Radio evidence for a shock wave reflected by a coronal hole
Journal
Date Issued
2021
Author(s)
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Taricco, Carla
Abstract
We report the first unambiguous observational evidence in the radio range of
the reflection of a coronal shock wave at the boundary of a coronal hole. The
event occurred above an active region located at the northwest limb of the Sun
and was characterized by an eruptive prominence and an extreme-ultraviolet
(EUV) wave steepening into a shock. The EUV observations acquired by the
Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics
Observatory(SDO) and the Extreme Ultraviolet Imager (EUVI) instrument on board
the Solar TErrestrial RElations Observatory(STEREO-A) were used to track the
development of the EUV front in the inner corona. Metric type II radio
emission, a distinguishing feature of shock waves propagating in the inner
corona, was simultaneously recorded by ground-based radio spectrometers. The
radio dynamic spectra displayed an unusual reversal of the type II emission
lanes, together with type III-like herringbone emission, indicating
shock-accelerated electron beams. Combined analysis of imaging data from the
two space-based EUV instruments and the Nancay Radioheliograph (NRH) evidences
that the reverse-drifting typeiiemission was produced at the intersection of
the shock front, reflected at a coronal hole boundary, with an intervening
low-Alfv\'en-speed region characterized by an open field configuration. We also
provide an outstanding data-driven reconstruction of the spatiotemporal
evolution in the inner corona of the shock-accelerated electron beams produced
by the reflected shock.
Volume
651
Start page
L14
Issn Identifier
0004-6361
Rights
open.access
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