It has now been well established that apart from eleven year solar cycle, the Sun also show variation over multiple cycles or even longer than that which is termed as long-term variability and believed to have a great impact on the climate of Earth. So, to understand the physics behind this long-term variation, the researchers at ARIES study different aspects of long-term variability and some of these are:

• Study of solar surface features

  Sunspots, plages, filaments, network-bright points are the solar surface features that act as the proxies for the magnetic field in the Sun. So, the long-term study of these features enables us to trace back the magnetic history of our life-giving star. To study these aspects, we use the data from different ground-based observatories such as Kodaikanal Solar Observatory (KoSO), Big Bear Solar Observatory (BBSO) etc. and space-based data from SOHO and SDO. Our researchers work in collaboration with different scientists around the globe to study these aspects and answered some of the unresolved problems.



• Solar Dynamo

  The solar dynamo is the mechanism which is responsible for all these 11 years cycle as well as long-term variation. In collaboration with other scientists in India and abroad, here in ARIES we also study some aspects of solar dynamo modelling as well as the numerical simulation. These studies have raised some basic questions about our understanding of fluids and plasma physics.

The branch of solar physics (heliophysics) to study the effect of the Sun on the interplanetary space focused on the near-Earth environment is termed as space weather. Just as the weather on Earth primarily includes the description of temperature, wind speed etc., space weather constitutes of parameters related to ambient solar wind describing the plasma density, speed, temperature, magnetic field etc. It has been established that Coronal Mass Ejections are major drivers of space weather phenomena. These events are of great importance from our viewpoints due to several impacts on our lives. Some of the noticeable effects of space weather are:

• The beautiful auroras observed near the polar regions.
• Power grid failures.
• Interruption of communication satellites.
• Effects on the astronauts on-board International Space Station.
• Radiation hazard to the flights travelling through polar regions.

Due to the severity of space weather, it is needed to understand their drivers. This would also help in forecasting the weather so that necessary steps could be taken at right time to reduce the damage and hence socio-economic losses.

• Flare Studies

  Solar flares apart from a sudden increase in intensity across the spectrum are also responsible for accelerating the charged particles into the interplanetary space and sometimes are also associated with CMEs. Dr Wahab Uddin leads this field of study in ARIES to monitor the flares regularly with the help of a 15 cm H-alpha telescope in high spatial and temporal resolutions. Such data combined with other ground and space-based observations have provided a significant understanding of the flares and related phenomena.

• Coronal Mass Ejections (CMEs) science

  CMEs are the primary drivers of space weather. Members of this group under Prof. Dipankar Banerjee have been actively involved in improving our understanding about the initiation, evolution and propagation of these large-scale solar transients with various manual and automated algorithms. One of the main aims is to understand the behaviour of CMEs through heliosphere which will contribute to enhance the prediction of space weather near Earth. The research in collaboration with scientists around the world involves analysis combining data from several space-based observatories like SOHO, STEREO, SDO, PROBA-2 etc and ground-based observatory like MLSO.

The solar atmosphere consists of the photosphere, chromosphere, transition region and corona. Even after several years of research plenty of mysteries still lie in these layers. Some of these unanswered questions such as coronal heating, the magnetic field of solar corona etc are being the area of research of this group. Moreover, several transient events including flares and CMEs along with waves and loop oscillations have their roots in these layers.

The future of solar physics in India context is as bright as the Sun on a sunny afternoon. ARIES is involved in two of the major science projects approved by the Government of India. These upcoming facilities will help us to improve our understanding of the Sun and its relation of the Earth.

• Aditya-L1

  Aditya-L1 with its suite of 7 payloads having a combination of remote sensing and in-situ instruments is India’s first dedicated mission to study the Sun. This mission is led by Indian Space Research Organisation (ISRO) with primary goals to understand the initiation and early kinematics of the CMEs, probe different layers of the solar atmosphere and answer one of the mysteries, why is the solar corona hotter than the surface of the Sun. Prof. Dipankar Banerjee is the Chair of the Science Working Group of Aditya-L1. This group is involved in the planning of the science cases towards the fulfilment of the Aditya-L1 goals.



• National Large Solar Telescope (NLST)

  National Large Solar Telescope (NLST) is an upcoming world-class facility which is a planned 2-meter class solar telescope to be installed near the Pangong lake at Merak site in Ladakh. With the high-resolution observations of the solar atmosphere, this facility aims in understanding the dynamo mechanism of the Sun, small- and large-scale transients’ origin, and the magnetic field in a higher atmosphere. This observatory will complement the Aditya-L1 mission proving the necessary group support.