A coronal wave and an asymmetric eruptive filament in SUMER, CDS, EIT, and TRACE co-observations^⋆

Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
e-mail: madj@arm.ac.uk

Received: 5 August 2014
Accepted: 31 October 2014

Abstract

Context. The investigation covers the complex subject of coronal waves and the phenomena contributing to and/or causing their formation.

Aims. The objectives of the present study is to provide a better physical understanding of the complex inter-relation and evolution of several solar coronal features comprising a double-peak flare, a coronal dimming caused by a coronal mass ejection (CME), a CME-driven compression, and a fast-mode wave. For the first time, the evolution of an asymmetric eruptive filament is analysed in simultaneous Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectroscopic and Transition Region and Coronal Explorer (TRACE) and Extreme-ultraviolet Imaging Telescope (EIT) imaging data.

Methods. We use imaging observations from EIT and TRACE in the 195 Å channel and spectroscopic observations from the Coronal Diagnostic Spectrometer (CDS) in a rastering and SUMER in a sit-and-stare observing mode. The SUMER spectra cover spectral lines with formation temperatures from log  T(K) ~ 4.0 to 6.1.

Results. Although the event was already analysed in two previous studies, our analysis brings a wealth of new information on the dynamics and physical properties of the observed phenomena. We found that the dynamic event is related to a complex flare with two distinct impulsive peaks, one according to the Geostationary Operational Environmental Satellite (GOES) classification as C1.1 and the second – C1.9. The first energy release triggers a fast-mode wave and a CME with a clear CME driven compression ahead of it. This activity is related to, or possibly caused, by an asymmetric filament eruption. The filament is observed to rise with its leading edge moving at a speed of ~300 kms^-1 detected both in the SUMER and CDS data. The rest of the filament body moves at only ~150 kms^-1 while untwisting. No signature is found of the fast-mode wave in the SUMER data, suggesting that the plasma disturbed by the wave had temperatures above 600 000 K. The erupting filament material is found to emit only in spectral lines at transition region temperatures. Earlier identification of a coronal response detected in the Mg x 609.79 Å line is found to be caused by a blend from the O iv 609.83 Å line.

Conclusions. We present a unique analysis of the complex phenomenon called “EIT/coronal wave”, confirming its bimodal nature. We suggest that the disintegration of the dimming/CME and the CME-driven compression are either caused by a CME-CME interaction taking place in the low solar atmosphere or by an impulsive CME cavity overexpansion in the low solar atmosphere.