Scientists analysing observations from India’s Aditya-L1 solar observatory have discovered that a coronal mass ejection expanded asymmetrically, providing new insights into solar eruptions and their potential effects on space weather.
India’s first space-based solar observatory, Aditya-L1, has helped researchers uncover new details about the expansion of a coronal mass ejection (CME), a type of solar eruption. The findings could improve scientists’ understanding of space-weather disturbances that may affect satellites and communication networks.
Launched in September 2023, Aditya-L1 is operational at the Sun–Earth L1 point, where it continuously observes the Sun. The spacecraft carries seven scientific payloads, including the Visible Emission Line Coronagraph (VELC), its primary instrument, which is designed to observe the solar corona simultaneously in different modes.
Researchers from the Indian Institute of Astrophysics (IIA), an autonomous institution under the Department of Science and Technology (DST), combined VELC observations with data from NASA’s Solar Dynamics Observatory (SDO) and three-dimensional modelling to reconstruct the geometry and dynamics of a solar eruption.
Aditya-L1 and NASA Observations Reveal Uneven CME Expansion
The researchers examined a CME that occurred on August 5, 2024, originating from an active region near the Sun’s western limb.
“We observed the CME that occurred on 5 August 2024 using the VELC as well as data from the Atmospheric Imaging Assembly (AIA) onboard NASA’s Solar Dynamics Observatory (SDO)”, explained Saurabh Tripathi, a PhD student at IIA, and lead author of the study.
VELC’s spectroscopic observations detected an unusual Doppler pattern involving both blueward and redward shifts in the emission. These shifts indicate plasma moving towards and away from the observer, respectively.
“Our results show that the CME did not expand uniformly. The AIA images captured how the CME propagated across the sky, while VELC revealed the motion of the expanding CME bubble towards and away from us,” Tanmoy Samanta, a solar astronomer at IIA and the corresponding author of the study elaborated.
Together, the observations showed that the eruption developed an asymmetric shape because of its non-uniform expansion.
VELC Spectroscopy Helps Track Plasma Motion
VELC studies newly developing CMEs through spectroscopy using the 530.3-nanometre green emission line produced by highly ionised iron atoms in the solar corona.
This emission captures hot coronal plasma at temperatures of approximately 1.8 million Kelvin. Changes in the wavelength of the emission, known as Doppler shifts, provide information about plasma velocity along the line of sight and close to the solar disk.
The instrument was designed and fabricated by IIA at its MGK Menon Lab for Space Sciences on the CREST campus in Hosakote, with substantial support from the Indian Space Research Organisation (ISRO).
Three-Dimensional Model Confirms Asymmetric Solar Eruption
To investigate the unusual spectral observations, researchers developed a three-dimensional geometric-kinematic model of the expanding CME.
“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 researchers used the model to examine how the CME’s orientation and uneven sideways expansion could produce the observed spectral structures.
A model assuming symmetric expansion failed to reproduce the observations. However, a model incorporating an inclined CME axis and asymmetric lateral expansion generated a spectral pattern and temporal evolution similar to those recorded by VELC.
The team plans to apply this technique to other CMEs to reconstruct their motion without depending entirely on observations from multiple viewing positions in space.
This approach is particularly useful in the lower solar corona, where CMEs evolve rapidly and imaging alone cannot determine plasma motion along the line of sight.
Findings Could Improve Understanding of Space Weather
The discovery could have implications for understanding how solar eruptions travel through space and potentially affect Earth.
“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”, said Joshi.
By revealing the three-dimensional behaviour of CMEs during their early development, the study provides additional insights into the processes that influence solar eruptions and their propagation towards Earth.
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