Aditya-L1 data show solar eruption expanding unevenly

IIA scientists combined spectra from Aditya-L1's VELC with NASA SDO images and a 3-D model to show that a coronal mass ejection of 5 August 2024 grew asymmetrically, not as a simple bubble - a finding relevant to predicting its arrival at Earth.

What happened

• Aditya-L1, India's first space-based solar observatory, helped scientists understand how a coronal mass ejection (CME) expands; the satellite, launched in September 2023, operates at the Sun-Earth L1 point with 7 payloads.
• The Visible Emission Line Coronagraph (VELC), the primary payload, studies nascent CMEs through spectroscopy in the 530.3 nm green line of highly ionised iron, tracing plasma at about 1.8 million kelvin.
• IIA scientists combined VELC with images from NASA's SDO/AIA and a 3-D model to study the CME of 5 August 2024; VELC showed both blueshifted and redshifted emission.
• A symmetric-expansion model could not reproduce the pattern; an inclined axis with asymmetric lateral expansion did, so the CME was not a simple spherical bubble.
• The study in Astrophysical Journal Letters says early CME shape affects drag and thus speed and arrival time at Earth; the team plans to apply the method to other CMEs.

For Prelims

• Coronal mass ejection: a large expulsion of plasma and magnetic field from the Sun's corona; when directed at Earth it can cause geomagnetic storms. It differs from a solar flare, a burst of radiation.
• Aditya-L1: ISRO's first solar mission, launched on PSLV-C57 on 2 September 2023 and placed in a halo orbit around L1 in January 2024, about 1.5 million km from Earth.
• Payloads: seven in all - VELC, SUIT, ASPEX, PAPA, SoLEXS, HEL1OS and a magnetometer; VELC is the primary payload and was built by IIA with ISRO support.
• Coronagraph: an instrument that blocks the Sun's bright disc, an artificial eclipse, so that the faint corona can be seen; 'internally occulted' means the blocking disc sits inside the instrument.
• Doppler shift: emission from plasma moving towards the observer is shifted to shorter (blue) wavelengths and from plasma moving away to longer (red) ones; this gives line-of-sight velocity that imaging alone cannot.
• Lagrange point L1: a gravitationally balanced point on the Sun-Earth line that gives an uninterrupted view of the Sun without eclipses by Earth.
• Space weather: CMEs and solar wind can damage satellites, disturb radio and navigation signals and stress power grids; the 1859 Carrington event is the classic extreme case.
• IIA and SDO: the Indian Institute of Astrophysics (Bengaluru) is an autonomous institute of DST; NASA's Solar Dynamics Observatory, launched in 2010, carries the Atmospheric Imaging Assembly.

For Mains

Syllabus: GS3.13 · GS3.11 · Linkage L1