Enigmatic centi-SFU and mSFU nonthermal radio transients detected in the middle corona
Authors
Surajit Mondal
Bin Chen
Sijie Yu
Xingyao Chen
Peijin Zhang
Dale Gary
Marin M. Anderson
Judd D. Bowman
Ruby Byrne
Morgan Catha
Sherry Chhabra
Larry D Addario
Ivey Davis
Jayce Dowell
Gregg Hallinan
Charlie Harnach
Greg Hellbourg
Jack Hickish
Rick Hobbs
David Hodge
Mark Hodges
Yuping Huang
Andrea Isella
Daniel C. Jacobs
Ghislain Kemby
John T. Klinefelter
Matthew Kolopanis
Nikita Kosogorov
James Lamb
Casey Law
Nivedita Mahesh
Brian O Donnell
Corey Posner
Travis Powell
Vinand Prayag
Andres Rizo
Andrew Romero Wolf
Jun Shi
Greg Taylor
Jordan Trim
Mike Virgin
Akshatha Vydula
Sandy Weinreb
Scott White
David Woody
Thomas Zentmeyer
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 $\sim 3-7R_\odot$, which do not have any obvious counterparts in other wavebands, like white-light and extreme ultra-violet. 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 been 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.
