studying the chromosphere. Aditya has seven payloads in total – the primary being a coronograph (VELC), an imaging telescope (SUIT), accompanied by a magnetometer, two X-­ray spectrometers (SoLEX and HEL1OS) and two particle detectors (ASPEX which includes the SWISS,STEPS­1 and PAPA). Aditya is scheduled for launch in 2019-­2020.

The SUIT payload is being developed under the leadership of Professor A N Ramaprakash (Instrument Principal Investigator and payload manager) and Professor Durgesh Tripathi (Principal Investigator) at IUCAA, Pune. Professor Dibyendu Nandi leads the science team of one of the science goals of the SUIT instrument. Current work on the instrument includes optical designing, component selection and performance modelling - on which CESSI personnel deployed at various national research centres are working. For more information on Aditya, visit - http://www.isro.gov.in/aditya-l1-first-indian-mission-to-study-sun

Space Weather:

The conditions of the immediate space surrounding Earth ( thermosphere, ionosphere, magnetosphere and the interplanetary space between Earth and Sun ) is modulated by the magnetic activity of the Sun. A space weather event is typically associated with the Sun ejecting huge amounts of magnetized plasma and energetic particles into space. Such events despite creating beautiful auroras, pose a threat to telecommunications systems, satellites and power grids among other undesirable effects.

We at CESSI direct our efforts towards both predicting and analysing the impact of space weather events through numerical simulations and multi-spacecraft observations. We use numerical models to study the large scale magnetic field of the Solar corona, the dynamics of which is thought to be the main driver of space weather events. Observations from numerous satellites are extensively used to constrain our theoretical models and conduct studies on the dependence of CME properties on their sources on the solar surface, the effect of CMEs on the thermosphere and ionosphere with the goal of assessing the pathways through which space weather effects are mediated.