Aditya-L1 observations reveal asymmetric expansion of solar eruptions, advancing space-weather research
Observations from Aditya-L1’s VELC instrument, combined with NASA data and 3D modelling, show that coronal mass ejections can expand unevenly, offering new insights into their movement and potential impact on
(Left) Composite image of the Sun’s corona combining data from India's Aditya-L1/VELC (outer part, 1.05–1.5 solar radii) and NASA’s SDO/AIA (inner disk). (Top right) Aditya-L1/VELC spectra recorded during the eruption, showing two distinct branches of emission — one shifted toward shorter wavelengths (plasma moving toward us) and one toward longer wavelengths (plasma moving away) — the spectral signature of a three-dimensional, asymmetric solar eruption. (Bottom right) Model spectra reproducing the observed pattern, confirming asymmetric lateral expansion of the CME in the inner corona
NEW DELHI: Observations from India’s Aditya-L1 solar observatory have revealed that coronal mass ejections (CMEs) can expand asymmetrically rather than as uniformly expanding bubbles, providing scientists with new insights into the dynamics of solar eruptions and their potential effects on space weather.
The findings, based on data from the spacecraft’s Visible Emission Line Coronagraph (VELC), could improve the understanding of how these eruptions travel towards Earth and influence satellites and communication networks.
Scientists from the Indian Institute of Astrophysics (IIA), an autonomous institution under the Department of Science and Technology, reconstructed the three-dimensional geometry and dynamics of a solar eruption by combining VELC observations with data from NASA’s Solar Dynamics Observatory (SDO) and three-dimensional modelling.
The study, published in The Astrophysical Journal Letters, examined a coronal mass ejection that occurred on August 5, 2024, originating from an active region near the western limb of the Sun.
The researchers found that the CME did not expand uniformly. Instead, its expansion varied across different directions, resulting in an asymmetric shape. Such differences in expansion could influence the speed at which a CME travels towards Earth and contribute to space-weather disturbances.
VELC, Aditya-L1’s primary payload, is an internally occulted coronagraph designed to observe the solar corona in multiple modes. It studies nascent CMEs through spectroscopy using the 530.3 nm green emission line produced by highly ionised iron atoms in the corona. The emission captures plasma at temperatures of around 1.8 million Kelvin.
Changes in the wavelength, known as Doppler shifts, help scientists determine the velocity of plasma moving towards or away from the observer along the line of sight.
In the August 2024 event, VELC detected an unusual pattern of blueward and redward shifts, indicating plasma moving in opposite directions relative to the observer. While images from SDO’s Atmospheric Imaging Assembly showed how the CME propagated across the sky, VELC provided information about its motion towards and away from the observer.
The team used these observations to develop a three-dimensional geometric-kinematic model to understand how the CME’s orientation and uneven lateral expansion could produce the observed spectral pattern. A model assuming symmetrical expansion could not reproduce the observations. A model incorporating an inclined CME axis and asymmetric sideways expansion produced results consistent with the observed spectral structures and their evolution over time.
The researchers plan to apply this technique to other CMEs. The approach could help reconstruct their motion without depending entirely on observations from multiple space-based viewpoints.
This capability is particularly relevant in the lower solar corona, where CMEs evolve rapidly and their movement along the line of sight cannot be determined through imaging alone.
Aditya-L1 was launched in September 2023 and is operational at the Sun–Earth L1 point, where it provides continuous observations of the Sun. The spacecraft carries seven scientific payloads. VELC was designed and fabricated by IIA at its MGK Menon Laboratory for Space Sciences at the CREST campus in Hosakote, with substantial support from ISRO.
“To understand the unusual spectral pattern observed by VELC, we then developed a 3-D geometric-kinematic model of an expanding CME,” said Jayant Joshi of IIA and a co-author.
“The asymmetric shape of an early CME can have important implications for how it interacts with the solar wind and experiences drag during its propagation through the heliosphere. Such effects can influence the CME’s speed and, ultimately, its arrival time at Earth,” he added.
