arXiv subjects

V. Muthu Priyal

Publications and source records attributed to V. Muthu Priyal.

5 recordsLinked to original sources

arXiv2026

Coordinated Coronagraphic Observations from Proba-3 and Aditya-L1: Investigating CME Energetics in the Inner Corona

Constraining the plasma properties and energetics of coronal mass ejections (CMEs) in the inner corona is essential for understanding their early evolution, yet remains challenging because of limited observations. We investigate the mass and density evolution, and energy partitioning of two CMEs observed on 2025 September 14 and 16, and assess the potential of coordinated Proba-3/ASPIICS and Aditya-L1/VELC observations to constrain CME energetics in the low corona. We present the first coordinated observations of CMEs obtained simultaneously by Proba-3/ASPIICS and Aditya-L1/VELC. Using ASPIICS white-light observations, we estimate the CME mass, volume, number density, and the evolution of kinetic, thermal, and magnetic energies. Magnetic energies are estimated from observed CME properties using observationally constrained, physically motivated assumptions. Simultaneous VELC Fe XIV 5303 Angstorm observations provide independent estimates of the emission measure, electron number density, thermal energy, and CME lateral extent. The two events exhibit markedly different energy partitioning in the low corona. For the 14 September CME, the kinetic and magnetic energies are comparable, while the thermal energy remains nearly two orders of magnitude smaller, indicating limited plasma heating. In contrast, the 16 September CME exhibits a substantial thermal-energy enhancement, with thermal energy eventually becoming comparable to kinetic energy. For both CMEs, the estimated magnetic energy remains comparable to or exceeds the kinetic energy over the observed height. Our results demonstrate the scientific potential of synergetic ASPIICS and VELC observations for constraining CME mass, density, and energetics in the inner corona, providing new observational constraints on the early evolution of CMEs.

astro-ph.SR↗

arXiv2026

Aditya-L1/VELC observations of CME associated broadening of 5303Å coronal emission line

We present Aditya-L1/VELC spectroscopic observations of 5303Å coronal emission line widths before and after coronal mass ejections (CMEs) which showed coronal dimming. The sit \& stare mode of observations enabled us to study the changes in the line widths for the `limb' CMEs noticed on 16 July 2024 and 05 August 2024. The emission line widths during the pre-CME phase are higher than the thermal values in both the cases. After the onset of the CMEs, the widths increased further by ${\approx}15\%$ on 16 July 2024 and ${\approx}7\%$ on 05 August 2024. We find that the power spectral density (PSD) distributions of the line widths for the two events exhibits a power-law behavior. The PSD slopes, measured before and after the CMEs are nearly the same, and close to the Kolmogorov slope of ${-5/3}$. The results suggest that the observed larger than thermal width of the 5303Å emission line, before and after CMEs, is mostly due to turbulence. The additional increase in the line widths after the onset of the CMEs in both the cases are likely because of enhanced turbulence caused by the CME associated coronal dimmings and subsequent coronal magnetic field reconfiguration.

astro-ph.SR↗

arXiv2026

A consistency check for the calibration of 5303Å solar coronal emission line observations with Aditya-L1/VELC

We carried out radiometric calibration of the Visible Emission Line Coronagraph (VELC) onboard Aditya-L1 at 5303Å using observations of the Sun itself, a novel approach compared to the calibration using bright stars in the other currently operational space solar coronagraphs. The measured VELC detector count corresponding to the center of Sun's disk is ${\approx}(1.70{\pm}0.12){\times}10^{8}\, \rm sec^{-1}Å^{-1}$, which relates to Sun's flux at 1\,AU in 5303Å, ${\approx}3.0456{\times}10^{6}\, \rm {erg\,sec^{-1} cm^{-2} Å^{-1}}$. We verified the above calibration using observations of the bright star Sirius-A whose estimated flux at 1\,AU in 5303Å is ${\approx}1.44{\times}10^{-8}\,\mathrm{erg\,sec^{-1} cm^{-2} Å^{-1}}$. The expected detector count with VELC in this case is ${\approx}19{\pm}1.4\, \rm sec^{-1}Å^{-1}$, and the measured count is ${\approx}23{\pm}0.4\, \rm sec^{-1}Å^{-1}$. The reasonable agreement between the expected and observed values for Sirius-A in this initial consistency check after two years of observations with VELC, indicates that measurements of coronal brightness at 5303Å with the VELC and its conversion into absolute physical units using observations of the Sun disk light are in order. Using the Sirius-A observations we measured the point spread function (PSF) of the VELC in its 5303Å channel also. Its full width at half maximum (FWHM) is ${\approx}3.8^{\prime\prime}$.

astro-ph.SR↗

arXiv2025

Visible Emission Line Coronagraph (VELC) onboard ADITYA-L1

Aditya-L1, India's first dedicated mission to study the Sun and its atmosphere from the Sun-Earth Lagrangian L1 location was successfully launched on 2023 September 2. It carries seven payloads. The Visible Emission Line Coronagraph (VELC) is a major payload on Aditya-L1. VELC is designed to carry out imaging and spectroscopic observations (the latter in three emission lines of the corona), simultaneously. Images of the solar corona in the continuum at 5000 A, with a field of view (FoV) from 1.05 Ro to 3 Ro can be obtained at variable intervals depending on the data volume that can be downloaded. Spectroscopic observations of the solar corona in three emission lines, namely 5303 A Fexiv, 7892 A Fexi, and 10747 A Fexiii are possible simultaneously, with different exposure times and cadence. Four slits, each of width 50 um, separated by 3.75 mm help to simultaneously obtain spectra at four positions in the solar corona at all the aforementioned lines. A Linear Scan Mechanism (LSM) makes it possible to scan the solar corona up to +/-1.5 Ro. The instrument has the facility to carry out spectropolarimetric observations at 10747 A also in the FoV range 1.05 - 1.5 Ro. Various components of the instrument were tested interferometrically on the optical bench before installation. The individual components were aligned and performance of the payload was checked in the laboratory using a laser source and tungsten lamp. Wavelength calibration of the instrument was verified using Sun as a light source. All the detectors were calibrated for different parameters such as dark current and its variation with exposure time. Here, we discuss the various features of the VELC, alignment, calibration, performance, possible observations, initial data analysis and results of initial tests conducted in-orbit.

astro-ph.SR↗

arXiv2024

New Results on the Onset of a Coronal Mass Ejection from 5303 Å Emission Line Observations with VELC/ADITYA-L1

We report on the onset of a coronal mass ejection (CME) using spectroscopic observations in 5303 Å coronal emission line with the Visible Emission Line Coronagraph (VELC) onboard ADITYA-L1, the recently launched first Indian space solar mission. The CME was observed on 16 July 2024 in association with a X1.9 class soft X-ray flare from heliographic location S05W85. The VELC observations were near the west limb of Sun during the CME. The results obtained helped to constrain the onset time of the CME. In addition, they indicate ${\approx}$50% decrease in the coronal intensity near the source region of the CME due to mass depletion, ${\approx}$15% enhancement in the emission line width, and redshifted Doppler velocity of about ${\approx}10$ km/s. The non-thermal velocity associated with the line broadening is ${\approx}24.87$ km/s.

astro-ph.SR↗