Separating the effects of earthside and far side solar events. A case study.
Silja Pohjolainen Submitted: 2023-09-20 13:34
On 8 November 2013 a halo-type coronal mass ejection (CME) was observed,
together with flares and type II radio bursts, but the association
between the flares, radio bursts, and the CME was not clear.
Our aim is to identify the origin of the CME and its direction of
propagation, and to exclude features that were not connected to it.
On the Earth-facing side, a GOES C5.7 class flare occurred close to the
estimated CME launch time, followed by an X1.1 class flare.
The latter flare was associated with an EUV wave and metric type II
bursts. On the far side of the Sun, a filament eruption, EUV dimmings, and
ejected CME loops were observed by
imaging instruments onboard the Solar TErrestrial RElations Observatory
(STEREO) spacecraft that were viewing the backside of the Sun. The STEREO
radio instruments observed an interplanetary (IP) type II radio burst at
decameter-hectometric wavelengths, which was not observed by the radio
instrument onboard the Wind spacecraft located at L1 near Earth.
We show that the halo CME originated from the eruption on the far side
of the Sun, and that the IP type II burst was created by a shock wave
ahead of the halo CME. The radio burst remained unobserved from the
earthside, even at heliocentric source heights larger
than 9 solar radii. During the CME propagation, the X-class flare eruption
caused a small plasmoid ejection earthward, the material of which was
superposed on the earlier CME structures observed in projection.
The estimated heights of the metric type II burst match well with the
EUV wave launched by the X-class flare. As this radio emission did not
continue to lower frequencies, we conclude that the shock wave did not
propagate any further. Either the shock driver died out, as a blast
wave, or the driver speed no longer exceeded the local Alfvén speed.
Authors: Silja Pohjolainen, Nasrin Talebpour Sheshvan, Christian Monstein
Publication Status: Advances in Space Research, in press (Open Access)
Last Modified: 2023-09-25 15:13