Head of the division: Prof. Dibyendu Chakrabarty 

Deputy Head-1: Prof. Lokesh Kumar Sahu [Budget and Technical]

Deputy Head-2: Prof. Som Kumar Sharma [Academic and Admin.]

Overview

The research activities in the Space and Atmospheric Sciences (SPASC) division are aimed at understanding the radiative, chemical, ionization, and dynamical processes in the Earth's atmosphere and near-Earth space environment by employing state-of-the-art and in-house built rocket-, balloon, and ground-based experiments, optical and radio probing techniques, laboratory experiments along with theoretical simulation, numerical modelling, artificial intelligence/machine learning tools.

The current research foci of the SPASC division include the studies of Sun-Earth interactions, space weather, coupling, energetics and dynamics of atmospheric regions, investigations of solar disturbances/geomagnetic storms, global-scale atmospheric circulation, characterization of aerosols and their impact on Earth’s radiation budget, chemistry and dynamics of trace gases and volatile organic compounds, cloud and boundary layer dynamics, and global warming/ climate change. 

Opportunities also exist for use of data from the experiments of ongoing Indian space missions like Aditya-L1, and upcoming dual-aeronomy satellite mission DISHA (Disturbed and quiet time Ionosphere-thermosphere System at High Altitudes), and missions to Venus/Mars.

Under the broader area of space physics, the SPASC division is involved in the investigations of solar terrestrial interactions, solar effects on the interplanetary medium, earth’s magnetosphere-ionosphere-thermosphere interactions, space weather and its effects on societal applications, mesosphere-lower thermosphere dynamics, building of ground- and space-based optical and radio instruments. The Division plays an important role in the Indian space science programs, namely, Aditya-L1 mission, the upcoming dual satellite Aeronomy mission, DISHA, as well as missions to Venus/Mars, wherein PRL is the Science lead of ISRO’s DISHA mission.

SPASC faculty members are playing lead roles in major international programs such as the PRESTO (Predictability of the Variable Solar-Terrestrial Coupling) of the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP).

1. Investigations using indigenous space-borne measurements

Solar wind and heliospheric studies: Opportunities exist to investigate solar and heliospheric processes using the multi-directional, alpha-proton separated measurements from the Aditya Solar wind Particle EXperiment (ASPEX) on-board Aditya-L1 mission. 

Energetic particles in the solar wind: Multi-directional measurements of energetic ions in the solar wind by ASPEX can be used to understand the source population and energization mechanisms of suprathermal and Solar Energetic Particles (SEPs). 

ASPEX measurements are unique and have the potential to make significant impact in the respective fields. For more information about ASPEX, please visit https://www.prl.res.in/ASPEX/

Ionosphere-thermosphere system and Space weather: To investigate the near-Earth space environment, PRL is playing the lead role. Future Aeronomy mission like DISHA is being planned and the background science issues are being addressed to prepare the background for this mission. High frequency Langmuir Probe, Ion Drift Meter and Airglow Photometer payloads are being designed and fabricated at PRL for the DISHA mission.

2. Magnetosphere-Ionosphere-Thermosphere (MIT) Coupling: The energy and momentum transfer from the solar wind and magnetosphere to the Ionosphere-Thermosphere (IT) system changes the electric field, ion drifts, electron density, neutral density, neutral wind, etc. For a comprehensive assessment of the impact of space weather at the IT heights, various space and ground-based experiments are used to understand the plasma and neutral processes and their interactions.

3. Ionospheric electrodynamics: The low latitude ionosphere exhibit high degree of spatio-temporal variability. Intense gradients in the plasma density distribution and irregular structures generated by several electrodynamic and plasma processes degrade the performance of navigation systems (GNSS, GPS, IRNSS/NaVIC etc.). Digisonde and optical experiments are used to understand these processes. 

4. Vertical coupling in the atmosphere:  In addition to the solar forcing, IT system is also affected by forcing from the lower atmosphere through gravity waves, tides, planetary waves etc. This is investigated by using unique, state-of-the-art daytime optical airglow emissions at different wavelengths, radio measurements at different latitudes, magnetic and neutral wind measurements.

5. Topside ionospheric dynamics: The topside part of the ionosphere is the major contributor to the ionospheric Total Electron Content (TEC), which is a crucial parameter for estimating range delays experienced by the trans-ionospheric radio waves. Sparse observations due to the limitations of exploring this region pose several ambiguities in models. Employing the modelling and assimilation techniques to explore the topside ionospheric dynamics is essential for ionospheric characterization with improved accuracies.

6. Optical instrumentation for ground-based investigations: For upper atmospheric and space weather research, PRL has been leading in the country in building, in-house, several state-of-the-art ground-based optical instruments. These include high spectral resolution and large field of view multi-wavelength spectrographs for daytime airglow emission measurements in the visible, ultraviolet and infra-red spectral regions, narrow bandwidth and narrow field-of-view photometers, multi-wavelength photometers, wide-field optical imagers etc. Those with a flare of instrumentation can get involved in building such instruments and obtain exciting science results.

 7. Space weather forecasting using AI/ML techniques: Machine learning approach can be applied to ASPEX data to develop a space weather flag that can capture the geo-effectiveness of the solar disturbances in generating geomagnetic storms and magnetospheric substorms.

Projects funded by ISRO/DOS or other agencies

• Aditya Solar wind Particle EXperiment (ASPEX) on board Aditya-L1 mission (funded by ISRO, Ongoing)
• Characterization of bottom side ionosphere for improving accuracies of electron content estimation (funded by SERB under SRG scheme, Ongoing)
• Sensor payload development for VENUS Mission (funded by ISRO, Completed)

 Instrument facilities

• All-sky Imager (ASI)
• CCD-based Daytime Airglow Photometer (CDAP)
• CCD-based Multiwavelength Airglow Photometer (CMAP)
• CCD-based Photometer for Mesospheric Temperature (CPMT)
• Digisonde Portable Sounder (DPS-4D) 
• Fabry-Perot Interferometer (FPI) *
• GPS/GNSS/IRNSS Receivers
• High Throughput Imaging Echelle Spectrograph (HiTIES)
• Mesosphere-Thermosphere Airglow Photometer (MTAP)
• Multiwavelength Imaging Spectrograph using Echelle grating (MISE)
• Narrow-band Narrow-field of view photometer (NBNFPM)
• Near Infrared Imaging Spectrograph (NIRIS)
• PRL-Airglow Infra-red Spectrometer (PAIRS)
• Short-wave Infra-Red Imager (SIRI) *                                                                                                                  *Under development

Atmospheric Sciences

The research in this area pertains to studies of physicochemical and radiative processes in the lower atmosphere, tropospheric-stratospheric interactions, and middle-atmospheric dynamics. High quality and outstanding research with focus on characterisation of atmospheric aerosols, their spatial and temporal variations, their linkages with physical, chemical and dynamical process and their impact on environment, radiation budget, radiative forcing and climate are conducted through state-of-the-art  observations and modelling. Comprehensive measurements and modelling of ozone, volatile organic compounds (VOCs) and other trace gases, cloud characteristics and boundary layer dynamics are being conducted. SPASC faculty lead the ISRO's Atmospheric Trace Gases-Chemistry, Transport, and Modelling (AT-CTM), and serve as Principal Investigator in the National Carbonaceous Aerosols Programme (NCAP) Carbonaceous Aerosol Emissions, Source apportionment and Climate impacts (COALESCE) under the Ministry of Environment, Forests, and Climate Change, and provide the technical support to the National Clean Air Program.

Current research topics

1. Atmospheric Aerosols: Characteristics, and Radiative Impact through observations and modeling: The objectives are to characterize the different aerosol types in the atmosphere, document their spatial, temporal and altitudinal variations, understand and examine their linkages with physical, chemical and dynamical processes, and investigate their impact on environment, radiation budget, radiative forcing and climate through high quality, state-of-the-art observations, and modelling.

2. Atmospheric Clouds and Boundary Layer:  PRL has initiated Lidar network programme over the Indian region for the investigations of the cloud cover, vertical and layered structures of clouds, and Atmospheric Boundary Layer (ABL) which is the lowest layer in the troposphere and is highly variable temporally, regionally and seasonally and also works as packing volume of the atmospheric pollutants. The studies would be invaluable in the context of Earth's radiation budget as well as the hydrological cycle. 

3. Emissions and Photochemistry governing tropospheric ozone: The emissions and atmospheric processes influencing the ambient concentrations of various trace gases, such as CO, NOx, methane, VOCs, etc. are investigated in different environments (urban, suburban, coastal, remote forest, oceanic, etc.) of India employing well-resolved in-situ measurements. The main objective is to understand the relative contributions of anthropogenic, biogenic, and biomass-burning sources to abundance of trace gases, and to assess atmospheric reactivity and ozone formation potential of VOCs.

4. Air-Sea Exchange of Trace Gases: The transport and air-sea exchange of VOCs over the northern Indian Ocean is being investigated. The spatial and temporal variations of VOCs in the marine air is analyzed comprehensively in the context of the changes in key meteorological and sea surface physical parameters. The contributions of continental transport and oceanic emissions and their role in atmospheric chemistry over the Arabian Sea and Bay of Bengal is being studied. A recent focus has been to study the air-sea exchange of reduced sulfur compounds (e.g., DMS) along with VOCs and their photo-oxidation in the marine air masses of the northern Indian Ocean.

5. Atmospheric modelling and AI/ML: The main objective of atmospheric model simulations is to understand the roles of key physical, chemical, and dynamical processes governing the distributions and impacts of trace gases, VOCs, and aerosols over the Indian Subcontinent. Simulations include the radiative transfer, photochemical box, and regional chemistry-transport models. As a new initiative, long-term systematic observation and model simulation data are being used to train the AI/ML algorithms for accurate and computationally inexpensive simulations. Most of the model works are being performed using the PARAM Vikram 1000 HPC facility of PRL.

6. Middle atmospheric wave dynamics: Investigations are being carried out to understand critical dynamical processes, e.g., wave-wave interaction, wave-mean flow interaction, wave driven changes in the ambient atmosphere, impact of the waves on the large-scale atmospheric disturbances etc. with the help of ground-based radar, lidar, airglow and satellite-based observations.

Projects funded by ISRO/DOS or other agencies

• Atmospheric Trace Gases- Chemistry, Transport and Modelling (AT-CTM) (funded under ISRO GBP, Ongoing)
• Aerosol Radiative Forcing over India (ARFI) (funded under ISRO GBP, Ongoing)
• Investigations of the Water vapour, Clouds, Boundary Layer, and related parameters using Lidar and Ceilometer over India (funded under ISRO-GBP, ongoing)
• Network of Volatile Organic Compounds (VOCs) Measurements in India: Biosphere-Atmosphere Exchange (funded under ISRO-GBP, ongoing)

Instrument facilities