We present a multiwavelength study of the large-scale coronal disturbances associated with the CME -flare event recorded on 24 December 1996. The kinematics of the shock wave signature, the type II radio burst, is analyzed and compared with the flare evolution and the CME kinematics. We employ radio dynamic spectra, position of the Nançay Radioheliograph sources, and LASCO-C1 observations, providing detailed study of this limb event. The obtained velocity of the shock wave is significantly higher than the contemporaneous CME velocity (1000 and 235 km s −1 , respectively). Moreover, since the main acceleration phase of the CME took place 10 -20 min after the shock wave was launched, we Radio Physics and the Flare-CME Relationship Guest Editors: Karl-Ludwig Klein and Silja Pohjolainen J. Magdalenić is now also at SIDC, Royal Observatory

Context. In the solar corona, shocks are formed when the speed of a disturbance exceeds the local magnetosonic speed. In the active region corona the Alfvén speed can drop to a few hundred km s −1 , but globally it is much higher. There has been a long debate on whether the shocks responsible for type II bursts are created by bow shocks in front of coronal mass ejections (CMEs), shocks in the flanks of CMEs, or by flare (blast) waves. Aims. We study the alternative explanations for type II bursts in events where we have a slow CME, flare(s), and associated type II burst emission. Methods. We use multi-wavelength observations to analyse the height-time evolution of CMEs and compare it with the evolution of shock signatures in radio and EUV. Results. Three flare-associated halo-type CME events were observed on October 30, 2004. Velocity estimates (260, 325, and 920 km s −1 ) from the first plane-of-the-sky CME leading front observations suggested that the first two were very slow compared to halo CMEs, on average. The CMEs were associated with flares (M 4.2, X1.2, and M 5.9) and each event was also associated with coronal (metric) type II emission that is known to be a signature of a propagating shock front. After the flare starts, loop displacements and large-scale dimmings were observed in EUV. The two slow halo CMEs started as filament eruptions, but the CME velocities and/or bulk motions were affected at the times of flares. We find support for the idea that the cause of metric type II bursts in these two events is flare-related. The later CME velocity changes (acceleration around 4-5 solar radii) could also be explained by eruptions associated with later flares. The repeating homologous flare-halo CME events indicate a restoration of the same large-scale structures within 5-6 h.

A high-speed halo-type coronal mass ejection (CME), associated with a GOES M4.6 soft X-ray flare in NOAA AR 0180 at S12W29 and an EIT wave and dimming, occurred on 9 November 2002. A complex radio event was observed during the same period. It included narrow-band fluctuations and frequency-drifting features in the metric wavelength range, type III burst groups at metric-hectometric wavelengths, and an interplanetary type II radio burst, which was visible in the dynamic radio spectrum below 14 MHz. To study the association of the recorded solar energetic particle (SEP) populations with the propagating CME and flaring, we perform a multi-wavelength analysis using radio spectral and imaging observations combined with white-light, EUV, hard X-ray, and magnetogram data. Velocity dispersion analysis of the particle distributions (SOHO and Wind in situ observations) provides estimates for the release times of electrons and protons. Our analysis indicates that proton acceleration was delayed compared to the electrons. The dynamics of the interplanetary type II burst identify the burst source as a bow shock created by the fast CME. The type III burst groups, with start times close to the estimated electron release times, trace electron beams travelling along open field lines into the interplanetary space. The type III bursts seem to encounter a steep density gradient as they overtake the type II shock front, resulting in an abrupt change in the frequency drift rate of the type III burst emission. Our study presents evidence in support of a scenario in which electrons are accelerated low in the corona behind the CME shock front, while protons are accelerated later, possibly at the CME bow shock high in the corona.

ABSTRACTpresent the first ever measurement of the 3 He energy spectrum in such an event. The particle event was associated with an impulsive flare and an interplanetary shock wave. The type II radio burst was observed with the WAVES experiment on board the Wind spacecraft before and then simultaneously with the 3 He-rich event registered with ERNE. The analysis shows that the high-energy 3 He-rich event refers to the flare material reaccelerated by the interplanetary coronal mass ejection (CME). Onset of the high-energy 3 He-rich event was observed in the far upstream region, when the CME-driven shock was at about 0.3 AU from the Sun. A spectrum of protons and spectra of the two helium isotopes closely resemble an exponent in the ion speed.