Multi-wavelength Observations of a Metric Type-II Event

Abstract

We have studied a complex metric radio event which originated in a compact flare, observed with the ARTEMIS-JLS radiospectro-graph on February 12, 2010. The event was associated with a surge observed at 195 and 304 Å and with a coronal mass ejection observed by instruments on-board STEREO A and B near the East and West limbs respectively. On the disk the event was observed at 10 frequencies by the Nancay Radioheliograph, in Ha by the Catania observatory, in soft x-rays by GOES SXI and Hinode XRT and in hard x-rays by RHESSI. We combined these data, together with MDI longitudinal magnetograms, to get as complete a picture of the event as possible. Our emphasis is on two type-II bursts that occurred near respective maxima in the GOES light curves. The first, associated with the main peak of the event, showed an impressive F-H structure, while the emission of the second consisted of three well-separated bands with superposed pulsations. Using positional information for the type-IIs from the NRH and triangulation from STEREO A and B, we found that the type IIs were associated neither with the surge nor with the disruption of a nearby streamer, but rather with an EUV wave probably initiated by the surge. The fundamental-harmonic structure of the first type II showed a band split corresponding to a magnetic field strength of 18G, a frequency ratio of 1.95 and a delay of 0.23-0.65s of the fundamental with respect to the harmonic; moreover it became stationary shortly after its start and then drifted again. The pulsations superposed on the second type II were broadband and had started before the burst. In addition, we detected another pulsating source, also before the second type II, polarized in the opposite sense; the pulsations in the two sources were out of phase and hence hardly detectable in the dynamic spectrum. The pulsations had a measurable reverse frequency drift of about 2/s.

Accepted for Publication in A&A, Article Number: aa41672-21

References in corpus (12)

• The formation heights of coronal shocks from 2D density and Alfvén speed maps
• Understanding the Physical Nature of Coronal "EIT Waves"
• The improved ARTEMIS IV multichannel solar radio spectrograph of the University of Athens
• Three-dimensional reconstruction of CME-driven shock-streamer interaction from radio and EUV observations: a different take on the diagnostics of coronal magnetic fields
• Understanding CME and associated shock in the solar corona by merging multi wavelengths observation
• First Observation of a Type II Solar Radio Burst Transitioning Between a Stationary and Drifting State
• Using radio triangulation to understand the origin of two subsequent type II radio bursts
• CME liftoff with high-frequency fragmented type II burst emission
• LOFAR observations of a jet-driven piston shock in the low solar corona
• The Relation Between Large-Scale Coronal Propagating Fronts and Type II Radio Bursts
• Parametric simulation studies on the wave propagation of solar radio emission: the source size, duration, and position
• Detection of spike-like structures near the front of type-II bursts

Cited by in corpus (4)

• Imaging-spectroscopy of a band-split type II solar radio burst with the Murchison Widefield Array
• Resolving spatial and temporal shock structures using LOFAR observations of type II radio bursts
• First detection of metric emission from a solar surge
• Modelling gyrosynchrotron emission from coronal energetic electrons in a CME flux rope