भारतीय खगोलभौतिकी संस्थान
Indian Institute of Astrophysics
Exploring the Universe since 1786
An Autonomous Institute under the
Department of Science & Technology
Government of India
Research Highlights
RESEARCH HIGHLIGHTS | IIA
Study of evolution and geo-effectiveness of coronal mass ejection–coronal mass ejection interactions using magnetohydrodynamic simulations with SWASTi framework
WAGEESH MISHRA | Nov 20, 2024
The geo-effectiveness of coronal mass ejections (CMEs) is a critical area of study in space weather, particularly in the lesser-explored domain of CME–CME interactions and their geomagnetic consequences. This study leverages the Space Weather Adaptive SimulaTion framework to perform 3D MHD simulation of a range of CME–CME interaction scenarios within realistic solar wind conditions. The focus is on the dynamics of the initial magnetic flux, speed, density, and tilt of CMEs, and their individual and combined impacts on the disturbance storm time (Dst) index. Additionally, the kinematic, magnetic, and structural impacts on the leading CME, as well as the mixing of both CMEs, are analyzed. Time-series in situ studies are conducted through virtual spacecraft positioned along three different longitudes at 1 au. Our findings reveal that CME–CME interactions are nonuniform along different longitudes, due to the inhomogeneous ambient solar wind conditions. A significant increase in the momentum and kinetic energy of the leading CME is observed due to collisions with the trailing CME, along with the formation of reverse shocks in cases of strong interaction. These reverse shocks lead to complex wave patterns inside CME2, which can prolong the storm recovery phase. Furthermore, we observe that the minimum Dst value decreases with an increase in the initial density, tilt, and speed of the trailing CME.
RESEARCH HIGHLIGHTS | IIA
Calibration of spectropolarimetry channel of visible emission line coronagraph onboard Aditya-L1
SASIKUMAR RAJA, K | Oct 01, 2024
The magnetic field strength and its topology play an important role in understanding the formation, evolution, and dynamics of the solar corona. Also, it plays a significant role in addressing long-standing mysteries such as coronal heating problem, origin and propagation of coronal mass ejections, drivers of space weather, origin and acceleration of solar wind, and so on. Despite having photospheric magnetograms for decades, we do not have reliable observations of coronal magnetic field strengths today. To measure the coronal magnetic field precisely, the spectropolarimetry channel of the Visible Emission Line Coronagraph (VELC) on board the Aditya-L1 mission is designed. Using the observations of coronal emission line Fe XIII [10747Å ], it is possible to generate full Stokes maps (I, Q, U, and V) that help in estimating the Line-of-Sight (LOS) magnetic field strength and to derive the magnetic field topology maps of solar corona in the Field of View (FOV) (1.05 – 1.5 R⊙). In this article, we summarize the instrumental details of the spectropolarimetry channel and detailed calibration procedures adopted to derive the modulation and demodulation matrices. Furthermore, we have applied the derived demodulation matrices to the observed data in the laboratory and studied their performance.
RESEARCH HIGHLIGHTS | IIA
First measurements of the airglow emissions from Kolhapur using an in-house developed Fabry–Perot interferometer
SRIRAM, S | Jun 01, 2024
First-time airglow observations of the nighttime thermospheric wind from an in-house developed ground-based Fabry–Perot Interferometer are recorded from the Kolhapur location of India. This was the first attempt to build such an instrument, and thus the quality of the data recorded in the field is satisfactory. The instrument has been thoroughly calibrated in the laboratory, and the accuracy of the important parameter finesse of the etalon is found to be ≈94% in agreement with the value supplied by the manufacturer. The airglow observations from the field indicate that the vertical wind observed looking toward Zenith over the course of the night is zero, ensuring a 100% accuracy. However, the temperature measurements were found to be approximately 30% in agreement with the measurements repoted in literature. To improve this measurement, improvements in the optical design need to be made. The paper concludes with conclusions and a brief idea of the proposed improvisations in the design.
Press Releases
PRESS RELEASES | SCOPE
Iron lines in the X-ray detected from a binary black hole system that can help infer their properties
SCOPE | Jan 10, 2025
A study led by astronomers at the Indian Institute of Astrophysics has detected the Fe K spectral lines of ionized Iron atoms from the well-known binary Active Galactic Nucleus system 4C+37.11 using data from the Chandra Space Telescope. This is the first such detection from a binary black hole system, and they were able to conclude that this emission arises from both the accretion disk and the collisionally ionized plasma surrounding the pair of supermassive black holes in this object.
This is based on the recently published paper titled "Detection of the Fe K lines from the binary AGN in 4C+37.11", by Mondal et al, 2024, Astronomy & Astrophysics, 279, 7.
Press release by PIB published here.
Press release issued by DST here.
Download the paper from here.
PRESS RELEASES | SCOPE
International solar conference celebrates 125 years of solar physics research in India
SCOPE | Jan 24, 2025
More than 200 solar physicists from India and abroad have come together in Bengaluru this week for an international conference on “Sun, Space Weather, and Solar-Stellar Connections”. The conference is being organised by the Indian Institute of Astrophysics to commemorate the 125th anniversary of the Kodaikanal Solar Observatory and the birth of solar astrophysics in the country (conference webpage)
Download the PIB press release from here.
PRESS RELEASES | SCOPE
Thermal structure of solar coronal holes and their magnetic fields unveiled
SCOPE | Feb 18, 2025
A new study has accurately estimated the physical parameters of thermal and magnetic field structures of solar coronal holes which have significant influence on space weather. They found that there is no latitudinal variation of temperature structure of coronal holes, suggesting that coronal holes are likely to originate from the deep interior, and also that there is a latitudinal variation of strength of magnetic field structure of coronal holes that increases from the solar equator to the pole suggesting that coronal holes might have formed from the superposition of Alfven wave perturbations.
This is based on the paper titled "Thermal and magnetic field structure of near-equatorial coronal holes", by Hegde, M. and K.M. Hiremath, 688, A35, 2024, Astronomy & Astrophysics, 279, 7.
Press release by PIB published here.
Press release issued by DST here.
Download the paper from here.
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IIA offers a vigorous programme of graduate studies that forms a vital component of research & training. The programme is overseen by the board of graduate studies. The Institute is also a major partner in the Joint Astronomy Programme (JAP), organized by the Indian Institute of Science.
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PhD applications may be submitted through the IIA PhD online applications portal in May. After the initial screening, shortlisted candidates will be interviewed in June. The final list of selected candidates will be announced in July, followed by the commencement of the programme in August. .
Research Fields
Solar Studies
Studies of the Sun and solar system have been the longest pursued discipline at IIA. Members of the group conduct theoretical, numerical modeling, and observational studies in solar physics.
Stars & Galaxies
Research interests of the group members range from exoplanets, star formation, stellar evolution, end states of stars, Interstellar medium, the milky way Galaxy, nearby galaxies, active galaxies and time domain astronomy.
Theory
Members of the theoretical Astrophysics group work on a broad range of topics such as black hole astrophysics, pulsars, exoplanets, astrophysical turbulence & magnetic fields, MHD, cosmology and early universe.
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