Enigmatic Centi-SFU and mSFU Nonthermal Radio Transients Detected in the Middle Corona

Abstract Decades of solar coronal observations have provided substantial evidence for accelerated particles in the corona. In most cases, the location of particle acceleration can be roughly identified by combining high spatial and temporal resolution data from multiple instruments across a broad frequency range. In almost all cases, these nonthermal particles are associated with quiescent active regions, flares, and coronal mass ejections (CMEs). Only recently, some evidence of the existence of nonthermal electrons at locations outside these well-accepted regions has been found. Here, we report for the first time multiple cases of transient nonthermal emissions, in the heliocentric range of ∼3–7 R ⊙ , which do not have any obvious counterparts in other wave bands, like white-light and extreme ultraviolet. These detections were made possible by the regular availability of high dynamic-range low-frequency radio images from the Owens Valley Radio Observatory’s Long Wavelength Array. While earlier detections of nonthermal emissions at these high heliocentric distances often had comparable extensions in the plane of sky, they were primarily associated with radio CMEs, unlike the cases reported here. Thus, these results add on to the evidence that the middle corona is extremely dynamic and contains a population of nonthermal electrons, which is only becoming visible with high dynamic-range low-frequency radio images.

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Publication Details

Journal
The Astrophysical Journal
Published
2025-11-28
DOI
https://doi.org/10.3847/1538-4357/ae113b
Primary Topic
Solar and Space Plasma Dynamics
Type
article
Field-Weighted Citation Impact
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article

Enigmatic Centi-SFU and mSFU Nonthermal Radio Transients Detected in the Middle Corona

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

Enigmatic Centi-SFU and mSFU Nonthermal Radio Transients Detected in the Middle Corona

Grégory Hellbourg, Akshatha K. Vydula, Mark Hodges, Nikita Kosogorov, Charlie Harnach, J. Hickish, Morgan Catha, Xingyao Chen, Jayce Dowell, James W. Lamb, Nivedita Mahesh, Surajit Mondal, Daniel Jacobs, D. P. Woody, Matthew Kolopanis, Gregg Hallinan, Yuping Huang, Sijie Yu, Dale E. Gary, Peijin Zhang, Ruby Byrne, Mike Virgin, Rick Hobbs, Casey Law, Marin M. Anderson, Sherry Chhabra, Ivey Davis, Scott White, S. Weinreb, Judd D. Bowman, David O. Hodge, Bin Chen, Jun Shi, Andrea Isella, Ghislain Kemby, John T. Klinefelter, Jordan Trim, Larry D’Addario, Brian O’Donnell
article en

Abstract

Abstract Decades of solar coronal observations have provided substantial evidence for accelerated particles in the corona. In most cases, the location of particle acceleration can be roughly identified by combining high spatial and temporal resolution data from multiple instruments across a broad frequency range. In almost all cases, these nonthermal particles are associated with quiescent active regions, flares, and coronal mass ejections (CMEs). Only recently, some evidence of the existence of nonthermal electrons at locations outside these well-accepted regions has been found. Here, we report for the first time multiple cases of transient nonthermal emissions, in the heliocentric range of ∼3–7 R ⊙ , which do not have any obvious counterparts in other wave bands, like white-light and extreme ultraviolet. These detections were made possible by the regular availability of high dynamic-range low-frequency radio images from the Owens Valley Radio Observatory’s Long Wavelength Array. While earlier detections of nonthermal emissions at these high heliocentric distances often had comparable extensions in the plane of sky, they were primarily associated with radio CMEs, unlike the cases reported here. Thus, these results add on to the evidence that the middle corona is extremely dynamic and contains a population of nonthermal electrons, which is only becoming visible with high dynamic-range low-frequency radio images.

The Astrophysical JournalVol. 994(2)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Nuclear Safety and Security Commission, Nanjing Institute of Technology, Jet Propulsion Laboratory
Openalex Percentile: Top 79%
Solar and Space Plasma Dynamics
DOIOpen Access PDFOpenAlex
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