Probing the Turbulent Corona and Heliosphere Using Radio Spectral Imaging Observation during the Solar Conjunction of the Crab Nebula

Abstract Measuring plasma parameters in the upper solar corona and inner heliosphere is challenging because of the region’s weakly emissive nature and inaccessibility for most in situ observations. Radio imaging of broadened and distorted background astronomical radio sources during solar conjunction can provide unique constraints for the coronal material along the line of sight. In this study, we present radio spectral imaging observations of the Crab Nebula (Tau A) from 2024 June 9 to June 22 when it was near the Sun with a projected heliocentric distance of 5–27 solar radii, using the Owens Valley Radio Observatory’s Long Wavelength Array at multiple frequencies in the 30–80 MHz range. The imaging data reveal frequency-dependent broadening and distortion effects caused by anisotropic wave propagation through the turbulent solar corona at different distances. We analyze the brightness, size, and anisotropy of the broadened images. Our results provide detailed observations showing that the eccentricity of the unresolved source increases as the line of sight approaches the Sun, suggesting a higher anisotropic ratio of the plasma turbulence closer to the Sun. In addition, the major axis of the elongated source is consistently oriented in the direction perpendicular to the radial direction, suggesting that the turbulence-induced scattering effect is more pronounced in the direction transverse to the coronal magnetic field. Lastly, when the source undergoes large-scale refraction as the line of sight passes through a streamer, the apparent source exhibits substructures at lower frequencies. This study demonstrates that observations of celestial radio sources with lines of sight near the Sun provide a promising method for measuring turbulence parameters in the inner heliosphere.

Authors

Publication Details

Journal
The Astrophysical Journal
Published
2025-10-09
DOI
https://doi.org/10.3847/1538-4357/adff56
Citations
1
Primary Topic
Solar and Space Plasma Dynamics
Type
article
Field-Weighted Citation Impact
1.15
Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

Probing the Turbulent Corona and Heliosphere Using Radio Spectral Imaging Observation during the Solar Conjunction of the Crab Nebula

Grégory Hellbourg, Akshatha K. Vydula, Mark Hodges, Nikita Kosogorov et al.
1 citations
The Astrophysical Journal
Solar and Space Plasma Dynamics
1.15
article

Probing the Turbulent Corona and Heliosphere Using Radio Spectral Imaging Observation during the Solar Conjunction of the Crab Nebula

Grégory Hellbourg, Akshatha K. Vydula, Mark Hodges, Nikita Kosogorov, Charlie Harnach, J. Hickish, Morgan Catha, Xingyao Chen, Kathryn Plant, Jayce Dowell, James W. Lamb, Nivedita Mahesh, Surajit Mondal, Daniel Jacobs, D. P. Woody, Vinand Prayag, Matthew Kolopanis, Gregg Hallinan, G. B. Taylor, Yuping Huang, Larry R. D’Addario, Katherine Elder, Sijie Yu, Dale E. Gary, Peijin Zhang, Ruby Byrne, Mike Virgin, Rick Hobbs, Casey Law, Marin M. Anderson, Sherry Chhabra, Ivey Davis, S. Weinreb, Judd D. Bowman, A. Romero‐Wolf, Bin Chen, Jun Shi, Brian O’Donnell, Andrea Isella, Travis Powell, David Hodge, Ghislain Kemby, John T. Klinefelter, Andres Rizo, Jordan Trim
article en
1 citations

Abstract

Abstract Measuring plasma parameters in the upper solar corona and inner heliosphere is challenging because of the region’s weakly emissive nature and inaccessibility for most in situ observations. Radio imaging of broadened and distorted background astronomical radio sources during solar conjunction can provide unique constraints for the coronal material along the line of sight. In this study, we present radio spectral imaging observations of the Crab Nebula (Tau A) from 2024 June 9 to June 22 when it was near the Sun with a projected heliocentric distance of 5–27 solar radii, using the Owens Valley Radio Observatory’s Long Wavelength Array at multiple frequencies in the 30–80 MHz range. The imaging data reveal frequency-dependent broadening and distortion effects caused by anisotropic wave propagation through the turbulent solar corona at different distances. We analyze the brightness, size, and anisotropy of the broadened images. Our results provide detailed observations showing that the eccentricity of the unresolved source increases as the line of sight approaches the Sun, suggesting a higher anisotropic ratio of the plasma turbulence closer to the Sun. In addition, the major axis of the elongated source is consistently oriented in the direction perpendicular to the radial direction, suggesting that the turbulence-induced scattering effect is more pronounced in the direction transverse to the coronal magnetic field. Lastly, when the source undergoes large-scale refraction as the line of sight passes through a streamer, the apparent source exhibits substructures at lower frequencies. This study demonstrates that observations of celestial radio sources with lines of sight near the Sun provide a promising method for measuring turbulence parameters in the inner heliosphere.

The Astrophysical JournalVol. 992(1)
Openalex Percentile: Top 16%
Solar and Space Plasma Dynamics
1.15
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.