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
CMEs evolve in the interplanetary medium to double their predicted geo-effectiveness
WAGEESH MISHRA | Jun 01, 2024
Context. We explore the impact of interactions between coronal mass ejections (CMEs) – known as CME–CME interactions – on Earth using remote-sensing and in situ observations and estimate the amplification of the geo-effectiveness of the individual CMEs by a factor of ∼2 due to CME–CME interactions.
Aims. We present 3D reconstructions of interacting CMEs, which provide essential information on the orientation and interaction of the events. Additionally, we analysed coronal evolution of CMEs and their in situ characteristics at 1 AU to explore the impact of interactions between CMEs on their geo-effectiveness.
Methods. We analysed CME interaction using white light data from LASCO and STEREO COR-A. The reported CMEs were reconstructed using the gradual cylindrical shell (GCS) model and simulated self-consistently with the physics-based 3D MHD model EUHFORIA (EUropean Heliosphere FORecasting Information Asset). By running different simulations, we estimated the geo-effectiveness of both individual and interacting CMEs using an empirical relationship method for the disturbance storm index.
Results. The SOHO/LASCO spacecraft observed three CMEs erupting from the Sun within an interval of 10 h during a very active period in early November 2021. There were two partial halo CMEs that occurred on 1 Nov. 2021 at 19:00 UT and 22:00 UT, respectively, from the active region 12887 (S28W58), and a third halo CME occurred from AR 12891 (N17E03) on 2 Nov. 2021 at 02:48 UT. By combining remote observations close to the Sun, in situ data at 1 AU, and further numerical analyses of each individual CME, we are able to identify the initial and interplanetary evolution of the CMEs.
Conclusions. (i) White light observations and a 3D reconstruction of the CMEs show cannibalism by CME-2 on CME-1 and a flank interaction of CME-3 with the merged CME-1 and CME-2 at 45–50 Rs. (ii) Interacting CMEs exhibit an increase in geo-effectiveness compared to an individual CME.
RESEARCH HIGHLIGHTS | IIA
Low-frequency solar radio type II bursts and their association with space weather events during the ascending phase of solar cycle 25
SASIKUMAR RAJA, K | Jul 01, 2024
Type II solar radio bursts are signatures of the coronal shocks and, therefore, particle acceleration events in the solar atmosphere and interplanetary space. Type II bursts can serve as a proxy to provide early warnings of incoming solar storm disturbances, such as geomagnetic storms and radiation storms, which may further lead to ionospheric effects. In this article, we report the first observation of 32 type II bursts by measuring various plasma parameters that occurred between May 2021 and December 2022 in solar cycle 25. We further evaluated their accompanying space weather events in terms of ionospheric total electron content (TEC) enhancement using the rate of TEC index (ROTI). In this study, we find that at heliocentric distance ∼1–2 R⊙, the shock and the Alfvén speeds are in the range 504–1282 and 368–826 km‑1, respectively. The Alfvén Mach number is of the order of 1.2≤MA≤1.8 at the above-mentioned heliocentric distance. In addition, the measured magnetic field strength is consistent with the earlier reports and follows a single power law B(r)=6.07r-3.96G. Based on the current analysis, it is found that 19 out of 32 type II bursts are associated with immediate space weather events in terms of radio blackouts and polar cap absorption events, making them strong indications of space weather disruption. The ROTI enhancements, which indicate ionospheric irregularities, strongly correlate with GOES X-ray flares, which are associated with the type II radio bursts recorded. The diurnal variability in ROTI is proportional to the strength of the associated flare class, and the corresponding longitudinal variation is attributed to the difference in longitude. This article demonstrates that since type II bursts are connected to space weather hazards, understanding various physical parameters of type II bursts helps to predict and forecast the space weather.
RESEARCH HIGHLIGHTS | IIA
Exploring the Archives: A Search for Novae in UVIT Snapshots of M31
JUDHAJEET BASU | Aug 10, 2024
Extensive multiwavelength studies of novae have been carried out in our galaxy and in M31 for decades. However, UV studies of extragalactic novae are limited, especially those in quiescence. For the first time, we present a UV catalog of novae in M31 using the archival AstroSat Ultraviolet Imaging Telescope (UVIT) imaging data. We used two image subtraction techniques to retrieve objects located deep into the M31 central region. We have found 42 novae in total in the UVIT images, 15 of which have been detected in multiple filters in the far-ultraviolet (FUV) and near-ultraviolet. The novae detected at quiescence show signatures of accretion disk from their UV spectral energy distributions, whereas those in the outburst phase show signatures of a pseudo-photosphere. A few novae were also detected in multiple epochs. Some show a near-constant FUV magnitude at quiescence, while others caught near the outburst reveal pre-eruption dips in their light curves. We conclude with a discussion on the significance of UV surveys in illuminating theoretical predictions for novae systems, including detecting the elusive early UV flash.
Press Releases
PRESS RELEASES | SCOPE
Astronomers unveil observational evidence of how cosmic dust grains line up with the Galaxy’s magnetic field
SCOPE | Sep 03, 2025
Scientists have long believed that just like dust particles dancing in a ray of light, tiny cosmic particles floating between stars in the Milky Way act as storytellers of the universe. Now a team of astronomers, has just uncovered the strongest observational evidence yet of how these interstellar dust grains align themselves with magnetic fields in our Galaxy.
This is based on the paper titled "B-fields and Dust in Interstellar Filaments Using Dust Polarization (BALLAD-POL). III. Grain Alignment and Disruption Mechanisms in G34.43+0.24 Using Polarization Observations from JCMT/POL-2", by Saikhom Pravash, Archana Soam, Pham Ngoc Diep, Thiem Hoang, Nguyen Bich Ngoc, and Le Ngoc Tram, The Astrophysical Journal, 2025, 981, 128.
Press release by DST published here.
Press release by PIB published here.
Download the paper here.
PRESS RELEASES | SCOPE
Hanle Dark Sky Reserve star party brings together astronomy enthusiasts for the third year
SCOPE | Sep 26, 2025
Astronomy enthusiasts from across the country participated in amateur astronomy and astrophotography related activities at the third edition of the HDSR Star Party that was jointly organised by the Indian Institute of Astrophysics (IIA), Department of Wildlife Protection of UT Ladakh, and Bhabha Atomic Research Centre (BARC) between 18 and 23 September.
The PIB press release is here.
The DST press release is here.
PRESS RELEASES | SCOPE
Black holes and cosmic jets join forces to shape galaxies
SCOPE | Oct 21, 2025
Black hole activities suppress the birth of new stars around it, shows a new study that can help in a deeper understanding of how galaxies evolve and may provide answers to why some have very low star-formation rates.
This study was published in the Astrophysical Journal, titled “Warm Ionized Gas Outflows in Active Galactic Nuclei: What Causes Them?”, and is authored by Payel Nandi and C.S. Stalin from IIA and D.J. Saikia from IUCAA.
The PIB press release is here.
The DST press release is here.
The paper can be downloaded 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. .
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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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